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Carbon dioxide (CO2) enrichment of anaerobic digesters (ADs) without hydrogen addition has been demonstrated to provide a potential solution to manage CO2 streams generated in the water and organic waste sectors, with concomitant increases in methane (CH4) production. This study investigates the CO2 utilization mechanisms, by considering chemical and biological pathways in food waste and sewage sludge ADs. Methanosaetaceae was observed to be the dominant methanogen in sewage sludge ADs (Abundance of 83.8–98.8%) but scarce in food waste units (3.5–5.8%). Methanosarcinaceae was dominant in food waste (14.3–32.4%), likely due to a higher tolerance to the free ammonia nitrogen concentration recorded (885 mg L−1). RMethanosaetaceae (ratio of Methanosaetaceae fluorescence signal between test and control) of 1.45 and 1.79 were observed for sludge ADs enriched once and periodically with CO2, respectively (p-value <.05), suggesting a higher Methanosaetaceae activity associated with CO2 enrichment. Reduction of CO2 by homoacetogenesis followed by acetoclastic methanogenesis was proposed as a CO2 utilization mechanism, which requires validation by radiolabelling or carbon isotope analysis. [ABSTRACT FROM AUTHOR]

Municipal effluents contain heavy metals in particular copper, lead, nickel, zinc and mercury. The concern regarding the impact of these contaminants in the aquatic environment is reflected in the latest criteria revisions to water-related legislation, such as the Clean Water Act in the US and the Water Framework Directive in Europe. These revisions may lower metal concentrations considered acceptable in final effluents. The study of metal behaviour within the wastewater treatment process is crucial to develop and optimise systems to achieve acceptable metal concentrations in effluent discharges. To comply with more stringent environmental quality standards, utilities may require the implementation of additional treatment technologies. This review evaluates the performance of conventional municipal wastewater treatment processes, that is, primary sedimentation and biological treatment via the activated sludge and trickling filter processes. The mechanisms and parameters influencing metal removal are discussed to evaluate how an understanding of metal behaviour within wastewater treatment processes may allow optimisation and enhancement of conventional treatment processes, or inform the selection of new technologies to enhance trace metal removal. The performance of advanced treatment technologies capable of removing metals from municipal wastewater under real-world conditions has also been evaluated. [ABSTRACT FROM AUTHOR]

To ensure compliance with regulatory standards, it is important to examine the potential of treatment technologies to enhance trace metal removal from wastewater. This study investigated the effectiveness of coagulation–flocculation at removing trace metals from humus effluent with ferric chloride (FeCl3), the synthetic polymer polyethyleneimine (PEI) and the biopolymers chitosan and floculan. Effluent samples were collected from a trickling filter treatment works operating in the UK and contained 21 ± 4 μg/L Cu, 0.8 ± 0.1 μg/L Pb, 4 ± 1 μg/L Ni and 43 ± 9 μg/L Zn. The influence of coagulant dosage and the velocity and time of the slow mixing stage were studied via a series of jar tests. Chitosan and PEI had a moderate effect on the removal of trace metals (≤ 35%). FeCl3 removed 48% Cu, 56% Pb and 41% Zn at the optimised dose of 0.10 mg/L. At the optimised dose of 0.25 mg/L, floculan removed 77% Cu, 68% Pb and 42% Zn. The dominant mechanism for particle removal by FeCl3 was enmeshment in the precipitates (i.e. sweep flocculation), whereas, for floculan, inter-particle bridging was the dominant removal mechanism. Overall, FeCl3 and floculan were found to be most effective at removing trace metals from wastewater. [ABSTRACT FROM AUTHOR]

It is important to understand the fate of Hg and Sb within the wastewater treatment process so as to examine potential treatment options and to ensure compliance with regulatory standards. The fate of Hg and Sb was investigated for an activated sludge process treatment works in the UK. Relatively high crude values (Hg 0.092 μg/L, Sb 1.73 μg/L) were observed at the works, whilst low removal rates within the primary (Hg 52.2 %, Sb 16.3 %) and secondary treatment stages (Hg 29.5 %, Sb −28.9 %) resulted in final effluent concentrations of 0.031 μg/L for Hg and 2.04 μg/L for Sb. Removal of Hg was positively correlated with suspended solids (SS) and chemical oxygen demand (COD) removal, whilst Sb was negatively correlated. Elevated final effluent Sb concentrations compared with crude values were postulated and were suggested to result from Sb present in returned sludge liquors. Kepner Tregoe (KT) analysis was applied to identify suitable treatment technologies. For Hg, chemical techniques (specifically precipitation) were found to be the most suitable whilst for Sb, adsorption (using granulated ferric hydroxide) was deemed most appropriate. Operational solutions, such as lengthening hydraulic retention time, and treatment technologies deployed on sludge liquors were also reviewed but were not feasible for implementation at the works. [ABSTRACT FROM AUTHOR]

Anaerobic treatment of municipal wastewater offers the prospect of a new paradigm by reducing aeration costs and minimizing sludge production. It has been successfully applied in warm climates, but does not always achieve the desired outcomes in temperate climates at the biochemical oxygen demand (BOD) values of municipal crude wastewater. Recently the concept of ‘fortification' has been proposed to increase organic strength and has been demonstrated at the laboratory and pilot scale treating municipal wastewater at temperatures of 10–17°C. The process treats a proportion of the flow anaerobically by combining it with primary sludge from the residual flow and then polishing it to a high effluent standard aerobically. Energy consumption is reduced as is sludge production. However, no new treatment process is viable if it only addresses the problems of traditional pollutants (suspended solids – SS, BOD, nitrogen – N and phosphorus – P); it must also treat hazardous substances. This study compared three potential municipal anaerobic treatment regimes, crude wastewater in an expanded granular sludge blanket (EGSB) reactor, fortified crude wastewater in an EGSB and crude wastewater in an anaerobic membrane bioreactor. The benefits of fortification were demonstrated for the removal of SS, BOD, N and P. These three systems were further challenged with the removal of steroid estrogens at environmental concentrations from natural indigenous sources. All three systems removed these compounds to a significant degree, confirming that estrogen removal is not restricted to highly aerobic autotrophs, or aerobic heterotrophs, but is also a faculty of anaerobic bacteria. [ABSTRACT FROM PUBLISHER]

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Methane (CH) formation in wastewater treatment is linked to long residence times under anaerobic conditions such as those in sewers and primary treatment units. Emissions of this methane to the atmosphere can occur under turbulent flows and, potentially, during aeration in an activated sludge plant. An online, 8-week monitoring campaign of CH emissions and operational conditions was conducted to study emissions from a full-scale nitrifying activated sludge plant (ASP). Significant emissions were found throughout the aerated lane, with the highest values observed two thirds down the lane. Emissions had high diurnal and spatial variability, with values ranging from 0.3 to 24 g CH/h. No significant correlations were found between dissolved oxygen, aeration or influent loads. The results suggest that emissions are linked to upstream process conditions, with potential for methane generation in-lane due periods of limited oxygen availability. The dynamic oxygen profile observed suggests that aerobic and anoxic conditions coexist in the lane, leading to limited oxygen diffusion from the bulk liquid to the inner regions of the floc where anoxic/anaerobic layers may allow methanogenic microorganisms to survive. The average emission factor was 0.07 % of removed chemical oxygen demand, giving a total of 668 kg CH/year and 14,000 CO equivalents/year. The operational carbon associated with the energy requirements of the ASP increased by 5 %. With emerging legislation requiring the reporting of greenhouse gas emissions, the carbon impact may be significant, particularly as the industry moves towards a carbon-reducing future. Therefore, an adequate profiling of full-scale emissions is critical for future proofing existing treatment technologies. [ABSTRACT FROM AUTHOR]

An ultra-performance liquid chromatography method using a triple quadrupole mass spectrometer was developed and validated for the determination of steroid oestrogens in wastewater matrices. To date, analytical methods established in the literature for 17α-ethinylestradiol have been unable to achieve the proposed predicted no effect concentration of 0.1 ng l−1. The extensive sample pretreatment and analytical methodology proposed herein enable 17α-ethinylestradiol to be determined at very low background concentrations with a theoretical method detection limit of 0.06 ng l−1which has been applied in real environmental matrices. During the validation process, a trickling filter wastewater treatment works was monitored to demonstrate the method's application. Oestrogen removal across the filters demonstrated good removals of natural free oestrogens (≥62.0%) with lower removals of the synthetic oestrogen 17α-ethinylestradiol (29.2%) from wastewaters at 10°C. The method's application illustrates its capability of detecting oestrogen concentrations in real wastewater samples comprising complex organics of comparatively high concentration. Furthermore, a complete process mass balance for 17α-ethinylestradiol is now attainable which has previously posed a challenge owing to the low environmental concentrations typically exhibited, but more significantly as a result of the lower sensitivity inherent in previously reported analytical methods. [ABSTRACT FROM PUBLISHER]

BACKGROUND There is a need to examine the impact of anaerobic reactor type and wastewater strength on anaerobic-aerobic two-stage biological systems for temperate wastewater treatment An expanded granular sludge blanket reactor and an anaerobic membrane bioreactor for crude wastewater treatment with downstream aerobic biological treatment were studied together with increasing the organic concentration by fortifying the crude wastewater with primary sludge. RESULTS A chemical oxygen demand and ammonia compliant effluent was produced from the anaerobic-aerobic two-stage process. Due to the enhanced organics removal achieved by the membrane, a lower denitrification rate, kd, was recorded for the anaerobic membrane bioreactor effluent treatment. However, the residual organic carbon in the anaerobic effluents from both the expanded granular sludge blanket reactor and the anaerobic membrane bioreactor treating crude wastewater was not of sufficient quality to support denitrification. Complete nitrification was achieved during downstream treatment of the fortified effluent. In addition, fortification increased kd to values analogous to exogenous carbon substrates. CONCLUSIONS It is postulated that fortification currently presents the most sustainable strategy for anaerobic-aerobic two-stage biological systems due to a combination of enhanced methane production and denitrification. © 2013 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

BACKGROUND Fortification utilizes pre-hydrolysed sludge to increase organic sewage strength for support of anaerobic development. Significantly, enhancing organic strength also permits organic loading rate to be de-coupled from hydraulic retention time, enabling greater contact times for temperate, municipal wastewater. This study therefore describes the application of fortification to facilitate anaerobic treatment of crude wastewater in temperate climates. RESULTS Fortification with primary sludge significantly increased methane ( CH4) from 0.021 m3CH4 m-3 for crude wastewater to 0.095 m3CH4 m-3. This increased yield demonstrates that fortification enables methane yields equivalent to conventional full-flow anaerobic treatment through only partial treatment of wastewater (up to 50%) which lowers both capital and operational costs. Total chemical oxygen demand ( COD) and soluble COD removals of 89% and 5 % were recorded following fortified crude wastewater treatment, permitting a similar effluent COD profile to treated crude wastewater. Pre-hydrolysis of the fortified wastewater maximized methane production to 0.156 m3CH4 m-3. Furthermore, a similar yield was reported for wastewater fortified with pre-hydrolysed waste activated sludge, providing new opportunities for on-site treatment with concomitant benefits in sludge reduction and enhanced energy production. Solids breakthrough occurred with pre-hydrolysed fortification and reduced effluent quality; it is postulated that optimizing pre-treatment and upflow velocity will improve effluent quality to that attained with standard fortification. However, fortification also reduced losses of dissolved methane in the effluent stream. CONCLUSIONS With a reduction in aeration requirements and potential savings in primary treatment and sludge treatment, fortification represents a major advance upon current practice. © 2012 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

An ultra performance liquid chromatography method coupled to a triple quadrupole mass spectrometer was developed to determine nonylphenol and 15 of its possible precursors (nonylphenol ethoxylates and nonylphenol carboxylates) in aqueous and particulate wastewater matrices. Final effluent method detection limits for all compounds ranged from 1.4 to 17.4 ng l in aqueous phases and from 1.4 to 39.4 ng g in particulate phases of samples. The method was used to measure the performance of a trickling filter wastewater treatment works, which are not routinely monitored despite their extensive usage. Relatively good removals of nonylphenol were observed over the biological secondary treatment process, accounting for a 53 % reduction. However, only an 8 % reduction in total nonylphenolic compound load was observed. This was explained by a shortening in ethoxylate chain length which initiated production of shorter polyethoxylates ranging from 1 to 4 ethoxylate units in length in final effluents. Modelling the possible impact of trickling filter discharge demonstrated that the nonylphenol environmental quality standard may be exceeded in receiving waters with low dilution ratios. In addition, there is a possibility that the EQS can be exceeded several kilometres downstream of the mixing zone due to the biotransformation of readily degradable short-chained precursors. This accentuates the need to monitor 'non-priority' parent compounds in wastewater treatment works since monitoring nonylphenol alone can give a false indication of process performance. It is thus recommended that future process performance monitoring and optimisation is undertaken using the full suite of nonylphenolic moieties which this method can facilitate. [ABSTRACT FROM AUTHOR]

An anaerobic waste stabilisation pond (AWSP) has been assessed to enable energy neutral wastewater treatment at decentralised works. During start-up, chemical oxygen demand (COD) removal efficiency was comparable to full-scale AWSPs operated in moderate climates, thereby establishing the potential for treating wastewater in the less conducive European climate. The linear relationship between COD removal and time demonstrated that the AWSP had not reached steady-state, indicating further improvement in COD removal is expected. Data modelled on a 10 000 population equivalent catchment indicated that integrating an AWSP upstream of trickling filters presented the optimum configuration to minimise on-site electrical demand. Anaerobic WSP can generate sufficient electricity onsite to offset electrical demand. Anaerobic WSP can generate sufficient electricity onsite to offset electrical demand, recording a net on-site energy balance of +379·5 kWhe d. Using an AWSP for on-site sludge treatment also reduced exported sludge volume, markedly reducing the wastewater treatment total carbon dioxide equivalent emissions (carbon footprint) compared to conventional technologies. This study established AWSP as a significant future technology for sustainable decentralised wastewater treatment. [ABSTRACT FROM AUTHOR]

Intermittent aeration of activated sludge plants (ASPs) is a potential strategy that may help deliver reduced operational costs while providing an adequate effluent quality. This review paper critically assesses the implications of temporary turning aeration off in continuous flow nitrifying ASPs, including impact on dissolved oxygen concentrations, process biology and operational parameters. The potential savings and pitfalls of the approach are further illustrated through an example scenario. Findings from this review indicate rapid dissolved oxygen depletion times of 1–60 minutes and a significant reduction of nitrification rates from 0.12 to less than 0.04 g NH4-N/g VSS/d. Further negative impacts include a potential increase in nitrous oxide emissions from 0.07% to 27% N2O-N per mole of NH4-N oxidized; enhanced filamentous bacteria growth; a noticeable increase in effluent turbidity developing within one hour of air supply interruption; and, if no mechanical mixing is in place, risk of mixed liquor suspended solids settling in the bioreactor within short times (23–53 min). However, the potential savings in terms of aeration costs could amount to 33%–45% if instrumentation adequacy and impact on process biology and carbon equivalent emissions are excluded from the economic analysis. Further research on the areas of nitrous oxide emissions and the use of hybrid systems to provide resilience and robustness to the intermittent operation of continuous flow nitrifying ASPs is recommended. [ABSTRACT FROM PUBLISHER]

The partitioning of steroid estrogens in wastewater treatment and receiving waters is likely to influence their discharge to, and persistence in, the environment. This study investigated the partitioning behaviour of steroid estrogens in both laboratory and field studies. Partitioning onto activated sludge from laboratory-scale Husmann units was rapid with equilibrium achieved after 1 h. Sorption isotherms and Kd values decreased in the order 17α-ethinyl estradiol > 17α-estradiol > estrone > estriol without a sorption limit being achieved (1/ n >1). Samples from a wastewater treatment works indicated no accumulation of steroid estrogens in solids from primary or secondary biological treatment, however, a range of steroid estrogens were identified in sediment samples from the River Thames. This would indicate that partitioning in the environment may play a role in the long-term fate of estrogens, with an indication that they will be recalcitrant in anaerobic conditions. [ABSTRACT FROM AUTHOR]

On 3 October 2007, 40 participants with diverse expertise attended the workshop Tamiflu and the Environment: Implications of Use under Pandemic Conditions to assess the potential human health impact and environmental hazards associated with use of Tamiflu during an influenza pandemic. Based on the identification and risk-ranking of knowledge gaps, the consensus was that oseltamivir ethylester-phosphate (OE-P) and oseltamivir carboxylate (OC) were unlikely to pose an ecotoxicologic hazard to freshwater organisms. OC in river water might hasten the generation of OC-resistance in wildfowl, but this possibility seems less likely than the potential disruption that could be posed by OC and other pharmaceuticals to the operation of sewage treatment plants. The workgroup members agreed on the following research priorities: a) available data on the ecotoxicology of OE-P and OC should be published; b) risk should be assessed for OC-contaminated river water generating OC-resistant viruses in wildfowl; c) sewage treatment plant functioning due to microbial inhibition by neuraminidase inhibitors and other antimicrobials used during a pandemic should be investigated; and d) realistic worst-case exposure scenarios should be developed. Additional modeling would be useful to identify localized areas within river catchments that might be prone to high pharmaceutical concentrations in sewage treatment plant effluent. Ongoing seasonal use of Tamiflu in Japan offers opportunities for researchers to assess how much OC enters and persists in the aquatic environment. [ABSTRACT FROM AUTHOR]

The interaction of tetracycline with struvite during adsorption and precipitation processes was investigated. Tetracycline removal by adsorption was affected by solution pH, contact time, and struvite concentration. The lowest tetracycline removal (8.4%) was observed at pH 7.7, the dissociation constant (pKa2) of tetracycline. Because of the electrostatic repulsion, the amount of tetracycline adsorbed on the surface was low. The small amount of adsorption was the result of surface complexation between tetracycline ions and metal ions. Calcium (Ca2+) ions in the adsorbent enhanced the binding of tetracycline. Freundlich (KF: 0.04, n: 1.49) and Redlich-Peterson (KR: 0.08, αR: 0.98, βR: 0.49) models best defined the equilibrium data. In the case of struvite precipitation, approximately 22% of tetracycline was removed as a result of binding to struvite alongside struvite formation. [ABSTRACT FROM AUTHOR]

This study focused on whether or not atrazine could be degraded by indigenous groundwater bacteria as part of an in situ remediation approach. Groundwater was taken from an unconfined middle upper chalk site where concentrations of atrazine and nitrate were typically in the ranges 0.02-0.2 μg litre-1 and 11.6-25.1 mg NO3-N litre-1 respectively. Sacrificial batch studies were performed using this groundwater spiked with atrazine at a concentration of 10 μg litre-1 in conjunction with a minimal mineral salts liquid (Glu-MMSL) medium which contained glucose as the sole carbon source. Treatments comprised either the Glu-MMSL groundwater cultured bacteria or Pseudomonas sp. strain ADP. Results from sacrificial batches indicated the occurrence of bacterial growth and denitrification as monitored by optical density (absorbance at 600 nm) and NO3-N content. Analysis of atrazine content by solid phase extraction coupled with high-performance liquid chromatography showed no degradation of atrazine over a period of 103 days in either treatment. These results indicated that no acclimatised bacterial community featuring positive degraders to the herbicide atrazine had become established within this chalk aquifer in response to the trace levels encountered. [ABSTRACT FROM AUTHOR]

Contamination of drinking water with bromate (BrO 3 - ) at levels ranging from 0.4 to 60 µ g L -1 may be found following ozonation of water containing background bromide (Br - ). Based on rodent studies, bromate is classified as a “possible human” carcinogen, and drinking water standards of 10–25 µ g L -1 are now implemented in many countries. Bromate is highly soluble, stable in water, and difficult to remove using conventional treatment technologies. This has led to investigations into novel removal techniques, but many have not developed beyond laboratory trials. Analytical advances have recently led to detection of bromate contamination within both rivers and groundwater, which has provided an additional requirement for bromate remediation. This review summarizes bromate environmental characteristics and the regulatory situation, and outlines bromate remediation processes, including filtration, ultraviolet irradiation, catalysis, chemical reduction, activated carbon, and biodegradation. These techniques are evaluated for developmental progress in a potable water system and also for potential application within the natural water environment. [ABSTRACT FROM AUTHOR]

The article “Coagulation-flocculation process with metal salts, synthetic polymers and biopolymers for the removal of trace metals (Cu, Pb, Ni, Zn) from municipal wastewater”, written by Andrew J. Hargreaves, Peter Vale, Jonathan Whelan, Luca Alibardi, Carlos Constantino, Gabriela Dotro, Elise Cartmell and Pablo Campo, was originally published Online First without open access. [ABSTRACT FROM AUTHOR]