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Depending on design capacity, agitators consume about 5 to 20% of the total energy consumption of a wastewater treatment plant. Based on inhabitant-specific energy consumption (kWh PE120-1 a-1; PE120 is population equivalent, assuming 120 g chemical oxygen demand per PE per day), power density (W m-3) and volume-specific energy consumption (Wh m-3 d-1) as evaluation indicators, this paper provides a sound contribution to understanding energy consumption and energy optimization potentials of agitators. Basically, there are two ways to optimize agitator operation: the reduction of the power density and the reduction of the daily operating time. Energy saving options range from continuous mixing with low power densities of 1 W m-3 to mixing by means of short, intense energy pulses (impulse aeration, impulse stirring). However, the following correlation applies: the shorter the duration of energy input, the higher the power density on the respective volume-specific energy consumption isoline. Under favourable conditions with respect to tank volume, tank geometry, aeration and agitator position, mixing energy can be reduced to 24 Wh m-3 d-1 and below. Additionally, it could be verified that power density of agitators stands in inverse relation to tank volume. [ABSTRACT FROM AUTHOR]

Treatment of municipal wastewaters with aerobic granular sludge (AGS) has been extensively researched in the past decade and has now become a mature option for implementation. Aerobic granules are distinguished from activated sludge flocs through their larger size and more compact and spherical structure. Due to these properties, granules settle rapidly and can therefore contribute to compact treatment processes through high sludge concentrations and short settling times. In this review, the factors that promote granulation in treatment processes are identified and discussed and the experience of municipal wastewater treatment with AGS at laboratory-, pilot-, and full-scale are critically evaluated. The most important factors to promote granulation include exposing the biomass to relatively high concentrations of contaminants in sequencing batch reactors, promoting slow-growing microorganisms and applying a relatively short settling time. Enhanced biological phosphorus removal is preferably integrated with AGS and the large size of the granules makes simultaneous nitrification (at the surface of the granules) and denitrification (at the inner, anoxic parts) feasible. We propose directions for future research including further optimization of AGS to obtain stable and low effluent nutrient concentrations in line with increasingly stringent upcoming effluent demands. [ABSTRACT FROM AUTHOR]

In this investigation, a new, green photo-Fenton process for wastewater treatment is proposed, involving the use of a natural iron source and natural additives, deriving from wastes, acting as iron chelators. The use of mineral iron as precursor in the photo-Fenton process, instead of iron salts, was still able to promote E. coli inactivation. Furthermore, the addition of four low weight organic acids (citric, tartaric, ascorbic and caffeic) showed a significant enhancement of the process, reaching total inactivation except for caffeic acid, which showed no significant effects. Two natural products, rich in the promising organic acids were tested as additives, lime and orange juice, plus their infusion. Lime-based additives showed better results compared to orange-based ones, which could be attributed to the excessive addition of organic matter in the orange systems. The formation of photoactive complexes with the mineral iron and the organic acids from the natural products induced the production of reactive species and ferrous ion, sustaining a homogeneous Fenton reaction. Finally, the proposed modified process was tested against different secondary effluents from a municipal wastewater treatment plant. Total bacterial inactivation was reached in the lime-based system, with no visible microorganism regrowth after 48 h. Additionally, the process was able to eliminate 40% of the total identified micropollutants of the secondary effluent reaching almost 50% of removal of the total effluent organic matter. [ABSTRACT FROM AUTHOR]

Maximizing the energy-profitable treatment of municipal wastewater (MW) is of significance to achieve energy-neutral operation for wastewater treatment plant. Direct membrane filtration technology has been considered as an effective way to separate organic carbon from MW for subsequent anaerobic energy-recovering process, but its application is restrained by severe membrane fouling issues. Thus, it is essential to identify the substances in MW that are responsible for membrane fouling and find out efficient anti-fouling methods. In this work, an integrated approach through combining multivariate curve resolution–alternating least squares analysis with infrared attenuated total reflection mapping was adopted to explore the membrane fouling process, and three coagulants, i.e., polyacrylamide, Al 2 (SO 4 ) 3 and FeCl 3 , were individually used to mitigate membrane fouling. Results show that the 1–8 μm biopolymer clusters, i.e., humic-like and protein-like substances, were the predominant foulants in MW. In addition, membrane fouling caused by proteins was found to be more severe than that by humic substances. Coagulation pretreatment was demonstrated to be effective in mitigating membrane fouling. Al 2 (SO 4 ) 3 or FeCl 3 had superior anti-fouling performance comparing to that of polyacrylamide. The dosage of polyacrylamide needs to be optimized according to the actual MW characteristics as its overdose would cause a substantial decline of membrane flux. These results provide a deep understanding of the membrane fouling mechanisms for organic carbon separation from MW and are beneficial for developing efficient and cost-effective membrane fouling mitigation strategies. [ABSTRACT FROM AUTHOR]

This paper covers the pitfalls, recommendations and a new methodology for assessing micropollutant removal efficiencies in wastewater treatment plants. The proposed calculation rules take into account the limit of quantification and the analytical and sampling uncertainty of measured concentrations. We identified six cases for which a removal efficiency value is reliable and four other cases where result is highly variable (uncertain) due to very low or unquantified concentrations in effluent or when the influent--effluent concentrations differential is below the measurement uncertainty. The influence of the proposed calculation rules on removal efficiency values was scrutinized using actual results from a research project. The paper arrives at detailed recommendations for limiting the impact of other sources of uncertainty during sampling (sampling strategy, cleaning and field blank), chemical analyses (suspended solids and sludge) and data processing according to the targeted objectives. [ABSTRACT FROM AUTHOR]

Background: Microbial electrolysis cells (MECs) use bioelectrochemical reactions to remove organic contaminants at the bioanode and produce hydrogen gas at the cathode. High local pH conditions near the cathode can also be utilized to produce struvite from nutrient-rich wastewater. This beneficial aspect was investigated using lab-scale MECs fed with dewatering centrate collected at a local wastewater treatment plant. The main objective was to improve phosphorus recovery by examining various cathode configurations and electric current conditions. Results: The stainless steel mesh (SSM) cathode was relatively inefficient to achieve complete phosphorus recovery because struvite crystals were smaller (a few to tens of micrometers) than the open space between mesh wires (80 μm). As a result, the use of multiple pieces of SSM also showed a limited improvement in the phosphorus recovery up to only 68% with 5 SSM pieces. Readily available organic substrates were not sufficient in the dewatering centrate, resulting in relatively low electric current density (mostly below 0.2 A/m²). The slow electrode reaction did not provide sufficiently high pH conditions near the cathode for complete recovery of phosphorus as struvite. Based on these findings, additional experiments were conducted using stainless steel foil (SSF) as the cathode and acetate (12 mM) as an additional organic substrate for exoelectrogens at the bioanode. With the high electric current (>2 A/mBackground: Microbial electrolysis cells (MECs) use bioelectrochemical reactions to remove organic contaminants at the bioanode and produce hydrogen gas at the cathode. High local pH conditions near the cathode can also be utilized to produce struvite from nutrient-rich wastewater. This beneficial aspect was investigated using lab-scale MECs fed with dewatering centrate collected at a local wastewater treatment plant. The main objective was to improve phosphorus recovery by examining various cathode configurations and electric current conditions. Results: The stainless steel mesh (SSM) cathode was relatively inefficient to achieve complete phosphorus recovery because struvite crystals were smaller (a few to tens of micrometers) than the open space between mesh wires (80 μm). As a result, the use of multiple pieces of SSM also showed a limited improvement in the phosphorus recovery up to only 68% with 5 SSM pieces. Readily available organic substrates were not sufficient in the dewatering centrate, resulting in relatively low electric current density (mostly below 0.2 A/m2). The slow electrode reaction did not provide sufficiently high pH conditions near the cathode for complete recovery of phosphorus as struvite. Based on these findings, additional experiments were conducted using stainless steel foil (SSF) as the cathode and acetate (12 mM) as an additional organic substrate for exoelectrogens at the bioanode. With the high electric current (>2 A/m2), a thick layer of struvite crystals was formed on the SSF cathode. The phosphorus recovery increased to 96% with the increasing MEC operation time from 1 to 7 days. With the high phosphorus recovery, estimated energy requirement was relatively low at 13.8 kWh (with acetate) and 0.30 kWh (without acetate) to produce 1 kg struvite from dewatering centrate. Conclusions: For efficient phosphorus recovery from real wastewater, a foil-type cathode is recommended to avoid potential losses of small struvite crystals. Also, presence of readily available organic substrates is important to maintain high electric current and establish high local pH conditions near the cathode. Struvite precipitation was relatively slow, requiring 7 days for nearly complete removal (92%) and recovery (96%). Future studies need to focus on shortening the time requirement. Keywords: Phosphorus recovery, Municipal wastewater treatment, Struvite, Dewatering downstream, Microbial electrochemistry, Cathode structure ), a thick layer of struvite crystals was formed on the SSF cathode. The phosphorus recovery increased to 96% with the increasing MEC operation time from 1 to 7 days. With the high phosphorus recovery, estimated energy requirement was relatively low at 13.8 kWh (with acetate) and 0.30 kWh (without acetate) to produce 1 kg struvite from dewatering centrate. Conclusions: For efficient phosphorus recovery from real wastewater, a foil-type cathode is recommended to avoid potential losses of small struvite crystals. Also, presence of readily available organic substrates is important to maintain high electric current and establish high local pH conditions near the cathode. Struvite precipitation was relatively slow, requiring 7 days for nearly complete removal (92%) and recovery (96%). Future studies need to focus on shortening the time requirement. [ABSTRACT FROM AUTHOR]

• PN/AMX pilot plant treated municipal wastewater without temperature control. • Stable two-stage system coping with wastewater characteristic fluctuations. • NOB suppression was rapidly started up by overloading and maintained by FNA. • NOB were inactive but still present in the nitritation unit. • Nitrogen removal efficiencies of 80 % were achieved in the anammox reactor. Two-stage partial nitritation (PN) and anammox (AMX) systems showed promising results for applying autotrophic nitrogen removal under mainstream conditions. In this study, a pilot-scale (600 L per reactor) two-stage PN/AMX system was installed in a municipal wastewater treatment plant (WWTP) provided with a high-rate activated sludge (HRAS) system for organic carbon removal. The PN/AMX system was operated without temperature control (ranging from 11 to 28 °C) and was subjected to the same variations in wastewater characteristics as the WWTP (22 to 63 mg NH 4 +- N/L). The developed strategy is simple, does not require the addition of chemicals and is characterised by short start-up periods. The PN process was established by applying a high hydraulic load and maintained by in situ accumulated free nitrous acid (FNA) of 0.015–0.2 mg HNO 2 -N/L. Based on pH value, a controlled aeration strategy was applied to achieve the target nitrite to ammonium ratio in the effluent (1.1 g NO 2 –-N/g NH 4 +-N) to feed the AMX reactor. Although NOB were not fully washed out from the system, nitrite accumulation remained (>99 %) stable with no evidence of NOB activity. In the AMX reactor, an overall nitrogen removal efficiency of 80 % was achieved. Regarding effluent quality, 12 ± 3 mg TN/L was obtained, but 5 mg NO 3 –-N/L was already in the HRAS effluent. The relative abundance of NOB showed a strong negative correlation with the FNA concentration, providing a good strategy for establishing PN under mainstream conditions. [ABSTRACT FROM AUTHOR]

[Display omitted] • VAnMBR achieved better organics removal and fouling control than CAnMBR. • Vibrating membrane concurrently mitigated the reversible and irreversible fouling. • Stronger biogas sparging induced more colloids and EPS in CAnMBR. • VAnMBR enhanced antifouling performance due to the reduced colloids and EPS. • VAnMBR achieved co-benefits of limiting foulant development and its sources. Vibrating membrane (VM) technology has shown low energy demands for in-situ antifouling enhancement in aerobic membrane bioreactors, and is expected to have greater potential for sustainable wastewater treatment applied in anaerobic membrane bioreactors (AnMBRs). However, it remains unclear how VM improves antifouling performance in AnMBRs and how the membrane fouling orignates, develops and diminishes in comparison to the conventional in-situ biogas scouring. This study reported the successful adoption of VM as a effective antifouling strategy for the vibrating AnMBR (V-AnMBR) in long-term (514 days) municipal wastewater treatment. The V-AnMBR showed superior performance, achieving 61.8%–89.4% longer filtration time, 0.68%–1.04% more organics removal and 10.7%–30.6% higher methane yields compared to the conventional biogas-scouring AnMBR (C-AnMBR). Both AnMBRs showed that membrane foulant layer (FL) was dominated in the order of colloid (FL) > EPS (FL) > SMP (FL) , which could be reduced by VM to lower 10.7%–11.5% of the reversible fouling and 21.4%–26.9% of the irreversible fouling compared to biogas scouring. Furthermore, VM minimized the breakdowns of biomass typically caused by biogas scouring and reduced the release of fouling contributors from the mixed liquor, including the half of reductions of biopolymers and aromatic proteins. This work offers in-depth explanations of how membrane fouling develops in AnMBRs treating municipal wastewater, and elucidates the mechanisms of how VM achieves dual benefits on preventing foulant self-development and reducing membrane fouling contributors. Such mechanistic insights into fouling development and membrane fouling contributors would advance the understandings of antifouling mechanisms and guide next-generation sustainable AnMBR technology for mainstream wastewater treatment. [ABSTRACT FROM AUTHOR]

This study aims at assessing the economic performance of a projected full-scale anaerobic membrane bioreactor (AnMBR) for urban wastewater (UWW) treatment at ambient temperature. To this aim, data from an AnMBR demonstration plant (industrial prototype, TRL 6) was used, which was operated for 3 years treating real UWW, allowing gathering a robust set of information for scaling-up to full scale. The obtained results revealed that reactor mixing (0.056–0.124 kWh·kgCOD rem -1; 34–57%), and membrane scouring (0.048–0.120 kWh·kgCOD rem -1; 22–48%) were the main contributors to the total energy demand; while net energy productions between 0.210 and 0.645 kWh·kgCOD rem -1 were achieved. Capital expenditure was highly influenced by UF membranes (€0.029–0.073 kgCOD rem -1; 31–49%), combined heat and power technology for energy recovery (€0.012–0.023 kgCOD rem -1; 8–24%), and reactor construction (€0.07–0.014 kgCOD rem -1; 8–13%); while the main contributors to operating expenditure were energy requirements (€0.042–0.069 kgCOD rem -1; 41–46%), membrane replacement (€0.011–0.028 kgCOD rem -1; 9–17%), and discharge fee (€0.010–0.020 kgCOD rem -1; 9–12%). Total annualized costs showed high variability, between €− 0.003 and 0.188 kgCOD rem -1. Results presents AnMBR as a competitive technology for UWW treatment compared to conventional aerobic technologies (e.g., CAS). Membrane fouling control; hydraulic retention time; biogas requirements for reactor mixing and membrane stirring; and energy recovery efficiency were identified as key parameters for improving economic sustainability of AnMBR technology. [Display omitted] • Economic feasibility of a projected full-scale AnMBR was evaluated. • Net energy productions up to 0.645 kWh·kgCOD rem -1 were achieved. • CAPEX varied between €0.080 and 0.147 kgCOD rem -1. • OPEX was in the €− 0.099–0.041 kgCOD rem -1 range. • TAC between €− 0.003 and 0.188 kgCOD rem -1 was obtained. [ABSTRACT FROM AUTHOR]

In this study, sequencing batch operation was successfully combined with a pilot-scale anaerobic biofilm-modified anaerobic/aerobic membrane bioreactor to achieve anaerobic ammonium oxidation (anammox) without inoculation of anammox aggregates for municipal wastewater treatment. Both total nitrogen and phosphorus removal efficiencies of the reactor reached up to 80% in the 250-day operation, with effluent concentrations of 4.95 mg-N/L and 0.48 mg-P/L. In situ enrichment of anammox bacteria with a maximum relative abundance of 7.86% was observed in the anaerobic biofilm, contributing to 18.81% of nitrogen removal, with denitrification being the primary removal pathway (38.41%). Denitrifying phosphorus removal (DPR) (40.54%) and aerobic phosphorus uptake (48.40%) played comparable roles in phosphorus removal. Metagenomic sequencing results showed that the biofilm contained significantly lower abundances of NO-reducing functional genes than the bulk sludge ( p < 0.01), favoring anammox catabolism in the former. Interactions between the anammox bacteria and flanking community were dominated by cooperation behaviors (e.g., nitrite supply, amino acids/vitamins exchange) in the anaerobic biofilm community network. Moreover, the hydrolytic/fermentative bacteria and endogenous heterotrophic bacteria ( Dechloromonas , Candidatus competibacter ) were substantially enriched under sequencing batch operation, which could alleviate the inhibition of anammox bacteria by complex organics. Overall, this study provides a feasible and promising strategy for substantially enriching anammox bacteria and achieving partial mainstream anammox as well as DPR.

The aim of this research is to study the performance of microalgae Chlamydomonas in orthophosphate removal from municipal wastewater. In this research three treatments in three replications were applied. The treatments were free and immobilized cells of Chlamydomonas in alginate and blank (without microalgae). Three treatments were added into bioreactors with different rate of aeration (0, 1 and 2.5 Lmin-1), containing 1.5 litre of secondary effluent of Shiraz wastewater treatment plant. Orthophosphate removal from wastewater was examined for 14 days. The highest orthophosphate removal rate (10.33 percent per day) belonged to the immobilized microalgae treatment with 2.5 Lmin-1 aeration rate. Furthermore, for the immobilized microalgae treatments, removal efficiency decreased as a result of decrease in aeration rate. The results of free Chlamydomonas with 1 Lmin-1 aeration rate in orthophosohate removal were remarkable. Immobilization of microalgae with increasing aeration rate would improve algal- bacterial process and also would increase efficiency of orthophosphate removal.

Purpose: Urbanization and industrial development intensify water utilization and wastewater generation. The efficiency of wastewater treatment systems varies and depends on system design and wastewater condition. The research aims to examine seven existing centralized municipal wastewater treatment plants (WWTPs) in Bangkok to discover which system configuration yields the best environmental and economic performance. The degree of environmental impact and operational costs from different system designs were investigated to help select future wastewater treatment systems. Methods: Life cycle assessment (LCA) has been conducted to evaluate environmental impacts from centralized municipal wastewater treatment systems. Life cycle impact assessment method based on endpoint modeling (LIME) was applied, with three major potential environmental impact categories including eutrophication, global warming, and acidification. All seven centralized municipal WWTPs in Bangkok were investigated as case studies. The system configurations are classified into five types of activated sludge (AS) systems. The contribution of impacts from individual processes in each type of AS system was analyzed. The methodology covered major on-site and off-site operational processes excluding construction and maintenance phases. Average annual data were calculated to develop an inventory dataset. JEMAI-Pro software was utilized in this study to analyze the life cycle impact of the systems. Results and discussion: The level of environmental impact from a WWTP depends on the configuration of the AS system. The highest potential environmental impact from a municipal WWTP is eutrophication, which is obviously affected by ammonium and phosphorous discharges into water bodies. The vertical loop reactor activated sludge (VLRAS) system yielded the best treatment performance among the five AS sub-systems. The consumption of electricity used to operate the system contributed significantly to global warming potential and correlated considerably with operating costs. Comparing among three system sizes, the large-scale WWTP revealed inefficient electricity consumption, whereas the medium plant provided better performance in chemical use and operating costs. Conclusions: Centralized municipal WWTPs with capacities ranging from 10 to 350 × 10 m/day were evaluated with respect to environmental performance and costs during the operating phase. Among all case studies, a medium-scale WWTP with a VLRAS system offered the best operating performance in terms of low environmental impact, resource consumption, and cost. To enhance WWTP management, it is vital to improve the efficiency of electricity consumption in primary and secondary treatment processes and increase wastewater collection efficiency to maximize the plant operating capacity and minimize overall environmental impacts. [ABSTRACT FROM AUTHOR]

Background and Objective: Being low cost of building and operation, anaerobic baffled reactor is considered superior to aerobic methods of wastewater treatment, especially for small communities. However, it needs to be studded for upgrade and overcome of its limitations. The purpose of this study was to evaluate the performance of FABR and RABR reactors for the municipal wastewater treatment at laboratory scale and in field conditions to determine their optimum conditions in reaching effluent discharge standards. Materials and Methods: This study was conducted in Khoy wastewater treatment plant. FABR was operated for 267 days with hydraulic retention time of 18-48 h and RABR was operated for 90 days with media bad rotation of 10-50 rpm. The reactors were fed in line from the wastewater canal. Using composite sampling, 224 samples were taken from the inflow and outflow of the reactors and each sample was analyzed for parameters of COD, BOD, TSS, VSS, TKN, and TP. Results: The reactor startup took about 107 days. FABR removal efficiency was 93-80, 21-10, and 30-21% for COD, TKN, and PO4 respectively at HRT of 48-18 h. FABR reached effluent disposal standard of TSS, COD, and BOD in all conditions and optimum HRT of 36 h. RABR reached to these standards at HRT 24 h and 50 rpm. However, none of them could meet the nutrient effluent standards. Conclusion: FABR is an appropriate system for municipal wastewater treatment but for reaching N and P effluent standard, it should be combined with aerobic post-treatment. Moreover, in order to reuse the reactor's nutrient-rich effluent for irrigation; it can be reused as subsurface irrigation. [ABSTRACT FROM AUTHOR]

The effect of titanium dioxide nanoparticles (TiO NPs) on biological wastewater treatment in a sequencing batch reactor was investigated. The overall removal of chemical oxygen demand (COD) and NH -N were relatively unaffected; efficiencies remained at >95 % and around 99 %, respectively, after 30 days of continuous exposure to the NPs. However, TiO NPs resulted in increased conversion of NO -N to NO -N and caused slight inhibition effect on denitrification, with the total nitrogen removal reduced from 95 to 90 %. Several shifts in the bacteria community composition were noted. However, the overall community structure and biodiversity remained relatively unchanged. The polysaccharide content in the extracellular polymeric substances (EPS) was generally unaffected, suggesting a low potential of substantial shock or damage that may result in cytoplasmic leakage. However, a decrease in protein content occurred and indicated the inhibitive effects of the NPs. TiO NPs were removed in the system mainly via deposition into the sludge. The removal efficiency decreased from 90 to 70 % after 4 weeks, due to sorption saturation as well as the change in the EPS content of the activated sludge. [ABSTRACT FROM AUTHOR]

The effect of silver nanoparticles on the system performance and the bacterial community dynamics in a sequencing batch reactor was investigated, along with the removal and the fate of silver nanoparticles within the system. Results showed that silver nanoparticles did not significantly affect organic matters removal, nitrification and denitrification. However, adverse effects were observed on sludge settleabilities, which were related to the over-production of extracellular polymeric substances and a sequential change in activated sludge structure and morphology. Polymerase chain reaction–Denaturing gradient gel electrophoresis revealed that silver nanoparticles caused significant shifts in bacterial community structures. Different species were affected and eliminated at each dosage of silver nanoparticles. Silver nanoparticles were effectively removed in the bioreactor, with the main removal pathway being deposited in the activated sludge. [ABSTRACT FROM AUTHOR]

Inspired by iron fertilization experiments in HNLC (high-nitrate, low-chlorophyll) sea areas, we proposed the use of iron-rich engineered microalgae for microbial contaminant control in iron-free culture media. Based on the genome sequence and natural transformation system of Synechocystis sp. PCC6803, ftnA (encoding ferritin) was selected as our target gene and was cloned into wild-type Synechocystis sp. PCC6803. Tests at the molecular level confirmed the successful construction of the engineered Synechocystis sp. PCC6803-ftnA. After Fe 3 + -EDTA pulsing, the intracellular iron content of Synechocystis sp. PCC6803-ftnA was significantly enhanced, and the algae was used in the microbial contamination control system. In the coupled Synechocystis sp. PCC6803-ftnA production and municipal wastewater (MW, including Scenedesmus obliquus and Bacillus ) treatment, Synechocystis sp. PCC6803-ftnA accounted for all of the microbial activity and significantly increased from 70% of the microbial community to 95%. These results revealed that while the stored iron in the Synechocystis sp. PCC6803-ftnA cells was used for growth and reproduction of this microalga in the MW, the growth of other microbes was inhibited because of the iron limitation, and these results provide a new method for microbial contamination control during a coupling process. [ABSTRACT FROM AUTHOR]

A laboratory fed-batch reactor has been used to study under controlled conditions the performance of partial nitritation/anammox for the 200,000 m3/day step-feed activated sludge process at the Changi Water Reclamation Plant, Singapore. The similarity of the concentrations of NH4, NO2, NO3, PO4, suspended chemical oxygen demand (sCOD), pH, and alkalinity (ALK) between the on-site process and laboratory reactor illustrates that the laboratory fed-batch reactor can be used to simulate the site performance. The performance of the reactor fed by primary effluent illustrated the existence of anammox and heterotrophic denitrification and apparent excessive biological phosphorus removal as observed from the site. The performance of the reactor fed by final effluent proved the presence of anammox process on site. Both the laboratory reactor and on-site process showed that higher influent 5-day biochemical oxygen demand/total nitrogen (BOD5/TN) (COD/TN) ratio increases the nitrogen removal efficiency of the process. [ABSTRACT FROM AUTHOR]

The present studies report the synthesis of a novel graft copolymer “polymethyl methacrylate-grafted oatmeal” (OAT-g-PMMA) using “conventional”technique. Grafting of PMMA chains on the backbone of parent biopolymer (oatmeal) was confirmed through various physicochemical techniques like intrinsic viscosity, FTIR, elemental analysis (C, H, N, S and O), scanning electron microscopy, thermal gravimetric analysis, number-average molecular weight, solubility,13C-CP/MAS solid-state NMR spectroscopy and P-XRD. The intrinsic viscosity of oatmeal substantially improved after grafting of PMMA chains. The grafted biopolymers were assessed for its implication as a potential flocculant by standard “jar test” and “settling test” protocol. Flocculation characteristics of the synthesized OAT-g-PMMA were compared with parent biopolymer (oatmeal) and alum in 0.25 wt.% kaolin suspension and then in municipal wastewater through standard “jar test” protocol which showed encouraging results. [ABSTRACT FROM PUBLISHER]

This paper reports on the preliminary tests carried out to characterize the wastewater and the activated sludge from a sequencing batch reactor (SBR) municipal wastewater treatment plant (WWTP) to evaluate possibility of introduction of enhanced biological phosphorus removal (EPBR) into the plant. Wastewater which was treated at the WWTP was municipal wastewater of medium strength, with some peak organic loads due to industrial discharge. Operating conditions were often changed in order to satisfy effluent discharge requirements. Biological methods for sludge characterisation including anaerobic P-release test, aerobic P-uptake test and anoxic P-uptake test were used to determine the presence of polyphosphate accumulating organisms (PAO) within the sludge of the WWTP, along with nitrification and denitrification tests. Anaerobic phosphorus release rate on acetate was low 0.19-2.41 mgP/gVSS*h. Aerobic P-uptake rate was in all our tests lower than 1.0 mg P/gVSS*h and anoxic P-uptake was lower than 0.63 mgP/gVSS*h. EPBR could not be achieved with the activated sludge from the plant but it may be possible, after introducing optimal conditions and regime. [ABSTRACT FROM AUTHOR]

The electrochemical oxidation of acesulfame (acesulfame potassium (ACE-K)) on different electrodes or in various aqueous solutions was investigated in this study. The performance in terms of ACE-K degradation and total organic carbon (TOC) removal of tested anodes was in the order boron-doped diamond (BDD) > PbO 2 > Pt, although ACE-K could not be directly oxidized on these electrodes in cyclic voltammetric analysis. At the same electrolysis time, the ACE-K degradation and TOC removal efficiencies increased with an increasing current density or anode area, but decreased with the increase of initial ACE-K concentration. The ACE-K degradation was slightly influenced by temperature at 25−50 °C. The apparent pseudo-first-order rate constants of ACE-K oxidation were similar in ACE-K-spiked 1 M Na 2 SO 4 solution and municipal wastewater matrices (influent (IN), before biological treatment (BBT), and after biological treatment (ABT)) ((1.73 – 2.32) × 10 −3 s −1 ). Although the TOC removal (consistent with mineralization current efficiency) in these wastewater matrices followed the order ABT ≈ IN > BBT, the complete mineralization of ACE-K and TOC was achieved. Accordingly, the electrooxidation process has great potential to be used to improve the biodegradation-resistant ACE-K degradation and TOC removal in secondary biological wastewater treatment. [ABSTRACT FROM AUTHOR]

This paper conducts a comparative assessment of the environmental impacts of three methods of treating primary clarifier effluent in wastewater treatment plants (WWTPs) through life cycle assessment methodology. The three technologies, activated sludge (AS), high rate anaerobic-aerobic digestion (HRAAD), and trickling filter (TF), were assessed for treatment of wastewater possessing average values of biochemical oxygen demand and total suspended solids of 90 mg L-1 and 70mg L-1, respectively. The operational requirements to process the municipal wastewater to effluent that meets USEPA regulations have been calculated. The data for the AS system were collected from the East Honolulu WWTP (Hawaii, USA) while data for the HRAAD system were collected from a demonstrationscale system at the same plant. The data for the TF system were estimated from published literature. Two different assessment methods have been used in this study: IMPACT 2002þ and TRACI 2. The results show that TF had the smallest environmental impacts and that AS had the largest, while HRAAD was in between the two but with much reduced impacts compared with AS. Additionally, the study shows that lower sludge production is the greatest advantage of HRAAD for reducing environmental impacts compared with AS. [ABSTRACT FROM AUTHOR]

Despite a quick shift of global goals toward carbon-neutral infrastructure, activated sludge based conventional systems inhibit the Green New Deal. Here, a municipal wastewater treatment plant (MWWTP) for carbon neutrality and energy sustainability is suggested and discussed based on realizable technical aspects. Organics have been recovered using variously enhanced primary treatment techniques, thereby reducing oxygen demand for the oxidation of organics and maximizing biogas production in biological processes. Meanwhile, ammonium in organic-separated wastewater is bio-electrochemically oxidized to N 2 and reduced to H 2 under completely anaerobic conditions, resulting in the minimization of energy requirements and waste sludge production, which are the main problems in activated sludge based conventional processes. The anaerobic digestion process converts concentrated primary sludge to biomethane, and H 2 gas recovered from nitrogen upgrades the biomethane quality by reducing carbon dioxide in biogas. Based on these results, MWWTPs can be simplified and improved with high process and energy efficiencies. [Display omitted] • Wastewater treatment process (WWTP) manages the environment and improve quality of life. • A future-oriented and sustainable WWTP is suggested and discussed. • WWTPs face higher energy consumption resulting in inefficiency. • Bioelectrochemical system (BES) is expected to support future WWTPs. • Future WWTPs should be simplified and made more energy efficient. [ABSTRACT FROM AUTHOR]

The effects of CeO2 nanoparticles (NPs) on the system performance and the bacterial community dynamics in a sequencing batch reactor (SBR) were investigated, along with the fate and removal of CeO2 NPs within the SBR. Significant impact was observed on nitrification; NH+4-N removal efficiency decreased from almost 100% to around 70% after 6 days of continuous exposure to 1.0 mg/L of CeO2 NPs, followed by a gradual recovery until a stable value of around 90% after 20 days. Additionally, CeO2 NPs also led to a significant increase in the protein content in the soluble microbial products, showing the disruptive effects of CeO2 NPs on the extracellular polymeric substance matrix and related activated sludge structure. Denaturing gradient gel electrophoresis analysis showed remarkable changes in the bacterial community structure in the activated sludge after exposure to CeO2 NPs. CeO2 NPs were effectively removed in the SBR mainly via sorption onto the sludge. However, the removal efficiency decreased from 95 to 80% over 30 days. Mass balance evaluation showed that up to 50% of the NPs were accumulated within the activated sludge and were removed with the waste sludge. [ABSTRACT FROM AUTHOR]

The studies report the synthesis of novel graft copolymer of oatmeal. Polymethyl methacrylate grafting was carried out on oatmeal backbone via 'microwave assisted' approach. The graft copolymers were optimized by varying monomer and CAN concentration. The synthesized graft copolymers were characterized by intrinsic viscosity, FTIR, TGA, SEM, Elemental Analysis, number average molecular weight and solubility. All the grades of graft copolymers were assessed for its potential application as a flocculant in 1 wt% coal-fine suspension, 0.25 wt% kaolin suspension and municipal wastewater using standard 'jar test' protocol. The flocculation efficacy of synthesized graft copolymers was compared with commercially available coagulant (alum) in 1 wt% coal-fine and 0.25 wt% kaolin suspensions and was found to exhibit better potential as a flocculant than alum and oatmeal. Among diverse grades of graft copolymers, OAT-g-PMMA-5 exhibits higher percentage grafting, intrinsic viscosity and flocculation efficacy for removal of heavy metal ions, suspended particles and organic loads from wastewater. [ABSTRACT FROM AUTHOR]

This study on the removal of microplastics during different wastewater treatment unit processes was carried out at Viikinmäki wastewater treatment plant (WWTP). The amount of microplastics in the influent was high, but it decreased significantly during the treatment process. The major part of the fibres were removed already in primary sedimentation whereas synthetic particles settled mostly in secondary sedimentation. Biological filtration further improved the removal. A proportion of the microplastic load also passed the treatment and was found in the effluent, entering the receiving water body. After the treatment process, an average of 4.9 (±1.4) fibres and 8.6 (±2.5) particles were found per litre of wastewater. The total textile fibre concentration in the samples collected from the surface waters in the Helsinki archipelago varied between 0.01 and 0.65 fibres per litre, while the synthetic particle concentration varied between 0.5 and 9.4 particles per litre. The average fibre concentration was 25 times higher and the particle concentration was three times higher in the effluent compared to the receiving body of water. This indicates that WWTPs may operate as a route for microplastics entering the sea. [ABSTRACT FROM AUTHOR]

A pilot-scale anaerobic–anoxic–oxic membrane bioreactor (A2O-MBR) was applied to treat Shiraz municipal wastewater with high ratio of total phosphorous (TP): total nitrogen (TN): chemical oxygen demand (COD) (3.4: 21.4: 100) and remarkable nitrate concentration. Various operating conditions were tested to investigate nutrient and organic matter removal as well as membrane capacity and biomass development. The pilot system was operated at a constant sludge retention time of 60 d. During different runs, the biomass concentration increased with a reduction of HRT while the F/M ratio was stable around an average of 0.087 gCOD g −1 MLSS d −1 . Results also showed that the treatment performance of A2O-MBR system was extremely stable and was not affected by aerobic hydraulic retention time (HRT) changes (12, 10, 8, 6 h). COD reduction reached over 95% and nitrification was completed. The maximum efficiency of TN and TP removal was 86.2% and 55.9%, respectively, which occurred with an overall HRT of 12 h, external and internal mixed liquor recycle rate of 200%. Membrane capacity measurements showed an average flux of 5.5 L m −2 h −1 with a mean transmembrane pressure of 30 kPa under periodical air backwashing without any chemical cleaning over three months. [ABSTRACT FROM AUTHOR]

This work aims to evaluate the applicability of EDDS (ethylenediamine-N,N′-disuccinic acid) as an iron chelating agent for photo-Fenton treatment of municipal wastewater spiked with organic contaminants at near-neutral pH. A series of laboratory scale experiments are conducted under simulated sunlight in accordance with a central composite experimental design in order to define the most favorable conditions in terms of initial iron concentration (maintaining a molar ratio 1:2 of Fe:EDDS), H 2 O 2 and pH. The system is evaluated in terms of degradation efficiency, H 2 O 2 consumption and iron availability. The simulated system has been compared in terms of degradation efficiency with a 60 L compound parabolic collector (CPC), and significant correlation has been observed. An approach for estimating near-optimal regions of operability is also demonstrated. [ABSTRACT FROM AUTHOR]

Two identical bench scale inclined plate membrane bioreactors (ip-MBRs) were operated for the treatment of real municipal wastewater for 1 year. Sludge retention time (SRT) was varied over the course of operation to investigate the effects on inclined plate function, treatment performance and sludge characteristic. Removal rates of chemical oxygen demand and ammonia over 90% and of total nitrogen (TN) more than 70% were achieved when ip-MBRs were operated under SRTs between infinite and 40 days while short SRT (20 days) negatively affected TN removal. When the sludge concentration in anoxic tank exceeded 15 g/L, the failure of the inclined plate function was observed, resulting in no difference in sludge concentrations between aerobic and anoxic tanks. To avoid severe effects on inclined plate function and treatment performance, an SRT range of 40-80 days was recommended for ip-MBRs. Moreover, sludge floc size under prolonged SRT became smaller than that under short SRT due to increased attrition among the sludge floc particles caused by strong aeration needed for keeping a sufficient dissolved oxygen level. [ABSTRACT FROM AUTHOR]

Increasing use of silica nanoparticles (SiO 2 NPs) in consumer products and industrial processes leads to SiO 2 NP discharge into wastewater. Thus, there is a need to understand the fate of SiO 2 NPs during wastewater treatment. However, the detection of SiO 2 NPs in environmental systems is hindered by the elevated background levels of natural silicon. In this work, laboratory-synthesized fluorescent core-shell SiO 2 NPs were used to study the fate of these NPs during secondary wastewater treatment. Fluorescent measurements provided an easy and fast method for SiO 2 NP tracking. A laboratory-scale activated sludge system consisting of an aeration tank and a settler was fed with synthetic wastewater containing ca. 7.5 mg L −1 of fluorescent SiO 2 NPs for 30 days. SiO 2 NPs were effectively removed from the wastewater (>96%) during the first 6 days, however the concentration of SiO 2 NPs in the effluent gradually increased afterwards and the NP discharge was as high as 65% of the input after 30 days of NP dosing. The poor removal of the SiO 2 NPs was related to the high colloidal stability of the NPs in the wastewater and their limited propensity to biosorption. Although some degree of NP adsorption on the biomass was observed using fluorescence microscopy, the affinity of SiO 2 NPs for the activated sludge was not enough for a sustained and effective removal of the SiO 2 NPs from the wastewater. [ABSTRACT FROM AUTHOR]

Activated sludge systems are commonly used for robust and efficient treatment of municipal wastewater. However, these systems cannot achieve their maximum potential to recover valuable resources from wastewater. This study demonstrates a procedure to design a feasible novel configuration for maximizing energy and nutrient recovery. A simulation model was developed based on literature data and recent experimental research using steady-state energy and mass balances with conversions. The analysis showed that in the Netherlands, proposed configuration consists of four technologies: bioflocculation, cold partial nitritation/Anammox, P recovery, and anaerobic digestion. Results indicate the possibility to increase net energy yield up to 0.24 kWh/m 3 of wastewater, while reducing carbon emissions by 35%. Moreover, sensitivity analysis points out the dominant influence of wastewater organic matter on energy production and consumption. This study provides a good starting point for the design of promising layouts that will improve sustainability of municipal wastewater management in the future. [ABSTRACT FROM AUTHOR]

The objective of this study is to improve knowledge on the integrated fixed-film-activated sludge (IFAS) system designed for nitrogen removal. Biofilm growth and its contribution to nitrification were monitored under various operating conditions in a semi-industrial pilot-scale plant. Nitrification rates were observed in biofilms developed on free-floating media and in activated sludge operated under a low sludge retention time (4 days) and at an ammonia loading rate of 45-70 gNH4-N/kgMLVSS/d. Operational conditions, i.e. oxygen concentration, redox potential, suspended solids concentration, ammonium and nitrates, were monitored continuously in the reactors. High removal efficiencies were observed for carbon and ammonium at high-loading rate. The contribution of biofilm to nitrification was determined as 40-70% of total NOx-N production under the operating conditions tested. Optimal conditions to optimize process compacity were determined. The tested configuration responds especially well to winter and summer nitrification conditions. These results help provide a deeper understanding of how autotrophic biomass evolves through environmental and operational conditions in IFAS systems. [ABSTRACT FROM AUTHOR]

PCN bacteria capable of heterotrophic-aerobic nitrogen removal was successfully applied for bioaugmented treatment of municipal wastewater in a pilot-scale SBR. At an appropriate COD/N ratio of 8, the bioaugmentation system exhibited stable and excellent carbon and nutrients removal, the averaged effluent concentrations of COD, NH 4 + -N, TN and TP were 20.6, 0.69, 14.1 and 0.40 mg/L, respectively, which could meet the first class requirement of the National Municipal Wastewater Discharge Standards of China (COD < 50 mg/L, TN < 15 mg/L, TP < 0.5 mg/L). Clone library and real-time PCR analysis revealed that the introduced bacteria greatly improved the structure of original microbial community and facilitated their aerobic nutrients removal capacities. The proposed emerging technology was shown to be an alternative technology to establish new wastewater treatment systems and upgrade or retrofit conventional systems from secondary-level to tertiary-level. [ABSTRACT FROM AUTHOR]

The aim of the study is to determine environmentally friendlier construction materials for constructed wetland facilities treating wastewater. This is done by computing the environmental footprint of the facility based on the methodology of life cycle assessment (LCA). This methodology reveals the dominant aggravating processes during the construction of a constructed wetland (CW) and can help to create alternative environmentally friendlier solutions. This methodology was applied for the determination of the overall environmental profile of a hybrid CW facility. The LCA was applied first to the facility as originally designed, where reinforced concrete was used in some components. Then, alternative construction materials to reinforced concrete were used, such as earth covered with high density polyethylene (HDPE) or clay, and LCA was applied again. Earth structures were found to have reduced environmental impact compared to concrete ones, and clay was found environmentally friendlier compared to HDPE. Furthermore, estimation of the construction costs of the three scenarios indicate that the last scenario is also the least expensive. [ABSTRACT FROM AUTHOR]

A pilot-scale process was operated over 22 months at the Brussels North Wastewater Treatment Plant (WWTP) in order to evaluate polyhydroxyalkanoate (PHA) production integration with services of municipal wastewater and sludge management. Activated sludge was produced with PHA accumulation potential (PAP) by applying feast–famine selection while treating the readily biodegradable COD from influent wastewater (average removals of 70% COD, 60% COD sol , 24% nitrogen, and 46% phosphorus). The biomass PAP was evaluated to be in excess of 0.4 gPHA/gVSS. Batch fermentation of full-scale WWTP sludge at selected temperatures (35, 42 and 55 °C) produced centrate (6–9.4 gCOD VFA /L) of consistent VFA composition, with optimal fermentation performance at 42 °C. Centrate was used to accumulate PHA up to 0.39 gPHA/gVSS. The centrate nutrients are a challenge to the accumulation process but producing a biomass with 0.5 gPHA/gVSS is considered to be realistically achievable within the typically available carbon flows at municipal waste management facilities. [ABSTRACT FROM AUTHOR]

The operation of aerobic granular sludge reactors with a completely granulated sludge bed is often associated with effluent suspended solids concentrations above the required limits. In this work it can be shown that the amount of aerobic granules on the total biomass concentration is a key operation tool to control the suspended solids effluent concentration. Low effluent concentrations could be achieved only when the granule content was below 80%. A pilot scale reactor with a working volume of 4 m 3 was used to treat municipal wastewater with aerobic granules and was operated for 247 days. The chosen sequential batch operation consisted of five phases: a short influent, anaerobic mixing, aeration, settling and effluent. The anaerobic mixing is innovative as it provides the same conditions for all granules. Additionally, by choosing an anaerobic mixing step the activated sludge granulation can be applied independently to the reactor geometry. Total suspended solids concentrations of 12 g TSS /L in the reactor and effluent suspended solids concentration below 50 mg TSS /L could be achieved. During the reactor start-up a high hydraulic selection pressure was not required to induce the granule formation. Hence, a complete nitrification was achieved already during start up. The added phosphorus was completely removed biologically by the granules. [ABSTRACT FROM AUTHOR]

Ozone has been shown to be effective in the transformation of several chemicals of emerging concern that escape the wastewater treatment process, but there is concern whether toxic transformation products are formed. Two parallel biofilter columns with granular activated carbon (GAC) and filter sand following a pilot-scale ozone unit to treat secondary treated municipal wastewater were studied. Results show reduced wastewater genotoxicity following ozonation and further reduction following biofiltration. The BAC biofilter outperformed the sand biofilter in terms of reduction in both organics and genotoxicity. Biofilter performance correlated with biological indicators (dissolved oxygen reduction and effluentE. colicounts) but not with ATP bioactivity measurements. Limited bacterial (E. coli) regrowth was observed in treated effluent from both biofilters. [ABSTRACT FROM PUBLISHER]

[Display omitted] • Current biological processes in WWTPs are being challenged by sustainability. • Anammox-based energy-saving processes are reviewed. • HRAS followed with anaerobic fermentation processes for carbon recovery are discussed. • Integration of energy-saving and carbon recovery processes is prospected. • Future research toward ultimate carbon neutrality goals is discussed. Municipal wastewater treatment that mainly performed by conventional activated sludge (CAS) process faces the challenge of intensive aeration-associated energy consumption for oxidation of organics and ammonium, contributing to significant directly/indirectly greenhouse gas (GHG) emissions from energy use, which hinders the achievement of carbon neutral, the top priority mission in the coming decades to cope with the global climate change. Therefore, this article aimed to offer a comprehensive analysis of recently developed biological treatment processes with the focus on reducing discharge and CO 2 footprint. The biotechnologies including "Zero Carbon", "Low Carbon", "Carbon Capture and Utilization" are discussed, it suggested that, by integrating these processes with energy-saving and carbon recovery, the challenges faced in current wastewater treatment plants can be overcome, and a carbon–neutral even be possible. Future research should investigate the integration of these methods and improve anammox contribution as well as minimize organics lost under different scales. [ABSTRACT FROM AUTHOR]

Numerous initiatives have been undertaken to circumvent the problem of antibiotic resistance, including the development of new antibiotics, the use of narrow spectrum antibiotics, and the reduction of inappropriate antibiotic use. We propose an alternative but complimentary approach to reduce antibiotic resistant bacteria by implementing more stringent technologies for treating municipal wastewater, which is known to contain large quantities of antibiotic resistant bacteria and antibiotic resistance genes (ARGs). In this study, we investigated the ability of conventional aerobic digestion to reduce the quantity of ARGs in untreated wastewater solids. A bench-scale aerobic digester was fed untreated wastewater solids collected from a full-scale municipal wastewater treatment facility. The reactor was operated under semi-continuous flow conditions for more than 200 days at a residence time of approximately 40 days. During this time, the quantities of tet(A), tet(W), and erm(B) decreased by more than 90%. In contrast, intI1 did not decrease, and tet(X) increased in quantity by 5-fold. Following operation in semi-continuous flow mode, the aerobic digester was converted to batch mode to determine the first-order decay coefficients, with half-lives ranging from as short as 2.8 days for tet(W) to as long as 6.3 days for intI1. These results demonstrated that aerobic digestion can be used to reduce the quantity of antibiotic resistance genes in untreated wastewater solids, but that rates can vary substantially depending on the reactor design (i.e., batch versus continuous-flow) and the specific ARG.

The main objective of this study is to propose guidelines for designing submerged anaerobic MBR (AnMBR) technology for municipal wastewater treatment. The design methodology was devised on the basis of simulation and experimental results from an AnMBR plant featuring industrial-scale hollow-fibre membranes. The proposed methodology aims to minimise both capital expenditure and operating expenses, and the key parameters considered were: hydraulic retention time, solids retention time, mixed liquor suspended solids concentration in the membrane tank, 20 °C-standardised critical flux, specific gas demand per square metre of membrane area, and flow of sludge being recycled from the membrane tank to the anaerobic reactor. An AnMBR WWTP operating at 15 and 30 °C with both sulphate-rich (5.7 mg COD mg −1 SO 4 -S) and low-sulphate (57 mg COD mg −1 SO 4 -S) municipal wastewater was designed. The minimum cost of the designed plant was €0.097 and €0.070 per m 3 when treating sulphate-rich and low-sulphate wastewater, respectively. [ABSTRACT FROM AUTHOR]

This study reports the use of an osmotic membrane bioreactor (OMBR) for municipal wastewater treatment. The effects of silver nanoparticles (Ag-NPs) on the system performance were also examined. Using NaCl as the draw solution (DS) (at 49 g/L), a submerged OMBR system was developed and operated continuously for 108 days. Significant salt accumulation was observed at the beginning of the operation, which resulted in a mild deterioration in biological activity in the bioreactor, where NH 4 + –N accumulated to around 10.0 mg/L in the first 15 days. However, the treatment efficiency recovered rapidly as the microbial community acclimatized to the elevated saline environment. Ag-NPs caused a significant decrease in nitrifying efficiency from 98% to 15% and an increase in the extracellular polymeric substances (EPS) content in the activated sludge by 77.8%. A major shift in the bacterial community structure and decrease in community diversity was revealed in 16S rRNA gene based polymerase chain reaction–denaturing gradient gel electrophoresis (PCR–DGGE) analysis. [ABSTRACT FROM AUTHOR]

The rapidly increasing use of engineered nanoparticles (NPs) in consumer products inevitably leads to their greater presence in wastewater treatment plants. In this study, the effects of zinc oxide nanoparticles (ZnO-NPs) on system performance and bacterial community dynamics of biological wastewater treatment in a lab-scale sequencing batch reactor were evaluated, along with their fate within the system. It was found that ZnO-NPs caused poor settleability of the activated sludge and a significant decrease in the removal of nitrogen and phosphorus over time. Denaturing gradient gel electrophoresis analysis revealed that the bacterial community in the activated sludge became less diverse after exposure to ZnO-NPs. In addition, the production of extracellular polymeric substances (EPS) increased, with the EPS forming a tight matrix to protect the cells from the NPs. The NPs were removed very effectively from wastewater, mainly via sorption to the sludge. [ABSTRACT FROM AUTHOR]