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New pollutants, pharmaceuticals and personal care products (PPCPs), accumulate in sewage sludge (SS) in wastewater treatment plants (WWTPs), posing risks to the environment and to human health. In the present study, the fates of typical PPCPs, carbamazepine (CBZ), triclosan (TCS), ibuprofen (IBU) and galaxolide (HHCB), were examined during WW treatment. Additionally, SS collected from a WWTP was used for aerobic composting to investigate the influences of micron-sized Fe 3 O 4 (M-Fe) and nano-sized Fe 3 O 4 (N–Fe) on the degradation of these PPCPs and the succession of microbial communities during the composting process. The results showed that the mean concentrations of CBZ, TCS, IBU and HHCB in the influent of the WWTP were 926.5, 174.4, 8869, and 967.3 ng/g, respectively, and in the effluent were 107.6, 47.0, 283.4, and 88.4 ng/g, respectively. The removal rate averaged ∼80%, while the enrichment rates of the PPCPs in SS ranged from 37.2% to 60.5%. M-Fe and N–Fe reduced NH 3 emissions by 32.9% and 54.1% and N 2 O emissions by 26.2% and 50.8%, respectively. Moreover, the addition of M-Fe and N–Fe effectively increased PPCP degradation rates 1.12–1.66-fold. During the whole process, the additions of M-Fe and N–Fe significantly shifted microbial community structure, and the abundances of Proteobacteria, Chloroflexi, and Actinobacteria were increased during the thermophilic stage, marking them as key PPCP-degrading phyla. Taken together, our results indicated that the addition of M-Fe and N–Fe is an effective method for improving the quality of end compost and accelerating the degradation of PPCPs. The removal rate of the four PPCPs averaged ∼80% after the wastewater treatment plant (WWTP), while the enrichment rates of the PPCPs in sewage sludge (SS) ranged from 37.2% to 60.5%. The M-Fe and N–Fe reduced NH 3 emission by 32.9% and 54.1%, and N 2 O emission by 26.2% and 50.8%, respectively. Meanwhile, adding M-Fe and N–Fe effectively promoted the PPCPs degradation rates by 1.12–1.66 times. During the whole process, the additions of M-Fe and N–Fe significantly shifted the microbial community structure, and the abundances of Proteobacteria, Chloroflexi, and Actinobacteria were boosted during the thermophilic stage, marking as key PPCPs-degrading phyla. [Display omitted] • The enrichment rates of four PPCPs in sewage sludge ranged from 37.2% to 60.5%. • M-Fe and N–Fe reduced NH 3 emission by 32.9% and 54.1%, and N 2 O by 26.2% and 50.8%. • M-Fe and N–Fe effectively promoted the PPCPs degradation rates by 1.12–1.66 time. • M-Fe and N–Fe were effective method to improve compost and PPCPs degradation. [ABSTRACT FROM AUTHOR]

This paper reviewed systematically the odor production and emissions in wastewater systems including sewer and wastewater treatment plants (WWTP). The subjective and objective characterization of wastewater odor was briefly discussed while the recent literature data of the measured concentrations of various odor compounds is collated with their odor description, threshold value, and human health limits. The extensive compiled data provide a full range of spatial and temporal variations. It was found that hydrogen sulfide, organic sulfur compounds, and aldehydes are the key odorants in sewer emissions. The odor emission from different treatment units of a WWTP are distinct from each other. The primary treatment odor is similar to that from the sewer with high level of hydrogen sulfide. In contrast, the odor from sludge handling units are characterized with high organic compounds and very low level of hydrogen sulfide. Odor from both sewer and WWTP are affected by the operation and environmental conditions. Typical diurnal and seasonal pattern can be observed due to the hydraulic patterns. A prioritization framework is proposed to rank the complicated odorants in wastewater emissions for the design and optimization of treatment and control measures. [ABSTRACT FROM PUBLISHER]

On-line process control may cause substantial changes to the microbial community in a biological wastewater treatment system. Recent studies have shown such effects can be exploited in control system design to achieve an optimised microbial community. Excellent progress has been made on the elimination of nitrite-oxidising bacteria (NOB) in biological nitrogen removal wastewater treatment systems using on-line aeration control, enabling nitrogen removal via the nitrite pathway. Control methods for eliminating NOB are now available for both continuous systems and sequencing batch reactors, and have been demonstrated with both domestic and various types of industrial wastewaters. The elimination or reduced growth of glycogen accumulating organisms (GAOs), a competitor of polyphosphate accumulating organisms (PAOs), in enhanced biological phosphorus removal (EBPR) systems via pH and carbon source control has been conceptually demonstrated through the use of enriched cultures. However, these strategies are not yet ready for the control of practical EBPR processes. Sludge population optimisation also involves selecting the most desirable organism or a consortium of organisms to perform a required function. This is particularly important for nitrification, one of the most important and delicate steps in modern wastewater treatment plants. Results from both experimental and simulation studies suggest that reactor operation could have a major impact on the nitrifier community structure, which should be further investigated in future studies. [ABSTRACT FROM AUTHOR]

• Influent quality highly affected the overall performance of a WWTP. • WWTP with high strength influent had the lower environmental impact and cost. • Loose effluent standard resulted in the lower cost of a WWTP. • Restricted effluent standard decreased resource recovery potential. Influent concentration and effluent standards have strong impacts on technology selection by wastewater treatment plants (WWTPs) and on resource recovery processes. In this paper, resource recovery simulation scenarios incorporated with conventional WWTP models were designed in an imitation of typical existing facilities. We integrated economic analysis and a life cycle assessment to evaluate the impacts of treatment technologies selected for different influent conditions and effluent standards. The results revealed that high concentration influents required the most complicated treatment processes to meet a strict effluent standard. The pattern of total impacts was strongly dependent on the influent conditions. High concentration influent was found to correlate with low energy consumption, low costs, a high nutrient recovery potential but also a high global warming potential when removing 1 kg of pollutants. The incorporation of resource recovery improved the overall performance of WWTPs; however, low concentration influents were not suitable for resource recovery due to their limited benefits. The strict effluent standard limited the resource recovery potential from wastewater, and a loose effluent standard may improve the resource recovery performance, especially for high concentration influents. [ABSTRACT FROM AUTHOR]

[Display omitted] • IWWTPs bacterial communities exhibited a clear species abundance distribution. • Deterministic processes dominate IWWTPs bacterial communities assembly. • Different IWWTPs harbor unique core bacterial community. • IWWTP bacterial community was strongly linked to activated sludge function. Microbial communities are responsible for biological treatment of many industrial wastewater, but our knowledge of their diversity, assembly patterns, and function is still poor. Here, we analyzed the bacterial communities of wastewater and activated sludge samples taken from 11 full-scale industrial wastewater treatment plants (IWWTPs) characterized by the same process design but different wastewater types and WWTP compartments. We found significantly different diversity and compositions of bacterial assemblages among distinct wastewater types and IWWTPs compartments. IWWTPs bacterial communities exhibited a clear species abundance distribution. The dispersal-driven process was weak in shaping IWWTP communities. Meanwhile, environmental and operating conditions were important factors in regulating the structure of the activated sludge community and pollutants removal, indicating that bacterial community was largely driven by deterministic mechanisms. The core microbial community in IWWTPs was different from that in municipal wastewater treatment plants (MWWTPs), and many taxa (e.g. the genus Citreitalea) rarely were detected before, indicating IWWTPs harbored unique core bacterial communities. Furthermore, we found that bacterial community compositions were strongly linked to activated sludge function. These findings are important to both microbial ecologists and environmental engineers, who may optimize the operation strategies jointly for maintaining biodiversity, which in turn may promote a more stable performance of the IWWTP. Overall, our study enhances the mechanistic understanding of the IWWTP microbial community diversity, assembly patterns, and function, and provides important implications for microbial ecology and wastewater treatment processes. [ABSTRACT FROM AUTHOR]

Sulfide is produced in sewer networks, and previous studies suggest that sulfide in sewage could alter the activity of heterotrophic denitrification and lead to N2O accumulation during biological wastewater treatment. However, the details of this phenomenon are poorly understood. In this study, the potential inhibitory effects of sulfide on nitrate, nitrite, and N2O reduction were assessed with a methanol-utilizing denitrifying culture both prior to and after its exposure and adaptation to sulfide. Hydrogen sulfide was found to be strongly inhibitory to N2O reduction, with 50% inhibition observed at H2S concentrations of 0.04 mg H2S-S/L and 0.1 mg H2S-S/L for the unadapted and adapted cultures, respectively. In comparison, both nitrate and nitrite reduction was more tolerant to H2S. A 50% inhibition of nitrite reduction was observed at approximately 2.0 mg H2S-S/L for both unadapted and adapted cultures, while no inhibition of nitrate reduction occurred at the highest H2S concentrations applied (2.0 mg H2S-S/L) to either culture. N2O accumulation was observed during nitrate and nitrite reduction by the adapted culture when H2S concentrations were above 0.5 and 0.2 mg H2S-S/L, respectively. Additionally, we reveal that hydrogen sulfide (H2S), rather than sulfide, was likely the true inhibitor of N2O reduction, and the inhibitory effect was reversible. These findings suggest that sulfide management in sewers could potentially have a significant impact on N2O emission from wastewater treatment plants. [ABSTRACT FROM AUTHOR]

• Dosing Mg (OH) 2 in sewers increases sewage pH and reduces the transfer of H 2 S. • Long-term pH elevation partially inhibits biological processes in sewers. • Mg (OH) 2 offers additional alkalinity which improves nitrification rate. • In sewer Mg (OH) 2 -dosing reduces soluble phosphate concentration in digested sludge. • Mg (OH) 2 -dosing improves sludge settleability and digested sludge dewaterability. Magnesium hydroxide [ Mg (OH) 2 ] is a non-hazardous chemical widely applied in sewer systems for managing odour and corrosion. Despite its proven effectiveness in mitigating these issues, the impacts of dosing Mg (OH) 2 in sewers on downstream wastewater treatment plants have not been comprehensively investigated. Through a one-year operation of laboratory-scale urban wastewater systems, including sewer reactors, sequencing batch reactors, and anaerobic sludge digesters, the findings indicated that Mg (OH) 2 dosing in sewer systems had multifaceted benefits on downstream treatment processes. Compared to the control, the Mg (OH) 2 -dosed experimental system displayed elevated sewage pH (8.8 ± 0.1 vs 7.1 ± 0.1), reduced sulfide concentration by 35.1 % ± 4.9 % (6.7 ± 0.9 mg S L − 1 ), and lower methane concentration by 58.0 % ± 4.9 % (19.1 ± 3.6 mg COD L − 1 ). Additionally, it increased alkalinity by 16.3 % ± 2.2 % (51.9 ± 5.4 mg CaC O 3 L − 1 ), and volatile fatty acids concentration by 207.4 % ± 22.2 % (56.6 ± 9.0 mg COD L − 1 ) in sewer effluent. While these changes offered limited advantages for downstream nitrogen removal in systems with sufficient alkalinity and carbon sources, significant improvements in ammonium oxidation rate and NOx reduction rate were observed in cases with limited alkalinity and carbon sources availability. Moreover, Mg (OH) 2 dosing in upstream did not have any detrimental effects on anaerobic sludge digesters. Magnesium-phosphate precipitation led to a 31.7 % ± 4.1 % reduction in phosphate concertation in anaerobic digester sludge supernatant (56.1 ± 10.4 mg P L − 1 ). The retention of magnesium in sludge increased settleability by 13.9 % ± 1.6 % and improved digested sludge dewaterability by 10.7 % ± 5.3 %. Consequently, the use of Mg (OH) 2 dosing in sewers could potentially reduce downstream chemical demand and costs for carbon sources (e.g., acetate), pH adjustment and sludge dewatering. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract The effect of iron-dosing in the sewer system, on wastewater treatment processes, was investigated using laboratory-scale wastewater systems comprising sewers, wastewater treatment reactors, sludge thickeners, and anaerobic sludge digesters. Two systems, fed with real domestic wastewater, were operated for over a year. The experimental system received ferric chloride (FeCl 3) dosing at 10 mgFe L−1 in the sewer reactor whereas the control system received none. Wastewater, sludge and biogas were extensively sampled, and analysed for relevant parameters. The FeCl 3 -dosed experimental system displayed a decreased sulfide concentration (by 4.3 ± 0.5 mgS L−1) in sewer effluent, decreased phosphate concentration (by 4.7 ± 0.5 mgP L−1) in biological treatment reactor effluent, and decreased hydrogen sulfide concentration in biogas (911.5 ± 189.9 ppm to 130.0 ± 5.9 ppm), as compared with the control system. The biological nitrogen removal performance of the treatment reactor, and biogas production in the anaerobic digester were not affected by FeCl 3 -dosing. Furthermore, the dewaterability of the anaerobically digested sludge was enhanced by 17.7 ± 1.0%. These findings demonstrate that iron-dosing to sewers can achieve multiple benefits including sulfide removal in sewers, phosphorus removal during wastewater treatment, and hydrogen sulfide (H 2 S) removal during biogas generation. Therefore, an integrated approach should be taken when considering iron salts usage in an urban wastewater system. Highlights • Dosing of FeCl 3 in sewers can effectively decrease dissolved sulfide concentration. • In sewer Fe-dosing contributes to P removal in the downstream wastewater treatment. • In sewer Fe-dosing decreases the H 2 S content in biogas. • In sewer Fe-dosing enhances dewaterability of digested sludge. [ABSTRACT FROM AUTHOR]

Improvement of sludge dewaterability is crucial for reducing the costs of sludge disposal in wastewater treatment plants. This study presents a novel method based on combined conditioning with zero-valent iron (ZVI) and hydrogen peroxide (HP) at pH 2.0 to improve dewaterability of a full-scale waste activated sludge (WAS). The combination of ZVI (0–750 mg/L) and HP (0–750 mg/L) at pH 2.0 substantially improved the WAS dewaterability due to Fenton-like reactions. The highest improvement in WAS dewaterability was attained at 500 mg ZVI/L and 250 mg HP/L, when the capillary suction time of the WAS was reduced by approximately 50%. Particle size distribution indicated that the sludge flocs were decomposed after conditioning. Economic analysis showed that combined conditioning with ZVI and HP was a more economically favorable method for improving WAS dewaterability than the classical Fenton reaction based method initiated by ferrous salts and HP. [ABSTRACT FROM AUTHOR]

Abstract: The quantification of nitrous oxide (N2O) emissions from open-surface wastewater treatment systems with surface aerators is difficult as emissions from the surface aerator zone cannot be easily captured by floating hoods. In this study, we propose and demonstrate a novel methodology to estimate N2O emissions from such systems through determination of the N2O transfer coefficient (k L a) induced by surface aerators based on oxygen balance for the entire system. The methodology is demonstrated through its application to a full-scale open oxidation ditch wastewater treatment plant with surface aerators. The estimated k L a profile based on a month-long measurement campaign for oxygen balance, intensive monitoring of dissolved N2O profiles along the oxidation ditch over a period of four days, together with mathematical modelling, enabled to determine the N2O emission factor from this treatment plant (0.52 ± 0.16%). Majority of the N2O emission was found to occur in the surface aerator zone, which would be missed if the gas hood method was applied alone. [Copyright &y& Elsevier]

Abstract: Sludge treatment and disposal is one of the major challenges for biological wastewater treatment plants and can represent up to 60% of their total operating costs. This study presents a novel strategy based on free nitrous acid (FNA or HNO2) treatment to achieve sludge reduction. Two sequencing batch reactors treating synthetic domestic wastewater were used, with one serving as an experimental reactor and the other as a control. In the experimental system, 50% of the excess sludge was exposed to FNA at 2.0 mg N/L for 24–42 h in an FNA treatment unit and then returned to the parent reactor. The sludge wastage flow from the experimental reactor was adjusted to obtain a similar mixed liquor suspended solids concentration to that in the control reactor, which was operated at a sludge retention time of 15 days. It was found that sludge production in the experimental system was 28% lower in comparison to the control. The addition of the FNA-treated sludge did not negatively affect the treatment performance and sludge properties of the experimental reactor, namely the organic carbon and nitrogen removal, nitrous oxide (N2O) emission and sludge settleability. Endogenous denitrification batch tests indicate that FNA-treated sludge is available as a carbon source for denitrification. [Copyright &y& Elsevier]

The application of aerobic sludge granules in wastewater treatment could increase the intensity of wastewater treatment processes because of their greater density and size relative to conventional sludge flocs. It has been suggested that granules are distinguished from flocs by gel forming exopolysaccharides. In this study, evidence is presented linking a specific exopolysaccharide component with granule extracellular polymeric substance (EPS) gelation. Granular EPS comprised three components: high-molecular-weight (MW) exopolysaccharide, medium-MW proteins and glycosides, and low-MW proteins and glycosides. The high-MW fraction was separated by fractional precipitation and preparatory-scale gel permeation chromatography (GPC). The MW profile of this fraction appears to be exclusively attributable to high-MW polysaccharide. The exopolysaccharide exists as a gel at normal wastewater treatment operating pH (i.e., 6.0-8.5), whereas the low/medium-MW material does not. Conformational analysis by atomic force microscopy (AFM) of the dried material showed that the polysaccharide forms pearl-necklace-like, intramolecularly condensed structures when dissolved in Milli-Q water and partially relaxed helical aggregates when in alkali solution. Consequently, the gel-forming property of EPS in the aerobic sludge granules tested is probably associated with high-MW polysaccharide components. [ABSTRACT FROM AUTHOR]

Abstract: Methane formation and emission in sewer systems has not received as much attention as hydrogen sulphide formation. Through field measurements from two rising mains, with an average sewage temperature of 28.4 and 26.6°C, respectively, at the time of sampling, this study shows that a significant amount of methane can be produced in sewer systems, and that this production is positively correlated with the hydraulic retention time of wastewater in these systems. The experimental results from a laboratory-scale sewer system fed with real sewage with a temperature of approximately 21°C confirmed these field observations and further revealed that methanogenesis and sulphate reduction occur simultaneously in sewers, with methane production contributing considerably more to the loss of soluble COD in sewers than sulphate reduction. The production of methane in sewers at levels revealed by this study is a serious environmental concern as it potentially results in greenhouse emissions that is comparable to that caused by the energy consumption for the treatment of the same wastewater. Further, methane production in sewers influences sulphide production and its management due to the competition between methanogens and sulphate-reducing bacteria for potentially the same electron donors. The potential interactions between sulphate-reducing and methanogenic bacteria in sewer networks are discussed. [Copyright &y& Elsevier]

• An acidic aerobic digestion system treating anaerobically-digested sludge was established. • The acidic condition (4.8 ± 0.2) was self-sustained by Ca. Nitrosoglobus. • The total solids of anaerobically-digested sludge was markedly reduced by 22.6 ± 5.5%. • The stabilization level of anaerobically-digested sludge was improved to class A. Anaerobic digestion is a commonly used process for the reduction and stabilization of wasted activated sludge generated in wastewater treatment plants. However, anaerobically-digested (AD) sludge is still a problematic waste stream due to its large volume and often poor quality. In this study, two aerobic digesters were set up to treat anaerobically-digested sludge, with one digester operated in self-generated acidic condition as the experimental reactor, and one at neutral pH as the control reactor. The acidic condition in the experimental reactor was driven by an inoculated special ammonia-oxidizing bacterium, ' Candidatus Nitrosoglobus', which can tolerate low pH. As a result of ammonium oxidation by Ca. Nitrosoglobus, the pH decreased to 4.8 ± 0.2 and nitrite accumulated to and stayed at 200.0 ± 17.2 mg N L−1, from which free nitrous acid (FNA) at 8.5 ± 1.8 mg HNO 2 N L−1 formed in-situ. As a combined effect of low pH and high concentration of FNA, the experimental reactor reduced the total solids (TS), volatile solids (VS) and non-volatile solids (NVS) in the AD sludge by 25.2 ± 7.0%, 29.8 ± 4.3%, and 22.6 ± 5.5%, respectively. In contrast, the control reactor without Ca. Nitrosoglobus inoculation (operated at a near-neutral pH of 6.8 ± 0.3 and no FNA formation) only reduced VS in the AD sludge by 10.4 ± 4.3%, along with negligible NVS reduction. Additionally, the acidic aerobic digestion in the experimental reactor significantly stabilized AD sludge, decreasing the specific oxygen uptake rate (SOUR) to 0.5 ± 0.1 mg O 2 g−1VS h−1 and the most probable number (MPN) of Faecal Coliforms to 2.4 ± 0.1 log(MPN g−1TS), both of which meet USEPA standards for Class A biosolids. In comparison, the control reactor produced biosolids at Class B level only, with an SOUR of 1.8 ± 0.2 mg O 2 g−1VS h−1 and a Faecal Coliforms MPN of 3.6 ± 0.1 log(MPN g−1TS). By reducing the volume and improving the quality of the AD sludge, the acidic aerobic digestion of AD sludge enabled by Ca. Nitrosoglobus has the potential to significantly save the sludge disposal costs in wastewater treatment. [Display omitted] [ABSTRACT FROM AUTHOR]

• First reported N 2 O mitigation strategy permanently implemented at full-scale. • 35% N 2 O emission reduction was achieved with 20% less operational cost. • N 2 O mitigation did not affect nutrient removal performance. • Validated multi-pathway N 2 O model at full-scale to evaluate mitigation strategies. • Proposed a standard approach for mitigating N 2 O emissions at full-scale plants. Mitigation of nitrous oxide (N 2 O) emissions is of primary importance to meet the targets of reducing carbon footprints of wastewater treatment plants (WWTPs). Despite of a large amount of N 2 O mitigation studies conducted in laboratories, full-scale implementation of N 2 O mitigation is scarce, mainly due to uncertainties of mitigation effectiveness, validation of N 2 O mathematical model, risks to nutrient removal performance and additional costs. This study aims to address the uncertainties by investigating the quantification, development and implementation of N 2 O mitigation strategies at a full-scale sequencing batch reactor (SBR). To achieve this, N 2 O emission dynamics, nutrient removal performance and operation of the SBR were monitored to quantify N 2 O emissions, and identify the N 2 O generation mechanisms. N 2 O mitigation strategies centered on reducing dissolved oxygen (DO) levels were consequently proposed and evaluated using a multi-pathway N 2 O production mathematical model before implementation. The implemented mitigation strategy resulted in a 35% reduction in N 2 O emissions (from the emission factor of 0.89 ± 0.05 to 0.58 ± 0.06%), which was equivalent to annual reduction of 2.35 tonne of N 2 O from the studied WWTP. This could be mainly attributed to reductions in N 2 O generated via the NH 2 OH oxidation pathway due to the lowering of DO level. As the first reported mitigation strategy permanently implemented at a full scale WWTP, it showcased that the mitigation of N 2 O emissions at full-scale is feasible and that widely accepted N 2 O mitigation strategies developed in laboratory studies are also likely effective in full-scale plants. Furthermore, the close agreement between the validated and predicted N 2 O emission factors (0.58% vs 0.55%, respectively), showed that the N 2 O mathematical model is a useful tool to evaluate N 2 O mitigation strategies at full-scale. Importantly this work demonstrated that N 2 O mitigation does not necessarily require additional operational cost to meet reduction targets. In contrast, the N 2 O mitigation applied here reduced energy requirements for aeration by 20%. Equally important, long-term monitoring identified that N 2 O mitigation did not affect the nutrient removal performance of the plant. Finally, with the knowledge acquired in this study, a standard approach for mitigating N 2 O emissions from full-scale treatment plants was proposed. Image, graphical abstract [ABSTRACT FROM AUTHOR]