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Preliminary media screening for application in the removal of clofibric acid, carbamazepine and ibuprofen by SSF-constructed wetlands
Abstract
The aim of the present work was to evaluate the sorption capacity of light expanded clay aggregates (LECA) to remove mixtures of ibuprofen, carbamazepine and clofibric acid in water and wastewater. High removal efficiencies were attained for carbamazepine and ibuprofen while a less satisfactory performance was observed for clofibric acid. In a mixture of the three compounds in water a slight decrease in the sorbed amounts is observed in comparison with solutions of the single compounds, indicating some competitive sorption. In wastewater, the pharmaceuticals mixture also undergoes a slight reduction in the sorbed amounts of carbamazepine and ibuprofen, probably due to the presence of dissolved organic matter which increases their solubility. These compounds were removed in the following order of efficiencies in all the tested conditions: carbamazepine > ibuprofen > clofibric acid. Two other clay materials – sepiolite and vermiculite – were tested for the removal of the more recalcitrant clofibric acid, and vermiculite exhibited higher removal efficiency than LECA. The sorption is characterized by an initial fast step, with most pharmaceuticals being removed within the first 24 h. The results of this study are a first step in the process of selecting an appropriate material or combination of materials to be used as media in SSF-CWs designed for the removal of pharmaceuticals from wastewaters.
... Clofibric acid has the chemical name 2-(4-chlorophenoxy)-2-methyl-propanoic acid, its sorption coefficient (log K ow ) in the order of 0.9, 1.36, and 1.88, and its melting point is between 120 °C -122 °C 13 . It is widely used as an active ingredient in blood lipid regulators clofibrate, etofyllinclofibrate and etofibrate. ...
... Layered double hydroxides (LDHs) or anionic clays, and their calcined products (CLDHs), have been widely used as degradation photocatalysts or as adsorbent of a wide variety of micropollutants [29][30][31][32] . Several studies have evoked the elimination of this pollutant using adsorbents, such as plants, clays, activated carbon, chitosan, and resins 13,[33][34][35][36] . Most of these studies have not explored the possibilities of recycling and regenerating their materials with regard to this pollutant, or compared their results concerning the capacity and rate of adsorption with those of other adsorbents while optimising the various factors influencing elimination. ...
... This drug is considered an active metabolite of clofibrate and a lipid-lowering active ingredient. It allows reduction of blood lipid levels and acts against the excess of cholesterol 13 . ...
Clofibric acid (CA) is widely used as regulator of lipid levels in blood; it is considered one of the residual drugs that have a high persistence in the aquatic environment. After wastewater treatment, only a small amount of CA can be removed. The aim of this work was to investigate the reduction of CA in contaminated wastewater using calcined anionic clay ZnAl-CO 3 , which was chosen for its higher adsorption capacity, recycla-bility, and non-regeneration of sludge. The maximum retention amount, Q m , exceeded 2220 mg g-1 , and the value of DH° suggested a physical process. The removal rate achieved 90 %, and the remaining quantity was widely below the tolerance thresholds. Retention was achieved by hydrogen bonds and electrostatic interactions between the adsorbate molecules. Recycling tests clearly suggested that this material is recyclable, promising, and very effective compared to other adsorbents. This retention contributes to the attenuation of persistent lipid regulator.
... Clofibric acid has the chemical name 2-(4-chlorophenoxy)-2-methyl-propanoic acid, its sorption coefficient (log K ow ) in the order of 0.9, 1.36, and 1.88, and its melting point is between 120 °C -122 °C 13 . It is widely used as an active ingredient in blood lipid regulators clofibrate, etofyllinclofibrate and etofibrate. ...
... Layered double hydroxides (LDHs) or anionic clays, and their calcined products (CLDHs), have been widely used as degradation photocatalysts or as adsorbent of a wide variety of micropollutants [29][30][31][32] . Several studies have evoked the elimination of this pollutant using adsorbents, such as plants, clays, activated carbon, chitosan, and resins 13,[33][34][35][36] . Most of these studies have not explored the possibilities of recycling and regenerating their materials with regard to this pollutant, or compared their results concerning the capacity and rate of adsorption with those of other adsorbents while optimising the various factors influencing elimination. ...
... This drug is considered an active metabolite of clofibrate and a lipid-lowering active ingredient. It allows reduction of blood lipid levels and acts against the excess of cholesterol 13 . ...
Clofibric acid (CA) is widely used as regulator of lipid levels in blood; it is considered one of the residual drugs that have a high persistence in the aquatic environment.
After wastewater treatment, only a small amount of CA can be removed. The aim of this work was to investigate the reduction of CA in contaminated wastewater using calcinedanionic clay ZnAl-CO3, which was chosen for its higher adsorption capacity, recyclability, and non-regeneration of sludge. The maximum retention amount, Qm, exceeded 2220 mg g–1, and the value of DH° suggested a physical process. The removal rate achieved 90 %, and the remaining quantity was widely below the tolerance thresholds. Retention was achieved by hydrogen bonds and electrostatic interactions between the adsorbate molecules. Recycling tests clearly suggested that this material is recyclable, promising, and very effective compared to other adsorbents. This retention contributes to the attenuation of persistent lipid regulator.
... In addition to low removal rates, the unknown and potentially harmful by-products are disadvantages of AOPs. Adsorption of CA using different adsorbents like activated carbon, clay, and polymers was also studied by different researchers [12,[20][21][22]. Dordio [20] investigated adsorption of CA using a modified clay (light expanded clay aggregates) and they reported low removal efficiencies (31-58%). ...
... Adsorption of CA using different adsorbents like activated carbon, clay, and polymers was also studied by different researchers [12,[20][21][22]. Dordio [20] investigated adsorption of CA using a modified clay (light expanded clay aggregates) and they reported low removal efficiencies (31-58%). For the initial CA concentration of 40 mg/L, adsorption capacities of 70-120 mg/g were obtained by Gao and Deshusses [21] with powdered activated carbon. ...
... The chemicals used for the experiments were analytical grade and purchased from Sigma Aldrich. The clofibric acid (2-(4-chlorophenoxy)-2-methylpropionic acid) of 97% purity has following physicochemical properties: molecular weight, 214.65 g/mol; water solubility, 582.5 mg/L (25°C) [20]; pKa, 3.35 and log K ow , 2.57 [35]. The CA solutions used in the experiments were prepared by diluting stock solution (200 mg/L) with distilled water to [30]. ...
In this study, a commercial magnetic ion exchange (MIEX) resin was used for the removal of clofibric acid (CA), one of the most persistent pharmaceutical active compounds (PhACs) in the environment, from aqueous solutions. As a result of batch experiments, optimum conditions were determined as pH = 4–7, equilibrium time = 240 min., and resin dosage = 26 mL/L for the removal of CA with MIEX resin. Freundlich isotherm model and pseudo-second order kinetic model showed the best fit for the sorption data with correlation coefficients higher than 0.99. Thermodynamic calculations indicated that the ion exchange process betweenMIEX resin and CA was a thermodynamically feasible and spontaneous process. Regeneration studies showed that the repeated use of MIEX resin is possible. The effect of all coexistent anions (chloride, carbonate and sulphate) was found to be close to each other for molar ratios of CA:coexisting anion = 1–3. Fourier transform infrared (FTIR) spectrum and environmental scanning electron microscopy (ESEM) images were used to examine the interactions of resins with CA and to see the changes that could occur in the resins after regeneration. The most obvious changes in MIEX resin due to CA sorption are found in the 1712 cm⁻¹, 1480 cm⁻¹, 1238 cm⁻¹and 963 cm⁻¹ bands. This study revealed that the mechanism of removal of the CA by MIEX resin is ion exchange and is reversible.
... LECA physico-chemical characterization details are reported in Dordio et al. (2009a) and include: particle-size distribution on a weight basis, analysed according Day (1965); Apparent porosity and bulk density, determined as described in Brix et al. (2001) and Del Bubba et al. (2003) with 5 replicates; and additionally Point of Zero Charge (PZC) was analysed using the mass titration method. Table 1 shows the main physical and chemical characteristics of LECA. ...
... For all concentrations LECA achieved higher removal efficiency than Cork granulates, with minimum removal values of 89.2% and 72.9% respectively. The same behaviour has been found in others studies, where LECA achieved also the highest removals for PhACs compared to others different adsorbents (Dordio et al., 2009a(Dordio et al., , 2011(Dordio et al., and 2017. Removal efficiencies were significantly different between both materials (P < 0.001), for all concentrations. ...
... This behaviour is in accordance with previous reports (Brix et al., 2001;Drizo et al., 1999;Mysore et al., 2005;Wen et al., 2013). The presence in this material's composition of some alkaline components such as oxides and carbonates, as was verified in XDR mineralogical characterizations (Dordio et al., 2009a), may be responsible for this basic character of LECA. Its PZC (Table 1) indicates that amphoteric groups at LECA's surfaces are likely to be protonated to some extent under experimental pH conditions (pH 7.7e8). ...
The removal efficiency of LECA and cork granulates as support matrix for pharmaceuticals active compounds in a constructed wetland system was investigated using the diuretic drug Furosemide. Kinetics studies were performed testing three different concentrations of Furosemide in an ultrapure water matrix, along seven days. LECA achieved higher removal values compared to cork granulates. However, cork granulates presented a higher removal in the first 24 h of contact time compared to the other adsorbent. The kinetic studies showed that LECA and cork granulates have different adsorption behaviours for Furosemide which is controlled by different adsorption mechanisms. Both materials showed good removal efficiencies and a combination of the two should be further explored in order to applied both materials as support matrix to cope with different furosemide concentrations.
... However, the electrostatic interaction of cations presents in the surface of NZ with the target pollutants, and the hydrogen bonding significantly promotes the removal with zeolites [48,49]. Moreover, LECA possesses a positively charged surface over it, which might have resulted in a faster breakthrough of ATL (cationic pollutant) than the other pollutants [50]. ...
... The sorption of basic pollutants (ATL) over the media was governed by the electrostatic attraction between ATL and negatively charged biofilm covering the media. It is in concurrence with previous reports [10,50]. Interestingly, the concentration of PhACs adsorbed over the substrate materials was comparably lower than that observed with the batch adsorption studies [14]. ...
Constructed wetland (CW) is being used to attenuate pharmaceutically active compounds (PhACs) from wastewater. In this study, the fate of three PhACs – atenolol (ATL), carbamazepine (CBZ), and diclofenac (DCF) was investigated in each component of the CW. The acclimatized microbes showed effective degradation of PhACs at initial concentrations of 100 µg/L under different redox conditions, with degradation rates in the order of ATL > CBZ > DCF. The hydroponics study with Canna indica removed 19.3 to 31.2% without substrate materials (initial PhACs:100 µg/L each). The breakthrough and sorption capacity of unplanted CW followed the order: natural zeolite (1.6-2.15 µg/g) < Light-weight expanded clay aggregate (LECA) (5.37-8.27 µg/g) < waste autoclaved aerated concrete (AAC) block (9.27-10.79 µg/g) < wood charcoal (24.1-26.4 µg/g), according to their surface and textural properties. Eventually, four laboratory-scale CW units with enriched microbes, C. indica, and different supporting materials were monitored for the removal of organics, nutrients, and PhACs. A significant variation (p<0.05) in the pollutant’s removal was observed with the four supporting materials. The synergistic interaction among AAC blocks, macrophytes, and microbial population in the system exhibited higher removal of COD, TN, TP, and PhACs as 88.6%, 81.6%, 77.6%, and 95.3%, respectively. In addition, the estimated PhACs mass balance corroborated that biodegradation (80.57 to 93%) dominated over sorption and phytodegradation in the CWs. The abundance of Proteobacteria, Bacteroidetes, Actinobacteria, and Planctomycetes in enriched consortia contributed to the degradation of PhACs. Owing to the highly porous nature of waste AAC blocks, a relatively higher microbial activity was observed in the CW unit with AAC as substrate material.
... Aluminumpillared-layered montmorillonites also proved their potential as a sorbent in removing The adsorption and advanced oxidation of diverse pharmaceuticals and personal care products from the water were studied by Masud et al. (2020). Interestingly, they started assuming that their model pollutants are found as a complex mixture in wastewater and the environment and used reduced graphene oxide as a support for nano-zerovalent iron against a complex mixture of 12 diverse personal care products (Dordio et al., 2009;Styszko et al., 2015), chloramphenicol (Lawal and Moodley, 2018), cinnamic acid (Calabrese et al., 2017), ciprofloxacin (Hamilton et al., 2014), diclofenac (Styszko et al., 2015;Pierucci et al., 2017), furosemide (Machado et al., 2017), gemfibrozil , ibuprofen (Dordio et al., 2009;Styszko et al., 2015), ketoprofen (Styszko et al., 2015), mefanamic acid , metronidazole (Calabrese et al., 2013;Kalhori et al., 2017), nalidixic acid (Lawal and Moodley, 2018), naproxen , ofloxacin , oxytetracycline (Figueroa et al., 2004), promethazine (Gereli et al., 2006;Yurdakoç, 2009), propranolol (Pierucci et al., 2017), sulfamethoxazole (Lawal and Moodley, 2018), tetracycline (Figueroa et al., 2004;Liu et al., 2011;Lawal J o u r n a l P r e -p r o o f and Moodley, 2018), trimethoprim (Bekçi et al., 2006) and venlafaxine (Silva et al., 2018). ...
... Aluminumpillared-layered montmorillonites also proved their potential as a sorbent in removing The adsorption and advanced oxidation of diverse pharmaceuticals and personal care products from the water were studied by Masud et al. (2020). Interestingly, they started assuming that their model pollutants are found as a complex mixture in wastewater and the environment and used reduced graphene oxide as a support for nano-zerovalent iron against a complex mixture of 12 diverse personal care products (Dordio et al., 2009;Styszko et al., 2015), chloramphenicol (Lawal and Moodley, 2018), cinnamic acid (Calabrese et al., 2017), ciprofloxacin (Hamilton et al., 2014), diclofenac (Styszko et al., 2015;Pierucci et al., 2017), furosemide (Machado et al., 2017), gemfibrozil , ibuprofen (Dordio et al., 2009;Styszko et al., 2015), ketoprofen (Styszko et al., 2015), mefanamic acid , metronidazole (Calabrese et al., 2013;Kalhori et al., 2017), nalidixic acid (Lawal and Moodley, 2018), naproxen , ofloxacin , oxytetracycline (Figueroa et al., 2004), promethazine (Gereli et al., 2006;Yurdakoç, 2009), propranolol (Pierucci et al., 2017), sulfamethoxazole (Lawal and Moodley, 2018), tetracycline (Figueroa et al., 2004;Liu et al., 2011;Lawal J o u r n a l P r e -p r o o f and Moodley, 2018), trimethoprim (Bekçi et al., 2006) and venlafaxine (Silva et al., 2018). ...
Adsorption is a unit operation widely used for the tertiary treatment of the most diverse effluents, whose mechanism is based on removing recalcitrant compounds from the organic and inorganic origin. In this process, choosing a suitable adsorbent is a fundamental point. This review article focuses on the adsorbents with natural geological origin: minerals, clays, geopolymers, and even wastes resulted from mining activity. Therefore, over 450 articles and research papers were explored. These materials' main sources are described, and their characteristics, composition, and intrinsic properties are related to adsorption. Herein, we discuss the effects of several process parameters, such as pH, temperature, pollutant, and adsorbent concentration. Furthermore, equilibrium, kinetics, and thermodynamic aspects are also addressed, and relevant regeneration prospects and final disposal. Finally, some suggestions and perspectives on applying these adsorbents in wastewater treatment are presented as future trends.
... As previously described, LECA is a thermally modified clay mineral with a limited adsorption capacity (Drizo et al., 1999). However, thermal treatment causes the collapse of the interlayer space, limiting the swelling behavior which is the main limitation for the use of this adsorbent in fixed-bed columns (Le Forestier et al., 2010;Lozano-Morales et al., 2018), and increases the porosity of the media, increasing the adsorption kinetic in comparison to raw clay minerals (Dordio, Estêvão Candeias, et al., 2009). Several mesocosm studies have demonstrated the significant removal (i.e. ...
... temperature. For example, the lowest adsorption capacity of carbamazepine, as well as of other PPs such as ibuprofen, is displayed by LECA(Dordio, Estêvão Candeias, Pinto, Teixeira da Costa, & Palace Carvalho, 2009;Dordio, Miranda, Ramalho, & Carvalho, 2017). Only one study found very significant adsorption of a neutral PP (i.e. ...
The occurrence of pharmaceutical products (PPs) within environmental compartments challenges the scientific community and water treatment operators to find suitable and practicable removal solutions. Clay minerals are among the oldest and cheapest adsorbents used for the removal of organic and inorganic pollutants. However, despite their significant adsorption properties, little is known about their potential to remove organic contaminants such as pharmaceutical products from wastewater effluents. Hence, based on the latest published articles this review aims to standardize the adsorption properties of clay minerals for the removal of PPs. Specifically, the charge state of PPs appears to play a key role in their adsorption mechanism. In order to overcome the limitations of batch experiments (i.e. idealized solutions, static conditions) and design of a field solution, the impact of external parameters on the adsorption capacities of clay minerals is reviewed. The effect of thermal treatment and acid activation of clay minerals is also assessed in order to better understand the consequences of such modifications on the adsorption properties of clay-based adsorbents. Finally, even if most authors agree on the potential of clay-based adsorbents for the removal of PPs from wastewater, there remain significant gaps in the existing literature that need to be filled, with the aim of forecasting the real potential of clay-based treatment for the removal of pharmaceutical products at industrial scale.
... In this applicative research, we focused the attention on plant uptake ability (presence and type of vegetation used), since the role carried out by plants within a CW wastewater treatment system results to be crucial (Lee and Scholz 2007; Dordio et al. 2009;Zhang et al. 2012) and to better understand the influence of plants, we assessed the comparative removal efficiency of planted CWs with herbaceous on one hand and arboreal plant species on the other hand (P. australis-CWs and S. matsudana-CWs) with reference to unplanted CWs (control). ...
... Some authors found that among different substrates (vesuvianite, gravel, and zeolite), gravel appeared to be the most efficient filter material (Xiaoyan et al. 2015). The sorption capacity of light expanded clay aggregates was proved evaluating the ability to remove carbamazepine, clofibric acid, and ibuprofen (Dordio et al. 2009). In July, in CWs with only clay and gravel, the removal capability for diclofenac, ketoprofen, and atenolol was lower compared to CWs vegetated with willow and common reed, indicating the importance to introduce also plants for improving the removal activity of micro-pollutants ( Figs. 1 and 2). ...
This study assessed the ability to remove micro-pollutants from wastewater using herbaceous species (Phragmites australis L.) and trees (Salix matsudana Koidz.) in constructed wetland (CW) systems. The targets of the study were as follows: (i) pharmaceuticals like diclofenac, ketoprofen, and atenolol; (ii) 4-n-NP (4-n-nonylphenol) and the ethoxylated derivatives monoethoxylated nonylphenol (NP1EO) and diethoxylated nonylphenol (NP2EO); (iii) triclosan, a bactericide used in personal care products. The 12 CW systems, filled with clay and gravel, were irrigated with wastewater from municipal area of Pagnana (Tuscany, Italy) and influent and effluent water samples analyzed periodically by gas chromatography-mass spectrometry (GC-MS/MS). The removal efficiency of CWs planted with willow and common red ranged from 8.4 up to 100%, with the higher removal efficiency for triclosan. On the contrary, the removal efficiency of NPs and NPEOs appears lower than pharmaceuticals. Data demonstrated that P. australis efficiently removed NP, diclofenac, and atenolol, while S. matsudana preferentially removed NP1EO, NP2EO, ketoprofene, and triclosan. A specific selection of plants used in CWs could be exploited for the removal of specific xenobiotics from wastewater.
... However, the outlet concentration of orthophosphates increased in 2015 and was higher than the MPC by 6%. In 2015, both RE and MR of most of the studied pharmaceuticals increased (Table 4 (Dordio et al., 2009). ...
... Additionally, sorption/sedimentation is considered to be less dependent on seasonal conditions than photodegradation (Dordio et al., 2010). It is generally believed that sorption is the main water phase removal mechanism for carbamazepine (Park et al., 2009;Dordio et al., 2009;Tejeda et al., 2017), naproxen (Matamoros et al., 2005) and propranolol (Matamoros et al., 2005). In particular because of their hydrophobicity, these compounds tend to accumulate in sediments of CWs. ...
Pharmaceuticals in surface water are a threat to drinking water supplies. The removal of 12 pharmaceuticals was investigated in a full scale constructed wetland processing hospital wastewaters in East Ukraine. Passive in-tegrative samplers POCIS were used to monitor target compounds in the wastewater inlet and outlet at the beginning of the constructed wetland operation in 2012 and three years later in 2015. Pharmaceuticals were effectively removed; however, their removal efficiency differed among the compounds and years of the operation. An increase of removal efficiency was observed for androstenedione, carbamazepine, caffeine, diclofenac, estrone, ibuprofen, paracetamol, propranolol and triclosan with greater water residence time and an increase in macrophyte cover. Removal patterns of pharmaceuticals were discussed based on specific physical chemical properties of molecules, changes in the operational conditions of the constructed wetland and inlet pollutant concentrations. Further research is needed to fully understand how the maturation of constructed wetlands influences the removal of emerging contaminants from wastewater.
... This was consistent with previous adsorption studies for the removal efficiencies of GB and MA employing clay material, which are 10-40% [84,85]. However, a reasonably high efficiency of 95-97% is achieved using LECA for all three medicines, which is consistent with earlier investigations of other substances [86,87] Rafati et al. [88] employed a nano-composite adsorbent CCP (Clay/-CD/PVP) to clean up an aqueous solution containing Ibuprofen and tested its effectiveness using fixed-bed column experiments. The functionalized nano-clay composite allows for 94.5% ibuprofen elimination efficiency. ...
Clay minerals are eco-friendly adsorbent materials that are abundant in nature. The usage of nano-clay for the cleanup of contaminated water has grown recently due to its distinctive physicochemical properties and characteristics. Emerging contaminants, such as pharmaceutical residue, are not typically monitored in the environment and are not controlled in our wastewater. However, due to environmental dangers and their influence on human and aquatic life, removing pharmaceutical residues and their metabolites from wastewater has piqued attention. Several researchers have investigated the application of natural clay, clay-carbon, and clay-polymer composites, among others, to remove this specific pollutant. In addition, to enhance the adsorption efficiency of natural clay minerals, the adsorption sites can be improved by acid activation, thermal treatment, or incorporation of functional groups into the clay mineral layers, which have a strong affinity for the adsorption of pharmaceutical resides. The literature review findings show that modified clays are better adsorbents for the remediation of pharmaceutical residues in wastewater than natural clays and represent an economically viable and efficient option for the cleanup of wastewater containing this contaminant. Consequently, this review gives an inclusive overview of current trends in employing clay minerals for the remediation of pharmaceutical residues in wastewater and outlines the research gaps for future research. K E Y W O R D S Pharmaceutical residues Adsorbent Clay minerals Remediation Wastewater Clay-based nanocomposite can be utilized as a cost-effective adsorbent for the adsorption of pharmaceutical residues from wastewater. The adsorption sites of clay minerals can be improved by acid activation or incorporation of functional groups with an affinity for the contaminant. Modified clays are better adsorbents for the remediation of pharmaceutical residues in waste water compared to natural clays.
... Samples were collected from the tank at time intervals of 1 h during 6 h. Then, they were filtered through syringe filters (Anotop 25) and CA was quantified by HPLC with UV detection [18]. The analyses were carried out in a Waters chromatograph with a RP C-18 column (XTerra ® ). ...
Radiation modeling and kinetics in two different packed-bed reactors filled with TiO2-coated glass rings are presented. The first reactor was cylindrical, irradiated from one end by a 150 W mercury lamp. It was employed to obtain the values of the intrinsic kinetic parameters of the degradation of the emerging contaminant clofibric acid (CA). The expression to represent the kinetics of the pollutant was derived from a proposed reaction scheme, and it includes explicitly the effect of photon absorption rate on the reaction rate. The second reactor was annular, irradiated internally and externally by 40 UV-LED lamps. The kinetic parameters calculated in the first reactor were directly employed to simulate the performance of the second one, without using any adjustable parameter. The Monte Carlo method was applied to solve the radiation models in both reactors. Good agreement was obtained between simulation results and experimental data under different operating conditions, with a percentage root-mean-square error of 4.6%. The kinetic parameters proved to be independent of the irradiation source, reactor geometry, and catalyst film thickness, and can be readily applied to design real scale devices.
... Zhang [108] concluded that the presence of plants in CWs significantly improved the degree of ACB removal, achieving 39% removal at 4-days HRT in a HF compared to 33% removal in an unplanted HF. On the other hand, Dordio [121] added expanded clay to the CW bed and observed that sorption was the dominant mechanism for ACB removal. Dordio [92] obtained a moderate removal by sorption, whereas the authors observed that planted systems improved removal efficiencies. ...
The presence of emerging organic contaminants (EOCs) in the environment is increasing and requires the development of technologies for their effective removal. Therefore, a literature review on the behavior of EOCs during municipal wastewater treatment, both in major treatment systems and particularly in constructed wetlands (CWs), was carried out. The study also reviewed the behavior of EOCs in anaerobic digesters (ADs) and advanced oxidation processes, particularly in TiO2-based photocatalysis, which are being proposed as promising pre- and post-treatments for combination with CW. The following ten compounds were screened: acetaminophen (ACE), ofloxacin (OFL), caffeine (CAF), carbamazepine (CBZ), ketoprofen (KET), ibuprofen (IBU), diclofenac (DCL), clofibric acid (ACB), bisphenol A (BPA), and sotalol (SOT). The degradation pathways of the selected EOCs are largely influenced by their physicochemical and biochemical properties. Sorption and biodegradation are the main elimination mechanisms found in AD and CW treatment systems, where the combination of anaerobic and aerobic environments improves the elimination efficiency of EOCs. However, various contaminants appear recalcitrant. In this sense, in combination with CWs, TiO2-based photocatalysis emerges as a promising post-treatment for advanced EOC removal from wastewater.
... The solubility of the ECs also has a decent impact, followed by their biodegradability and chemical structure. Some of the widely-used macrophyte species employed for eradicating ECs are Typha latifolia, Typha augustifolia, Phragmites australis, Juncus effusus, and Iris pseudacorus (Carvalho 2020;Dordio et al. 2009b;Zhang et al. 2016). However, as time progresses, the planted CWs get clogged due to biofilm formation, reducing the EC removal efficiency. ...
... Apart from the aforementioned factors, the soil matrix has a noticeable impact on pharmaceutical removal in SSF-CWs because of the following: (1) it acts as the support matrix that allows the plants and microbes to flourish; and (2) it acts as an adsorbent for the pharmaceuticals (Dordio et al. 2011c), which signifies the importance of the proper selection of the bed material that has a higher adsorption capacity (i.e., with a high specific surface area). Dordio et al. (2009c) used LECA as the bed material and observed that the LECA could adsorb some selected pharmaceuticals, such as IP, CA, and CMZ. In addition, the soil matrix with high hydraulic conductivity promoted better contaminant-soil interactions that enhanced the pharmaceutical removal efficiency. ...
Emerging contaminants (ECs), especially pharmaceuticals and personal care products (PPCPs), that are present in aquatic and soil matrixes, have become a major concern for the competent authorities, because they are persistent and pose potential threats to human health, aquatic life, and the soil ecosystem. As an environmentally sustainable and economical EC remediation technology, constructed wetlands (CWs) and vermifiltration (VF) have become popular for treating wastewater and vermicomposting (VC) has gained the attention of the researchers as a sewage sludge or solid waste treatment technology. Although extensive literature is available on the potential of CWs for the remediation of ECs, a review of earthworm-based EC removal technologies has not been performed, to the best of the authors' knowledge. Therefore, this paper aims to review the potential of all the aforementioned natural EC remediation technologies. CWs and VF could emerge as suitable alternatives to conventional wastewater remediation methods to eradicate ECs, and VC has the potential to substantially eliminate ECs from organic solid wastes. In addition, risk assessments suggest that these technologies are more efficient in expurgating the level of toxicity imposed by ECs on the ecosystems that receive them than the conventional treatment methods.
... First of all, a certain amount of operational time is basically needed for the maturity of a system (Nilsson et al., 2020). Furthermore, while sorption has been claimed by several studies to be a major sink for TrOCs (Dordio et al., 2009;Dordio et al., 2011;Hussain and Prasher, 2011;Park et al., 2018), the adsorption capacity of bare support matrix is limited (Zhang et al., 2018). Meanwhile, absorption cannot be counted on as a long-term mechanism, unless coupled to efficient microbial degradation. ...
Constructed wetlands (CWs) are a promising technique to mitigate trace organic contaminants (TrOCs). The current review used meta-analysis to investigate the TrOC removal in CWs on the basis of 92 selected paper and 2373 observations. The results indicated no regular trend shown for the TrOC removal by using logPow or pKa, whereas TrOCs with molecular weight greater than 358.60 g mol⁻¹ were found generally more recalcitrant than smaller molecules. It was found that solid–water distribution coefficient (logD) can be effective in distinguishing the readily removable TrOCs. Moreover, different patterns of TrOC removal were found correlated with CW conditions (i.e., CW type, CW scale, CW vegetation, and influent type and quality). By quadratic curves fittings, parameters including pH, DO, Eh, TrOC initial concentration, and CW operational time were found to determine the removal efficiency of TrOCs, whereas logD, COD, NH4⁺-N, and TP were found to be linked to TrOC removal only if the CW conditions were specified. These results also suggested that single factors can hardly determine the fate of TrOCs in CWs. However, some universal patterns could exist for the determination. More attention should be placed in diminishing the scale bias in the future.
... The removal efficiency of PPCPs in adsorptive substrate systems was significantly higher than that in sand systems. A possible explanation could be that these three substrates have a higher adsorption capacity of PPCPs than sand Dordio et al., 2009;Dordio and Carvalho, 2013), which could contribute to absorb more PPCPs from the aqueous phase and retain inside the CWs. Meanwhile, the porous structures and large surface area of adsorptive substrates can provide more microbial attachment interfaces (Fig. 1), which could benefit the growth and development of microbes and the adsorption of PPCPs , thus enhancing the biodegradation of PPCPs. ...
This study investigated the effects of substrates (sand, perlite, vermiculite, and biochar) on the colonization of arbuscular mycorrhizal fungi (AMF) in the roots of Glyceria maxima in constructed wetlands (CWs) and the impacts of AMF inoculation on the removal of six selected pharmaceuticals and personal care products (PPCPs). Results showed that the application of adsorptive substrates (perlite, vermiculite, and biochar) in CWs had positive effects on AMF colonization. AMF could influence the uptake and translocation of PPCPs in plant tissues. The amount of PPCPs in the roots of inoculated plants was increased by 21–193% and 67–196% in sand and vermiculite systems but decreased by 13–55% and 51–100% in perlite and biochar systems, respectively, compared to the non-inoculated controls. Meanwhile, AMF enhanced the translocation of PPCPs to plant shoots, resulting in higher accumulations of PPCPs in the shoots of inoculated plants than that of non-inoculated plants. AMF had positive effects on removing PPCPs in sand systems but insignificant effects in adsorptive substrate systems. Therefore, these results indicated that the symbiotic relationship between AMF and plant roots could affect the accumulation and translocation of PPCPs in plants, and substrate type can influence this function. This study could be a starting point for exploring the potential role of AMF in PPCPs removal in CWs.
... and Phragmites ssp. are the most popular species used in CWs , while the type of substrate matrix and their respective depths are very adaptable according to the implemented CWs (Dordio et al., 2009;Kumar and Dutta, 2019;Song et al., 2009). In general, the applications of CW systems have important advantages, such as moderate capital costs, low energy consumption, small maintenance requirements and benefits for wildlife habitats . ...
Aquaculture is the fastest growing animal food-producing sector. Water is the central resource for aquaculture, and it is essential that its quality be preserved. Micropollutants (MPs) can reach aquaculture through anthropogenic addition or inlet water, and may cause harmful effects such as endocrine disruption and antibiotic resistance, adversely affecting the fish species being farmed. Furthermore, the discharge of aquaculture effluents into the environment may contribute to the deterioration of water courses. In this sense, the implementation of environmentally responsible measures in aquaculture farms is imperative for the protection of ecosystems and human health. The European Commission has recently launched a guiding document promoting ecological aquaculture practices; however, options for water treatment are still lacking. Conventional processes are not designed to deal with MPs; this review article consolidates relevant information on the application of advanced oxidation technologies (AOTs) and constructed wetlands (CWs) (singly applied or combined) as potential strategies in this regard. Although 161 studies on the application of AOTs or CWs in aquaculture have already been published, only 34 focused on MPs (28 on AOTs and 6 on CWs), whereas the others reported the removal of contaminants such as bacteria, organic matter, solids and inorganic ions. No study coupling both treatments has been reported to date for the removal of MPs from aquaculture waters. AOTs and CWs are prospective alternatives for the treatment of aquacultural aqueous matrices. However, the type of aquaculture activity and the specifications of these available technologies should be considered while selecting the most suitable treatment option.
... The main reason may be that the type of substrates changes the operating conditions inside the CWs, which directly influences plant growth and CECs removal. Compared with sand, the porous structure of vermiculite and perlite could increase the retention of available nutrients and water (SI , Table S4), which significantly promotes plant growth (SI , Table S5), thereby enhancing the removal of CECs (Dordio et al., 2009). However, the oxidative damage of G. maxima in biochar systems was higher than that in sand systems. ...
This study investigated the role of arbuscular mycorrhizal fungal (AMF) for the removal of ibuprofen (IBU) and diclofenac (DCF) in constructed wetlands (CWs) with four different substrates. Results showed that AMF colonization in adsorptive substrate (perlite, vermiculite, and biochar) systems was higher than that in sand systems. AMF enhanced the tolerance of Glyceria maxima to the stress of IBU and DCF by promoting the activities of antioxidant enzymes (peroxidase and superoxide dismutase) and the contents of soluble protein, while decreasing the contents of malondialdehyde and O2•-. The removal efficiencies of IBU and DCF were increased by 15%–18% and 25%–38% in adsorptive substrate systems compare to sand systems. Adsorptive substrates enhanced the accumulation of IBU and DCF in the rhizosphere and promoted the uptake of IBU and DCF by plant roots. AMF promoted the removal of IBU and DCF in sand systems but limited their reduction in adsorptive substrate systems. In all scenarios, the presence of AMF decreased the contents of CECs metabolites (2-OH IBU, CA IBU, and 4′-OH IBU) in the effluents and promoted the uptake of IBU by plant roots. Therefore, these results indicated that the addition of adsorptive substrates could enhance the removal of IBU and DCF in CWs. The role of AMF on the removal of IBU and DCF was influenced by CW substrate. These may provide useful information for the application of AMF in CWs to remove contaminants of emerging concern.
... These organisms contribute to Nr uses such as microbial interactions and uptake by vegetation. Abiotic mechanisms include sedimentation, filtration, chemical precipitation, and adsorption (Dordio et al., 2009). Organic matter is excreted in SSF built up in wetlands by aerobic bacteria that adhere to porous media and plant roots. ...
Reactive Nitrogen (Nr) is produced from natural and human activity, the use of fuel, the activities of industry, and agriculture. The Nr from agriculture is used to produce food crops, but excess Nr has an impact on the surrounding land. Landfills also generate Nr from the decomposition of waste which then releases the leachate containing Nr. This study aimed to determine the value of Nr generated by landfills, the effect of Nr on the environment, and the performance of Nr when used in Constructed Wetlands (CW). Review papers were collected from several studies and publications. Nr commonly found in leachate landfills include: NH4, NH3, NO2, and NO3. The Nr present in landfill leachate at CW can be used for proper plant development and growth, which significantly increases and enhances its quality and yield by playing an important role in the biochemical and physiological functions of plants. In addition, the content of hazardous substances in landfill leachate can also be processed using CW. This review paper discusses the effects of Nr from human activities ending up in landfills. The landfill leachate with Nr content can be used in CW for plant growth.
... Wastewater treatment plants (WWTPs) effluents represent a major source of pharmaceuticals in the aquatic environment (Dordio et al., 2009;Rivera-Utrilla et al., 2013). Removal efficiencies (RE) of NSAIDs in WWTPs have shown a wide range of values even for the same drug, confirming that conventional WWTPs treatments (mainly primary and secondary, rarely tertiary) are not sufficiently specialized in their removal (Gros et al., 2010;Lolić et al., 2015;Loos et al., 2013;Margot et al., 2013;Płuciennik-Koropczuk, 2015;Sousa et al., 2018;Tiedeken et al., 2017). ...
Composites of two natural zeolites – clinoptilolite and phillipsite, and cationic surfactants (cetylpyridinium chloride and Arquad® 2HT-75) were tested for the removal of two emerging contaminants – ibuprofen and naproxen. For each zeolite-rich rock, two different modifications of the zeolitic surfaces were prepared (monolayer and bilayer surfactant coverage). The influence of the initial drug concentrations and contact time on adsorption of these drugs was followed in buffer solution. The Langmuir model showed the highest adsorption capacity for the composite characterized by a bilayered surfactant at the clinoptilolite surface: 19.7 mg/g and 16.1 mg/g for ibuprofen and naproxen, respectively. Also, to simulate real systems, drug adsorption isotherms were conducted in natural water (Grindstone creek water – Columbia, Missouri, USA) by using the best performing adsorbent; in this case, a slight decrease of drug adsorption was recorded. Kinetic runs were performed in distilled water as well as in the presence of ions such as sulfates and bicarbonates; also, in this case, the interfering agents defined an adsorption decrease for bilayer composites.
... For this reason, studies on their effects on human and environmental health are still rare (Daughton and Ternes, 1999). Although PCPCs are present in low concentrations in aquatic ecosystems, typically at trace levels (ng L −1 to μg L −1 ), they can still induce adverse effects due to cumulative effects and continuous exposure (Boudrahem et al., 2017;Dordio et al., 2009). Paracetamol (N-4-hydroxyphenylacetamide or acetaminophen), a common analgesic and anti-inflammatory for humans and animals, is usually chosen as a model molecule (García-Mateos et al., 2015;Lladó et al., 2015;Mestre et al., 2015Mestre et al., , 2011Spessato et al., 2020;Terzyk, 2001;Terzyk et al., 2003;Terzyk and Rychlicki, 2000) because it is a pharmaceutical compound used worldwide and does not require medical prescription. ...
Biochar was obtained from Eucalyptus pruning residues with a non-conventional device named Kon-Tiki kiln. The average heat of combustion of the biochar, 27.3 MJ kg −1 , was higher than that of Eucalyptus wood, 17.8 MJ kg −1. Activation with CO 2 was performed by varying the activation time from 0 to 60 minutes. The activated carbons (ACs) and the carbon precursor have been characterised and tested for paracetamol removal in the liquid phase, studied in both kinetic and equilibrium aspects. ACs presented an increase in BET area (up to 845 m 2 /g), total pore volume and microporosity with the activation time. The pseudo-second order model was the one that best fitted the experimental data. Elimination of paracetamol was much faster when using ACs, 5 h, than when using the biochar, 3 days. However, pollutant removal was greater than 95 % for all materials, which is a promising result for low-cost biochars in a difficult economic context. All the adsorption equilibrium experiments exhibited multilayer behaviour, showing values up to 98 mg g −1 for the maximum monolayer-ad-sorption capacity.
... There are different techniques for the uptake of EDCs from wastewater; these include: membrane filtration (Zhang et al. 2014), oxidation processes (Garoma and Matsumoto 2009), ultrasonic treatment (Méndez-Arriaga et al. 2008), electrochemical degrading (Ciriaco et al. 2009), miniature created wetlands (Dordio et al. 2009(Dordio et al. , 2010, and adsorption (Choi et al. 2005). Among the various clean-up methods available, adsorption method with activated carbon is the most sustainable because it is eco-friendly and is mostly used for EDC removal. ...
This study investigates the sorption of a non-steroidal anti-inflammatory drug, ibuprofen, (IBP) using acid activated carbon prepared from orange peel (OPA). OPA was characterized via the use of Fourier transform infrared and scanning electron microscopy techniques. Four isotherm models were utilized to assess the adsorption data: Langmuir, Freundlich, Temkin, and Dubinin–Raduskevich, respectively. It was established that the IBP adsorption onto OPA fitted Langmuir isotherm model most. The optimum monolayer adsorption capacity of OPA was 49.30 mg/g at 50 °C. The adsorption data was subjected to kinetic test using pseudo-first-order and pseudo-second-order, Elovich, and intraparticle diffusion models. The sorption process was best described by pseudo-second-order kinetic model. The mean heat of adsorption, Ea at all temperatures studied was < 8.00 kJmol−1, signifying that the sorption mechanism is physisorption. Thermodynamic study reveals that the adsorption is spontaneous and exothermic. OPA was established to be a viable and effective adsorbent for the sorption of IBP from aqueous medium.
... These processes might be the dominant removal pathways of PCPs in winter being less temperature-sensitive compared with biodegradation [10,16,17,19,21]. Furthermore, several studies suggested that sorption processes in CWs become more complex when the wastewater matrix becomes more concentrated, possibly due to the competition processes (e.g., References [21,[53][54][55]). ...
This research presents the correlation analysis of selected design and operational factors (depth, area, hydraulic and organic loading rate, and hydraulic retention time), and physicochemi-cal parameters (pH, temperature, and dissolved oxygen) of constructed wetlands (CWs) with the removal efficiency of personal care products (PCPs). The results demonstrated that the removal ef-ficiencies of the studied PCPs exhibit a significant correlation with two or more of these factors. The role of plants in the removal of PCPs is demonstrated by the higher performance of planted compared with unplanted CWs due to direct uptake of PCPs and their aerobic biodegradation. The enhanced removal of PCPs was achieved with the use of substrate material of high adsorption capacity and with high surface area in CWs. The removal efficiency of almost all of the studied PCPs revealed seasonal differences, but significant difference was established in the case of galaxolide and methyl dihydrojasmonate. Most of the examined PCPs demonstrated adsorption and/or sorption as their most dominant removal mechanism followed by biodegradation and plant uptake. Therefore, the efficient removal of PCPs demands the integrated design ensuring suitable environment for the occurrence of these processes along with the optimal values of design and operational factors, and physicochemical parameters.
... Effluents from wastewater treatment plants represent the main source for the entry of CBZ into aquatic ecosystems [6]. CBZ is a drug used to treat a large number of mental diseases and compulsive disorders [5,7] and it is widely consumed worldwide, reaching up to 96% of the world pharmaceutical market [8]. As a consequence, according to some studies, CBZ is one of the drugs that is most frequently detected in aquatic environments around the world [9,10]. ...
Iris sibirica and Zantedeschia aethiopica are ornamental species that have previously been used in pilot-scale treatment wetlands (TWs) focused on the removal of carbamazepine (CBZ), in which good results were obtained; however, the plant influence was not completely determined. In addition, plant uptake has been reported to play a crucial role in CBZ removal in comparison to other mechanisms. Therefore, the aim of this study was to evaluate the capacity of I. sibirica and Z. aethiopica to take up, translocate, and accumulate CBZ in hydroponic conditions using a nutrient solution spiked with the drug. The maximum CBZ tolerance threshold for the two species was found to be 10 mg/L, which was used to carry out the uptake experiments. The results showed a better performance of I. sibirica compared to Z. aethiopica reaching 31.1% and 20.9% of removal efficiency, respectively. The parent compound accumulated mainly on the leaves of both species. Furthermore, a high proportion of the CBZ taken up by the plants (up to 70%) was metabolized by both species. The performance of the two species suggests the importance of plant harvesting in TWs in order to promote CBZ removal and indicates the need for future works.
... When adsorption to the substrate and sorption onto organic surfaces are considered as the dominant removal mechanism, the compounds showed moderate or low removal (e.g., triclosan, triclocarban, cashmeran, galaxolide, tonalide, tributyl phosphate, and tris (2-chloroethyl) phosphate), even in the CWs that can provide media for adsorption and sorption (Table 3, Table S6, Supplementary Materials). The complication in the occurrence of adsorption and sorption processes in CWs might be due to the creation of biofilms around the filter media obstructing their access to adsorption/sorption surfaces [37,38]. The other process considerably contributing to the removal of some of the studied PCPs is photodegradation (e.g., methylparaben, propylparaben, triclosan, and tonalide), which also demonstrates low to moderate removal efficiencies of these PCPs (Table 3, Table S6, Supplementary Materials). ...
This research investigates the performance of four types of constructed wetlands (CWs): free water surface CW (FWSCW), horizontal flow CW (HFCW), vertical flow CW (VFCW), and hybrid CW (HCW) for the removal of 20 personal care products (PCPs), based on secondary data compiled for 137 CWs reported in 39 peer reviewed journal papers. In spite of considerable variation in the removal efficiency of PCPs, CWs prove to be a promising treatment technology. The average removal efficiency of 15 widely studied PCPs ranged from 9.0% to 84%. Although CWs effectively reduced the environmental risks caused by many PCPs, triclosan was still classified under high risk category based on effluent concentration. Five other PCPs were classified under medium risk category (triclocarban > methylparaben > galaxolide > oxybenzone > methyl dihydrojasmonate). In most of the examined PCPs, adsorption and/or sorption is the most common removal mechanism followed by biodegradation and plant uptake. The comparatively better performance of HCW followed by VFCW, HFCW, and FWSCW might be due to the coexistence of aerobic and anaerobic conditions, and longer hydraulic retention time enhancing the removal of PCPs (e.g., triclosan, methyl dihydrojasmonate, galaxolide, tonalide, and oxybenzone), which are removed under both conditions and by adsorption/sorption processes.
... After a sufficient period of time, the total adsorbed mass of reversibly adsorbed compounds should theoretically desorb (Corwin and Summers, 2011). Indeed, sorption onto cork is, thus, expected to be essentially due to interactions of van der Waals type (Dordio et al., 2009). ...
... After a sufficient period of time, the total adsorbed mass of reversibly adsorbed compounds should theoretically desorb (Corwin and Summers, 2011). Indeed, sorption onto cork is, thus, expected to be essentially due to interactions of van der Waals type (Dordio et al., 2009). ...
Biopurification systems (BPS) constitute a valuable approach to mitigate/reduce the contamination of water sources with pesticides. These systems employ the degrading capacity of a biomixture to avoid/minimize, in a simple and low cost way, the pollution of discharging of pesticide containing wastewaters in the aquatic environment.
Therefore, processes and parameters controlling depuration ability of BPS systems should be a priority research issue due to the lack of alternative treatments.
The aim of this work was to evaluate the performance of three fungi, selected and isolated from different primed materials, to biodegrade the pesticides terbuthylazine, difenoconazole, diflufenican, and pendimethalin, in a biomixture containing soil and cork as substrate. Experiments using only sterilized soil were carried out as control. Each fungus species was inoculated individually (in the biomixture or soil), and their ability to biodegrade the target pesticides was evaluated during 120 days.
All the fungi strains inoculated (Fusarium oxysporum PP0030, Paecilomyces variotii PP0040 and Trichoderma viride PP0050), proved to be valuable as active pesticide-degrading microorganisms, demonstrating a very high biotransformation ability of the target pesticides, particularly in the biomixture.
Fusarium oxysporum PP0030 generally biodegraded higher amounts of the pesticides terbuthylazine, difenoconazole and diflufenican, followed by P. variotii PP0040 and T. viride PP0050. After 120 days, maximum biodegradation of terbuthylazine, difenoconazole and diflufenican, in inoculated biomixture with Fusarium oxysporum PP0030, was 89.4%, 81.5% and 74.7%, respectively. Moreover, a biodegradation for pendimethalin close to 100% was achieved by all fungi.
This paper is also a breakthrough on the understanding of the metabolic pathways used by fungi to biodegrade pesticides. With the results presented, it seems to be clear that the metabolization of terbuthylazine by fungi follow different metabolic routes in different media, leading to the production of different metabolites. This conclusion had already been advanced in our previous studies, using the white-rot fungus L. edodes, being now reiterated and confirmed with different fungi species.
In this study, it was also possible to identify a pendimethalin metabolite that had already been indicated as a degradation product of this herbicide by bacteria, but as far as we known, it was never described as intermediate metabolite of pendimethalin biotransformation by fungi.
Sorption process to cork by pesticides studied proved to be a reversible process, which potentially allows the complete biodegradation of the pesticides. This reversibility of the pesticides sorption processes on cork, establish that the use of these biomixtures can reduce the amount of contaminated waste by using the same substrate in successive applications of wastewaters, increasing the sustainability of the system.
In conclusion, our results are very useful and can be used as important data in the construction of sustainable BPS, suitable for the depuration and detoxification of wastewaters containing the target pesticide or other with similar intrinsic characteristics, contributing to the protection of aquatic resources as well as maintaining their quality and reducing the wastes.
... On the other hand, the SHs showed a moderate removal, if adsorption onto the substrate and/or sorption onto organic surfaces are considered the dominant removal mechanism (e.g., 17α-ethinylestradiol, and estriol) ( Tables 5 and S6). The creation of biofilms around the filter media might obstruct the access of SHs to adsorption and/or sorption surfaces [81,82]. Similarly, despite photodegradation contributed significantly to the removal of some of the studied SHs (e.g., 17α-ethinylestradiol, 17ß-estradiol, and testosterone), these SHs demonstrated moderate removal (Tables 5 and S6). ...
The performance of four types of constructed wetlands (CWs) namely, free water surface CW (FWSCW), horizontal flow CW (HFCW), vertical flow CW (VFCW) and hybrid CW (HCW) was comprehensively and critically evaluated for the removal of steroidal hormones (SHs) based on peer-reviewed literature. The average removal efficiency of 11 widely studied SHs ranged from 55% to 100%. Although the effluent concentration of SHs was decreased after the treatment, the environmental risk posed by them was not considerably reduced in most cases. For instance, estimated risk quotient of five out of nine examined SHs (i.e., 17α-ethinylestradiol, 17ß-estradiol, testosterone, estrone and estriol) was extremely high for the effluent of CWs. In most of the examined SHs, biodegradation (aerobic and/or anaerobic) is the most dominant removal mechanism followed by plant uptake and adsorption and/or sorption, along with the physicochemical properties of SHs playing an important role in the elimination processes. Among the studied CWs, the VFCW performed better followed by HFCW, HCW and FWSCW. The aerobic biodegradation being more efficient than anaerobic explains the better removal in VFCW compared with HFCW, also because several SHs showed better biodegradation under aerobic conditions (e.g., 17α-ethinylestradiol, estriol, progesterone and testosterone). Additionally, plants and support matrix as well as other governing factors such as design and operational factors (area, depth, hydraulic loading rate, hydraulic retention time and organic loading rate), and physicochemical parameters (effluent dissolved oxygen, temperature and pH) of CWs also play a considerable role in the removal of the examined SHs.
... Probably the most important sources of pharmaceuticals are their ineffective removal from effluents from traditional wastewater treatment plants (WWTPs) [6]. Non-Steroidal completely removed from water and confirming that WWTPs effluents represent major sources of pharmaceuticals in the aquatic environment [2,[4][5][6][7][8][9][12][13][14]16]. ...
In this study, composites of the natural zeolites and cationic surfactants cetylpyridinium chloride and Arquad® 2HT-75 were used for removal of two emerging contaminants – diclofenac sodium and ketoprofen. Modifying a clinoptilolite- and a phillipsite-rich tuff, with surfactants with one or two hydrophobic tails, resulted in composites in monolayer and bilayer forms. The intention was to better evaluate interactions of composites with selected molecules. Starting materials and composites were characterized by ATR–FTIR and STA coupled with EGA. The adsorption capacities of the prepared sorbents were estimated by determination of adsorption isotherms and kinetic runs. Maximum adsorption capacity, obtained from the Langmuir model, showed that the best results were for the bilayer form of the composites up to 35 mg/g. Between the two surfactants, composites with cetylpyridinium chloride gave better results. Zeta potential measurements showed that the surfactants turned out to be unstable on the zeolite surface, the only exception being bilayers prepared using the two-tailed surfactant Arquad® 2HT-75. These results suggested possible applications of these composites for water treatment purposes.
... The proper selection of the plant species and the support matrix can help to build the optimized constructed wetland to remove the particular contaminants from wastewater. The suitable support matrix such as lightweight expanded clay aggregate (Leca) can remove the nonbiodegradable compounds including phenolic compounds, pharmaceuticals, and pesticides from wastewater due to their high sorption capacity (Reddy and DeLaune, 2008;Imfeld et al., 2009;Ahmad et al., 2010;Passeport et al., 2011) and help the growth of the plants and microorganisms in the constructed wetlands (Calheiros et al., 2008;Dordio et al., 2007Dordio et al., , 2009Dordio et al., , 2010. Özengin and Elmaci (2016) reported that the carbamazepine adsorbed into the structure of Leca and the body and leaves of P. australis in constructed wetlands, whereas ibuprofen and sulfadiazine did not. ...
... Studies have demonstrated that wetland plants play a positive role in the removal of certain pharmaceuticals such as diclofenac, ibuprofen, ketoprofen, NPX, salicylic acid, amoxicillin, ampicillin, erythromycin, sulfadiazine, sulfamethazine, SMX, atenolol, clofibric acid, carbamazepine, and CAFF (Dordio et al., 2009b(Dordio et al., , 2010Xian et al., 2010;Hijosa-Valsero et al., 2011a,b,c;Zarate et al., 2012;Zhang et al., , 2012a. ...
The widespread use and presence of Pharmaceuticals and Personal care products (PPCPs) in aquatic environment throughout the world and their potential biological activity suggest, that understanding how these compounds can influence aquatic ecosystem functions is an important research direction. PPCPs are widely studied and the number of papers published in SCI journals is > 1500 in 2017 itself and > 7000 since 2012. (https://scholar.google.co.in).
The present chapter discusses the classification and possible environmental sources of PPCPs. It also details the fate, pathways, persistence and eco-toxicological profile of these compounds focusing on aquatic environment. The efficiency and limitations of the existing conventional/ advanced water/wastewater treatment systems in the removal of these compounds, is also overviewed to understand the aquatic environmental pathway of PPCPs.
The chapter describes the steps towards directives and regulations and the key strategy adopted for the basis of concern.
... The influent solutions had an average pH of 7.12 ± 0.23 (after adjustment), which increased to 7.96 ± 0.33 and 8.15 ± 0.32 in the CWC and CWP outflows, respectively. Besides the previously reported pH-buffering capacity of the LECA material (Dordio et al., 2009), the higher pH values at the CWP outflow could be attributed to the enhanced aerobic conditions that dominate in planted CWs Tatoulis et al., 2016;Schultze-Nobre et al., 2017). The pH values at the middle sampling points of the units had midway values of 7.08 ± 0.36 and 7.29 ± 0.33, respectively. ...
The feasibility and treatment efficiency of horizontal subsurface flow constructed wetlands (HSFCW) was assessed for the first time for cork boiling wastewater (CBW) through laboratory experiments. CBW is known for its high content of phenolic compounds, complex composition of biorecalcitrant and toxic nature. Two lab-scale units, one planted with Phragmites australis (CWP) and one unplanted (CWC), were used to evaluate the removals of COD, BOD, total phenolic compounds (TPh) and decolourization over a 2.5-years monitoring period under Mediterranean climatic conditions. Seven organic and hydraulic loading rates ranging from 2.6 to 11.5 g COD/m2/d and 5.7-9.1 L/m2/d were tested under average hydraulic retention time (HRT) of 5 ± 1 days required due to the CWB limited biodegradability (i.e., BOD5/COD of 0.19). Average removals of the CWP exceeded those of the CWC and reached 74.6%, 91.7% and 69.1% for COD, BOD5 and TPh, respectively, with respective mass removals rates up to 7.0, 1.7 and 0.5 (in g/m2/d). Decolourization was limited to 35%, since it mainly depends on physical processes rather than biodegradation. CBW concentration of nine phenolic compounds ranged from 1.2 to 38.4 mg/L (for the syringic and ellagic acids, respectively) in the raw CBW, with respective removals in the CWP unit ranging from 41.8 to 76.3%, higher than those in the control unit. Despite CBW high concentration of TPhs (average of 116.3 mg/L), the HSFCW reached organic load removals higher than those of conventional biological treatment methods.
... A suitable choice of the latter is especially important for the removal of non-biodegradable compounds (including phenolic compounds, pharmaceuticals, and pesticides) from wastewater, for which sorption processes can play a major role (23)(24)(25)(26). In the previous studies, lightweight expanded clay aggregate (Leca) materials have been shown to be suitable for the development of the plants and microorganisms in the constructed wetlands, as well as exhibiting a high capacity for adsorbing many types of the organic molecules (27)(28)(29)(30)(31)(32)(33). ...
Background
There is growing interest in the natural and constructed wetlands for wastewater treatment. While nutrient removal in wetlands has been extensively investigated, information regarding the degradation of the pharmaceuticals and personal care products (PPCPs) has only recently been emerging. PPCPs are widely distributed in urban wastewaters and can be removed to some extent by the constructed wetlands. The medium-term (3-5 years) behavior of these systems regarding PPCP removal is still unknown.
Objectives
The efficiency of a Leca-based laboratory-scale constructed wetland planted with Phragmites australis (Cav.) Trin. Ex. Steudel in treating an aqueous solution of the pharmaceuticals, namely, carbamazepine, ibuprofen, and sulfadiazine, was to investigate.
Materials and Methods
The two pilot-scale constructed wetlands (CW) were operated in parallel; one as an experimental unit (a planted reactor with P. australis) and the other as a control (an unplanted reactor with Leca). Pretreatment and analyses of the carbamazepine, ibuprofen, sulfadiazine, and tissue samples (Leca, P. australis body and P.australis leaf) were conducted using HPLC.
Results
The carbamazepine, ibuprofen, and sulfadiazine removal efficiencies for the planted and unplanted reactors were 89.23% and 95.94%, 89.50% and 94.73%, and 67.20% and 93.68%, respectively. The Leca bed permitted an efficient removal. Leca has a high sorption capacity for these pharmaceuticals, with removal efficiencies of 93.68-95.94% in the unplanted reactors.
Conclusions
Sorption processes might be of a major importance in achieving efficient treatment of wastewater, particularly in the removal of organic material that are resistant to biodegradation, in which case the materials composing the support matrix may play an important role. The results obtained in the present study indicate that a constructed wetland with Leca as a substrate and planted with P. australis is effective in the treatment of wastewater contaminated with carbamazepine, ibuprofen, and sulfadiazine.
... Thus, increases in plant biomass during the second sampling period improved target PhAC accumulation in plants, and enhanced removal of the studied PhACs. Second, microorganisms in the constructed wetlands that were seeded with activated sludge acclimated to the environment, and the ceramisite substrate promoted the formation of biofilms via its large specific surface area ( Dordio et al., 2009;Wu et al., 2010;Zarate et al., 2012). Thus, the enhancement of microbial biomass in constructed wetlands of the study as discussed in Section 3.3 could have contributed to higher removal of target PhACs during the second sampling period. ...
The release of pharmaceutically active compounds (PhACs) into water bodies is among the current concerns of the scientific community considering the associated environmental and health factors, such as the toxic effects on aquatic microorganisms as well as the generation of antibiotic-resistant bacteria (ARBs) and antibiotic resistance genes (ARGs). Hence, there has been a trend to develop efficient and low-cost techniques to address this issue. This chapter aims to discuss the applicability of constructed wetlands (CWs) for the removal of PhACs. The mechanisms involved and the effects of various operating parameters on the performance of CWs have also been discussed, and the possibility for the optimization of the performance of such systems has been explored.
A photocatalytic reactor under UV-LED illumination is presented. It is an annular, packed-bed reactor filled with TiO2-coated glass rings. The reactor is irradiated both internally and externally in order to minimize the presence of dark zones. The knowledge of the radiation distribution inside the reactor is a key aspect to optimize its design and improve its efficiency. A three-dimensional model has been developed to describe the distribution of the local rate of photon absorption inside the reactor. The Monte Carlo method was applied to solve the radiation model. Simulation results were validated with experimental measurements. The model was able to predict the influence of the catalyst film thickness and the illumination conditions on the radiation distribution and on the total rate of photon absorption. Also, degradation assays of the pharmaceutical clofibric acid were carried out in the reactor and the performance of different illumination conditions was evaluated by means of the quantum efficiency parameter.
The present work explores the structural parameters and vibrational frequencies as well as molecular interactions of benzodiazepine derivatives, such as clothiapine (CT), clozapine (CZ), and loxapine (LX). Employing fitting experimental data to theoretical results is used to assess the structural parameters of heading composites. The main assignment is passed out according to the overall distribution of energy of the vibrational modes. From the hyper-conjugative interaction, the permanency of the structure had been predicted through natural bond orbital analysis; it is also used to identify the bonding and antibonding regions of the molecules. Moreover, electrostatic potential (ESP), density of states (DOS), and charge transfer occurring of the molecule among HOMO as well as LUMO energy were calculated and presented; utilizing electron localized field (ELF), localized orbital locator (LOL), and reduced density gradient (RDG), the chemical interactive regions are found. Additionally, mean polarizability (αtot), the first-order hyperpolarizability (βtot), and softness and hardness of the entitled compounds were also performed. The interaction between protein–ligand was also predicted by docking studies.
The main objective of this study was to apply multivariate analysis, such as principal component analysis (PCA), to determine the influence of water quality parameters on the removal of triclosan (TCS) and ibuprofen (IB) in vertical subsurface flow constructed wetlands (VSSFs). For this purpose, two VSSFs were operated under TCS and IB concentrations of 10 μg/L. One VSSF system was planted with Agapanthus africanus and the other was left unplanted and used as a control. To determine the influence of water quality parameters on TCS and IB removal, the removal efficiencies for TCS, IB, organic matter and nutrients in VSSF systems were determined. Using these data, PCA was performed. The TCS and IB removal efficiencies in VSSF systems were found to vary between 60%–85% and 50%–84%, respectively. Regarding the effects of water quality parameters on TCS and IB removal, PCA showed that TCS removal has a strong association with the oxidation reduction potential. This result confirms that aerobic conditions for VSSF systems promote the removal of the TCS compound. For the case of IB, an association between IB and biological oxygen demand removal was observed. However, this relation was found to be not significant. This study reveals that PCA allows us to determine the association between different variables in VSSF systems. Moreover, this work will serve as the basis for future research for optimizing the performance for removing TCS and IB by focusing on the improvement of aerobic conditions.
The contamination of water resources with various pharmaceutical residues confirms the importance of developing their removal methods by introducing new efficient adsorbents. In this study, the potential of imidazole modified clinochlore (Im@clin) as a new adsorbent for removal of Ibuprofen (IBP) from polluted water was assessed. The characterization studies of synthesized Im@clin by using X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), scanning electron microscope (SEM), SEM-mapping, Fourier-transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA) confirms that the Im@clin is convenient for adsorption. Then, the adsorption capacity of synthesized Im@clin was assessed with regard to removing ibuprofen under different conditions such as varying pH levels of IBP solutions (2–11), initial IBP concentrations (5–200 mg L−1), contact time (5–60 min), and the amount of Im@clin as adsorbent (1.7–33.3 g L−1). The results demonstrate that maximum adsorption capacity of Im@clin for removal of IBP in aqueous solutions is 5.8 mg g−1. The pseudo-second-order and the Langmuir model successfully represented the adsorption kinetic and isotherm of procedure. The thermodynamic parameters such as ΔG0 (the Gibbs free-energy difference), ΔH0 (Enthalpy change difference), and ΔS° (Entropy change difference) are calculated. The endothermic nature (ΔH0 16.19 kJ mol−1) and spontaneous nature (Gibbs free energy change, ΔG0 − 2.03 kJ mol−1) of the IBP adsorption process by Im@clin were confirmed and this process is entropy derived (ΔS0 0.06 kJ mol−1).
In this study, the potential of eight low cost and readily available materials as adsorbents for the removal of pharmaceutically active compounds (carbamazepine (CBZ), diclofenac (DCF) and ibuprofen (IBU)) and nutrients was evaluated through batch studies under various environmental conditions. Results showed that wood charcoal, light-weight expanded clay aggregate (LECA), natural zeolites and waste AAC blocks has a potential as promising adsorbents for the elimination of micro-pollutants with the sorption capacity of 0.57–2.83 mg/g for the selected compounds due to their superior properties including higher surface area, pore volume and organic content. Studies revealed that hydrogen bonding, electrostatic and ligand interaction and Vander Waals force are the predominant mechanisms responsible for the sorption process. The selected materials exhibited better removal of phosphate (70–90%) than ammonia (20–81%) and nitrate (14.1–61.8%). Surface area, pore volume, organic content, cation exchange capacity and elemental content (CaO, Al2O3, K2O and Fe2O3) significantly influenced the pollutant removal by the substrates. Being hydrophobic and anionic in nature, DCF exhibited higher removal than IBU and CBZ. Based on the results, the order of preference of material as adsorbent is: wood charcoal > natural zeolite > waste AAC blocks > LECA > blast furnace slag > natural pyrite > brickbats > sand. The results of this batch study will be helpful for selecting appropriate substrate material for the low-cost natural treatment systems where the bio-enhanced sorption/degradation processes help to eliminate the toxic emerging contaminants (ECs) from wastewater.
This paper presents a comprehensive and critical analysis on the removal of pharmaceuticals (PhCs), the governing physicochemical properties, and removal mechanisms in constructed wetlands (CWs). The average removal efficiency of the most widely studied 34 PhCs ranges from 21% to 93%, with the exception of one PhC that exhibited negative removal. Moreover, CWs are effective in significantly reducing the environmental risk caused by many PhCs. Based on risk assessment, 12 PhCs were classified under high risk category (oxytetracycline > ofloxacin > sulfamethoxazole > erythromycin > sulfadiazine > gemfibrozil > ibuprofen > acetaminophen > salicylic acid > sulfamethazine > naproxen > clarithromycin), which could be considered for regular monitoring, water quality standard formulation and control purposes. Biodegradation (aerobic and anaerobic) is responsible for the removal of the majority of PhCs, often in conjunction with other mechanisms (e.g., adsorption/sorption, plant uptake, and photodegradation). The physicochemical properties of molecules play a pivotal role in the elimination processes, and could serve as important predictors of removal. The correlation and multiple linear regression analysis suggest that organic carbon sorption coefficient (Log Koc), octanol-water distribution coefficient (Log Dow), and molecular weight form a good predictive linear regression model for the removal efficiency of PhCs (R2 = 0.65, P-value <0.05).
In this chapter, a review is presented of the main processes of pharmaceuticals removal (degradation, transformation or retention) in constructed wetlands systems (CWS), the role played by CWS components (support matrix, plants and microorganisms) in such processes and how the overall performance of wastewater treatment is affected by all these parameters. Some attention is paid to recent publications on this subject, especially to studies involving specific CWS applications for the removal of pharmaceuticals that focus on the characterization and optimization of processes and to studies relevant to the selection of the most adequate CWS components. Some of the questions remaining to be addressed in the available literature about the removal mechanisms in CWS, as well as the aspects of CWS design and operation that are still insufficiently explored in the optimization of these systems, are also highlighted in this text.
The microbial community of seven different small‐scale constructed wetlands (CWs) treating urban wastewater was analyzed to establish possible relationships between microbial richness and pollutant removal [organic matter, nutrients and pharmaceuticals and personal care products (PPCPs)], and between microbial richness and physico‐chemical parameters inside the systems. Microbial richness on gravel and in the interstitial liquid were inversely related. The most oxygenated systems showed a greater gravel microbial richness (and this was related to caffeine and naproxen removal). CWs planted with Phragmites australis showed a higher root microbial richness and were more efficient in nutrient removal than Typha angustifolia systems. On the contrary, T. angustifolia systems obtained better performances for the removal of the PPCP carbamazepine. Positive correlations were detected between root microbial richness and dissolved oxygen concentration, redox potential and temperature, whereas a negative correlation was recorded between root microbial richness and the pH value.
In this study, the aim was to evaluate the adsorption capacity of a volcanic rock commonly used in Mexico as filter medium in constructed wetlands (locally named tezontle) for carbamazepine (CBZ) adsorption, as well as to analyze the change in its capacity with biofilm growth. Adsorption essays were carried out under batch conditions by evaluating two particle sizes of tezontle, two values of the solution pH, and two temperatures; from these essays, optimal conditions for carbamazepine adsorption were obtained. The optimal conditions (pH 8, 25 °C and 0.85–2.0 mm particle-size) were used to evaluate the adsorption capacity of tezontle with biofilm, which was promoted through tezontle exposition to wastewater in glass columns, for six months. The maximum adsorption capacity of clean tezontle was 3.48 µg/g; while for the tezontle with biofilm, the minimum value was 1.75 µg/g (after the second week) and the maximum, was 3.3 µg/g (after six months) with a clear tendency of increasing over time. The adsorption kinetic was fitted to a pseudo-second model for both tezontle without biofilm and with biofilm, thus indicating a chemisorption process. On clean tezontle, both acid active sites (AAS) and basic active sites (BAS) were found in 0.087 and 0.147 meq/g, respectively. The increase in the adsorption capacity of tezontle with biofilm, along the time was correlated with a higher concentration of BAS, presumably from a greater development of biofilm. The presence of biofilm onto tezontle surface was confirmed through FTIR and FE-SEM. These results confirm the essential role of filter media for pharmaceutical removal in constructed wetlands (CWs).
Pharmaceutical residues in wastewater pose a challenge to wastewater treatment technologies. Constructed wetlands (CWs) are common wastewater treatment systems in rural areas and they discharge often in small water courses in which the ecology can be adversely affected by the discharged pharmaceuticals. Hence, there is a need for studies aiming to improve the removal of pharmaceuticals in CWs. In this study, the performance of a full-scale aerated sub-surface flow hybrid CW treating wastewater from a healthcare facility was studied in terms of common water parameters and pharmaceutical removal. In addition, a preliminary aquatic risk assessment based on hazard quotients was performed to estimate the likelihood of adverse effects on aquatic organisms in the forest creek where this CW discharges. The (combined) effect of aeration and hydraulic retention time (HRT) was evaluated in a laboratory-scale batch experiment. Excellent removal of the targeted pharmaceuticals was obtained in the full-scale CW (>90%) and, as a result, the aquatic risk was estimated low. The removal efficiency of only a few of the targeted pharmaceuticals was found to be dependent on the applied aeration (namely gabapentin, metformin and sotalol). Longer and the HRT increased the removal of carbamazepine, diclofenac and tramadol.
In soils, organic matter and minerals are often associated such that it is unclear how the presence of the former component influences the sorptive properties of the latter one. In this study, sorption and desorption of the herbicides 4,6-dinitro-o-cresol (C7H6N2O5) and dichlobenil (C7H3Cl2N) by Ca2+-, K+-smectites, and humic acid-smectite complexes, was investigated using batch-equilibrations and x-ray diffraction (XRD). Greater sorption of 4,6-dinitro-o-cresol compared with dichlobenil was observed for both smectites and humic acid-smectite complexes. For both pesticides, K+ smectites were more effective sorbents than Ca2+ smectites, with the lower charge-density clay (SWy-2) displaying a greater sorption capacity than the higher charge-density clay (SAz-1). The presence of humic acid did not impact pesticide sorption by K+ clays, but could enhance or suppress pesticide sorption by Ca2+-clays. A composite model for estimating pesticide sorption, which assumes mineral and organic matter function individually as sorbent phases, predicted sorption within a factor of 0.8 to 1.5 times the measured values. Humic acid did not contribute to pesticide desorption hysteresis in K+-humic acid-clay complexes, but was a source of hysteresis in the corresponding Ca2+ complexes. The basal spacings of K-SWy-2 and humic acid-modified K-SWy-2 increased gradually from approximately 10.4 to 12.2 Å with increasing 4,6-dinitro-o-cresol loadings. Also, XRD patterns of humic acid-modified and unmodified K-SWy-2 smectite clays were found identical. These results demonstrate the intercalation of 4,6-dinitro-o-cresol and suggest that humic acids are restricted to the external surfaces of clay tactoids. Together, these results indicate that clay mineral fractions in soils, including those with organic coatings, may play an important role in the retention of certain pesticides.
Sepiolite is a hydrated magnesium silicate clay with a fibrous structure and binder properties. To calculate the potential use of sepiolite in removing atrazine [2-chloro-4-ethylamino-6-isopropilamino-1,3,5,-triazine], isoproturon [3-(4-isopropylphenyl)-1,1-dimethylurea] and imidacloprid [1-(6-chloro-3-pyridinylmethyl)-N-nitroimidazolin-2-ylideneamine] from water, the adsorption of atrazine, isoproturon and imidacloprid on sepiolite desiccated at 110°C from aqueous solution at 25°C has been studied by using batch experiments. In addition, column experiments were carried out with the sepiolite sample using aqueous solutions of atrazine, isoproturon and imidacloprid at a concentration of 20.0 x 10-4 cmoldm-3. The experimental data points have been fitted to the Langmuir equation to calculate the adsorption capacities (X(m)). Values for X(m) ranged from 2.70 x 10-1 cmolkg-1 for isoproturon up to 3.97 x 10-1 cmolkg-1 for atrazine. The removal efficiency (R) ranged from 36.7% for isoproturon up to 74.3% for atrazine. The batch experiments show that the sepiolite is more effective in adsorbing atrazine than imidacloprid and isoproturon. The column experiments show that sepiolite might be reasonably used in removing atrazine, the column efficiency being 46%. The data indicate that a readily available and inexpensive Spanish sepiolite can be employed as a filter for contaminated waters with these pesticides, controlling their release to the environment.
Increasing attention is being focused on the phosphorus retention capacity of wetlands. Several allempts have been made to improve the reduction of phosphorus in wastewater by the use of constructed wetlands. One way of improving the phosphorus reduction capacity is to use efficient filter materials in the wetland. Leca® (Light Expanded Clay Aggregates) has been tested in Norway, where laboratory and field investigalions gave promising results. To further study the chemical removal mechanism of Leca, an experiment utilising five columns was performed. A phosphate solution was applied to the columns intermittently and samples were taken twice a week. Parallel to this study. a P-fractionation experiment was conducled to find out how the phosphate was sorbed to various components of the material. Both experiments showed that only a small amount of the applied phosphate was sorbed by the Leca. The amount sorbed was primarily attached to Al-complexes. In a second column experiment Opoka, a reactive medium rich in CaCO3, was added to Leca and sand to investigate the P-sorption capacity. The results from this investigation showed a higher P-uptake than in the previous column experiment. The lime additive clearly increased the P-sorption and, in this study. Leca in its pure form could be considered as chemically non-reactive.
During the last three decades, the impact of chemical pollution has focused almost exclusively on the conventional "priority" pollutants, especially those acutely toxic/carcinogenic pesticides and industrial intermediates displaying persistence in the environment. This spectrum of chemicals, however, is only one piece of the larger puzzle in "holistic" risk assessment. Another diverse group of bioactive chemicals receiving comparatively little attention as potential environmental pollutants includes the pharmaceuticals and active ingredients in personal care products (in this review collectively termed PPCPs), both human and veterinary, including not just prescription drugs and biologics, but also diagnostic agents, "nutraceuticals," fragrances, sun-screen agents, and numerous others. These compounds and their bioactive metabolites can be continually introduced to the aquatic environment as complex mixtures via a number of routes but primarily by both untreated and treated sewage. Aquatic pollution is particularly troublesome because aquatic organisms are captive to continual life-cycle, multigenerational exposure. The possibility for continual but undetectable or unnoticed effects on aquatic organisms is particularly worrisome because effects could accumulate so slowly that major change goes undetected until the cumulative level of these effects finally cascades to irreversible change--change that would otherwise be attributed to natural adaptation or ecologic succession. As opposed to the conventional, persistent priority pollutants, PPCPs need not be persistent if they are continually introduced to surface waters, even at low parts-per-trillion/parts-per-billion concentrations (ng-microg/L). Even though some PPCPs are extremely persistent and introduced to the environment in very high quantities and perhaps have already gained ubiquity worldwide, others could act as if they were persistent, simply because their continual infusion into the aquatic environment serves to sustain perpetual life-cycle exposures for aquatic organisms. This review attempts to synthesize the literature on environmental origin, distribution/occurrence, and effects and to catalyze a more focused discussion in the environmental science community.
The fate of pesticides in aquifers is influenced by the small but not insignificant adsorption of pesticides to mineral surfaces. Batch experiments with five pesticides and four minerals were conducted to quantify the contributions to adsorption from different mineral surfaces and compare adsorption characteristics of selected pesticides. Investigated mineral phases included quartz, calcite, kaolinite, and alpha-alumina. Selected pesticides comprised atrazine (6-chloro-N2-ethyl-N4-isopropyl-1,3,5-triazine-2,4-diamine), isoproturon [3-(4-isopropylphenyl)-1,1-dimethylurea)], mecoprop [(RS)-2-(4-chloro-2-methylphenoxy)propionic acid], 2,4-D (2,4-dichlorophenoxyacetic acid), and bentazone [3-isopropyl-1H-2,1,3-benzothiadiazin-4-(3H)-one 2,2-dioxide]. Specific surface area and mineral surface charge proved to be important for the adsorption of these pesticides. Detectable adsorption of the anionic pesticides (mecoprop, 2,4-D, and bentazone) was only measured when positive sites were present on the mineral surface. However, when CaCl2 was added as an electrolyte, a detectable adsorption of mecoprop and 2,4-D was also measured on kaolinite (which exhibits a negative surface charge), probably due to formation of Ca-pesticide--surface complexes. Adsorption of the uncharged pesticides (atrazine and isoproturon) was detected only on kaolinite. The lack of adsorption on alpha-alumina indicates that the uncharged pesticides have a greater affinity for the silanol surface sites (=SiOH) than for the aluminol surface sites (=AlOH) in kaolinite. No measurable effect of ionic strength was found for the uncharged pesticides. The results indicate that quartz and calcite play a smaller role than clay minerals.
Sorption of phosphorus (P) to the bed sand medium is a major removal mechanism for P in subsurface flow constructed wetlands. Selecting a sand medium with a high P-sorption capacity is therefore important to obtain a sustained P-removal. The P-removal capacities of 13 Danish sands were evaluated and related to their physico-chemical characteristics. The P-removal properties of sands of different geographical origin varied considerably and the suitability of the sands for use as media in constructed reed beds thus differs. The P-sorption capacity of some sands would be used up after only a few months in full-scale systems, whereas that of others would subsist for a much longer time. The most important characteristic of the sands determining their P-sorption capacity was their Ca-content. Also the P-binding capacities of various artificial media were tested (light-expanded-clay-aggregates (LECA), crushed marble, diatomaceous earth, vermiculite and calcite). Particularly calcite and crushed marble were found to have high P-binding capacities. It is suggested that mixing one of these materials into the sand or gravel medium can significantly enhance the P-sorption capacity of the bed medium in a subsurface-flow constructed wetland system. It is also possible to construct a separate unit containing one of these artificial media. The media may then be replaced when the P-binding capacity is used up.
Increasing attention is being focused on the phosphorus retention capacity of wetlands. Several attempts have been made to improve the reduction of phosphorus in wastewater by the use of constructed wetlands. One way of improving the phosphorus reduction capacity is to use efficient filter materials in the wetland. Leca® (Light Expanded Clay Aggregates) has been tested in Norway, where laboratory and field investigations gave promising results. To further study the chemical removal mechanism of Leca, an experiment utilising five columns was performed. A phosphate solution was applied to the columns intermittently and samples were taken twice a week. Parallel to this study, a P-fractionation experiment was conducted to find out how the phosphate was sorbed to various components of the material. Both experiments showed that only a small amount of the applied phosphate was sorbed by the Leca. The amount sorbed was primarily attached to Al-complexes. In a second column experiment Opoka, a reactive medium rich in CaCO3, was added to Leca and sand to investigate the P-sorption capacity. The results from this investigation showed a higher P-uptake than in the previous column experiment. The lime additive clearly increased the P-sorption and, in this study, Leca in its pure form could be considered as chemically non-reactive.
Five light-weight aggregates (LWAs), suitable for filter media in subsurface flow constructed wetlands, were tested for potential removal of phosphorus (P). P-sorption variation is dependent on the chemical characteristics of the LWA. All LWAs exhibited high pH and high total metal content; however, P-sorption capacity varied by two orders of magnitude. Of the LWAs' chemical characteristics (total metal content, cation exchange capacity, and oxalate soluble Fe and Al), total metal content has the closest relationship with the P-sorption capacity. Among the four major metal ions (Mg, Ca, Fe and Al), Ca has the strongest correlation with the P-sorption capacity.
The mass titration method for determination of the zero point of charge (PZC) was proposed by Noh and Schwarz (J. Colloid Interface Sci.130, 157 (1989)). This method was developed for (hydr)oxides and is limited to pure samples. It is based on the fact that pH approaches the limiting value (pH∞) by addition of solid powder to an aqueous medium. The limiting pH∞ value, at a high solid content, is then equal to pHPZC. This article is an extension of the original work and concerns the samples contaminated with an acid or base which are not irreversibly bound. Numerical simulation, based on a “site binding” (“surface complexation”) model and on the Stern—Gouy—Chapman theory, showed a pronounced effect of contamination on the limiting pH∞ value: it is lower than pHPZC for acidic contaminations but higher in the case of basic impurities. The same approach suggested that inflection of the acid—base titration curve for a highly concentrated dispersion corresponds to PZC and to the degree of contamination of the original sample, regardless of the impurities. Accordingly, the PZC determination should involve two steps. In the first step, one performs mass titration of a solid sample and determines the amount of solid necessary to obtain the limiting pH∞ value. The next step is to titrate the acidified dispersion (of required mass concentration) with a base (or vice versa) and to determine the inflection point corresponding to PZC. The inflection point can also provide information on the contamination, i.e., on the fraction of acid or base in the original sample. The experimental results with hematite and anatase support the findings of numerical simulations.
A method is proposed to estimate the point of zero charge (pzc) of pure compounds which can be described accurately by the surface ionization model of amphoteric oxides. It is demonstrated that under the limiting conditions of “infinite” mass/volume ratio, the pH of the system will approach . Experimental values of the pH of the oxides of titanium, aluminum, a silicon suspended in a closed aqueous system exhibited the existence of a constant pH at high mass fractions. This limiting pH is found to be a reasonable estimate for the point of zero charge of each oxide.
Filtralite P® and shellsand as ideal constructed wetland substrates have been tested for their P sorption capacity, both with batch and column experiments. Two columns were filled with Filtralite P® and one column with shellsand. The shellsand (SSPS) and one of the Filtralite P® columns (FLSP) were loaded with a synthetic P solution, while the second Filtralite P® column (FLWW) was loaded with secondary wastewater. Ca, Mg, pH, and the P concentrations were measured in the inlet and the seven outlets along the height of the three vertical upflow columns for up to 303 days. An overall P removal rate of 92, 91, and 54% was measured in the columns SSPS, FLWW, and FLPS, respectively, for the entire experimental period. The comparison of FLWW and FLPS showed that FLWW kept its high P removal efficiency (91%) throughout the experimental period while the removal efficiency of FLPS decreased fast after reaching the 1ppm effluent P concentration. The competition of other negative ions and the development of biofilm did not have a negative effect on P removal from wastewater. The batch experiments showed a better sorption capacity of Filtralite P® at low initial concentrations, while for high initial concentrations the shellsand sorbed more. Shellsand had, however, a higher sorption capacity in batch experiments with used column material and high initial P concentrations. The results from both the batch and the column experiment suggest that the shellsand has a more durable P sorption capacity than the Filtralite P® material, possibly due to the persistent high concentrations of Ca in the shellsand.
The occurrence of 32 drug residues belonging to different medicinal classes like antiphlogistics, lipid regulators, psychiatric drugs, antiepileptic drugs, betablockers and β2-sympathomimetics as well as five metabolites has been investigated in German municipal sewage treatment plant (STP) discharges, river and stream waters. Due to the incomplete removal of drug residues during passage through a STP, above 80% of the selected drugs were detectable in at least one municipal STP effluent with concentration levels up to 6.3μgl−1 (carbamazepine) and thus resulting in the contamination of the receiving waters. 20 different drugs and 4 corresponding metabolites were measured in river and stream waters. Mainly acidic drugs like the lipid regulators bezafibrate, gemfibrozil, the antiphlogistics diclofenac, ibuprofen, indometacine, naproxen, phenazone and the metabolites clofibric acid, fenofibric acid and salicylic acid as well as neutral or weak basic drugs like the betablockers metoprolol, propranolol and the antiepileptic drug carbamazepine were found to be ubiquitously present in the riversand streams, mostly in the ngl−1-range. However, maximum concentrations were determined up to 3.1μgl−1 and median values as high as 0.35μgl−1 (both bezafibrate). The drugs detected in the environment were predominantly applied in human medicine. It can therefore be assumed that the load of municipal STP effluents in the surface water highly influences the contamination. Due to their wide-spread presence in the aquatic environment many of these drugs have to be classified as relevant environmental chemicals.
This research deals with an investigation of the adsorption of two acid dyes, namely Acid Red 57 (AR57) and Acid Blue 294 (AB294) onto sepiolite. Batch kinetics and isotherm studies were carried out. The results indicate that the adsorption of acid dyes obeys Freundlich isotherm and the second‐order kinetics model. In addition, the effectiveness of sepiolite on adsorption of AR57 and AB294 from aqueous solution was studied as a function of time, pH, and temperature. Thermodynamic parameters for the adsorption of dyes were calculated and are discussed. The maximum removals of acid dyes was observed around 90% and 75% at pH = 2 for AR57 and AB294, respectively.
Adsorption of Cd(II) and Pb(II) onto a suspension of vermiculite was studied as a function of ionic medium (0.002 or 0.02molL−1 KNO3) and pH (5.0, 6.0 and 7.0). In order to evaluate the influence of natural organic matter on the adsorption properties of vermiculite, the clay mineral was treated with a sedimentary humic acid under the above mentioned conditions of pH and ionic strength, followed by the addition of Cd(II) and Pb(II). Adsorption was studied by the batch approach using a continuous flow-anodic stripping voltammetry technique for determination of the equilibrium concentrations of the metal cations. With this technique, the determination of metal concentrations higher than 2.0×10−8molL−1 was possible, a feature that allowed us to perform the adsorption studies using a range of initial concentrations between 2.0×10−7 and 1.0×10−5molL−1, which is at least one order of magnitude lower than usually reported in adsorption studies. Adsorption of Cd(II) was strongly pH dependent, with maximum removal occurring at pH 7.0 in ionic medium of 0.002molL−1 KNO3. Adsorption of Pb(II) was much more intense than Cd(II), and less pH dependent, with the maximum removal occurring at pH 5 and ionic strength 0.002. Adsorption of Cd(II) was enhanced onto the humic acid modified vermiculite in medium of 0.020molL−1 KNO3 in the three pH studied, but in 0.002molL−1 KNO3, only at pH 5.0 the presence of humic acid enhanced the adsorption of Cd(II), demonstrating that at this pH the predominant adsorption mechanism is ion exchange. At pH 6.0 and 7.0 a combination of ion exchange and complexation seems to govern adsorption of Cd(II) onto the humic acid modified vermiculite. For Pb(II) a similar behavior was observed at pH 5.0 and 6.0, but at pH 7.0 in 0.002molL−1 KNO3 the presence of humic acid decreased the adsorption as a consequence of the formation of stable complexes in solution, which desorbed the humic acid molecules previously adsorbed on the vermiculite surface.
Water solubility is a critical property in risk assessments for chemicals, but measured values are often unavailable. The most practical approach to estimating solubility for diverse and complex structures involves regression against the logarithm of the octanol/water partition coefficient (log Kow). However, currently used equations were developed from relatively small training sets (200–300 compounds). Our objective was to upgrade log Kov-based methods by examining a much larger and diverse training set and, if possible, to improve estimation accuracy further by incorporating a series of simple correction factors. We also evaluated the contributions of melting temperature (Tm) and molecular weight (MW). Measured values of water solubility, log Kow and Tm (solids only) were available for all compounds in the training set (n = 1,450). The best equation for this dataset included log Kow, Tm, MW, and 12 correction factors as independent variables, with r2 = 0.970, SD = 0.409, ME = 0.313. Statistics for an independent validation set of 817 compounds were consistent with these results: r2 = 0.902, SD = 0.615, ME = 0.480. We found that Tm contributed significantly to estimation accuracy for solids; addition of MW also increased accuracy; measured values of log Kow and Tm produced more accurate solubility estimates than did estimated values; and the new method outperformed other widely used general-purpose equations based on log Kow.
Adsorption isotherms of 10 pesticides and their biodegradation intermediates on clay minerals and soils were investigated to predict the fate of pesticides in the environment. The adsorption isotherms were expressed by the Freundlich isotherm equation. Penta-chloronitrobenzene, 2,4,6-trichlorophenyl-4′-nitro-phenylether, and various intermediates were highly adsorbed on soils, although isoprothiolane was only slightly adsorbed. The adsorbabilities of pesticides on ando soil, gray lowland soil, and montmorillonite were higher than those on allophene and kaolinite. These results can be used to study the fate of pesticides.
The presence of human pharmaceutical compounds in surface wa-ters is an emerging issue in environmental science. In this study the occurrence and behavior of human pharmaceuticals in a va-riety of wastewater treatment processes is reviewed. Although some groups are not affected by sewage treatment processes others are amenable to degradation, albeit incomplete. While water purifica-tion techniques such as granular activated carbon could potentially remove these pollutants from wastewater streams, the high cost in-volved suggests that more attention should be given to the potential for the optimization of current treatment processes, and reduction at source in order to reduce environmental contamination.
The adsorption of isoproturon and two model compounds, N,N-dimethylurea and4-isopropylaniline, on clay minerals (bentonite,montmorillonite and kaolinite), organic matter (humic acid) and soil (with and without organic matter) has been studied using FT-infrared spectroscopy (IR), thermogravimetric analysis (TGA), high pressure liquid chromatography (HPLC) and X-ray diffraction (XRD).N,N-dimethylurea interacted with bentonite and montmorillonite by the coordination of the carbonyl group, directly or indirectly through water molecules, with exchangeable cations. Adsorption on humic acid was due to hydrogen bonding with the active sites of the adsorbent. The amino group ofN,N-dimethylurea appears tobe relatively inactive during adsorption. The mechanisms involved in the adsorption of 4-isopropylaniline were hydrogen bonding and protonation. No adsorption of 4-isopropylaniline was observed on kaolinite. The investigation of isoproturon suggested that both the carbonyl and amino groups of isoproturon were involved in interactions with the active sites of the adsorbents. Both the clay minerals and organic matter of soil contribute to the adsorption of organic compounds on soil but the clay minerals bentonite and montmorillonite play a major role in their adsorption on soil.
The adsorption kinetics of CI reactive blue 221 (RB221), an anionic dye, onto sepiolite was investigated in aqueous solution in a batch system with respect to stirring speed, contact time, initial dye concentration, pH, and temperature. Experimental results have shown that the acidic pH, increasing initial dye concentration and temperature favours the adsorption. Experimental data related to the adsorption of RB221 on sepiolite under different conditions were applied to the pseudo-first-order equation, the pseudo-second-order equation and the intra-particle diffusion equation, and the rate constants of first-order adsorption (k1), the rate constants of second-order adsorption (k2) and intra-particle diffusion rate constants (kint) were calculated, respectively. The experimental data fitted very well the pseudo-second-order kinetic model and also followed the intra-particle diffusion model up to 20 min, whereas diffusion is not only the rate controlling step. The activation energy of system (Ea) was calculated as 7.73 kJ mol−1. The thermodynamics parameters of activation such as Gibbs free energy, enthalpy, entropy were also evaluated and found that ΔG∗, ΔH∗, and ΔS∗ are 47.9 (49.4, 50.0, 51.3) kJ mol−1, 5.30 (5.21, 5.13, 5.05) kJ mol−1, and −145.3 (−148.8, −142.7, −143.1) J K−1 mol−1 at 20 (30, 40, 50) °C, respectively. The results indicate that sepiolite could be employed as a low-cost material for the removal of textile dyes from effluents.
This paper analyses the purification efficiency and mass removal of organic material, suspended solids, nitrogen and phosphorus in a hybrid constructed wetland (CW) system treating wastewater from a basic school in Paistu, Estonia. The CW consists of two subsurface flow filter beds using lightweight aggregates (LWA): a two-chamber vertical subsurface flow (VSSF) filter bed followed by a horizontal subsurface flow (HSSF) filter bed, with a total area of 432 m2. This CW was constructed in summer 2002 by the Centre for Ecological Engineering in Tartu (CEET). Eighteen series of water samples (from 30.10.2003 to 15.10.2005) were undertaken. The analyses show the outstanding purification effect of the system: for BOD7 the average purification efficiency is 91%; for total suspended solids (TSS)—78%, for total P—89%, for total N—63%, and for NH4N—77%. The average outlet values for the above-listed parameters were 5.5, 7.0, 0.4, 19.2 and 9.1 mg L−1, respectively. According to our results, the purification parameters meet the standards set by the Water Act of Estonia for wastewater treatment plants of 2000–9999 PE: 15, 25, and 1.5 mg L−1 for BOD7, TSS and total P, respectively. The results show that hybrid CW systems consisting of subsurface flow filter beds can work efficiently in conditions of changing hydraulic loading and relatively cold climate. We did not find significant differences between the removal efficiency, mass removal, and values of the first-order rate-constant k for most water quality indicators during the warm (May–October) and cold (November–April) periods. Locally produced LWA as a filter material in CWs has shown good hydraulic conductivity and phosphorus sorption capacity (k = 17.1 ± 12.4 m yr−1). The Paistu CW, with its proper design and outstanding purification results, can be considered one of the best systems in Estonia.
Packed-bed reactors were used to examine the effects of molecular size and charge on biofilm sorption of organic compounds selected for their similarity to the size and charge ranges of aquatic natural organic matter (NOM). In addition, the sorbate compounds were chosen for nonbiodegradability, which was verified by BOD tests. In experiments using uncharged NOM-surrogate compounds it was found that as sorbate molecular size increased, biofilm sorption decreased. Also, negatively charged NOM-surrogate compounds were found to be less well sorbed to biofilm than neutral molecules. Apparently biofilm sorption of small molecules is enhanced by diffusion of the sorbate into the porous biofilm matrix; whereas larger sorbate molecules probably accumulate at the biofilm-water interface because they are excluded from the biofilm pores. The observed decrease in biofilm sorption of anionic organic molecules compared to removal of neutral sorbates was thought to be the result of electrostatic repulsion between the negatively-charged sorbate and the negatively-charged biofilm particularly slowing diffusion of the sorbate molecules within the biofilm.
The relatively new issue of pharmaceutical contamination of the environment offers the opportunity to explore the application of values to the construction, communication and management of risk. The still-developing regulatory policies regarding environmental contamination with pharmaceuticals provide fertile ground for the introduction of values into the definition and management of risk. In this report, we summarize the current knowledge regarding pharmaceutical contamination of the environment and discuss specific attributes of pharmaceuticals that require special consideration. We then present an analysis showing that if values are incorporated into assessing, characterizing and managing risk, the results of risk assessments will more accurately reflect the needs of various stakeholders. Originating from an acknowledgement of the inherent uncertainty and value-laden nature of risk assessment, the precautionary principle (and later, the multi-criteria, integrated risk assessment), provides a direction for further research and policy development.
This paper presents a research strategy for evaluatung the capability of constructed, restored, and natural wetlands to assimilate and process pesticides associated with agricultural runoff from croplands. A modeling approach that is central to this research strategy is presented and the mathematical foundation is explicitly stated. This approach generates predictions that can be experimentally and rigorously tested. Criteria for selection of “model” pesticides for experimentation include factors such as use patterns and amounts as well as intrinsic characteristics of the pesticide. The design of the experimental constructed wetland cells for this research includes water flow and depth control, clay liners to prevent infiltration, and wetland vegetation as a variable. The experimental strategy should permit optimal transfer of study results from site to site and ultimately provide recommindations for pesticides that are compatible with wetlands as well as design characteristics for constructed wetlands to be used with specific crop-pesticide combinations.
Endocrine disrupting chemicals and pharmaceuticals represent two classes of emerging contaminants that are ubiquitously present in municipal wastewater effluents. Some of these contaminants have been shown to impact aquatic organisms at trace concentrations (i.e., ng/L). Moreover, the public has expressed human health concerns regarding the presence of emerging contaminants in water reuse projects. The primary objective of this investigation was to determine the efficacy of various membranes and activated carbons for the removal of endocrine disruptors, pharmaceuticals, and personal care products. A suite of structurally diverse target compounds was selected for evaluation based largely upon occurrence and molecular structure. Several membrane types and applications were evaluated at pilot- and/or full-scale, including: microfiltration, ultrafiltration, nanofiltration, reverse osmosis, electrodialysis reversal, membrane bioreactors, and combinations of membranes in series. Granular activated carbon was evaluated at bench-scale using rapid small scale column tests and at two full-scale utilities. Microfiltration and ultrafiltration were found to reject very few target compounds; however, some loss of steroidal type compounds was observed. Nanofiltration and reverse osmosis were capable of significant rejection of nearly all target compounds, though compounds were detectable at trace levels in permeates. Granular activated carbon was highly effective at removing all target chemicals. However, break-through curves clearly demonstrated that compounds with greater hydrophilicity breach activated carbon faster than hydrophobic compounds. In full-scale applications, the impact of regeneration was observed as activated carbon filters that received regular regeneration had minimal breakthrough of organic contaminants, while non-regenerated filters displayed no removal of target compounds. Findings confirm that membrane and carbon processes are capable of greatly reducing the concentrations of emerging contaminants; however, several compounds are detectable in membrane permeate and carbon effluent.
In the present work we studied the efficiency of a series of clay minerals (montmorillonite, illite, muscovite, sepiolite and palygorskite) modified with the cationic surfactant octadecyltrimetylammonium bromide (ODTMA) in the adsorption of the pesticides penconazole, linuron, alachlor, atrazine and metalaxyl. A study was also carried out on the effect of the structure (expansible and non-expansible layered, and non-layered), the surface area and charge density of the clay minerals, and the hydrophobicity of the pesticides (Kow) on the adsorption process. Adsorption–desorption isotherms of the pesticides by clay minerals were obtained and the constants of the Freundlich model (Kf and Kfd) (natural clays) and of the linear model (K and Kdes) (ODTMA-clays) were determined. Correlation coefficient values (r2) found between K and Kdes, and organic matter (OM) content of ODTMA-clays indicate a more effective partitioning of the pesticides in the organic phase of ODTMA after desorption. Furthermore the positive significant correlation found between the Kdesom values and the charge density of different ODTMA-clays indicates that a higher density of ODTMA in the clay gives rise to the formation of an organic phase more effective for the partition of the pesticides. This correlation explained that the highest Kdesom value obtained was for kaolinite and the lowest Kdesom value was for montmorillonite in the adsorption of all pesticides by the different organo clays. Simple correlations between adsorption constants and Kow values, and multiple correlations between these constants and clay OM contents and Kow values were also calculated. The results obtained indicate the interest of ODTMA-clays in the adsorption of hydrophobic pesticides. Non-expandible layered and fibrous clay minerals may also be of interest as adsorbents derived from their density charge, and these minerals, when modified with ODTMA, and used in appropriate amounts, higher than that of montmorillonite, or when present in soils with high clay contents, even in the absence of montmorillonite, may be good adsorbents for hydrophobic pesticides. According to the results of the study, ODTMA-clays and ODTMA-soils could be used as barriers to prevent the mobility of certain hydrophobic pesticides from a point source of pollution.
The occurrence of 32 drug residues belonging to different medicinal classes like antiphlogistics, lipid regulators, psychiatric drugs, antiepileptic drugs, betablockers and β2-sympathomimetics as well as five metabolites has been investigated in German municipal sewage treatment plant (STP) discharges, river and stream waters. Due to the incomplete removal of drug residues during passage through a STP, above 80% of the selected drugs were detectable in at least one municipal STP effluent with concentration levels up to 6.3 μg l−1 (carbamazepine) and thus resulting in the contamination of the receiving waters. 20 different drugs and 4 corresponding metabolites were measured in river and stream waters. Mainly acidic drugs like the lipid regulators bezafibrate, gemfibrozil, the antiphlogistics diclofenac, ibuprofen, indometacine, naproxen, phenazone and the metabolites clofibric acid, fenofibric acid and salicylic acid as well as neutral or weak basic drugs like the betablockers metoprolol, propranolol and the antiepileptic drug carbamazepine were found to be ubiquitously present in the riversand streams, mostly in the ng l−1-range. However, maximum concentrations were determined up to 3.1 μg l−1 and median values as high as 0.35 μg l−1 (both bezafibrate). The drugs detected in the environment were predominantly applied in human medicine. It can therefore be assumed that the load of municipal STP effluents in the surface water highly influences the contamination. Due to their wide-spread presence in the aquatic environment many of these drugs have to be classified as relevant environmental chemicals.
The objective was to provide selection criteria for substrates that would enhance phosphate removal from waste water in a constructed wetland system (subsurface horizontal flow). Measured properties of seven substrates (bauxite, shale, burnt oil shale, limestone, zeolite, light expanded clay aggregates (LECA) and fly ash) were: pH, cation exchange capacity (CEC), hydraulic conductivity, porosity, specific surface area, particle size distribution and phosphate (P) adsorption capacity. Fly ash and shale had the highest P adsorption values, followed by bauxite, limestone and LECA. Longer-term experiments in which synthetic waste water was passed over shale and bauxite gave maximum P uptake values of 730 and 355 mg P kg−1, respectively. X-ray fluorescence measurements showed that substantial precipitation of P had occurred on the shale surfaces. On the basis of these measurements it was concluded that, of the seven materials examined, shale had the best combination of properties as a substrate for constructed wetland systems (CWS).
Adsorption of the divalent organic cations paraquat (PQ), diquat (DQ) and methyl green (MG) on sepiolite was determined experimentally and investigated with an adsorption model. The largest amounts of DQ, PQ and MG adsorbed were between 100% and 140% of the cation exchange capacity (CEC) of sepiolite. In previous experiments with monovalent organic cations (dyes), the largest amounts of dyes adsorbed were about 400% of the CEC of sepiolite. Consequently, it was proposed that most of this adsorption was to neutral sites of the clay. The large differences between the adsorption of these divalent organic cations and the monovalent dyes may indicate that there is almost no interaction between DQ, PQ and MG and the neutral sites of sepiolite. This assumption was confirmed by infrared (IR) spectroscopy measurements, that did not show changes in the peaks arising from the vibrations of external SiOH groups of the clay when the divalent organic