Water Research

Published by Elsevier
Print ISSN: 0043-1354
This study measured the effect of germicidal ultraviolet (UV) light on Giardia lamblia and Giardia muris cysts, as determined by their infectivity in Mongolian gerbils and CD-1 mice, respectively. Reduction of cyst infectivity due to UV exposure was quantified by applying most probable number techniques. Controlled bench-scale, collimated-beam tests exposed cysts suspended in filtered natural water to light from a low-pressure UV lamp. Both G. lamblia and G. muris cysts showed similar sensitivity to UV light. At 3 mJ/cm2, a dose 10-fold lower than what large-scale UV reactors may be designed to provide, > 2-log10 (99 percent) inactivation was observed. These results, combined with previously published data showing other protozoa and bacteria have similar, high sensitivity to UV light, establish that UV disinfection of drinking water is controlled by viruses which may require over 10-fold more UV dose for the same level of control.
Filamentous bulking sludge due to excessive growth of filamentous bacteria is a serious operational problem in activated sludge plants. The addition of chemicals is one of widespread ways to control filamentous bulking. In this study, filamentous bulking in a continuous activated sludge system was found to be mainly caused by Eikelboom Type 021N filamentous bacteria likely due to low substrate concentration gradients. These Type 021N bacteria were found to be resistant to chlorination, maintaining cell integrity at a dosage of up to 80 mg Cl/gSS. An alternative biocidal agent, cetyltrimethyl ammonium bromide (CTAB), exhibited a much stronger biocidal effect on these filaments, which significantly improved sludge settleability. Type 021N with filamentous index of 5 was selectively killed, but floc-formers recovery their activity after CTAB termination. The study implied that CTAB might have more penetration capacity to cell wall of chlorine-resistant Type 021N bacteria. We therefore suggest the penetration property of filament cell wall should be considered or tested before the selection of biocide type in practice.
1,1,1-Trichloroethane (TCA) in groundwater is susceptible to a variety of natural degradation mechanisms. Evidence of intrinsic decay of TCA in aquifers is commonly observed; however, TCA remains a persistent pollutant at many sites and some of the daughter products that accumulate from intrinsic decay of TCA have been determined to be more toxic than the parent compound. Research advances from the past decade indicate that in situ enhanced reductive dechlorination (ERD) offers promise as a cost-effective solution toward the cleanup of groundwater contaminated with TCA and its transformation daughter products. Laboratory studies have demonstrated that pure or mixed cultures containing certain Dehalobacter (Dhb) bacteria can catalyze respiratory dechlorination of TCA and 1,1-dichloroethane (1,1-DCA) to monochloroethane (CA) in groundwater systems. 16S rRNA Dhb gene probes have been used as biomarkers in groundwater samples to both assess ERD potential and quantify growth of Dhb in ERD applications at TCA sites. Laboratory findings suggest that iron-bearing minerals and methanogenic bacteria that co-occur in reduced aquifers may synergistically affect dechlorination of TCA. Despite these advances, a number of significant challenges remain, including an inability of any known cultures to completely dechlorinate TCA to ethane. CA is commonly observed as a terminal product of the biological reductive dechlorination of TCA and 1,1-DCA. Also important is the lack of rigorous field studies demonstrating the utility of bioaugmentation with Dhb cultures for remediation of TCA in the field. In this paper we review the state-of-the-science of TCA degradation in aquifers, examining results from both laboratory experiments and twenty-two field case studies, focusing on the capabilities and limits of ERD technology, and identifying aspects of the technology that warrant further development.
The presence of other chloroethenes influences aerobic metabolic biodegradation of cis-1,2-dichloroethene (cDCE). A new metabolically cDCE degrading enrichment culture was identified as also being capable of degrading vinyl chloride (VC), but not 1,1-dichloroethene (1,1DCE), trans-1,2-dichloroethene (tDCE), trichloroethene (TCE), or tetrachloroethene (PCE). The fastest degradation of cDCE was observed in the absence of any other chloroethene. In the presence of a second chloroethene (40-90 microM), the rate of cDCE (60 microM) degradation decreased in the following order: cDCE (+PCE) > cDCE (+tDCE) > cDCE (+VC)>cDCE (+1,1DCE) approximately cDCE (+TCE). With increasing concentrations of VC, ranging from 10 to 110 microM, the rate of cDCE (60 microM) degradation decreased. This study demonstrates that the inhibiting effects of chloroethene mixtures have to be considered during laboratory studies and bioremediation approaches based on metabolic cDCE degradation.
Assessing changes in the isotopic signature of contaminants is a promising new tool to monitor microbial degradation processes. In this study, chloroethene degradation was proven by depletion of chloroethenes, formation of chloride, increase in protein content and stable carbon isotope fractionation. Aerobic degradation of vinyl chloride (VC) was found to proceed metabolically, with degradation rates of 0.48 and 0.29 d(-1); and growth yields of 9.7 and 6.4 g of protein/mol of VC at room and groundwater temperature, respectively. Cis-1,2-dichloroethene (cDCE) was degraded cometabolically under aerobic conditions when VC was provided as growth substrate. Aerobic degradation was associated with significant stable carbon isotope fractionation, with enrichment factors ranging from -5.4+/-0.4 per thousand for metabolic degradation of VC to -9.8+/-1.7 per thousand for cometabolic degradation of cDCE. Thus, it was demonstrated that stable carbon isotope fractionation is suitable for assessing aerobic chloroethene degradation, which can contribute significantly to site remediation.
The electrochemical degradation of 1,2-dichloroethane (DCA) was examined in a synthetic groundwater medium. An undivided electrolytic reactor constructed with 304 L-type stainless-steel plate electrodes was employed in all experiments. The removal of total organic carbon (TOC) content during the electrolysis of DCA was experimentally examined. Stainless-steel plate electrodes were effective in degrading DCA under experimental conditions including varying initial concentrations, chloride concentrations, electrolyte conductivities and applied current densities. A half-life method demonstrated TOC removal followed zero-order kinetics under the experimental conditions examined. Chlorides concentration and applied current affected the TOC removal rates. An increase in current density increased the rate of TOC removal but caused a reduction in mineralization current efficiency. Increase in electrolyte conductivity had no effect on TOC removal rates but it decreased the energy consumption by reducing the cell voltage. Reaction temperature was shown to affect the TOC removal and was modeled by the Arrhenius equation.
Carbon stable isotope fractionation during 1,2-dichloroethane (1,2-DCA), dichloroethene (DCE) and vinyl chloride (VC) dechlorination was analysed for two Dehalococcoides strains, Dehalococcoides mccartyi strain 195 (formerly Dehalococcoides ethenogenes strain 195) and D. mccartyi strain BTF08, and used to characterize the reaction. The isotope enrichment factors (εC) determined for 1,2-DCA were -30.8 ± 1.3‰ and -29.0 ± 3.0‰ for D. mccartyi strain BTF08 and D. mccartyi strain 195, respectively. Enrichment factors (εC) determined for chlorinated ethenes with strain BTF08 were -28.8 ± 1.5‰ (VC), -30.5 ± 1.5‰ (cis-DCE) and -12.4 ± 1.1‰ (1,1-DCE). Product, ethene, related enrichment factors (εC1,2-DCA-ethene) calculated for 1,2-DCA (-34.1 and -32.3‰ for strain BTF08 and strain 195, respectively) were similar to substrate based enrichment factors (εC1,2-DCA), supporting the hypothesis that ethene is the direct product of 1,2-DCA dichloroelimination but that VC was a side product as result of branching in the reaction.
Chlorinated hydrocarbons are widely used in chemical industries as solvents and intermediates for pesticides and dyes manufacture. Their presence was documented in rivers, groundwaters and seawaters. In this work, the oxidation of 1,2-dichlorobenzene in aqueous solutions by means of Fe(III) homogeneous photocatalysis under UV lamp and sunlight irradiations is studied. The results show that the best working conditions are found for pH=3.0 and initial [Fe(III)] concentration equal to 1.0x10(-4) molL(-1) although the investigated system can be utilized even at pH close to 4.0 but with slower abatement kinetics. Some dicholoroderivatives, such as 2,3-dichlorophenol, 3,4-dichlorophenol and 2-chlorophenol, are identified as oxidation intermediates. The values of the kinetic constant for the photochemical reoxidation of Fe(II) to Fe(III) are evaluated by a mathematical model in the range 1.58-3.78 Lmol(-1)s(-1) and 0.69-0.78 Lmol(-1)s(-1) for the systems irradiated by UV lamp and sunlight, respectively.
Insight into the pathways of biodegradation and external factors controlling their activity is essential in adequate environmental risk assessment of chlorinated aliphatic hydrocarbon pollution. This study focuses on biodegradation of 1,2-dichloroethane (1,2-DCA) in microcosms containing sediment sourced from the European rivers Ebro, Elbe and Danube. Biodegradation was studied under different redox conditions. Reductive dechlorination of 1,2-DCA was observed with Ebro and Danube sediment with chloroethane, or ethene, respectively, as the major dechlorination products. Different reductively dehalogenating micro-organisms (Dehalococcoides spp., Dehalobacter spp., Desulfitobacterium spp. and Sulfurospirillum spp.) were detected by 16S ribosomal RNA gene-targeted PCR and sequence analyses of 16S rRNA gene clone libraries showed that only 2-5 bacterial orders were represented in the microcosms. With Ebro and Danube sediment, indications for anaerobic oxidation of 1,2-DCA were obtained under denitrifying or iron-reducing conditions. No biodegradation of 1,2-DCA was observed in microcosms with Ebro sediment under the different tested redox conditions. This research shows that 1,2-DCA biodegradation capacity was present in different river sediments, but not in the water phase of the river systems and that biodegradation potential with associated microbial communities in river sediments varies with the geochemical properties of the sediments.
1,2-Dichloroethane (1,2-DCA) is a well-known recalcitrant groundwater contaminant. New environment-friendly approaches for the removal of 1,2-DCA that does not bring about volatilization of the compound are required. In this study, different anodophilic consortia enriched in microbial fuel cells (MFCs) operated under airtight conditions were shown to effectively degrade 1,2-DCA (up to 102mg per liter reactor volume per day), while concomitantly generating a current. An anodophilic consortium previously enriched with acetate as the electron donor changed its composition at the rate of 48% per week and increased its richness (Rr) 3-fold, upon adapting to 1,2-DCA as the new electron donor. After being stable, during 1month of operation, it removed up to 95% of the 1,2-DCA amount in the medium in the first 2weeks, while converting 43+/-4% of electrons available from the removal to electricity. A natural consortium from a 1,2-DCA contaminated site changed its composition at the rate of 9% per week and increased its Rr 2-fold, upon adapting to the MFC anode conditions with 1,2-DCA as the electron donor. After being stable, during 1month of operation, it removed up to 85% of the 1,2-DCA amount in the medium in the first 2weeks and the coulombic efficiency was 25+/-4%. The operation of the MFCs under closed circuit conditions resulted in higher 1,2-DCA removal rates than the operation under open circuit conditions, indicating that bioelectrochemical activities enhanced the removal of 1,2-DCA in the MFC anode. The production of ethylene glycol, acetate and carbon dioxide indicated that the anodophilic bacteria oxidatively metabolized 1,2-DCA, probably by means of a hydrolysis-based pathway. The results show that MFCs can be potentially used as a practically convenient technology for the biological removal of 1,2-DCA.
A mixed culture containing Dehalococcoides mccartyi strain 195 dechlorinated 1,2,3,7,8-pentachlorodibenzo-p-dioxin (1,2,3,7,8-PeCDD) and selected polychlorinated biphenyl (PCB) congeners in Aroclors 1260, 1254 and 1242. 1,2,3,7,8-PeCDD was dechlorinated to 1,3,7-trichlorodibenzo-p-dioxin (1,3,7-TrCDD) and/or 1,3,8-TrCDD via 1,3,7,8-tetrachlorodibenzo-p-dioxin (1,3,7,8-TeCDD), a pathway that excludes the production of the toxic congener 2,3,7,8-TeCDD. Dechlorination rate and extent was greatly enhanced by the addition of 1,2,3,4-tetrachlorobenzene (1,2,3,4-TeCB) as an alternate halogenated substrate and/or incubation temperature increase from 25 °C to 35 °C. The most extensive dechlorination of PCBs occurred for Aroclor 1260 with 13 major congeners making up 44.1 mol% of the original PCBs dechlorinated by 42% over 250 days at 25 °C. When 1,2,3,4-TeCB was amended as co-substrate, the extent of dechlorination increased to 82%, over 250 days. The mixed culture primarily dechlorinated the doubly-flanked chlorines on 2,3,4-, 2,3,4,6-, and 2,3,4,5,6-substituted chlorophenyl rings, whereas it primarily removed the doubly-flanked para chlorine from the 2,3,4,5-substituted chlorophenyl ring. Experiments using a 20% dilution of culture with 31.8 μg/mL 1,2,3,4-TeCDD or 2,3,4,4',5-pentachlorobiphenyl (PCB 114) as sole halogenated substrate exhibited less than 0.1 mol% dechlorination over 120 days. Further, dechlorination of PCBs and PCDDs by the fully grown culture in the absence of 1,2,3,4-TeCB eventually stopped or greatly slowed over the incubation period. Since Dehalococcoides spp. only gain energy for growth from organohalide respiration, absence of reductive dechlorination upon transfer and dilution or cessation of dechlorination after long incubation times suggest that it is unlikely that strain 195 can grow using the PCDDs or PCBs utilized in this study.
Recent studies indicate that the sodium salt of 1,3-benzenediamidoethanethiol (BDET) is both economical and effective in precipitating mercury and other heavy metals from water. Because wastewaters and contaminated natural waters may contain a variety of heavy metals, it is important to determine how different heavy metals may interact with BDET, and whether free metals may displace those that are bound. To explore this possibility, Cd-, Cu-, Pb-, Mn-, Hg- and Zn-BDET were leached separately under a nitrogen purge for up to 240 h in pH 3 aqueous solutions containing 0.100 mmol of all five heavy metals. The leaching studies indicate that dissolved Hg has a strong tendency to displace Cd, Cu, Mn, Pb, and Zn from the BDET structure.
RDX (hexahydro-1,3,5-trinitro-1,3,5-triazine) is a nitramine explosive that has contaminated soil and groundwater at military installations throughout the US. Although anaerobic RDX metabolism has been reported, the process is not well understood, as past studies have typically involved complex, undefined media with multiple potential electron donors and acceptors. In this study, bacteria enriched from RDX-contaminated aquifer sediments consumed RDX in a defined, bicarbonate-buffered, anaerobic medium containing hydrogen as the sole electron donor and RDX as a potential electron acceptor and sole nitrogen source. RDX was not consumed in live controls that did not contain hydrogen. Transient formation of mononitroso- and dinitroso-RDX metabolites (hexahydro-1-nitroso-3,5-dinitro-1,3,5-triazine and hexahydro-1,3-dinitroso-5-nitro-1,3,5-triazine, respectively) was documented by liquid chromatography-mass spectrometry. However, studies with 14C-labeled RDX suggested that mineralization to carbon dioxide was negligible (<2%), which is consistent with cometabolic transformation. Several lines of evidence suggest that the RDX-transforming bacteria under study were homoacetogens, including correlations between RDX consumption and acetate production. Methanogens were unlikely to be responsible for RDX metabolism, as the presence of 2-bromoethanesulfonate, an inhibitor of methanogenesis, did not appear to affect RDX metabolism. The presence of nitrate reversibly halted RDX metabolism, whereas ammonium had no discernible effect, which implies that: (i) nitrate, which commonly occurs in RDX-contaminated groundwater, may inhibit in situ RDX metabolism, and (ii) although RDX may act as both a nitrogen source and cometabolic electron sink, the latter role predominates, as RDX reduction will proceed regardless of whether or not a more favorable nitrogen source is present.
Oxidation of the high explosives hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) and octahydro-1,3,5,7-tetranitro-1.3,5,7-tetrazocine (HMX) using Fenton's reagent proceeds rapidly between 20 degrees C and 50 degrees C at pH 3. At an H2O2: Fe2+: RDX molar ratio of 5,178: 48: 1, RDX and HMX were completely removed in 1 to 2 h. All the experimental data could be fit to a pseudo first-order rate equation. The reaction rate was also strongly dependent on Fenton's reagent concentrations. NO3- and N2 were identified as nitrogen byproducts from RDX and HMX oxidation. The experiment with radiolabeled RDX showed that approximately 37% of organic carbon in RDX was mineralized to CO2. We observed formaldehyde and formic acid as a short-lived intermediate. No other volatile or nonvolatile byproducts were found from GC/MS analysis. The results show that RDX and HMX can be effectively mineralized with Fenton's reagents.
Characterisation of the concentrations and potential health risks of chemicals in recycled water is important if this source of water is to be safely used to supplement drinking water sources. This research was conducted to: (i) determine the concentration of volatile organic compounds (VOCs) in secondary treated effluent (STE) and, post-reverse osmosis (RO) treatment and to; (ii) assess the health risk associated with VOCs for indirect potable reuse (IPR). Samples were examined pre and post-RO in one full-scale and one pilot plant in Perth, Western Australia. Risk quotients (RQ) were estimated by expressing the maximum and median concentration as a function of the health value. Of 61 VOCs analysed over a period of three years, twenty one (21) were detected in STE, with 1,4-dichlorobenzene (94%); tetrachloroethene (88%); carbon disulfide (81%) and; chloromethane (58%) most commonly detected. Median concentrations for these compounds in STE ranged from 0.81 μg/L for 1,4-dichlorobenzene to 0.02 μg/L for carbon disulphide. After RO, twenty six (26) VOCs were detected, of which 1,4-dichlorobenzene (89%); acrylonitrile (83%) chloromethane (63%) and carbon disulfide (40%) were the more frequently detected. RQ(max) were all below health values in the STE and after RO. Median removal efficiency for RO was variable, ranging from -77% (dichlorodifluoromethane) to 91.2% (tetrachloroethene). The results indicate that despite the detection of VOCs in STE and after RO, their human health impact in IPR is negligible due to the low concentrations detected. The results indicate that 1,4-dichlorobenzene is a potential treatment chemical indicator for assessment of VOCs in IPR using RO treatment.
Advanced oxidation involving O(3)/H(2)O(2) was used to eliminate 1,4-dioxane and to enhance the biodegradability of dioxane-contaminated water. Oxidation experiments were carried out in a bubble column reactor operating in fed-batch. The rate of dioxane removal and enhancement in biodegradability was investigated at hydrogen peroxide to ozone ratios between 0 and 0.6mol:mol and pH between 5 and 11. A theoretical model was also applied to predict the experimental data and to investigate the effects of dioxane concentration, pH, and H(2)O(2) concentration. The model predictions fit the experimental data well and there was a linear correlation between dioxane oxidation and BOD enhancement. At low dioxane concentrations, the oxidation rate was first order and it gradually approached zero order with increasing dioxane concentration. Also, the biodegradability of the solution increased with pH up to about 9 and it stayed constant with further pH increase. Hydrogen peroxide initially enhanced dioxane removal and biodegradability enhancement of the solution. However, at H(2)O(2):O(3) ratios greater than about 0.4-0.45mol:mol, i.e. about 2.90mM for H(2)O(2) concentration, H(2)O(2) had negative impacts and resulted in reduced dioxane removal and biodegradability increase.
Potential health effects of 1,4-dioxane and the limited data on its occurrence in the water cycle command for more research. In the current study, mobility and persistence of 1,4-dioxane in the sewage-, surface-, and drinking water was investigated. The occurrence of 1,4-dioxane was determined in wastewater samples from four domestic sewage treatment plants (STP). The influent and effluent samples were collected during weekly campaigns. The average influent concentrations in all four plants ranged from 262 ± 32 ng L(-1) to 834 ± 480 ng L(-1), whereas the average effluent concentrations were between 267 ± 35 ng L(-1) and 62,260 ± 36,000 ng L(-1). No removal of 1,4-dioxane during water treatment was observed. Owing to its strong internal chemical bonding, 1,4-dioxane is considered non-biodegradable under conventional bio-treatment technologies. The source of increased 1,4-dioxane concentrations in the effluents was identified to originate from impurities in the methanol used in the postanoxic denitrification process in one of the STPs. In view of poor biodegradation in STPs, surface water samples were collected to establish an extent of 1,4-dioxane pollution. Spatial and temporal distribution of 1,4-dioxane in the Rivers Main, Rhine, and Oder was examined. Concentrations reaching 2200 ng L(-1) in the Oder River, and 860 ng L(-1) in both Main and Rhine River were detected. The average monthly load of 1,4-dioxane in the Rhine River was calculated to equal to 172 kg d(-1). In all rivers, concentration of 1,4-dioxane increased with distance from the spring and was found to negatively correlate with the discharge of the river. Additionally, bank filtration and drinking water samples from two drinking water facilities were analyzed for the presence of 1,4-dioxane. The raw water contained 650 ng L(-1)-670 ng L(-1) of 1,4-dioxane, whereas the concentration in the drinking water fell only to 600 ng L(-1) and 490 ng L(-1), respectively. Neither of the purification processes employed was able to reduce the presence of 1,4-dioxane below the precautionary guideline limit of 100 ng L(-1) set by the German Federal Environmental Agency.
This research investigates the effect of adding oxidants such as Fe0, Fe2+ and S2O8(2-) in the sonication of 1,4-dioxane (1,4-D). The results indicate that the degradation pattern of 1,4-D kinetically could be divided into three steps (initiation, acceleration, and stabilization), with the first two steps predominating. The initiation step agreed with zero order rate model, while the acceleration step was the pseudo-first order. In the presence of HCO3- as a radical scavenger, the degradations of 1,4-D and TOC were suppressed, indicating that OH radical is an important factor in the sonolysis, especially at the acceleration step. The overall degradation efficiency of 79.0% in the sonolysis of 1,4-D was achieved within 200 min. While Fe0, Fe2+ and S2O8(2-) were individually combined with sonication, the total degradation efficiency of 1,4-D increased 18.6%, 19.1% and 16.5% after 200 min, respectively. The addition of oxidants not only increased the rate constant in the acceleration step, but also changed the kinetic model from zero to pseudo-first order at the initiation step. The addition of oxidants such as Fe2+, Fe0 and S2O8(2-) in the sonication of 1,4-D also improved the mineralization of 1,4-D. However, the degradation efficiencies of 1,4-D and TOC were not statistically different (p = 0.709, ANOVA) with different oxidants such as Fe2+, Fe0 and S2O8(2-).
Ozonation combined with electrolysis (ozone-electrolysis) is a new advanced oxidation process for water treatment. The advantages of ozone-electrolysis are (1) that reagents such as hydrogen peroxide or ferrous salts are unnecessary, (2) there is less influence from chromaticity, and (3) electric power is only required for operation. However, electrolysis has a serious limitation, in that it requires electrical conductivity (EC). This research is aimed at developing an ozone-electrolysis reactor that is applicable to wastewater with low EC using a cation exchange membrane as solid electrolyte. Moreover, experimental evidence of hydroxyl radical (.OH) generation via the cathodic reduction of ozone was obtained. Competitive kinetics analysis, based on the experimental data from the ozone-electrolysis of a mixed solution of 1,4-dioxane and tert-butyl alcohol, revealed that .OH contributed to 1,4-dioxane degradation. The ozone-electrolysis reactor was successfully applicable to degradation of 1,4-dioxane in both 1,4-dioxane solution (EC: less than 0.30 microS/cm) and a landfill leachate treated by a low-pressure reverse osmosis membrane (EC: 0.06 mS/cm). The use of a solid electrolyte was also very effective in reducing the electric power required for electrolysis.
1,4-Dioxane is one of the most recalcitrant and toxic contaminants in the subsurface. This study investigated the potential to enhance dioxane biodegradation in both planted and unplanted soil, by adding the dioxane-degrading actinomycete, Amycolata sp. CB1190. Dioxane was not removed within 120 days in sterile controls or in viable microcosms not amended with CB 1190. Poplar root extract (40 mg/L as COD) stimulated dioxane degradation in bioaugmented soil, and 100 mg/L dioxane were removed within 45 days. Other co-substrates that enhanced dioxane degradation by CB1190 include tetrahydrofuran (THF) and 1-butanol, while glucose and soil extract did not affect dioxane degradation. The stimulatory effect of THF was partly due to enhanced enzyme induction, while that of root extract and 1-butanol was attributed to additional growth of CB1190. In another experiment with dioxane added at 10 mg/kg-soil. reactors planted with hybrid poplar trees removed (by evapotranspiration and biodegradation in the root zone) more dioxane within 26 days than unplanted reactors, regardless of whether CB1190 was added. Nevertheless, CB1190 enhanced mineralization of [14C]-dioxane in all experiments. This enhancement was more pronounced in unplanted soil because plant uptake reduced the availability of dioxane for microbial degradation. These results suggest that bioaugmented phytoremediation is an attractive alternative to remove dioxane from shallow contaminated sites.
In this study, the degradation mechanism of 1,4-dioxane using zero-valent iron (Fe0) in the presence of UV light was investigated kinetically. The degradation of 1,4-dioxane in Fe0-only, photolysis, and combined Fe0 and UV reactions followed the kinetics of a pseudo-first-order model. The degradation rate constant (19 x 10(-4)min(-1)) in the combined reaction with UV-C (4.2 mW cm(-2)) and Fe0 (5 mg L(-1)) was significantly enhanced compared to Fe0-only (4.8 x 10(-4) min(-1)) and photolytic reactions (2.25 x 10(-4)min(-1)), respectively. The removal efficiency of 1,4-dioxane in combined reaction with Fe0 and UV within 4 h was enhanced by increasing UV intensity at UV-C region (34% at 4.2 mW cm(-2) and 89% at 16.9 mW cm(-2)) comparing with the removal in the combined reaction with Fe0 and UV-A (29% at 2.1 mW cm(-2), and 33% at 12.6 mW cm(-2)). It indicates that 1,4-dioxane was degraded mostly by OH radicals in the combined reaction. The degradation patterns in both Fe(0)-only and combined reactions were well fitted to the Langmuir-Hinshelwood model, implying that adsorption as well as the chemical reaction occurred. The transformation of Fe0 to Fe2+ and Fe3+ was observed in the Fe0-only and combined reactions, and the transformation rate of Fe0 was improved by UV irradiation. Furthermore, the reduction of Fe3+ was identified in the combined reaction, and the reduction rate was enhanced by an increase of UV energy. Our study demonstrated that the enhancement of 1,4-dioxane removal rate occurred via an increased supply of OH radicals from the Fenton-like reaction induced by the photolysis of Fe0 and H2O, and with producing less sludge.
The enhanced ultrasonic decomposition of 1,4-dioxane by the addition of ferrous iron (Fe(II)) was investigated at 205, 358, 618, and 1071 kHz. The total organic carbon (TOC) remaining was also determined at each frequency. Addition of Fe(II) improved the 1,4-dioxane decomposition rate and mineralization efficiency at all frequencies studied. A nearly four-fold increase of the rate constant was observed at the optimal Fe(II) concentration and a frequency of 205 kHz. In the presence and absence of the iron, the fastest overall degradation and mineralization of 1,4-dioxane took place at 358 kHz where 95% of the initial 1,4-dioxane was removed after 50 min. Finally, although reduced, the ultrasonic decomposition of 1,4-dioxane was still significant at all frequencies in the presence of the hydroxyl radical scavenger bicarbonate.
Degradation of high concentrations of 1,4-dioxane in (a) microcosms bioaugmented with CB1190 (Treatment D) and (b) microcosms bioaugmented with DVS 5a1 (Treatment E). Microcosms with CB1190 outperformed those with DVS 5a1 at high dioxane concentrations, especially at warmer temperatures. Arrows indicate times when microcosms were re-spiked. 
,4-Dioxane degradation with initial concentration of 500 mg L-1 at 14 8C. Microcosms with DVS 5a1 outperformed those with CB1190 at low dioxane concentrations. 
1,4-Dioxane biodegradation was investigated in microcosms prepared with groundwater and soil from an impacted site in Alaska. In addition to natural attenuation conditions (i.e., no amendments), the following treatments were tested: (a) biostimulation by addition of 1-butanol (a readily available auxiliary substrate) and inorganic nutrients; and (b) bioaugmentation with Pseudonocardia dioxanivorans CB1190, a well-characterized dioxane-degrading bacterium, or with Pseudonocardia antarctica DVS 5a1, a bacterium isolated from Antarctica. Biostimulation enhanced the degradation of 50 mg L(-1) dioxane by indigenous microorganisms (about 0.01 mg dioxane d(-1) mg protein(-1)) at both 4 and 14 degrees C, with a simultaneous increase in biomass. A more pronounced enhancement was observed through bioaugmentation. Microcosms with 50 mg L(-1) initial dioxane (representing source-zone contamination) and augmented with CB1190 degraded dioxane fastest (0.16 +/- 0.04 mg dioxane d(-1) mg protein(-1)) at 14 degrees C, and the degradation rate decreased dramatically at 4 degrees C (0.021 +/- 0.007 mg dioxane d(-1) mg protein(-1)). In contrast, microcosms with DVS 5a1 degraded dioxane at similar rates at 4 degrees C and 14 degrees C (0.018 +/- 0.004 and 0.015 +/- 0.006 mg dioxane d(-1) mg protein(-1), respectively). DVS 5a1 outperformed CB1190 when the initial dioxane concentration was low (500 microg L(-1), which is representative of the leading edge of plumes). This indicates differences in competitive advantages of these two strains. Natural attenuation microcosms also showed significant degradation over 6 months when the initial dioxane concentration was 500 microg L(-1). This is the first study to report the potential for dioxane bioremediation and natural attenuation of contaminated groundwater in sensitive cold-weather ecosystems such as the Arctic.
The light-absorption ratio variation approach (LARVA) has been described and applied to the quantitative detection of ultramicro amounts of Ni by spectrophotometry, which raises notably the detection sensitivity. The complexation between 1, 5-di(2-hydroxy-5-sulfophenyl)-3-cyanoformazan (DSPCF) and Ni(II) at pH 9.11 was investigated and the binary complex was characterized by the spectral correction technique. Results have shown that deltaAr-1 (deltaAr--light-absorption ratio variation) is linear in the range of Ni(II) between 5 and 200 ng/ml. The limit of detection (3sigma) of Ni(II) is only 1.3 ng/ml. The complexation is selective in the presence of fluoride, hexametaphosphate, ethylene diamine tetraacetate and thioglycollic acid. It has been applied to analysis of water quality with satisfactory results.
The reaction kinetics and reaction pathway of methadone and its main human metabolite, 2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine (EDDP) in chlorine containing waters were investigated by direct injection of individual reaction time aliquots in a liquid chromatography-quadrupole-time-of-flight-mass spectrometry (LC-QTOF-MS) system. Factors potentially affecting the rate of the reaction were evaluated in detail by means of a Box-Behnken experimental design in which methadone and EDDP were considered separately. Sample pH and chlorine concentration turned out to be the two significant variables, enhancing the kinetics with an increase in their values. Transformation products (TPs) were first searched over sample chromatograms by comparing control, blank and time zero samples to aliquots stopped at different reaction times. Their tentative identity was further inferred by generating their empirical formulae from their accurate single MS spectra and, subsequently, by interpreting their fragmentation pattern from their tandem MS (MS/MS) spectra. In total, 8 TPs, arising from intra-molecular cyclation, dehydrogenation, oxidation and chlorination, could be detected in the case of methadone, one of them being the EDDP and another 3 coming from EDDP, so being common to both the precursor drug and its metabolite. A tentative transformation pathway was proposed, and the reaction was evaluated under potential real circumstances by chlorinating two different river samples. In this way, it was possible to demonstrate that its extension is highly affected by the content of dissolved organic matter, so both compounds were highly or completely transformed in samples with a low anthropogenic impact, whereas they were considerably more stable in waters with a high concentration of organic matter. Finally, the ecotoxicity of precursors and transformation species was predicted by software tools, revealing that, in some cases, the toxicological responses displayed by the TPs were up to 100 times higher than those of methadone. Copyright © 2014 Elsevier Ltd. All rights reserved.
Particulates extracted from a single section of a 10,000 year-old ice core melt sample exhibited characteristics of contemporary, airborne fine particulates: a majority were microcrystalline particulates and aggregated microcrystals, including some mixtures of microcrystals and carbonaceous matter. Particularly significant were the presence of carbon nanotubes and fullerene nanocrystals composing aggregated particulates reflecting global combustion products similar to contemporary, airborne carbon nanocrystal aggregates. ICP elemental analysis of the melt water showed significant concentrations of Ca, K and especially Na (corresponding to K, NaCl), S, Si, Se, and Zn. Overall, the elemental analysis of the melt water is similar to local tap water. However, lead was absent in the local tap water and only half the concentration of selenium was present in the tap water in contrast to the ice core water. While these observations cannot be generalized, the methodology illustrates the potential to characterize and compare airborne particulate regimes and water chemistries in antiquity.
A well-defined fractionation approach for sludge flocs was applied to a better understanding of the underlying mechanism of improving the production of volatile fatty acids (VFA) in the hydrolysis and acidification processes at pH 10.0. Specifically, sludge flocs were fractionated through centrifugation and ultrasound into four fractions: (1) slime, (2) loosely bound extracellular polymeric substances (LB-EPS), (3) tightly bound EPS (TB-EPS) and (4) pellet. Result showed that during 20 days of fermentation, the total VFA production at pH 10.0 was higher, from 2 to 34 times, than that at pH 5.5. At pH 10.0, however, the enzyme activities (i.e. protease, alpha-amylase, alkaline phosphatase and acid phosphatase) in all fractions of sludge flocs were all lower than pH 5.5, which strongly suggests that the biotic effect was not the leading cause of the VFA improvement. Further investigation suggests that pH 10.0 could significantly improve the VFA production through the break of sludge matrix which is usually hydrolyzed by the extracellular enzymes embedded in itself, increase the effective contact between extracellular organic matters and enzymes, and create a favorable environment for microbes to accumulate VFA. Hydrolysis and acidification at pH 10.0 can be considered as part of an appropriate solution for tertiary treatment and contribute to the headway toward the goal of sustainable water treatment technologies.
e Characteristics of WAS. a
e Carbon balance analysis of the fermentation system with fermentation time of 72 h.
Volatile fatty acids (VFA), the preferred carbon source for biological nutrients removal, can be produced by waste activated sludge (WAS) anaerobic fermentation. However, because the rate of VFA accumulation is limited by that of WAS hydrolysis and VFA is always consumed by methanogens at acidic or neutral pHs, the ultrasonic pretreatment which can accelerate the rate of WAS hydrolysis, and alkaline adjustment which can inhibit the activities of methanogens, were, therefore, used to improve WAS hydrolysis and VFA accumulation in this study. Experiment results showed that the combination of ultrasonic pretreatment and alkaline adjustment caused significant enhancements of WAS hydrolysis and VFA accumulation. The study of ultrasonic energy density effect revealed that energy density influenced not only the total VFA accumulation but also the percentage of individual VFA. The maximal VFA accumulation (3109.8mg COD/L) occurred at ultrasonic energy density of 1.0kW/L and fermentation time of 72h, which was more than two times that without ultrasonic treatment (1275.0mg COD/L). The analysis of VFA composition showed that the percentage of acetic acid ranked the first (more than 40%) and those of iso-valeric and propionic acids located at the second and third places, respectively. Thus, the suitable ultrasonic conditions combined with alkaline adjustment for VFA accumulation from WAS were ultrasonic energy density of 1.0kW/L and fermentation time of 72h. Also, the key enzymes related to VFA formation exhibited the highest activities at ultrasonic energy density of 1.0kW/L, which resulted in the greatest VFA production during WAS fermentation at pH 10.0.
Impregnated resins prepared by the immobilization of an ionic liquid (IL, Cyphos IL-101, tetradecyl(trihexyl)phosphonium chloride) into a composite biopolymer matrix (made of gelatin and alginate) have been tested for recovery of Bi(III) from acidic solutions. The concentration of HCl slightly influenced Bi(III) sorption capacity. Bismuth(III) sorption capacity increased with IL content in the resin but non-linearly. Maximum sorption capacity reached 110-130mgBig(-1) in 1M HCl solutions. The mechanism involved in Bi recovery was probably an ion exchange mechanism, though it was not possible to establish the stoichiometric exchange ratio between BiCl(4)(-) and IL. Sorption kinetics were investigated through the evaluation of a series of parameters: metal concentration, sorbent dosage, type and size of sorbent particles and agitation speed. In order to reinforce the stability of the resin particles, the IL-encapsulated gels were dried; this may cause a reduction in the porosity of the resin particle and then diffusion limitations. The intraparticle diffusion coefficients were evaluated using the Crank's equation. Additionally, the pseudo-first-order and pseudo-second-order equations were systematically tested on sorption kinetics. Metal can be desorbed from loaded resins using either citric acid or KI/HCl solutions. The sorbent could be recycled for at least three sorption/desorption cycles.
The concentrations and behaviour of 105 different active pharmaceutical ingredients (APIs) in the aqueous phase of sewage water within a municipal sewer collection system have been investigated. Sewage water samples were gathered from seven pump stations (one of which was located within a university hospital) and from sewage water treatment influent and effluent. The targeted APIs were quantified using a multi-residue method based on online solid phase extraction liquid chromatography tandem mass spectrometry. The method was thoroughly validated and complies with EU regulations on sample handling, limits of quantification, quality control and selectivity. 51 APIs, including antibiotics, antidepressants, hypertension drugs, analgesics, NSAIDs and psycholeptics, were found frequently within the sewer collection system. API concentrations and mass flows were evaluated in terms of their frequency of detection, daily variation, median/minimum/maximum/average concentrations, demographic dissimilarities, removal efficiencies, and mass flow profiles relative to municipal sales data. Our results suggest that some APIs are removed from, or introduced to, the aqueous phase of sewage waters within the studied municipal collection system.
A supercritical fluid extraction (SFE) procedure for Irgarol 1051 (i.e. 2-(tert-butylamino)-4-(cyclopropylamino)-6-(methylthio)-1,3,5-triazine) determination in marine sediments, which minimises the solvent usage, is developed and compared to a conventional extraction technique (i.e. sonication). First, the use of methanol (MeOH) in the presence of trifluoroacetic acid (TFA) as secondary modifier of supercritical carbon dioxide was evaluated. Extraction efficiency was strongly dependent on the modifier content but lesser on pressure (100-410 bar) and temperature (60-200 degrees C). In the selected extraction conditions (20% MeOH/TFA 0.65M, 370 bar, 150 degrees C) recoveries higher than 87% were obtained and the limit of detection was 3 ngg(-1) and the relative standard deviation of 10% (N=3) by GC coupled to mass spectrometry (GC-MS) in the electron impact mode. The developed SFE procedure is more convenient to extract Irgarol 1051 than the agitation plus sonication methods concerning on solvent usage (1.5 vs. 20 mL) being compatible with immunochemical procedures avoiding any solvent transfer step. The developed SFE combined with immunoaffinity chromatography (IAC) is highly selective allowing the determination of Irgarol by gas chromatography with nitrogen-phosphorus detection or in sediments at low ngg(-1) level (11-35 ngg(-1)) from Mediterranean marina and harbour sediments.
Irgarol 1051 is a recent herbicidal compound, inhibitor of photosynthesis, used in antifouling paints. This toxic is persistent in aquatic environments, with low abiotic and biotic degradation, highly phytotoxic, and has already been detected in estuaries and coastal areas, with suspected negative impacts on non-target organisms (aquatic plants and algae). We measured the toxicity of Irgarol 1051 to macrophytes and phytoplankton from Lake Geneva (between Switzerland and France) by determining chlorophyll fluorescence yield, and phytoplankton primary production. Long-term toxicity for phytoplankton was estimated in a microcosm study, and growth inhibition tests were performed with isolated algal strains. The concentration of Irgarol 1051 was analysed in the water, and the most polluted site showed a higher level (up to 135 ng/L) than the lowest observed effect concentration for phytoplankton (8-80 ng/L), while the macrophytes appeared to be more tolerant to Irgarol 1051 in short-term tests. The microcosm study showed that phytoplankton structure might be even more sensitive to Irgarol 1051.
In this study we investigated the co-occurrence of resistance to non-beta-lactams among cefotaxime-resistant extended-spectrum beta-lactamase (ESBL) producers (ESBL(+)) versus non-ESBL producers (ESBL(-)), from aquatic environments. Higher prevalence of resistance to tetracycline, fluoroquinolones and aminoglycosides were observed in ESBL(+). Among ESBL(+) resistant to tetracycline (n = 18), tet(A) was detected in 88.9% and tet(B) in 16.7%. Among fluoroquinolone-resistant-ESBL(+) (n = 15), aacA4-cr and qnrVC4 were identified in 26.6% and 40% strains, respectively. The qnrVC4 gene was detected for the first time in Pseudomonas sp. and Escherichia coli. Class 1 integrase genes were detected in 56.41% of ESBL(+) and in 27.67% ESBL(-). Gene cassette arrays identified conferred resistance to aminoglycosides (aadA-type genes and aacA4), trimethoprim (dfrA17), chloramphenicol (catB8), fluoroquinolones (qnrVC4) and beta-lactams (blaOXA-10). Conjugation experiments were performed with CTX-M-producers. Transconjugants showed multiresistance to 3 or more classes of antibiotics, and conjugative plasmids were assigned to IncF, IncK and IncI1 replicons. Results obtained showed that co-selection of resistance to aminoglycosides, quinolones and tetracyclines is prevalent among ESBL-producers and that these features are successfully mobilized by IncF, IncK and IncI1 conjugative plasmids. This study reinforces the importance of natural aquatic systems as reservoir of mobile genetic platforms carrying multiple resistance determinants. Moreover, to the best of our knowledge, this constitutes the first observation of IncK::CTX-M-3 in Aeromonas hydrophila and the first report of IncK plasmids in Portugal.
This study addresses the photobleaching (discoloration) and total organic carbon (TOC) reduction of the nonbiodegradable azo-dye Orange II with H5FeW12O40 in homogeneous solution and on H5FeW12O40/silica-structured fabrics in heterogeneous processes. The H5FeW12O40/silica fabric is able to catalyze Orange II bleaching only under light irradiation. In the dark, long-lived intermediates produced in solution were observed to preclude further degradation. The most efficient polytungstate was selected based on the performance during Orange II photobleaching in the presence of H2O2. The H5FeW12O40/silica fabric needed similar to60 min to photobleach 85% of an Orange II (0.2 mM) solution. The amount of H2O2 and the pH was optimized for the photobleaching of Orange II on the H5FeW12O40/ silica fabric. The photobleaching was more efficient as the intensity of the applied light was increased. Repetitive photobleaching cycles of Orange II (0.2 mM) on the H5FeW12O40/silica-structured fabric proceeded with the same kinetics, showing the stability of this fabric against oxidative radical attack and the absence of Fe-ions leaching into the solution during Orange II discoloration. The photobleaching times were similar for different concentrations of Orange II suggesting that it is controlled by mass transfer and not by a diffusion-controlled processes. The loading of the silica fabric was determined by elemental analysis to be 7.1% for Fe and 27.2% for W. By electron diffuse spectrometry W-clusters were identified on the silica fabrics and by high-resolution electron microscopy the W-clusters of the catalyst were observed to have sizes between 1 and 2 nm. By X-ray photoelectron spectroscopy, it is observed that the W-oxidation state is higher for the unused catalysts than in the catalyst after Orange II photobleaching. This lends support to a photo-assisted Fenton-like mechanism taking place in the H5FeW12O40/ silica-structured fabrics during Orange II decomposition.
The potential of using alumina, activated bauxsol-coated sand (ABCS), bark, bauxsol-coated sand (BCS), fly ash (FA), granulated activated carbon (GAC), granulated ferric hydroxide (GFH), iron oxide-coated sand (IOCS), natural zeolite (NZ), sand, and spinel (MgAl(2)O(4)) as sorbents for removing heavy metals from stormwater are investigated in the present study. The ability of the sorbents to remove a mixture of As, Cd, Cr, Cu, Ni and Zn from synthetic stormwater samples were evaluated in batch tests at a starting pH of 6.5. The metal speciation and saturation data is obtained using the PHREEQ-C geochemical model and used to elucidate the sorption data. It is found that BCS, FA, and spinel have significantly higher affinity towards heavy metals mainly present as cationic or non-charged species (i.e. Cd, Cu, Ni and Zn) compared to those present as anionic species (i.e. As and Cr). However, IOCS, NZ and sand have higher affinity towards As and Cr, while alumina has equally high affinity to all tested heavy metals. The Freundlich isotherm model is found to fit the data in many cases, but ill fitted results are also observed, especially for FA, BCS and GAC, possibly due to leaching of some metals from the sorbents (i.e. for FA) and oversaturated conditions making precipitation the dominant removal mechanism over sorption in batches with high heavy metal concentrations and pH. Calculated sorption constants (i.e. K(d)) are used to compare the overall heavy metal removal efficiency of the sorbents, which in a decreasing order are found to be: alumina, BCS, GFH, FA, GAC, spinel, ABCS, IOCS, NZ, bark, and sand. These findings are significant for future development of secondary filters for removal of dissolved heavy metals from stormwater runoff under realistic competitive conditions in terms of initial heavy metal concentrations, pH and ionic strength.
Regeneration of ion exchange resins with NaCl produces brine containing high concentrations of nitrate that can be difficult to remove using standard biological, physical, or chemical technologies. In this study. Halomonas campisalis (ATCC #700597) (Mormile et al., 1999) was shown to completely reduce nitrate at 125 g/L NaCl and pH 9. This organism was also used in experiments to determine nitrate-reduction rates and biomass yields. Kinetic parameters were measured separately with glycerol, lactate. acetate, ethanol, and methanol. The specific nitrate-reduction rate coefficient was highest in cultures amended with acetate, while lactate and glycerol (a natural osmoticum in hypersaline environments) had lower reduction rates. No evidence of nitrate reduction was observed when ethanol or methanol was provided as an electron donor. Kinetic modeling provided values for nitrate and nitrite-reduction rate coefficients and for biomass yields. Measured rates and yields were similar to reported parameters obtained from non-halophilic nitrate-reducing cultures under low salt concentrations. Therefore, for highly saline solutions, the use of halophiles to selectively remove nitrate from these brines may represent a viable treatment option.
Recent work has suggested that bacteriophages infecting Bacteroides are a potential tool for faecal source tracking, but that different host strains may be needed for different geographic areas. This study used a recently identified strain of Bacteroides (GB-124) to detect human sources of faecal pollution in a river catchment in southeast England (UK). A total of 306 river water, municipal wastewater and animal samples were obtained over a 16-month period. Bacteriophages capable of infecting GB-124 were present in all municipal wastewaters but were not detected in faecal samples from animals, and were detected at significantly lower levels (P< 0.001) in river waters directly downstream of a dairy farm. This last observation was despite the presence of high levels of faecal indicator bacteria at this site. The study suggests that GB-124 appears to be specific to human faeces. As such it may represent an effective and low-cost method of faecal source identification.
Degradation of Aroclor 1242 was studied in granular biofilm reactors with limited aeration. An aerobic biphenyl degrader, Rhodococcus sp. M5, was used to supplement a natural bacterial population present in a "bioaugmented" reactor, while the "non-bioaugmented" reactor only contained natural granular sludge. The bioaugmentation, however appeared to have no effect on the reactor performance. Aroclor measurements showed its disappearance in both reactors with only 16-19% of Aroclor recovered from the reactor biomass and effluent. Simultaneously, a chlorine balance indicated that dechlorination occurred at a specific rate of 1.43 mg PCB (g volatile suspended solids)(-1) d(-1), which was comparable to the observed rate of Aroclor disappearance. Intermediates detected in both reactors were biphenyl, benzoic acid, and mono-hydroxybiphenyls. This suggests that a near-complete mineralization of Aroclor can be achieved in a single-stage anaerobic/aerobic system due to a combination of reductive and oxidative degradation mechanisms.
The feasibility of long-term (>3 years), low-temperature (4–15 °C) and anaerobic bioreactor operation, for the treatment of acidified wastewater, was investigated. A hybrid, expanded granular sludge bed–anaerobic filter bioreactor was seeded with a mesophilic inoculum and employed for the mineralization of moderate-strength (3.75–10 kg chemical oxygen demand (COD) m⁻³) volatile fatty acid-based wastewaters at 4–15 °C. Bioprocess performance was assessed in terms of COD removal efficiency (CODRE), methane biogas concentration, and yield, and biomass retention. Batch specific methanogenic activity assays were performed to physiologically characterise reactor biomass.
e Properties of the three resins used for the removal of poorly soluble organic compounds.
e Effects of different rinsing of the filter cake on the yield and isotopic composition of cyanide after the removal of excess sulfate by precipitation as barium sulfate.
The occurrence of ferrocyanide, Fe(CN)(6)(4-), in aqueous environments is of concern, since it is potentially hazardous. For tracing the source of ferrocyanide in contaminated water we developed a method that relies on the determination of the stable isotope ratios of (13)C/(12)C and (15)N/(14)N of this complexed cyanide (CN) after precipitating it as cupric ferrocyanide, Cu(2)[Fe(CN)(6)] · 7H(2)O. The precipitate was combusted and the isotope ratios were determined by continuous flow isotope ratio mass spectrometry. At first, ferrocyanide enrichment from synthetic water containing cyanide with known isotopic composition was studied by using six commercial anion-exchange resins. Five resins revealed a quick and complete sorption of ferrocyanide. A nearly quantitative desorption was achieved using NaCl solutions of 5 and 10% by weight for four resins. Subsequent determination of the δ(13)C(CN) and δ(15)N(CN) values of the ferrocyanide revealed that no significant isotope fractionation occurred during this procedure. These results were reproduced even in column experiments using larger water volumes. Potential interferences were also addressed. Sulfate in excess competes for exchange sites but can be precipitated as BaSO(4) prior to ferrocyanide enrichment. Non-cyanide carbon compounds may co-precipitate with cupric ferrocyanide, thus possibly modifying the isotope ratios. However, neither dissolved inorganic carbon nor highly soluble organic compounds did interfere with the method. Poorly soluble organics like BTEX and PAH can be eliminated by passing the samples through appropriate adsorber resins in a prior step. The proposed method is an excellent way of precise determination of the stable cyanide-carbon and cyanide-nitrogen isotope ratios in ferrocyanide-containing aqueous samples, which was successfully applied to four contaminated groundwater samples since measured aqueous isotopes ratios match those of corresponding cyanide-bearing solid wastes.
The breakage and re-growth of flocs formed by polyaluminum chloride (PAC) and the Al(13)O(4) (OH)(24)(7+) (Al(13) for short) polymer were comparatively evaluated for the coagulation of humic acid (HA). A series of jar experiments were conducted to investigate the impacts of shear rate and solution pH on flocs breakage and re-aggregation potential. Results indicated that the responses of flocs to the increasing shear force and solution pH depend on the coagulant used. The ability of flocs to resist breakage decreased with the increasing shear rate. For all levels of shear force investigated in this study, the flocs formed by Al(13) polymer were weaker than those of PAC, whereas Al(13) polymer displayed a better recoverability than PAC. The similar results were obtained when pH of solution was changed. The flocs generated in acidic conditions were stronger and more recoverable than those generated in alkaline conditions no matter which coagulant was used.
To investigate the structural composition of natural organic matter (NOM), a 3-step micro- and ultrafiltration procedure was applied to 3 surface waters from southern Germany, and fractions from all filtration steps were collected. The NOM was characterized using solid-state 13C and 15N nuclear magnetic resonance (NMR) techniques. Routine integration of the 13C NMR spectra and extended data analysis procedures were carried out for a quantitative comparison of the structural components as well as for the elucidation of structural fractionation patterns. A common feature of the large molecular size fractions was the predominance of polysaccharide material, with the dissolved high molecular weight organics being mostly enriched in N-acetylated polysaccharides derived from microbial leftovers. Aromatic structures like lignin and tannin derivatives were most abundant in the intermediate size fraction. All membranes were found to be highly permeable for branched aliphatics, i.e. isoprenoids. Fouling layers of the ultrafiltration membrane were significantly enriched in long-chain aliphatics (lipids). Biofouling was not observed on any of the membranes. Overall, a strong interdependence between the chemical structural characteristics of NOM components and their size, shape, or interaction characteristics could be shown. The results provide the basis for a better understanding of water process technologies as treatment effectiveness is strongly dependent on the chemical composition and the "size" distribution of NOM.
It is difficult to assess the biological consequences of diffuse water contamination by micropollutants which are present in rivers at low, even sublethal levels. River biofilms, which respond quickly to changes of environmental parameters, are good candidates to acquire knowledge on the response of aquatic organisms to diffuse chemical contamination in the field. The study was designed as an attempt to link biofilm metal tolerance and metallic contamination in a field survey covering 13 different sampling sites in the Seine river basin (north of France) with low contamination levels. Cd and Zn tolerance of heterotrophic communities was assessed using a short-term toxicity test based on β-glucosidase activity. Metal tolerance levels varied between sites but there was no obvious correlation between tolerance and corresponding water contamination levels for Cd and Zn. Indeed, metallic contamination at the sampling sites remained subtle when compared to water quality standards (only two sampling sites had either Zn or both Cu and Zn concentrations exceeding the Environmental Quality Standards set by the EU Water Framework Directive). Yet, multivariate analysis of the data using Partial Least Squares Regression revealed that both metallic and environmental parameters were important variables explaining the variability of metal tolerance levels. Automated Ribosomal Intergenic Spacer Analysis (ARISA) was also performed on both bacterial and eukaryotic biofilm communities from the 13 sampling sites. Multivariate analysis of ARISA fingerprints revealed that biofilms with similar tolerance levels have similar ARISA profiles. Those results confirm that river biofilms are potential indicators of low, diffuse contamination levels of aquatic systems.
This work presents (131)I (t(½) = 8.04 d) concentrations in sewage effluent from the Stony Brook Water Pollution Control Plant (WPCP), a small plant serving a regional thyroid cancer treatment facility in Stony Brook, NY, USA. The concentrations detected in sewage effluent ranged from 1.8 ± 0.3 to 227 ± 2 Bq L(-1). The primary source of (131)I is excreta from thyroid cancer inpatients treated at the Stony Brook University Medical Center. Based on several time series measurements following known inpatient treatments, the mean sewage half-life (T(s)) of iodine is 3 d in this plant. The T(s), analogous to a radioactive half-life, describes the time it takes for half of a wastewater component to be removed from a WPCP. Flow recycling, or activated sludge, used to maintain bacterial populations necessary for sewage treatment causes iodine to remain in this plant far longer than its hydraulic retention time. The experimental results suggest that most (131)I entering the Stony Brook WPCP leaves in sewage effluent, not in sewage sludge. Patient treatments can result in continuous discharges of (131)I to surface waters where it can be used as a tracer of sewage-derived material and to understand the behavior of (131)I in aquatic environments.
Dispersion of pollutants in aquatic environments depends on their uptake by suspended solids. This work deals with the uptake kinetics of 133Ba (gamma-emitter and a good analogue of 226Ra) by suspended estuarine sediments (which can be resuspended into the water column under certain conditions). This study presents a wide set of tracing experiments, including second tracing, decantation and desorption processes. The purpose is to characterize 133Ba uptake by sediments and to investigate the use and limitations of box models in order to describe the uptake kinetics. Water and sediment samples were collected in the Huelva estuary (Spain), where environmental 226Ra concentrations have been increased by two phosphate fertilizer industries. Samples were characterized by granulometric, organic carbon content, cation exchange capacity and XRF-EP analyses. Results revealed three-step kinetics, with characteristic times of minutes, hours and days. These results enabled the selection and calibration of a suitable box model and facilitated the testing of its use as a fully predictive tool.
Cyanobacteria are common in eutrophic natural waters. Being favoured by warm, stable and nutrient-enriched waters they may constitute an important part of the phytoplankton community in Wastewater Treatment Plants (WWTP). The phytoplankton communities of two ponds (facultative and maturation) of the WWTP of Esmoriz (North Portugal) were studied, with particular importance given to cyanobacteria. Mouse bioassays were performed with cyanobacteria samples during some of the blooms and ELISA assays specific for hepatotoxic microcystins were carried out. During the study period (January-July 1999) cyanobacteria were frequently dominant in the ponds ranging from 15.2 to 99.8% of the total phytoplankton density. The main species were Planktothrix mougeotii, Microcystis aeruginosa and Pseudanabaena mucicola. Mouse bioassays were performed during Oscillatoria bloom period but the results were negative, in spite of the high cyanobacteria biomass. ELISA assays were performed for both ponds but only in the maturation pond positive values were found. Microcystin concentrations (as MCYST-LR equivalents) varied from 2.3 to 56.0 micrograms/l on the margin of the pond and between 1.7 and 4.6 micrograms/l in the outflow of this pond. These values indicate that WWTP may be a source of contamination of water bodies with cyanobacteria toxins.
Propionate is a key intermediate in the conversion of complex organic matter under methanogenic conditions. Oxidation of this compound requires obligate syntrophic consortia of acetogenic proton- and bicarbonate reducing bacteria and methanogenic archaea. Although H(2) acts as an electron-carrier in these consortia, evidence accumulates that formate plays an even more important role. To make energy yield from propionate oxidation energetically feasible for the bacteria and archaea involved, the concentrations of H(2) and formate have to be extremely low. On the other hand, the diffusion distance of these carriers has to be small to allow high propionate conversion rates. Accordingly, the high conversion rates observed in methanogenic bioreactors are due to the fact that the propionate-oxidizing bacteria and their methanogenic partners form micro-colonies within the densely packed granules.
Top-cited authors
Thomas Ternes
  • Bundesanstalt für Gewässerkunde
Gary Amy
  • King Abdullah University of Science and Technology
Zhiguo Yuan
  • The University of Queensland
Hajer Bader
  • Taibah University
Lars Håkanson
  • Uppsala University