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The potential of autochthonous microbial culture encapsulation in a confined environment for phenol biodegradation
Abstract
Olive mill wastewater (OMWW) is claimed to be one of the most polluting effluents produced by agro-food industries, providing high contaminants load that encase cytotoxic agents such as phenolic and polyphenolic compounds. Therefore, a significant and continuous stress episode is induced once the mixed liquor of the wastewater treatment plants (WWTP's) is being exposed to OMWW. The use of bio-augmentation treatment procedures can be useful to eliminate or reduce such stress episodes. In this study, we have estimated the use of autochthonous biomass implementation within small bioreactor platform (SBP) particles as a bio-augmentation method to challenge against WWTPs stress episodes. Our results showed that SBP particles significantly reduced the presence of various phenolics: tannic, gallic and caffeic acid in a synthetic medium and in crude OMWW matrix. Moreover, the SBP particles succeeded to biodegrade a very high concentration of phenol blend (3000 mg L(-1)). Our findings indicated that the presence of the SBP microfiltration membrane has reduced the phenol biodegradation rate by 50 % compared to the same suspended culture. Despite the observed reduction in biodegradation rate, encapsulation in a confined environment can offer significant values such as overcoming the grazing forcers and dilution, thus achieving a long-term sufficient biomass. The potential for reducing stress episodes caused by cytotoxic agents through bio-augmentation treatment procedure using the SBP technology is discussed.
... However, for several reasons, including negative interactions between the bioaugmented culture and natural local micro-flora (e.g., protozoan predators), as well as the continuous dilution of the https://doi.org/10.1016/j.jwpe.2020.101516 Received 5 April 2020; Received in revised form 1 July 2020; Accepted 8 July 2020 introduced bacterial culture in a continuous treatment system, achieving successful bioaugmentation treatment remains challenging [5][6][7]. ...
... The SBP technology allows for the introduction of an exogenous bacterial culture into a wastewater treatment bioreactor under conditions that favor the preservation of high concentrations of the introduced bacterial culture in a suspended state within the SBP capsules for several weeks (> 8 weeks). Based on existing literature, all previous studies involving the use of the SBP technology have been related to the batch treatment process [2,5,9,14]. Therefore, the novelty of this study is the use of the SBP culture encapsulation technology in a continuous phenol biodegradation model using a Pseudomonas putida culture. ...
... A strain of P. putida F1 (ATCC 700007) was purchased and provided by Prof. Carlos Dosoretz from the Technion, Israel Institute of Technology. The culture was encapsulated with SBP capsules as previously described for other microbial species [5]. The capsules were made from a spheroidal cellulose acetate microfiltration membrane (pore size ranging from 0.2-0.7 μm), which served as a physical barrier between the encapsulated P. putida culture and the outer bioreactor medium. ...
Bioaugmentation treatments in general and the use of encapsulated selected microbial cultures in particular are gaining significant attention as a promising approach for the treatment of wastewater containing phenols and other organic pollutants. Thus, the purpose of this study is to investigate the biodegradation performance of a Pseudomonas putida culture encapsulated in a unique 3-D capsule known as the small bioreactor platform (SBP). Batch and continuous bioreactors, bioaugmented with two different P. putida culture states, i.e., encapsulated and free suspended cells, were operated under different phenol loadings. During the batch experiments, the biodegradation rate of the suspended culture was equal to or higher than the encapsulated culture, except for the highest phenol concentration of 1000 mg/L, where the encapsulated bacterial culture exhibited a superior biodegradation rate (45 mg/L/h) relative to the free culture (16.7 mg/L/h). In addition, in the continuous bioreactor, at a hydraulic retention time (HRT) of up to 1 h, the encapsulated P. putida completely biodegraded the phenol in the influent with 50 mg/L phenol, showing a maximal biodegradation rate of 45 mg/L/h. However, decreasing the HRT to 0.5 and 0.25 h resulted in incomplete biodegradation, despite higher biodegradation rates (90 and 70 mg/L/h, respectively). Furthermore, a sharp decrease in the biodegradation process efficiency was observed when the suspended culture was released from the SBP capsules by cutting the microfiltration membrane of the capsules. Therefore, this study demonstrates that, compared with suspended cultures, SBP culture encapsulation achieves superior performance as a bioaugmentation strategy, especially in continuous bioreactors, such that it can be applied in the treatment of phenol rich wastewater.
... The main reasons for failure of the suspended culture are competition and negative interactions with the natural local microflora, in addition to constant culture dilution induced by the continuous inflow and outflow currents in WWTP [9,10]. Both abovementioned obstacles prevent the exogenous culture from achieving a sufficient biomass for performing the necessary metabolic bioprocess [11][12][13][14][15]. ...
... The ability of the SBP capsules to biodegrade several phenol compounds as well as phenols in olive mill wastewater (OMWW) using a batch treatment approach was the focus of Azaizeh et al. [11] work. Azaizeh et al. [11] reported that the required hydraulic retention time was approximately 24 h for synthetic phenol compounds and longer for reduction of phenols in OMWW. ...
... The ability of the SBP capsules to biodegrade several phenol compounds as well as phenols in olive mill wastewater (OMWW) using a batch treatment approach was the focus of Azaizeh et al. [11] work. Azaizeh et al. [11] reported that the required hydraulic retention time was approximately 24 h for synthetic phenol compounds and longer for reduction of phenols in OMWW. The study aimed to develop an effective and unique biological treatment for one of the most serious environmental contaminants, the phenol compounds, in order to create an efficient solution for their degradation. ...
The aim of the study was to evaluate the performance of batch and semi-continuous treatment systems for phenol degradation using a consortium of bacterial cultures that were encapsulated using the ‘Small Bioreactor Platform’ (SBP) encapsulation method. The maximal phenol biodegradation rate was 22 and 48 mg/L/h at an initial phenol concentration of 100 and 1000 mg/L in the batch and semi-continuous bioreactors, respectively. The initial phenol concentration played an important role in the degradation efficiency rates. The batch bioreactor results could be described by the Haldane model, where the degradation rate decreased under low as well as under very high initial phenol concentrations. Concentration equalization between the two sides of the SBP capsule's membrane occurred after 80 min. The microfiltration membrane is perforated with holes that have an average diameter of 0.2-0.7 µm. It is therefore suggested that the capsule's membrane is more permeable compared to other polymeric matrixes used for bacterial encapsulation (such as alginate). This study shows that the encapsulation of phenol degraders within microfiltration-membrane capsules which create a confined environment has a potential for enhancing phenol removal in phenol-rich wastewaters.
... A novel biotechnological method, presented as the "Small Bioreactor Platform" (SBP) technology, was recently developed and tested from a laboratory scale up to a full configuration treatment in a membrane bioreactor (MBR) WWTP (Azaizeh et al., 2015;Kurzbaum, 2016, 2014). Briefly, the SBP technology enables the introduction and maintenance of an exogenous bacterial culture in a wastewater bioreactor under conditions which preserve a high concentration of the introduced bacterial culture for several weeks (e.g., 12 weeks) within the SBP capsules. ...
... Structural 3D microfiltration membranes enable the creation of a sustainable confined environment which also functions as a protective barrier. The 3D capsule (2.5 cm long and 0.8 cm in diameter) physically separates the introduced microbial culture inside the capsule from the external natural microbial flora of the mixed liquor within the WWTP bioreactor, while enabling the diffusion of dissolved molecules and small colloids (e.g., nutrients and organics) through the capsule membrane (for more details see Fig. 1, Menashe and Kurzbaum, 2014;Azaizeh et al., 2015). One of the most significant advantages of the SBP technology is that a selective contaminant can be targeted in order to remove or significantly reduce its concentration in the water using the encapsulation of a particular bacterial culture. ...
... The structure, composition, and validation of the SBP capsules technology are presented in detail in the patent article number PCT/ IL2010/000256 (Menashe, 2010) and in Menashe and Kurzbaum (2014) and Azaizeh et al. (2015). Briefly, the SBP capsule encases an introduced culture using a cellulose acetate microfiltration membrane creating a confined 3D environment for the microbial cell suspension (Fig. 1). ...
Phenols are toxic byproducts from a wide range of industry sectors. If not treated, they form effluents that are very hazardous to the environment. This study presents the use of a Pseudomonas putida F1 culture encapsulated within a confined environment particle as an efficient technique for phenol biodegradation. The innovative encapsulation technique method, named the “Small Bioreactor Platform” (SBP) technology, enables the use of a microfiltration membrane constructed as a physical barrier for creating a confined environment for the encapsulated culture. The phenol biodegradation rate of the encapsulated culture was compared to its suspended state in order to evaluate the effectiveness of the encapsulation technique for phenol biodegradation. A maximal phenol biodegradation rate (q) of 2.12/d was exhibited by encapsulated P. putida at an initial phenol concentration of 100 mg/L. The biodegradation rate decreased significantly at lower and higher initial phenol concentrations of 50 and up to 3000 mg/L, reaching a rate of 0.1018/d. The results also indicate similar and up to double the degradation rate between the two bacterial states (encapsulated vs. suspended). High resolution scanning electron microscopy images of the SBP capsule's membrane morphology demonstrated a highly porous microfiltration membrane. These results, together with the long-term activity of the SBP capsules and verification that the culture remains pure after 60 days using 16S rRNA gene phylogenetic affiliation tests, provide evidence for a successful application of this new encapsulation technique for bioaugmentation of selected microbial cultures in water treatment processes.
... In addition, the technology is postulated as a useful method to avoid the possibility of exogenous microorganisms' dilution by a continuous incoming waste flow. [2,[14][15][16] This study presents more than a half year of full configuration treatment in a domestic WWTP which operates on the Membrane Bioreactor (MBR) process. The study's aims were to estimate the additive treatment effect by the use of the SBP technology on a high load organic matter treatment plant and to identify the initial effective SBP capsules' dose (number of SBP capsules to wastewater volume) that is required to stimulate an effective bioaugmentation treatment process that will eventually increase the biological treatment effectiveness. ...
... The structure, composition and validation of the SBP capsules are presented in detail in the patent article [14] and in [2] and [16]. Two formulation types of SBP capsules were used in this study under the commercial name of NatiCap Petroleum and NatiCap Municipal which encase a commercial blend of specific microorganisms (USA Bio Products, USA) PHC type 4 and FOG type 2, respectively. ...
... The additive treatment of several types of exogenous bacterial cultures used in the SBP technology allowed us to achieve wider metabolic activity and therefore to present a better solution to increase the bioprocess efficiency. [16] The use of SBP treatment as an additive and protective treatment in an alpha system study of the same wastewater as used in this study has already been described in Menashe and Kurzbaum. [2] The MBR Ha-Solelim plant has two identical bioreactors (pond A and pond B). ...
A novel bioaugmentation treatment approach, the Small-Bioreactor Platform (SBP) technology, was developed to increase the biological stabilization process in the treatment of wastewater in order to improve wastewater processing effectiveness. The SBP microfiltration membrane provides protection against the natural selection forces that target exogenous bacterial cultures within wastewater. As a result, the exogenous microorganisms culture adapt and proliferate, thus providing a successful bioaugmentation process in wastewater treatment. The new bioaugmentation treatment approach was studied in a full configuration Membrane Bioreactor (MBR) plant treating domestic wastewater. Our results present the potential of this innovative technology to eliminate, or reduce, the intensity of stress events, as well as shortening the recovery time after stress events, consequently elevating the treatment effectiveness. The effective dose of SBP capsules per cubic meter per day of wastewater was achieved during the addition of 3000 SBP capsules (1.25 SBP capsules per cubic meter per day), which provided approximately 4.5 liters of high concentration exogenous biomass culture within the SBP capsules internal medium. This study demonstrates an innovative treatment capability which provides an effective bioaugmentation treatment in a MBR domestic wastewater treatment plant.
... Azaizeh et al. [10] demonstrated the efficiency of an autochthonous bacterial consortium from olive mill wastewater in phenol biodegradation, while Kurzbaum et al. [11] demonstrated phenol biodegradation using SBP-encapsulated Pseudomonas putida F1. The phenol-biodegradation rate of the suspended form and the SBP-encapsulated form were similar, demonstrating the potential of the SBP technology. ...
... Bacterial cultures were encapsulated in SBP capsules. The encapsulation procedure and experimental validation are detailed in patent PCT/IL2010/00256 [18], Menashe and Kurzbaum [9], and Azaizeh et al. [10]. Briefly, the bacterial cultures were encapsulated in cellulose-acetate microfiltration membrane capsules (2.5 cm long and 0.8 cm in diameter). ...
A successful attempt to degrade synthetic estrogen 17α-ethynylestradiol (EE2) is demonstrated via combining photocatalysis employing magnesium peroxide (MgO2)/low-pressure ultraviolet (LP-UV) treatment followed by biological treatment using small bioreactor platform (SBP) capsules. Reusable MgO2 was synthesized through wet chemical synthesis and extensively characterized by X-ray diffraction (XRD) for phase confirmation, X-ray photoelectron spectroscopy (XPS) for elemental composition, Brunauer-Emmett-Teller (BET) to explain a specific surface area, scanning electron microscopy (SEM) imaging surface morphology, and UV-visible (Vis) spectrophotometry. The degradation mechanism of EE2 by MgO2/LP-UV consisted of LP-UV photolysis of H2O2 in situ (produced by the catalyst under ambient conditions) to generate hydroxyl radicals, and the degradation extent depended on both MgO2 and UV dose. Moreover, the catalyst was successfully reusable for the removal of EE2. Photocatalytic treatment by MgO2 alone required 60 min (~1700 mJ/cm2) to remove 99% of the EE2, whereas biodegradation by SBP capsules alone required 24 h to remove 86% of the EE2, and complete removal was not reached. The sequential treatment of photocatalysis and SBP biodegradation to achieve complete removal required only 25 min of UV (~700 mJ/cm2) and 4 h of biodegradation (instead of >24 h). The combination of UV photocatalysis and biodegradation produced a greater level of EE2 degradation at a lower LP-UV dose and at less biodegradation time than either treatment used separately, proving that synergetic photocatalysis and biodegradation are effective treatments for degrading EE2.
... Azaizeh et al. [10] demonstrated the efficiency of an autochthonous bacterial consortium from olive mill wastewater in phenol biodegradation, while Kurzbaum et al. [11] demonstrated phenol biodegradation using SBP-encapsulated Pseudomonas putida F1. The phenol-biodegradation rate of the suspended form and the SBP-encapsulated form were similar, demonstrating the potential of the SBP technology. ...
... Bacterial cultures were encapsulated in SBP capsules. The encapsulation procedure and experimental validation are detailed in patent PCT/IL2010/00256 [18], Menashe and Kurzbaum [9], and Azaizeh et al. [10]. Briefly, the bacterial cultures were encapsulated in cellulose-acetate microfiltration membrane capsules (2.5 cm long and 0.8 cm in diameter). ...
Hydrophobic aerogels were used to remove three types of persistent organic pollutants: pharmaceutical drugs (i.e. doxorubicin [DOX], paclitaxel [TAX]), phthalates (diethyl phthalate [DEP]), and hydrophilic rhodamine dye (RhB) from synthetic and real wastewaters, using Lumira granular aerogel from Cabot activated with EtOH (ET-GAG). The hydrophobic silica aerogel was characterized by X-ray diffraction (XRD), High-Resolution Transmission Electron Microscopy (HRTEM), Brunauer-Emmet-Teller (BET) and attenuated total reflection-Fourier transform infrared spectroscopy. The pollutants were analysed by high-performance liquid chromatography (HPLC)-UV and HPLC-mass spectrometry. The adsorption process was governed by hydrophobic- hydrophobic interactions between the ET-GAG and micropollutants. The adsorption capacity of ET-GAG, examined by batch experiments, for DOX, TAX and DEP were 13.80, 14.28 and 17.54 mg/g respectively. The rate of adsorption to ET-GAG is high in the initial 40 min followed by no change in the rate due to saturation of adsorption sites. ET-GAG was able to completely remove micropollutants from real leachate and hospital wastewater, implying practical applications. Regeneration of the aerogel was studied by solvent extraction. Et-GAG adsorbent demonstrated better removal of toxic chemotherapeutic drugs and phthalates than GAC.
... The SBP technology does not require cell immobilization into carriers or adsorption to gelatinous matrices, and the introduced cultures are in a free suspended state inside the capsules. In addition, this technique provides higher permeability rates of dissolved nutrients and oxygen compared to polymeric beads [32][33][34]. ...
Biofuel is considered one of the most viable alternatives to fossil fuels derived from the dwindling petroleum resources that damage the environment. Bioethanol could be manufactured from agricultural wastes, thus providing inexpensive natural resources. Several strategies have been utilized to convert lignocellulosic hydrolysate to bioethanol with various suspended microorganisms. In this study, we alternatively propose to encapsulate these microorganisms in bioreactor setups. An immobilized cell system can provide resistance to the inhibitors present in hydrolysates, enhance productivity, facilitate the separation process, and improve microorganism recycling. Herein, we developed a continuous bioethanol production process by encapsulating three types of micro-organisms: T. reesei, S. cerevisiae, and P. stipitis. These microorganisms were encapsulated in SBP (“Small Bioreactor Platform”) capsules and tested for their viability post encapsulation, biological activity, and bioethanol production. Encapsulating microorganisms in SBP capsules provided a confined protective environment for the microorganisms, facilitated their acclimation, and ensured their long-term prosperity and activity. An additional significant benefit of utilizing SBP capsules was the simultaneous availability of saccharification and fermentation over a very long time—about 2.5–3 months—with no need to renew the cells or encapsulating matrices. Two different configurations were tested. The first one consisted of columns packed with fungal cells and specific yeast cells together. In the second configuration, the fungal cells were separated from the yeast cells into two columns in series. The presented systems achieved an efficiency of 60–70%, suggesting the long-term prosperity and uninterrupted metabolic activity of the microorganisms.
... Failure to maintain sufficient biomass for biodegrading a target compound is a major obstacle in microbial pollutant degradation. Living organisms are susceptible to antimicrobial and inhibitory compounds, such as phenols, whose presence in wastewater may lead to insufficient wastewater treatment and collapse of microbial populations in a WWTP bioreactor [3,24]. While bioaugmentation (addition of specific bacterial cultures to a system) may accelerate the degradation kinetics of recalcitrant compounds and antimicrobial pollutants [26], the maintenance of a bioaugmented culture in a WWTP bioreactor still presents a challenge. ...
Efficient biofilm-forming bacteria are crucial for biofilm wastewater treatment reactors. Nevertheless, finding a suitable bacterial culture with high biodegradation capabilities and ability to grow a stable and effective biofilm that can survive the reactor environment poses a challenge. Here, we present a newly isolated bacterium Acinetobacter EMY that exhibits excellent growth rate, biofilm formation capability, and ability to biodegrade phenol at high concentrations. The phenol degradation rate of Acinetobacter EMY immobilized on polyethylene biocarriers in batch and continuous moving bed bioreactors (MBBRs) treated with phenol as the sole carbon source was significantly higher than that of a bacterial suspension. The continuous MBBR demonstrated impressive phenol removal rates (8.11 and 10.95 kg/m³/d at extremely short hydraulic retention times of 0.5 and 0.25 h, respectively). The phenol removal efficacy was 100% for hydraulic retention times of ≥0.5 h and 67.25% at 0.25 h. The Acinetobacter EMY biofilm batch bioreactor loaded with 165, 330, 665, 1150, and 2100 mg/L phenol achieved the maximum biodegradation rates of 7.65, 7.03, 9.15, 4.48, and 4.16 kg/m³/d, respectively. The new Acinetobacter EMY isolate showed enhanced phenol biodegradation capabilities compared with other isolates in similar studies. Chemical oxygen demand measurements proved that Acinetobacter EMY also consumed the intermediates of phenol degradation. In summary, Acinetobacter EMY is a promising bacterium for use in MBBR systems that treat water containing phenols.
... When the SBP is coated with a semipermeable membrane, penetration of UV light into the capsule medium is prevented, thus providing a protective shield against UV irradiation. The capsules, which work well at short hydraulic retention times (HRTs) typically <6 h, [24][25][26], allow only dissolved molecules to cross the membrane while retaining the microorganisms in the capsule [27][28][29]. This protective barrier allows the microbial culture to survive and prosper under the UV irradiation treatment commonly used in AOPs. ...
Degradation of 17α-ethynylestradiol (EE2) and estrogenicity were examined in a novel oxidative bioreactor (OBR) that combines small bioreactor platform (SBP) capsules and UV-LED (ultraviolet light emission diode) simultaneously, using enriched water and secondary effluent. Preliminary experiments examined three UV-LED wavelengths—267, 279, and 286 nm, with (indirect photolysis) and without (direct photolysis) H2O2. The major degradation wavelength for both direct and indirect photolysis was 279 nm, while the major removal gap for direct vs. indirect degradation was at 267 nm. Reduction of EE2 was observed together with reduction of estrogenicity and mineralization, indicating that the EE2 degradation products are not estrogens. Furthermore, slight mineralization occurred with direct photolysis and more significant mineralization with the indirect process. The physical–biological OBR process showed major improvement over other processes studied here, at a very short hydraulic retention time. The OBR can feasibly replace the advanced oxidation process of UV-LED radiation with catalyst in secondary sedimentation tanks with respect to reduction ratio, and with no residual H2O2. Further research into this OBR system is warranted, not only for EE2 degradation, but also to determine its capabilities for degrading mixtures of pharmaceuticals and pesticides, both of which have a significant impact on the environment and public health.
... A standard 3D cellulose acetate (CA) capsule, measuring 2.5 cm long and 0.8 cm in diameter, physically separates the introduced microbial culture within the capsule from outer natural microbial flora of the mixed liquor within the WWTP bioreactor. At the same time, it enables the diffusion of dissolved molecules and small colloids (eg, nutrients and organics) through the capsule membrane (for more details see Figure 1 6,7 ). The key element is a unique structural microfiltration membrane that enables us to protect the introduced bacterial culture by creating a confined aquatic medium. ...
Small bioreactor platform (SBP) capsules are designed to implement selective bacterial cultures within aquatic media, mainly wastewaters, in a bioaugmentation process. Such capsules, coated with cellulose acetate (CA) membranes to form three‐dimensional (3D) structural barriers, are intended to provide a long‐term protected and confined environment for the introduced bacterial cultures. These state‐of‐the‐art 3D membranes allow the tailored design of the encapsulated bacteria and adjustment to several environmental properties, such as organics and nutrients, pressure, and the natural flora. Our study characterizes, for the first time, the mechanical and thermal properties of the SBPCA structural membrane and the effects of water molecules on these properties. High‐resolution scanning electron microscopy images of the CA membranes show mesh‐like porous structures, crucial for mass transport both inside and outside the capsule. Thermal gravimetric analysis shows a reduction of ~115°C in the thermal decomposition temperature of wet capsules compared to that of dry capsules. Mechanical testing shows that the modulus and maximum stress of wet samples are each decreased by an order of magnitude compared to those of dry samples at similar maximum strain. The permeability of the CA membrane to phenol, a model water organic pollutant, was found to be 3 × 10−8 cm2 s−1. It is concluded that water molecules soften CA structural membranes, yielding soft amorphous structures, which are needed for the optimized processing of the SBP capsule. The plasticizing effect is important in the membrane architecture formation and fiber elasticity when used in an aqueous environment
... Additionally, more efficient and effective treatment can be anticipated when co-metabolic activities within microbial consortia complement each other. Currently, by developing specific consortia, researchers have successfully degraded various wastes, such as phenol, 90 organic acid, 91 nitrate and phosphate 92,93 and cellulose. 19 One example is consortia between cyanobacteria/microalgae and bacteria. ...
Biological wastewater treatment is the process in which toxic chemicals can be degraded into small, environmentally friendly molecules by various microorganisms. Given the fact that traditional physical and chemical purification methods are high-cost, unsustainable and unspecific, biotreatment is playing an increasingly important role in the wastewater treatment field. The effective implementation of biotreatment strategy relies strongly on the intrinsic degradation capability of the microorganisms as well as their interaction with pollutants. In this review, we will focus on recent technological advances in engineering and improving biotreatment at both biocatalyst and bioreactor levels. Specifically, we will discuss the progress in synthetic biology for enhancing biosorption and biotransformation, and the challenges in applying engineered microorganisms on contaminated sites. We will further review the latest development in bioreactor design, particularly the prospects of additive manufacturing/bioprinting to further optimize the mass transport inside bioreactors through complex 3-D structures and flexible material selections. These research efforts are redefining the frontier of biotreatment, and opening up new opportunities for cost-effective, efficient, and sustainable wastewater treatment.
... Three replicates were performed for each gallic acid concentration and control. The samples were centrifuged and the supernatant was sampled at different time points for gallic acid measurement according to the Folin-Ciocalteau reagent (Sigma, Israel) method with gallic acid as the standard (10-100 mg/L) (Azaizeh et al., 2015). The degradation kinetics of gallic acid were calculated in terms of % reduction. ...
Olive mill wastewater (OMWW) presents a challenge to the control of effluents due to the pres-ence of a high organic load, antimicrobial agents (monomeric-polymeric phenols, volatile acids, polyalcohols, and tannins), salinity and acidity. In this study, the production of extracellular laccase from an OMWW isolate based on its ability to biodegrade phenols and gallic acid as a model of phenolic compounds in OMWW was investigated. Phylogenetic analysis of the 16S RNA gene sequences identified the bacterial isolate (AcinetobacterREY) as being closest to Acinetobacter pittii. This isolate exhibited a constitutive production of extracellular lac-case with an activity of 1.5 and 1.3 U ml/L when supplemented with the inducers CuSO4 and CuSO4+phenols, respectively. Batch experiments containing minimal media supplemented with phenols or gallic acid as the sole carbon and energy source were performed in order to characterize their phenolic biodegradability. Acinetobacter REYwas capable of biodegrading up to 200 mg/L of phenols and gallic acid after 10 h and 72 h, respectively.
... Mixed cultures have an apparent advantages as the microbial consortia can communally perform the treatment efficiently which cannot be performed individually. Researchers started developing consortia for increasing the efficiency of wastewater treatment (Venkata Mohan et al., 2009), removal of contaminants like phenol (Azaizeh et al., 2015), nitrogen removal (Chen et al., 2015), to treat tobacco wastewater (Wang et al., 2009) etc. Treatment of different wastewaters differs as it dependent of the different contaminants they contain. Under such stipulation, microbial consortia with different organisms having different specificities can perform the treatment more efficiently which is intricate for individual strains or species. ...
Microorganisms play a vital role in efficient biological treatment. Supplementation of external microorganisms with high degradation rates can enhance the process efficiency significantly. Potential strains were isolated from long term wastewater treating reactors and identified using phylogenetic analysis of 16S rRNA gene fragments with the nearest neighbors extracted during BLAST search. Later the study was designed in two phases which revealed interesting findings. Phase I evaluates the potential of isolated strains viz., Pseudomonas otitidis, Bacillus firmus, Bacillus subtilis, and Bacillus circulans for their individual ability in terms of COD and nutrients removal. B. circulans showed highest carbon (COD) removal (70%; 0.56 kg CODR/m³-day), while maximum nutrients removal (nitrate, 81%; phosphate, 90%) was observed with B. subtilis. B. firmus showed maximum volatile fatty acid (VFA) production. Based on Phase I results, four synthetic consortia were designed in phase II with diverse combination of isolates and evaluated for their remediation efficiencies. Consortium 4 (P. otitidis, B. subtilis, and B. firmus) illustrated higher treatment potential [COD, 86%; SDR (cum): 0.64 kg CODR/m³-day; Nitrate, 87%; Phosphate, 97%]. The exploitation of such consortia can overcome the inefficiencies pre-existing with the biological wastewater treatment plants by acting as prospective candidates for bio-augmenting the native microflora. This communication illustrated development of the efficient consortia using lab isolated strains to improve the performance of wastewater treatment.
To tackle membrane fouling and limited removals of pollutants (nutrients and emerging pollutants) that hinder the wide applications of membrane bioreactor (MBR), attached growth MBR (AGMBR) combining MBR and attached growth process has been developed. This review comprehensively presents the up-to-date developments of media used in both aerobic and anaerobic AGMBRs for treating wastewaters containing conventional and emerging pollutants. It also elaborates the properties of different media, characteristics of attached biomass, and their contributions to AGMBR performance. Conventional media, such as biological activated carbon and polymeric carriers, induce formation of aerobic, anoxic and/or anaerobic microenvironment, increase specific surface area or porous space for biomass retention, improve microbial activities, and enrich diverse microorganisms, thereby enhancing pollutants removal. Meanwhile, new media (i.e. biochar, bioaugmented carriers with selected strain/mixed cultures) do not only eliminate conventional pollutants (i.e. high concentration of nitrogen, etc.), but also effectively remove emerging pollutants (i.e. micropollutants, nonylphenol, adsorbable organic halogens, etc.) by forming thick and dense biofilm, creating anoxic/anaerobic microenvironments inside the media, enriching special functional microorganisms and increasing activity of microorganisms. Additionally, media can improve sludge characteristics (i.e. less extracellular polymeric substances and soluble microbial products, larger floc size, better sludge settleability, etc.), alleviating membrane fouling. Future studies need to focus on the development and applications of more new functional media in removing wider spectrum of emerging pollutants and enhancing biogas generation, as well as scale-up of lab-scale AGMBRs to pilot or full-scale AGMBRs.
Bioaugmentation is an optimization method with great potential to improve the treatment effect by introducing specific strains into the biological treatment system. In this study, a comprehensive review of the mechanism of bioaugmentation from the aspect of microbial community structure, the optimization methods facilitating application as well as feasible approaches of scale-up application has been provided. The different contribution of indigenous and exogenous strains was critically analyzed, the relationship between microbial community variation and system performance was clarified. Operation regulation and immobilization technologies are effective methods to deal with the possible failure of bioaugmentation. The gradual expansion from lab-scale, pilot scale to full-scale, the transformation and upgrading of wastewater treatment plants through the combination of direct dosing and biofilm, and the application of side-stream reactors are feasible ways to realize the full-scale application. The future challenges and prospects in this field were also proposed.
Here, we report and discuss the applicability of Variovorax paradoxus strain BFB1_13 in the bioremediation of BTEX contaminated sites. Strain BFB1_13 was capable of degrading all the six BTEX-compounds under both aerobic (O 2 conc. 8 mg l ⁻¹ ) and micro-aerobic/oxygen-limited (O 2 conc. 0.5 mg l ⁻¹ ) conditions using either individual (8 mg‧l ⁻¹ ) or a mixture of compounds (~ 1.3 mg‧l ⁻¹ of each BTEX compound). The BTEX biodegradation capability of SBP-encapsulated cultures (SBP—Small Bioreactor Platform) was also assessed. The fastest degradation rate was observed in the case of aerobic benzene biodegradation (8 mg l ⁻¹ per 90 h). Complete biodegradation of other BTEX occurred after at least 168 h of incubation, irrespective of the oxygenation and encapsulation. No statistically significant difference was observed between aerobic and microaerobic BTEX biodegradation. Genes involved in BTEX biodegradation were annotated and degradation pathways were predicted based on whole-genome shotgun sequencing and metabolic analysis. We conclude that V. paradoxus strain BFB1_13 could be used for the development of reactive biobarriers for the containment and in situ decontamination of BTEX contaminated groundwater plumes. Our results suggest that V. paradoxus strain BFB1_13—alone or in co-culture with other BTEX degrading bacterial isolates—can be a new and efficient commercial bioremediation agent for BTEX contaminated sites.
Supplementation of consortium comprising of aboriginal bacterial species with high degradation capacity can significantly enhance the biodegradation process of the domestic wastewater. The present study examined the bioremediation of domestic wastewater using a novel bacterial consortium comprising of five autochthonous bacterial strains with high potential for reduction in BOD, COD and protein content to 89%, 55% and 86%, respectively after 24 h of incubation. HPLC and GC–MS analyses revealed that the chosen consortium had successfully degraded wide-ranging complex organic compounds, which is crucial in the decontamination of wastewater. Phytotoxicity assay of the effluent exhibited that the seeds of Vigna radiata showed better growth and germination when subjected to wastewater treated by novel bacterial consortium as compared to the seeds exposed to untreated wastewater. Further, raw and treated wastewater were assessed for their genotoxicity with comet assay which displayed the intensity of DNA damage in the Allium cepa root tip cells before and after exposure to treated effluent. It is evident from the demonstrated results that the formulated bacterial consortium can be used successfully in a small-scale wastewater treatment plant.
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Extracellular lipases from different microorganisms have a doubly important role in human health and biotechnology process. Example of this, are the yeasts of Candida gender, who can use extracellular lipases as virulence molecule to invade human tissue, or, on the other hand, use these proteins to metabolize glycerolipids present in wastewater from industry. So, this kind of enzyme has good potential as a drug target and bioremediation. Studies using different forms of encapsulate microorganism has shown an increase of specific metabolism when cells are exposed to correct stimuli. This fact can be used to study the form as different conditions could permit lipase expression. For the above, in this study yeast forms from Candida albicans were encapsulated and exposed in different media culture and temperature, for late measure changes in lipase gene expression.
To this, exponential growth cells were mixed with different relations of alginate and polyvinyl alcohol solution and dropped on CaCl2 solution. The beads obtained were washed and exposed to different culture media for 48H. As a control, free
Candida cells were exposed in the same conditions. Yeasts were fixed using RNA stabilized solution, and the relative expression of lip2 and lip6 gene were measured using direct RT-qPCR. Almost two different genes were used as reporters. The immobilized cells were kept at 4°C and -20°C for almost two weeks to evaluate the stability of gene expression.
Our result shows different expression levels of lip genes between free and a bead immobilized yeast. This model can help to study the conditions that modulate extracellular lipase expresión.
Bioaugmentation treatment approach presents both an economical and environmental friendly
solution for wastewater treatment. However, the use of exogenous bacterial culture presents
several limitations: negative interaction between microorganisms, and adaptation to new physical
and chemical composite environment. These selective forces create a significant challenge for the
new introduced culture to achieve the required biomass in order to conduct the target biological
treatment. The Small-Bioreactor Platform (SBP) technology is aimed to introduce exogenous
bacterial culture with some protection and reduce some of the natural selection process. The
current study was aimed to validate the use of the SBP technology to improve biological treatment,
especially during a stress period, by using macro-encapsulated bio-augmentation treatment. The
study results indicated that the use of the SBP technology elevate the stability of the biological
treatment, improving operational factors such as the reduction of foaming phenomena, and the
reduction of sludge accumulation. Still, a significant study needs to be conducted to understand the
potential of this technology; especially, the impact on the biological treatment by using different
types of microorganisms for different types of wastewaters and the relationship between the
biomass within the SBP capsules and the natural fauna.
In the Mediterranean basin about 3x107 m3 of olive oil mill wastewater is produced each
season. The high organic matter content of the wastewater, the presence of inhibiting substances,
the seasonality of the oil extraction process and the wide geographical dispersion of mills pose
considerable technical-economic difficulties for effluent disposal, also in relation to the ever-growing
concern over the prevention of water pollution. The experience with current technology for olive oil
mill effluent treatment and disposal induces to look for alternative systems for wastewater
management. Especially in particular situations (such as those of small oil mills located in rural
areas), wastewater application to soil by means of storage-irrigation systems could represent the
most efficient disposal solution from the economic and environmental point of view, because it is able
to valorize the natural effect of degradation performed by the soil avoiding the pollution of water
bodies due to the uncontrolled discharge of untreated effluents. The results of tests in Mediterranean
conditions have highlighted that the storage of oil mill wastewater, besides providing the spreading
system with an useful flexibility, can also play, in the medium term, a function of effluent
pretreatment. The preliminary results of the analysis of soil characteristics, after the application of
wastewater volumes much higher than Italian legislation standards, have not highlighted significant
problems of degradation.
Cited By (since 1996):7, Export Date: 24 April 2013, Source: Scopus, CODEN: FENBE, Language of Original Document: English, Correspondence Address: Iliopoulou-Georgudaki, J.; University of Patras, Department of Biology, Section of Animal Biology, 26500 Patras, Greece; email: j.iliopoulou@upatras.gr, References: Fountoulakis, M.S., Dokianakis, S.N., Kornaros, M.E., Aggelis, G.G., Lyberatos, G., Removal of phenolics in olive mill wastewaters using white-rot fungus Pleurotus ostreatus (2002) Water Research, 36 (19), pp. 4735-4744;
Olive mill wastewater (OMW) contains a substantial amount of valuable antioxidant phenols that can be recovered for industrial application as food additives and pharmaceuticals. The present study was aimed at extracting different phenolic OMW fractions, and determining their antioxidant potential. Five different OMW fractions were obtained using fractionation techniques, their antioxidant potential determined by DPPH, ORAC and a β-carotene bleaching test. The total phenol level ranged between 115 and 170mg/l. The phenolic compounds present in individual fractions were identified using the HPLC-PAD method, where the main compounds were hydroxytyrosol, tyrosol, caffeic acid, vanillic acid, verbascoside, oleuropein, ferulic acid, and p-coumaric acid. The five OMW fractions showed different antioxidant levels depending on the test used. DPPH test showed that the fraction of alkyl aromatic alcohols (AAAs) was the best with EC(50) of 20mg/l and the pure hydroxytyrosol with 2mg/l. ORAC test showed that AAA and semi hydrolysed total phenol (s-TP) fractions were significantly better than Trolox when compared to 20mg/l of Trolox.
The infection of grazing ruminants with gastro-intestinal nematodes (GINs) is a severe problem in the Middle East. However, goats that graze the south-western slopes of the Carmel Heights in Israel have very low faecal egg counts, despite high grazing density. We hypothesized that polyphenols from Pistacia lentiscus L. and/or Phillyrea latifolia L. - both prevalent woody species of the region that are consumed by goats - have anthelmintic bioactivity. We tested this hypothesis by using the larval exsheathment inhibition assay (LEIA). Extracts were prepared from leaves of either plant species using 70% ethanol (E70), 100% ethanol (E100), or boiling water (W). Larvae were incubated in a phosphate-buffered saline solution with or without plant extract (1200μg/ml) and then exposed to an exsheathment solution expected to elicit 100% exsheathment after one hour. All extraction methods of P. lentiscus were highly effective at inhibiting larval exsheathment, but higher potency was found for the E70 than for E100 extraction method, while W was intermediate. Only the E70 extract of P. latifolia was highly effective relative to the control. The E70 extract of P. lentiscus had more than 7 times the potency of the E70 extract of P. latifolia. Irrespective of solvent and tannin-equivalent used, P. lentiscus contained more than double the quantity of total polyphenols than P. latifolia. The polyphenols of P. lentiscus consisted mainly of galloyl derivatives (63.6%), flavonol glucosides (28.6%), and catechin (7.8%). In P. latifolia, oleuropein and its derivative tyrosol accounted for 49.3 and 23.1% of phenolics, respectively, the remainder being flavones (luteolin and quercetin) and their glucoside derivatives. Results of the LEIA test suggest that extracts of tannin-rich plants interfere with the very early stage of host invasion and that high concentration of galloylated derivatives may explain anthelmintic activity.
Olive mill waste water (OMW), a by-product of the olive mill industry, is produced in large amounts in Mediterranean countries. Olive mill waste water contains a high organic load, substantial amounts of plant nutrients but also several compounds with recognized toxicity towards living organisms. Moreover, OMW may represent a low cost source of water. Thus, the use of OMW for soil fertigation is a valuable option for its disposal, provided that its impact on soil chemical and biochemical properties is established. Investigations were performed on the short-term influence of OMW on several chemical and biochemical properties of a soil from a continental semi-arid Mediterranean region (Morocco). The soil was amended with 0, 18 and 36 ml 100 g−1 soil of OMW (corresponding to a field rate of 0, 40 and 80 m3 ha−1, respectively) and changes in various functionally related properties such as microbial biomass, basal respiration, extractable C and N, and soil hydrolases and oxido-reductases activities were measured over time. The variations of the main physical and chemical properties as well as the residual phytotoxicity of OMW amended and non-amended soils as assessed by tomato seed germination tests were also monitored. Temporary and permanent changes in several chemical and biochemical soil properties occurred following OMW application, thus being these properties varied in sensitivity to the applied disturbance. A sudden increase of total organic C, extractable N and C, available P and extractable Mn and Fe contents were measured. Simultaneously, a rapid increase of soil respiration, dehydrogenase and urease activities and microbial biomass (at 14 day incubation) of OMW amended soils occurred. In contrast, the activities of phosphatase, β-glucosidase, nitrate reductase and diphenol oxidase decreased markedly. The soil became highly phytotoxic after OMW addition (large decline of soil germination capability), mainly at 80 m3 ha−1 OMW. After 42 days' incubation, however, a complete recovery of the soil germination capability and a residual phytotoxicity of about 30% were observed with 40 and 80 m3 ha−1 OMW, respectively. These findings indicate that the impact of OMW on soil properties was the result of opposite effects, depending on the relative amounts of beneficial and toxic organic and inorganic compounds present. The toxic compounds contained in OMW most likely counteracted the beneficial effect of organic substrates provided, which promoted the growth and activity of indigenous microorganisms.
Polyphenols or phenolic compounds are groups of secondary metabolites widely distributed in plants and found in olive mill wastewater (OMW). Phenolic compounds as well as OMW extracts were evaluated in vitro for their antimicrobial activity against Gram-positive (Streptococcus pyogenes and Staphylococcus aureus) and Gram-negative bacteria (Escherichia coli and Klebsiella pneumoniae). Most of the tested phenols were not effective against the four bacterial strains when tested as single compounds at concentrations of up to 1000 μg mL(-1). Hydroxytyrosol at 400 μg mL(-1) caused complete growth inhibition of the four strains. Gallic acid was effective at 200, and 400 μg mL(-1) against S. aureus, and S. pyogenes, respectively, but not against the gram negative bacteria. An OMW fraction called AntiSolvent was obtained after the addition of ethanol to the crude OMW. HPLC analysis of AntiSolvent fraction revealed that this fraction contains mainly hydroxytyrosol (10.3%), verbascoside (7.4%), and tyrosol (2.6%). The combinations of AntiSolvent/gallic acid were tested using the low minimal inhibitory concentrations which revealed that 50/100-100/100 μg mL(-1) caused complete growth inhibition of the four strains. These results suggest that OMW specific fractions augmented with natural phenolic ingredients may be utilized as a source of bioactive compounds to control pathogenic bacteria.
Olive-mill wastes are produced by the industry of olive oil production, which is a very important economic activity, particularly for Spain, Italy and Greece, leading to a large environmental problem of current concern in the Mediterranean basin. There is as yet no accepted treatment method for all the wastes generated during olive oil production, mainly due to technical and economical limitations but also the scattered nature of olive mills across the Mediterranean basin. The production of virgin olive oil is expanding worldwide, which will lead to even larger amounts of olive-mill waste, unless new treatment and valorisation technologies are devised. These are encouraged by the trend of current environmental policies, which favour protocols that include valorisation of the waste. This makes biological treatments of particular interest. Thus, research into different biodegradation options for olive-mill wastes and the development of new bioremediation technologies and/or strategies, as well as the valorisation of microbial biotechnology, are all currently needed. This review, whilst presenting a general overview, focus critically on the most significant recent advances in the various types of biological treatments, the bioremediation technology most commonly applied and the valorisation options, which together will form the pillar for future developments within this field.
A nitrifying sequencing batch reactor was inoculated twice with the aerobic denitrifying bacterium Microvirgula aerodenitrificans and fed with acetate. No improvement was obtained on nitrogen removal. The second more massive inoculation was even followed by a nitrification breakdown, while at the same time, nitrification remained stable in a second reactor operated under the same conditions without bioaugmentation. Fluorescent in situ hybridization with rRNA-targeted probes revealed that the added bacteria almost disappeared from the reactor within 2 days, and that digestive vacuoles of protozoa gave strong hybridization signals with the M. aerodenitrificans-specific probe. An overgrowth of protozoa, coincident with the disappearance of free-living bacteria, was monitored by radioactive dot-blot hybridization only in the bioaugmented reactor. Population dynamics were analysed with a newly developed in situ quantification procedure of the probe-targeted bacteria. The nitrifying groups of bacteria decreased in a similar way in the bioaugmented and non-bioaugmented reactors. Other bacterial groups evolved differently. The involvement of different ecological parameters are discussed separately for each reactor. These results underline the importance of predator-prey interaction and illustrate the undesirable effects of massive bioaugmentation.
The losses of benzoic acid and a homologous series of both mono- and dibasic aliphatic acids in oil shale retort water were monitored with time (21 days) in liquid culture (4% retort water, vol/vol) inoculated with soil. The organic acids constituted approximately 12% of the dissolved organic carbon in retort water, which served as the sole source of carbon and energy in these studies. The levels of the acids in solution were reduced by 80 to 90% within 9 days of incubation. From mass balance calculations, the decrease in dissolved organic carbon with time of incubation was equal to the formation of CO(2) and bacterial cell carbon. The decrease in the level of the acid components, either from degradation to CO(2) or incorporation into bacteria, would account for approximately 70% of the loss in dissolved organic carbon within the first 9 days of incubation and would account for approximately 50% of the loss over the entire 21-day incubation period.
The bioaugmentation treatment approach presents both an economical and environmentally friendly solution for wastewater treatment. However, the use of exogenous bacterial cultures presents several limitations: negative interaction between microorganisms and adaptation to new physical and chemical composite environment. These selective forces create a significant challenge for the introduced culture to achieving the required biomass in order to conduct the target biological treatment. Small-bioreactor platform (SBP) technology is aimed at introducing exogenous bacterial culture with some protection to reduce some of the natural selection process. The current study was aimed at validating the use of SBP technology to improve biological treatment, especially during a stress period, by using macro-encapsulated bioaugmentation treatment. The study results indicate that the use of SBP technology elevates the stability of biological treatment, improving operational factors such as the reduction of foaming phenomena and sludge accumulation. Still, a significant study needs to be conducted to understand the potential of this technology; especially the impact on biological treatment by using different types of microorganisms for different types of wastewaters and the relationship between the biomass within the SBP capsules and the natural microorganisms.
The vast majority of olive oil production (>98%) occurs in the Mediterranean region, utilizing a tremendous volume of water (10–30millionm3) in an area of the world in which water resources are limited. Treatment and reuse of olive mill wastewater (OMWW) presents significant challenges both due to the nature of olive oil production (seasonal and small scale) and due to the characteristics of the wastewater (high chemical oxygen demand (COD), high phenolic content, and dark color). A number of different microorganisms (Archaea, Bacteria and fungi) and processes (aerobic or anaerobic bioreactors, composting) have been tested to treat OMWW. Aerobic bacteria have been tested primarily as an approach for removal of phytotoxic compounds from OMWW, although some studies have also focused on reduction of COD. Fungi on the other hand, have proven effective at reducing COD and toxicity. Anaerobic consortia can effectively reduce COD, but are sensitive to phenolics in OMWW. Biological processes provide some of the most viable options for the treatment of OMWW. Effective application of these techniques, yielding significant reductions in COD, phenolics, and color, will allow safe and economical disposal of OMWW.
The microbial degradation of phenols has been reviewed including the phenol‐degrading microbes, factors affecting degradability, and the use of biotechnology with emphasis on degradation mechanisms and their kinetics. The mechanism of microbial degradation depends on aerobic and anaerobic conditions. Under aerobic conditions, degradation of phenol was shown to be initiated by oxygenation into catechols as intermediates followed by a ring cleavage at either the ortho or meta position, depending on the type of strain. Anaerobic biodegradation of phenol occurs by carboxylation followed by dehydroxylation (reducing reaction) and dearomatisation. It was also clear that the parameters used in the Haldane model are not constants but vary, hence it may never be possible to describe the kinetic properties of a microbial cell with a single set of constants.
Acute toxicity of olive mill wastewaters (traditional and continuous processes) collected from different regions of Portugal was evaluated using three test species (Vibrio fischeri formerly Photobacterium phosphoreum, Thamnocephalus platyurus, and Daphnia magna) and correlated with several physical and chemical parameters. Acute toxicity of these effluents, expressed in LC50 or EC50, ranged from: 0.16 to 1.24% in Microtox test, 0.73 to 12.54% in Thamnotoxkit F test, and 1.08 to 6.83% in Daphnia test. These values reflect the high toxicity of the olive mill wastewaters to all test species. Statistical analysis of the results shows a high correlation between the two microcrustacean bioassays. Microtox test did not correlate significantly with the other bioassays used. A significative correlation (p≤0.05) could also be established between L(E)C50 obtained in the microcrustacean tests and some physicochemical parameters of the effluent. ©1999 John Wiley & Sons, Inc. Environ Toxicol 14: 263–269, 1999
Immobilized microbial cells have been used extensively in various industrial and scientific endeavours. However, immobilized cells have not been used widely for environmental applications. This review examines many of the scientific and technical aspects involved in using immobilized microbial cells in environmental applications, with a particular focus on cells encapsulated in biopolymer gels. Some advantages and limitations of using immobilized cells in bioreactor studies are also discussed.
Bioaugmentation of activated sludge systems with specialised bacterial strains could be a powerful tool to improve several
aspects in wastewater treatment processes, such as improved flocculation and degradation of recalcitrant compounds. This review
focuses on the addition of strains to activated sludge to enhance the biodegradation of recalcitrant compounds, either through
the activity of the inoculated strain or after transfer of degradative plasmids to activated sludge bacteria. Different factors
that improve the aggregation of the sludge flocs and their influence on biodegradation are described. This review further
deals with the role of bacterial plasmids in natural genetic exchange between inoculated and indigenous sludge bacteria, and
in the construction of new genetically modified organisms. The few successful cases of bioaugmentation described in this review,
together with future research, must lead to a better understanding of sludge bioaugmentation.
Background, aim, and scope:
Olive oil mill wastewater (OOMW) environmental impacts minimization have been attempted by developing more effective processes, but no chemical or biological treatments were found to be totally effective to mitigate their impact on receiving systems. This work is the first that reports simultaneously the efficiency of three different approaches: biological treatment by two fungal species (Trametes versicolor or Pleurotus sajor caju), enzymatic treatment by laccase, and chemical treatment by photo-Fenton oxidation on phenols removal.
Materials and methods:
Those treatments were performed on OOMW with or without phenol supplement (p-coumaric, vanillin, guaiacol, vanillic acid, or tyrosol). OOMW samples resulted from treatments were extracted for phenols using liquid-liquid extraction and analyzed by gas chromatography coupled to mass spectrometry.
Results:
Treatment with T. versicolor or P. sajor caju were able to remove between 22% and 74% and between 8% and 76% of phenols, respectively. Treatment by laccase was able to reduce 4% to 70% of phenols whereas treatment by photo-Fenton oxidation was responsible for 100% phenols reduction.
Discussion:
Range of phenol degradation was equivalent between T. versicolor, P. sajor caju and laccase for p-coumaric, guaiacol, caffeic acid, and tyrosol in supplemented OOMW, which enhances this enzyme role in the biological treatment promoted by these two species.
Conclusions:
Phenols were removed more efficiently by photo-Fenton treatment than by biological or enzymatic treatments.
Recommendations and perspectives:
Use of fungi, laccase, or photo-Fenton presents great potential for removing phenols from OOMW. This should be further assessed by increasing the application scale and the reactor configurations effect on the performance, besides a toxicity evaluation of treated wastewater in comparison to raw wastewater.
Growth and polyphenol biodegradation by three microorganisms namely Geotrichum sp., Aspergillus sp. and Candida tropicalis were studied on olive mill wastewater (OMW). These three microorganisms were selected for their tolerance to the polyphenols. The biodegradation process of OMW was investigated in batch regime by conducting experiments where the initial concentration of chemical oxygen demand (COD) was varied. Furthermore, some tests were performed to determine the most important nutrients necessary for aerobic degradation of OMW. Average COD removals were 55.0%, 52.5% and 62.8% in wastewaters fermented with Geotrichum sp., Aspergillus sp. and C. tropicalis, respectively. The maximum removal of polyphenols was 46.6% (Geotrichum sp.), 44.3% (Aspergillus sp.) and 51.7% (C. tropicalis). In addition, significant decolorization was evident.
Experiments carried out in lysimeters filled with two calcareous clayey soils (ca 40% CaCO3; ca 40% clay), showed that a 2m layer of soil almost completely removed the organic and inorganic components of olive oil mill wastewater (OMW) when it was applied in doses of 5000–10000m3ha−1year−1. This efficiency was maintained for at least 2 years. In field experiments, the application of OMW to one of these soils during three successive years at an annual rate of up to 6000m3ha−1 caused changes in some chemical properties of the soil, especially in the upper layer (0–50cm). Concentrations of soil organic matter, Kjeldahl N, soluble NO3 and available P increased enhancing soil fertility. On the other hand, soil electrical conductivity and sodium adsorption ratio also increased but below the levels representing salinization or sodification hazard for the soil. Furthermore, leaching of Na+ and NO3− below the 1 m layer were detected.
Flavonoid content of mulberry leaves of 19 varieties of species, determined spectrophotometrically in terms of rutin equivalent, varied from 11.7 to 26.6 mg g−1 in spring leaves and 9.84 to 29.6 mg g−1 in autumn leaves. Fresh leaves gave more extract than air-dried or oven-dried ones. HPLC showed that mulberry leaves contain at least four flavonoids, two of which are rutin and quercetin. The percentage superoxide ion scavenged by extracts of mulberry leaves, mulberry tender leaves, mulberry branches and mulberry bark were 46.5, 55.5, 67.5 and 85·5%, respectively, at a concentration of 5 μg ml−1. The scavenging effects of most mulberry extracts were greater than those of rutin (52.0%).
Catechol, 4-methylcatechol, tyrosol and hydroxytyrosol were isolated and characterized as the main polyphenols from olive oil mill waste waters. In addition, the corresponding acetates were prepared. In phytotoxicity assays carried out on tomato (Lycopersicon esculentum) and vegetable marrow (Cucurbita pepo) plants, the compounds were selectively toxic, except for 4-methylcatechol and its acetate. The vegetation waters remained phytotoxic even after total extraction of the polyphenols, suggesting that other chemical products contribute to the overall phytotoxicity.
This study investigated the impact of olive mill wastewater (OMW) as a pollutant of the marine environment, via the detection of stress indice alterations in mussels Mytilus galloprovincialis. Due to the absence of data concerning the levels of OMW in the receiving waters, mortality test (96h) was first performed in order to estimate the range of OMW concentration where no mortality occurs. OMW concentrations ranging from 0.01 to 0.1% (v/v) showed no increased mortality and thus were used for the determination of pre-pathological alterations in tissues of mussels. In particular, mussels exposed to either 0.1 or 0.01% (v/v) OMW for 5 days showed significant alterations of stress indices in their tissues. Specifically, decreased neutral red retention (NRR) assay time values, inhibition of acetylcholinesterase (AChE) activity, as well as a significant increase of micronucleus (MN) frequency and DNA damage were detected in haemolymph/haemocytes and gills, compared with values measured in tissues of control mussels. The results of the present study showed that OMW disposal into the marine environment could induce pre-pathological alterations in marine organisms, before severe disturbances, such as disease, mortality, or population changes occur.
Olive oil mill wastewater (OOMW) is responsible for serious environmental problems. In this study, the efficiency of two treatments involving fungi and photo-Fenton oxidation, sequentially applied to OOMW was analyzed for organic compounds degradation and toxicity mitigation. The treatment with fungi (especially Pleurotus sajor caju) of diluted OOMW samples promoted a reduction of their acute toxicity to Daphnia longispina. Although this fungi species have not induced significant color reduction it was responsible for 72,91 and 77% reductions in chemical oxygen demand (COD), total phenolic and organic compound contents. After biological treatment, photo-Fenton oxidation seemed to be an interesting solution, especially for color reduction. However, the OOMWs remained highly toxic after photo-Fenton oxidation. Considering the second sequence of treatments, namely photo-Fenton oxidation followed by biological treatment, the former revealed, once more, a great potential because it can be applied to non-diluted OOMW, with significant reductions in COD (53-76%), total phenolic content (81-92%) and organic compounds content (100%). Despite fungal species still have demonstrated a high capacity for bioaccumulation of organic compounds, resulting from photo-Fenton oxidation, the biological treatment did not cause substantial benefits in terms of COD, total phenolic content and toxicity reduction.
The growth behaviour of Alcaligenes eutrophus using various concentrations of benzoate was investigated. In batch culture, growth was exponential and growth rate (mu) and yields (Y) were high [mu = 0.51 h-1 and Yx/benzoate = 0.56 mol carbon (mol carbon)-1] when low concentrations of benzoate (< 5 mM) were used. These kinetic parameters were close to the maxima determined in a benzoate-limited chemostat [mu(max) = 0.55 h-1 and YX/benzoatemax = 0.57 mol carbon (mol carbon)-1] and the part of the energy for maintenance was limited (mATP = 4.3 +/- 2.2 mmol ATP g-1 h-1). When higher concentrations of benzoate were used (up to 40 mM), several metabolic limitations appeared. The specific rate of benzoate consumption was not altered, whereas growth was inhibited [Ki(benzoate) approximately 27 mM]. Furthermore, high concentrations of catechol together with some 1,2-dihydro-1,2-dihydroxybenzoate (DHB) transiently accumulated in the medium. The accumulation of catechol was attributed to limiting flux through catechol 1,2-dioxygenase estimated to be 5.2 mmol g-1 h-1, whereas that of DHB was provoked by an imbalance in the NADH/NAD+ intracellular content. The direct consequence of DHB accumulation was the induction of the meta pathway for the degradation of catechol, and this pathway contributed up to 20% of the total flux of catechol to the central metabolism. Finally, when very high concentrations of benzoate were used (55 mM), both growth and the specific rate of benzoate degradation were diminished due to a strong decrease in benzoate 1,2-dioxygenase specific activity.
To test the potential use of Phanerochaete chrysosporium and other white-rot fungi to detoxify olive mill wastewaters (OMW) in the presence of a complex activated sludge. To combine the aerobic with anaerobic treatment to optimize the conversion of OMW in biogas.
A 25-l air lift reactor was used to pretreat OMW by white-rot fungi. Detoxification of the OMW was monitored by size exclusion HPLC analysis, chemical oxygen demand (COD)/biological oxygen demand (BOD(5)) ratio evolution, and bioluminescence toxicity test. Anaerobic treatment of OMW was performed in a 12-l anaerobic filter reactor. Efficiency of the treatment was evaluated by organic matter removal, and biogas production. By comparison with the pretreatment by activated sludge only, the bioaugmentation with Phanerochaete chrysosporium or Trametes versicolor led to high removal of organic matter, decreased the COD/BOD(5) ratio and the toxicity. The subsequent anaerobic digestion of the OMW pretreated with activated sludge-white-rot fungi showed higher biomethanization yields than that pretreated with activated sludge only. Higher loading rates (7 g COD l(-1) day(-1)) were reached without any acidification or inhibition of biomethanization.
The use of white-rot fungi, even in the presence of complex biological consortia to detoxify OMW, proved to be possible and made the anaerobic digestion of OMW for methane production feasible.
The use of fungi for OMW reuse and energy production could be adapted to industrial applications.
Extremely high organic load and the toxic nature of olive mill wastewater (OMW) prevent their direct discharge into domestic wastewater treatment systems. In addition to the various treatment schemes designed for such wastewater, controlled land spreading of untreated OMW has been suggested as an alternative mean of disposal. A field study was conducted between October 2004 and September 2005 to assess possible effects of OMW on soil microbial activity and potential phytotoxicity. The experiment was carried out in an organic orchard located on a Vertisol-type soil (Jezre'el Valley, Israel) and included two application levels of OMW (36 and 72m(3)ha(-1)). Total microbial counts, and to less extent the hydrolytic activity and soil respiration were increased following the high OMW application level. A bench-scale lab experiment showed that the rate of OMW mineralization was mainly dependent on the general status of soil activity and was not related to previous acclimatization of the soil microflora to OMW. Soil phytotoxicity (% germination and root elongation) was assessed in soil extracts of samples collected before and after each OMW application, using germinating cress (Lepidium sativum L.) seeds. We found direct short-term effect of OMW application on soil phytotoxicity. However, the soil was partly or completely recovered between successive applications. No further phytotoxicity was observed in treated soils as compared with control soil, 3 months after OMW application. Such short-term phytotoxicity was not in correlation with measured EC and total polyphenols in the soil extracts. Overall, the results of this study further support a safe controlled OMW spreading on lands that are not associated with sensitive aquifers.
The degradability of phenol and trichloroethene (TCE) by Pseudomonas putida BCRC 14349 in both suspended culture and immobilized culture systems are investigated. Chitosan beads at a size of about 1-2mm were employed to encapsulate the P. putida cells, becoming an immobilized culture system. The phenol concentration was controlled at 100 mg/L, and that of TCE was studied from 0.2 to 20 mg/L. The pH, between 6.7 and 10, did not affect the degradation of either phenol or TCE in the suspended culture system. However, it was found to be an important factor in the immobilized culture system in which the only significant degradation was observed at pH >8. This may be linked to the surface properties of the chitosan beads and its influence on the activity of the bacteria. The transfer yield of TCE on a phenol basis was almost the same for the suspended and immobilized cultures (0.032 mg TCE/mg phenol), except that these yields occurred at different TCE concentrations. The transfer yield at a higher TCE concentration for the immobilized system suggested that the cells immobilized in carriers can be protected from harsh environmental conditions. For kinetic rate interpretation, the Monod equation was employed to describe the degradation rates of phenol, while the Haldane's equation was used for TCE degradation. Based on the kinetic parameters obtained from the two equations, the rate for the immobilized culture systems was only about 1/6 to that of the suspended culture system for phenol degradation, and was about 1/2 for TCE degradation. The slower kinetics observed for the immobilized culture systems was probably due to the slow diffusion of substrate molecules into the beads. However, compared with the suspended cultures, the immobilized cultures may tolerate a higher TCE concentration as much less inhibition was observed and the transfer yield occurred at a higher TCE concentration.
Olive mill wastes represent a significant environmental problem in Mediterranean areas where they are generated in huge quantities in a short period of time. Their high phenol, lipid and organic acid concentrations turn them into phytotoxic materials, but these wastes also contain valuable resources such as a large proportion of organic matter and a wide range of nutrients that could be recycled. Composting is one of the technologies used for the valorization of this effluent, producing a fertilizer useful for poor soils.The present work deals with the changes that occur in the content of phenolic compounds and the biotoxicity of the oxidized substrate which result from the composting of olive mill wastewater (OMW) sludge with sesame bark. The total organic matter decreased 52.72% while water-soluble phenol degradation decreased 72% after 7 months of processing. Gas chromatography coupled with mass spectroscopy was used to confirm the elimination of polyphenols during composting. Initially, the analysis showed three abundant polyphenolic compounds, one of which was identified as the 4-hydroxyphenyl-ethanol (tyrosol), a well-known antioxidant in OMW. After 7 months of composting, all of the phenolic compounds disappeared. The phytotoxic effects of OMW sludge, assessed by the plant index germination, increased during the composting to reach 80% after 210 days. This trend was confirmed by the correlation between physico-chemical and toxicity parameters. The results obtained confirmed the stability of the compost prepared from OMW sludge with sesame bark and indicated a gradual detoxification as the compost matured.
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