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In this work, the modification of Bi2MoO6 with critic acid (CA-BMO) to achieve enhanced adsorption of methylene blue (MB) solution in dark and desorption under visible light irradiation was reported. The as-prepared materials were synthesized by a hydrothermal method and characterized via SEM, FT-IR, XRD, and XPS techniques. Only 16.5% of 10 mg L−1 MB was removed within 10 min by using 0.5 g L−1 Bi2MoO6, while 92.9% removal of MB could be achieved by using 0.5 g L−1 CA-BMO, which enhanced the adsorption removal by a factor of 4.6. The adsorption capacity for MB was 18.9 mg g−1. Desorption efficiency of MB was only observed in CA-BMO system, and it depends on the wavelength of the light source, pH, and the presence of metal ions. Characterization results suggested that carboxyl groups, which were modified onto the surface of Bi2MoO6, could serve as adsorption sites for MB, and the connections were damaged under light, thus leading to the desorption of MB from the surface of the CA-BMO. This study provides a novel reagent-free desorption strategy for dye recovery without secondary pollution, which facilitates the development and application of Bi-based adsorbent for dye-containing wastewater treatment. [ABSTRACT FROM AUTHOR]

Anaerobic microorganisms are thought to play a critical role in regulating the flux of short-chain gaseous alkanes (SCGAs; including ethane, propane and butane) from terrestrial and aquatic ecosystems to the atmosphere. Sulfate has been confirmed to act as electron acceptor supporting microbial anaerobic oxidation of SCGAs, yet several other energetically more favourable acceptors co-exist with these gases in anaerobic environments. Here, we show that a bioreactor seeded with biomass from a wastewater treatment facility can perform anaerobic propane oxidation coupled to nitrate reduction to dinitrogen gas and ammonium. The bioreactor was operated for more than 1000 days, and we used 13C- and 15N-labelling experiments, metagenomic, metatranscriptomic, metaproteomic and metabolite analyses to characterize the microbial community and the metabolic processes. The data collectively suggest that a species representing a novel order within the bacterial class Symbiobacteriia is responsible for the observed nitrate-dependent propane oxidation. The closed genome of this organism, which we designate as 'Candidatus Alkanivorans nitratireducens', encodes pathways for oxidation of propane to CO2 via fumarate addition, and for nitrate reduction, with all the key genes expressed during nitrate-dependent propane oxidation. Our results suggest that nitrate is a relevant electron sink for SCGA oxidation in anaerobic environments, constituting a new microbially-mediated link between the carbon and nitrogen cycles. Anaerobic microorganisms can oxidize short-chain gaseous alkanes such as ethane, propane and butane using sulfate as electron acceptor. Here, the authors show that a bioreactor enrichment of a wastewater microbial community can perform anaerobic propane oxidation coupled to nitrate reduction. [ABSTRACT FROM AUTHOR]

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]

Photosynthetic bacteria (PSB) bioconversion is a new technology for wastewater treatment and resource recovery. The C/N ratio is an important factor in biological wastewater treatment. For the first time, the efficient C/N ratio range for PSB bioconversion, and the effects of the C/N ratio on wastewater treatment efficiency and cell proliferation, were studied. The results of this study showed that PSB bioconversion was efficient when the wastewater C/N ratio was within the range of 400-0.1. Chemical oxygen demand (COD) removal was higher than 60% in this C/N range. The change in the NH4 +-N concentration was fitted by the logistic model for each C/N ratio. The Vmax of nitrogen removal was similar to that of other technologies and it decreased as the C/N ratio decreased. This shows that this technology exhibits reliable pollutant removal in the C/N ratio range of 400-0.1. The nitrogen transformation study indicated that the PSB might use a specific mechanism under a low C/N ratio. PSB cell proliferation was fitted by the logistic model in the C/N ratio range of 400-2, and µmax was found to be not correlated with the C/N ratio. The protein content in the cells was 40-60% in the C/N ratio range of 400-0.1. The results showed that PSB bioconversion technology has a very high resource value and the value of the C/N ratio places little restriction on it. [ABSTRACT FROM AUTHOR]

Abstract: A lignocellulose-based composite hydrogel, as a novel biosorbent, was prepared for Cu2+ removal from wastewater. TEMPO-oxidized cellulose nanofibrils (TOCN) were dispersed in a 7 wt% NaOH/12 wt% urea aqueous solution at room temperature. Meanwhile, the dissolved cellulose was obtained in the same system at subzero temperature. The composite hydrogels were prepared by blending the dissolved cellulose solution, TOCN dispersion, and alkali lignin solution in an NaOH/urea aqueous solution. The composite hydrogel exhibits excellent adsorption capacity for heavy metals, which can be attributed to the synergistic effects of physical adsorption (porous 3D structure) and chemical adsorption (active sites: carboxyl and phenolic groups). The maximum amount of adsorbed Cu2+ onto composite hydrogel can reach 541 mg/g, which was achieved after 45 min. The adsorption behavior is well-described by the pseudo-second-order kinetics and the Freundlich model (R2 > 0.999). Furthermore, the composite hydrogel exhibits high-strength properties, indicating that the presence of TOCN and lignin contributes to mechanical improvements.Graphical abstract: [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]

This work evaluates the biodegradation of the antiviral drug acyclovir by an enriched nitrifying culture during ammonia oxidation and without the addition of ammonium. The study on kinetics was accompanied with the structural elucidation of biotransformation products through batch biodegradation experiments at two different initial levels of acyclovir (15 mg L −1 and 15 μg L −1 ). The pseudo first order kinetic studies of acyclovir in the presence of ammonium indicated the higher degradation rates under higher ammonia oxidation rates than those constant degradation rates in the absence of ammonium. The positive correlation was found between acyclovir degradation rate and ammonia oxidation rate, confirming the cometabolism of acyclovir by the enriched nitrifying culture in the presence of ammonium. Formation of the product carboxy-acyclovir (P239) indicated the main biotransformation pathway was aerobic oxidation of the terminal hydroxyl group, which was independent on the metabolic type (i.e. cometabolism or metabolism). This enzyme-linked reaction might be catalyzed by monooxygenase from ammonia oxidizing bacteria or heterotrophs. The formation of carboxy-acyclovir was demonstrated to be irrelevant to the acyclovir concentrations applied, indicating the revealed biotransformation pathway might be the dominant removal pathway of acyclovir in wastewater treatment. [ABSTRACT FROM AUTHOR]

Pharmaceutical residues could potentially pose detrimental effects on aquatic ecosystems and human health, with wastewater treatment being one of the major pathways for pharmaceuticals to enter into the environment. Enhanced removal of pharmaceuticals by ammonia oxidizing bacteria (AOB) has been widely observed in wastewater treatment processes. This article reviews the current knowledge on the biotransformation of pharmaceuticals by AOB. The relationship between the pharmaceuticals removal and nitrification process was revealed. The important role of AOB-induced cometabolism on the biotransformation of pharmaceuticals as well as their transformation products and pathways was elucidated. Kinetics and mathematical models describing the biotransformation of pharmaceuticals by AOB were also reviewed. The results highlighted the high degradation capabilities of AOB toward some refractory pharmaceuticals, with their degradations being clearly related to the nitrification rate and their transformation products being identified, which may exhibit similar or higher ecotoxicological impacts compared to the parent compound. [ABSTRACT FROM AUTHOR]

There is great potential to understand the functional diversity of microorganisms that are involved in waste water treatment through metagenomic analyses. This study presents the first metagenomic comparison of taxonomic and functional profiles of the microbial communities occurring in different aggregates from anaerobic ammonium-oxidizing (anammox) bioreactors. The anammox bacterial communities in both biofilm and granule sludge samples showed relatively high abundance and diversity compared with floccular sludge. Four of the five known genera of anammox bacteria were detected in the three cultures except Candidatus Jettenia, which was absent in the granules. C andidatus Kuenenia comprised the major population of anammox bacteria in these three sludges, independent of their growth morphologies. The genome assembled for the C andidatus Kuenenia in the granule was very similar to the published reference genome of C andidatus K. stuttgartiensis. Genes involved in the metabolism of the anammox process were highly detected in the biofilm and granule sludges. In particular, the abundance of hydrazine synthase gene ( hzs) in the biofilm was around 486 times more pronounced than that in the granules. The knowledge gained in this study highlights an important role of sludge aggregate in affecting community structure and metabolic potential of anammox systems. [ABSTRACT FROM AUTHOR]

This work explores the applicability of clay-polyelectrolyte based hybrid thin films to develop fouling resistant membrane surfaces for wastewater treatment applications. Clay nanoplatelets were layered on a commercial polyethersulfone membrane in conjunction with two oppositely charged polyelectrolytes via the aqueous-based layer-by-layer (LbL) assembly technique. These hybrid nanostructured membranes showed a high degree of fouling resistance as compared to other commercial membranes and the pure polyelectrolyte multilayer (PEM) membranes, when tested against an electrocoagulation-treated high strength wastewater. With the deposition of just 2.25 quadlayers, the clay-PEM (c‐PEM) membranes demonstrated good anti-fouling properties. On crosslinking the polyelectrolytes, the c‐PEM hybrid membranes showed higher reduction in the chemical oxygen demand (COD) value and enhanced fouling resistance as compared to their uncrosslinked counterparts, the pure PEM membranes (both uncross linked and crosslinked) and the bare membrane. However, the high fouling resistance of the c‐PEM membranes was attained at the cost of compromising the high initial flux value of the underlying membrane. Several possible optimization strategies have therefore been suggested in this paper, which can potentially increase the flux of the modified membranes. This work, for the first time, demonstrated an attempt to evaluate the performance of clay-polyelectrolyte nanocomposite membranes against a real wastewater effluent. [ABSTRACT FROM AUTHOR]

Greenhouse gas (GHG) accounting protocols have addressed emissions from wastewater conveyance and treatment using a variety of simplifying methodologies. While these methodologies vary to some degree by protocol, within each protocol they provide consistent tools for organizational entities of varying size and scope to report and verify GHG emissions. Much of the science supporting these methodologies is either limited or the protocols have failed to keep abreast of developing GHG research. This state-of-the-art review summarizes the sources of direct GHG emissions (both those covered and not covered in current protocols) from wastewater handling; provides a review of the wastewater-related methodologies in a select group of popular protocols; and discusses where research has out-paced protocol methodologies and other areas where the supporting science is relatively weak and warrants further exploration. [ABSTRACT FROM AUTHOR]

An integrated system of electrocoagulation and algal cultivation was developed to treat a high strength wastewater—anaerobic digestion liquid effluent for reclaimed water and value-added algal biomass production. The integrated system synergistically takes advantages of both electrocoagulation and algal cultivation to enhance the efficiencies of wastewater treatment. The electrocoagulation treated wastewater had low turbidity with better light penetration (108 NTU) to enable algal growth. The algal cultivation had high removal efficiencies of phosphorus (99.4%) and nitrogen (88.2%). The dissolved iron in the electrocoagulation treated wastewater enhanced lipid accumulation of the algae. The results present that total phosphorus and nitrogen in the reclaimed water were 0.78 g L −1 and 35.5 mg L −1 respectively, and the harvested algal biomass had 35% of lipid, 53% of protein, and 6.4% of carbohydrate. This study concluded a new route for agricultural wastewater treatment that turns wastewater from an environmental liability into a valuable asset. [ABSTRACT FROM AUTHOR]

Nitrous oxide (N 2 O) can be emitted from wastewater treatment contributing to its greenhouse gas footprint significantly. Mathematical modeling of N 2 O emissions is of great importance toward the understanding and reduction of the environmental impact of wastewater treatment systems. This article reviews the current status of the modeling of N 2 O emissions from wastewater treatment. The existing mathematical models describing all the known microbial pathways for N 2 O production are reviewed and discussed. These included N 2 O production by ammonia-oxidizing bacteria (AOB) through the hydroxylamine oxidation pathway and the AOB denitrification pathway, N 2 O production by heterotrophic denitrifiers through the denitrification pathway, and the integration of these pathways in single N 2 O models. The calibration and validation of these models using lab-scale and full-scale experimental data is also reviewed. We conclude that the mathematical modeling of N 2 O production, while is still being enhanced supported by new knowledge development, has reached a maturity that facilitates the estimation of site-specific N 2 O emissions and the development of mitigation strategies for a wastewater treatment plant taking into the specific design and operational conditions of the plant. [ABSTRACT FROM AUTHOR]

This study focused on developing a membrane-based purification process, coupled with electrocoagulation (EC) as the pretreatment step, to reduce the COD level of an anaerobic digestion effluent. Commercial brackish water reverse osmosis (RO) membranes offer high COD removal but very low water fluxes. In an effort to address this issue, polyelectrolyte multilayer (PEM) membranes were fabricated by the surface modification of loose nanofiltration membranes using layer-by-layer assembly technique. The application of PEM membranes to treat wastewater effluents has not been explored in details. Two polyelectrolyte combinations were tried – the first one consisted of poly (diallyl dimethyl ammonium chloride) and poly (styrene sulfonate) while the second one consisted of poly (allylamine hydrochloride) and poly (acrylic acid). In comparison to commercial RO membranes, these membranes offered significantly higher fluxes, albeit with equivalent COD reduction. The effect of effluent properties like pH and composition, on the performance of these membranes has been discussed. The PEM films were characterized based on properties like thickness and surface charge, which directly affected the separation behavior of the membranes. For the first time, the combination of EC and PEM membranes has been tried out as a simple, energy-efficient two-step process for treating high-strength wastewater. [ABSTRACT FROM AUTHOR]

Hydrogen sulfide is ubiquitously present in many waste streams originating from industrial activities as well as in sewage. It needs to be removed as it is toxic, corrosive, and odorous. Conventional abatement strategies involve physicochemical methods, which require significant amounts of chemicals and/or high energy input. Considering the limitations of physicochemical methods, there is a need for more cost-effective and sustainable abatement strategies. Recent advances in electrode materials and operation have stimulated interest in electrochemical methods for pollutant remediation. Several electrochemical approaches for sulfide abatement have been proposed over the last few years. Electrochemical techniques offer several advantages including the avoidance of dosage, handling, transport and storage of potentially hazardous chemicals, and the possibility of recovering sulfide or sulfur from wastewater as a product. This paper reviews electrochemical strategies that have been proposed for removal of dissolved and gaseous hydrogen sulfide. The advantages and disadvantages as well as the economic potential of each of the proposed methods are discussed. The technical aspects and key challenges to enable full-scale implementation are highlighted. Finally, opportunities for expanding electrochemical methods for sulfide abatement are presented. [ABSTRACT FROM AUTHOR]

Background: Anaerobic digestion has been widely applied to treat the waste activated sludge from biological wastewater treatment and produce methane for biofuel, which has been one of the most efficient solutions to both energy crisis and environmental pollution challenges. Anaerobic digestion sludge contains highly complex microbial communities, which play crucial roles in sludge treatment. However, traditional approaches based on 16S rRNA amplification or fluorescent in situ hybridization cannot completely reveal the whole microbial community structure due to the extremely high complexity of the involved communities. In this sense, the next-generation high-throughput sequencing provides a powerful tool for dissecting microbial community structure and methane-producing pathways in anaerobic digestion. Results: In this work, the metagenomic sequencing was used to characterize microbial community structure of the anaerobic digestion sludge from a full-scale municipal wastewater treatment plant. Over 3.0 gigabases of metagenomic sequence data were generated with the Illumina HiSeq 2000 platform. Taxonomic analysis by MG-RAST server indicated that overall bacteria were dominant (~93%) whereas a considerable abundance of archaea (~6%) were also detected in the anaerobic digestion sludge. The most abundant bacterial populations were found to be Proteobacteria, Firmicutes, Bacteroidetes, and Actinobacteria. Key microorganisms and related pathways involved in methanogenesis were further revealed. The dominant proliferation of Methanosaeta and Methanosarcina, together with the functional affiliation of enzymes-encoding genes (acetate kinase (AckA), phosphate acetyltransferase (PTA), and acetyl-CoA synthetase (ACSS)), suggested that the acetoclastic methanogenesis is the dominant methanogenesis pathway in the full-scale anaerobic digester. Conclusions: In short, the metagenomic sequencing study of this work successfully dissected the detail microbial community structure and the dominated methane-producing pathways of a full-scale anaerobic digester. The knowledge garnered would facilitate to develop more efficient full-scale anaerobic digestion systems to achieve high-rate waste sludge treatment and methane production. [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]

The discovery of denitrifying anaerobic methane oxidation (DAMO) has not only improved our understanding of global methane and nitrogen cycles, but also provided new technology options for removal of nitrate from nitrate-contaminated water. Previous studies have demonstrated DAMO organisms could remove nitrate and nitrite from wastewater under strictly anaerobically conditions. In the study, we investigate the feasibility of nitrate removal from groundwater, which contains dissolved oxygen in addition to nitrate. A membrane biofilm reactor (MBfR), inoculated with DAMO co-culture, was capable of treating synthetic groundwater containing highly contaminated nitrate (50  mg N/L) and oxygen (7–9 mg O 2 /L), with a maximum volumetric nitrate removal rate of 45 mg N/L-d. Accumulations of acetate and propionate were observed in some transient periods, indicating the possible involvement of acetate and propionate as intermediates in methane oxidation. The 16 S rRNA gene amplicon sequencing revealed that Candidatus Methylomirabilis, a known bacterial DAMO organism able to couple nitrite reduction with anaerobic oxidation of methane (AOM), was the dominant population. No archaeal DAMO organisms that are capable of coupling nitrate to AOM were observed, however, considerable amount of denitrifiers were developed in this system. Based on known metabolisms of these microorganisms and a series of batch studies, it was assumed that methane was oxidized into volatile fatty acids (VFAs) under oxygen-limiting conditions, then the generated VFAs served as carbon sources for these heterotrophic denitrifiers to remove nitrate. This study offers a potential technology for nitrate removal from groundwater by DAMO process in MBfR. [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]

Free nitrous acid (FNA i.e. HNO 2 ) was revealed to be effective in enhancing biodegradability of secondary sludge. Also, nitrite-oxidizing bacteria were found to be more susceptible to FNA than ammonium-oxidizing bacteria. Based on these findings, a novel FNA-based sludge treatment technology is proposed to enhance energy recovery from wastewater/sludge. Energy analysis indicated that the FNA-based technology would make wastewater treatment become an energy generating process (yielding energy at 4 kWh/PE/y; kWh/PE/y: kilowatt hours per population equivalent per year), rather than being a large energy consumer that it is today (consuming energy at 24 kWh/PE/y). Importantly, FNA required for the sludge treatment could be produced as a by-product of wastewater treatment. This proposed FNA-based technology is economically and environmentally attractive, and can be easily implemented in any wastewater treatment plants. It only involves the installation of a simple sludge mixing tank. This article presents the concept of the FNA-based technology. [ABSTRACT FROM AUTHOR]

[Display omitted] • The Zn substituted Co 3 O 4 catalysts were prepared and applied in PMS activation for florfenicol removal. • The Zn substitution induced electron rearrangement and promoted oxygen vacancies formation in Co 3 O 4. • The Zn substituted Co 3 O 4 (Zn 0.03 Co) exhibited superior florfenicol removal and higher reaction rate than Co 3 O 4. • The florfenicol degradation is highly dependent on PMS/Zn 0.03 Co/florfenicol dosage, temperature and initial pH. • The degradation mechanism and routes were proposed combining LC-MS/MS and theoretical calculation results. Florfenicol (FLO) is a broad-spectrum halogenated antibiotic (containing F and Cl atoms), and the discharged FLO in wastewater exhibits potential biotoxicity. Peroxymonosulfate (PMS) activation can generate reactive oxygen species (ROSs) to realize efficient degradation of organic pollutants. Herein, Zn-substituted Co 3 O 4 (Zn x Co) catalysts were prepared and applied in PMS activation for FLO degradation. The physicochemical properties were systematically studied by combining experiments and density functional theory (DFT) calculation. The Zn partial substitution induced electron rearrangement and promoted oxygen vacancy (OV) formation in Co 3 O 4. Zn 0.03 Co catalyst exhibited superior FLO removal, achieving a higher reaction rate of 0.112 min−1 than Co 3 O 4 (0.053 min−1). The FLO degradation was highly dependent on the factors of PMS/Zn 0.03 Co/FLO dosage, temperature, initial pH, and coexisting inorganic anions. The Zn 0.03 Co also displayed outstanding performance in PMS activation for degradation of various typical organic pollutants. Electron paramagnetic resonance (EPR) spectra and quenching experiments indicated that both radical species ( · OH , SO 4 · - , and · O 2 -) and nonradical species (1O 2) contribute to FLO removal. The redox cycle of Co3+/Co2+ and OVs played an essential role in PMS activation. The electron structure of FLO and parameters of PMS adsorbed on Zn x Co were calculated. The longer length of Co O and O O bonds for the adsorbed PMS could enhance its activation to generate ROSs. The intermediates were detected, and five degradation pathways were proposed. The acute and chronic toxicities of intermediates suggested that the dechlorination process is important for the toxicity attenuation of FLO. This study clarified the performance enhancement mechanism of Zn substitution on FLO degradation by PMS activation using Co 3 O 4 based catalyst, which favors the development of PMS-based advanced oxidation processes for wastewater treatment. [ABSTRACT FROM AUTHOR]

The formation of aerobic granular sludge (AGS) is relatively difficult during the treatment of refractory wastewater, which generally shows small granular sizes and poor stability. The formation of AGS is regulated by N-Acyl homoserine lactones (AHLs)-mediated quorum sensing (QS). However, the potential role of AHLs in AGS formation under the toxic stress of refractory pollutants and the heterogeneity in the distribution and function of AHLs across different aggregates are not well understood. This study investigated the potential effects of AHLs on the formation of AGS during phenolic wastewater treatment. The distribution and succession of AHLs across varying granular sizes and development stages of AGS were investigated. Results showed that AGS was successfully formed in 13 days with an average granular size of 335 ± 39 μm and phenol removal efficiency of >99%. The levels of AHLs initially increased and then decreased. C4-HSL and 3-oxo-C10-HSL were enriched in large granules, suggesting they may play a pivotal role in regulating the concentration and composition of extracellular polymeric substances (EPS). The content of EPS constantly increased to 149.4 mg/gVSS, and protein (PN) was enriched in small and large granules. Luteococcus was the dominant genus constituting up to 62% after the granulation process, and exhibited a strong association with C4-HSL. AHLs might also regulate the bacterial community responsible for EPS production, and pollutant removal, and facilitate the proliferation of slow-growing microorganisms, thereby enhancing the formation of AGS. The synthesis and dynamics of AHLs were mainly governed by AHLs-producing bacterial strains of Rhodobacter and Pseudomonas , and AHLs-quenching strains of Flavobacterium and Comamonas. C4-HSL and 3-oxo-C10-HSL might be the major contributors to promoting sludge granulation under phenol stress and play critical roles in large granules. These findings enhance our understanding of the roles that AHLs play in sludge granulation under toxic conditions. [Display omitted] • C4-HSL and 3-oxo-C10-HSL were mainly involved in granular formation. • Concentration of N-Acyl homoserine lactones (AHLs) in large granules was higher. • Protein was more effective in granules formation as compared to polysaccharides. • AHLs regulating functional microflora contributed to granules formation. • Mechanism of AHLs on granular formation under phenol condition was proposed. [ABSTRACT FROM AUTHOR]

• Stable NOB suppression is maintained in MABR treating low-strength wastewater for > 200 days. • Acidic pH of 5.0–5.2 and in situ FNA of 1 mg N/L jointly result in NOB suppression. • An unprecedentedly high AOB activity at around 2.4 kg N/(m3 d) is achieved at a short HRT of a mere 30 min. • Acid-tolerant AOB in MABR-biofilms show different apparent kinetics and responses to environmental factors. Shortcut nitrogen removal holds significant economic appeal for mainstream wastewater treatment. Nevertheless, it is too difficult to achieve the stable suppression of nitrite-oxidizing bacteria (NOB), and simultaneously maintain the activity of ammonia-oxidizing bacteria (AOB). This study proposes to overcome this challenge by employing the novel acid-tolerant AOB, namely " Candidatus Nitrosoglobus", in a membrane-aerated biofilm reactor (MABR). Superior partial nitritation was demonstrated in low-strength wastewater from two aspects. First, the long-term operation (256 days) under the acidic pH range of 5.0 to 5.2 showed the successful NOB washout by the in situ free nitrous acid (FNA) of approximately 1 mg N/L. This was evidenced by the stable nitrite accumulation ratio (NAR) close to 100 % and the disappearance of NOB shown by 16S rRNA gene amplicon sequencing and fluorescence in situ hybridization. Second, oxygen was sufficiently supplied in the MABR, leading to an unprecedentedly high ammonia oxidation rate (AOR) at 2.4 ± 0.1 kg N/(m3 d) at a short hydraulic retention time (HRT) of a mere 30 min. Due to the counter diffusion of substrates, the present acidic MABR displayed a significantly higher apparent oxygen affinity (0.36 ± 0.03 mg O 2 /L), a marginally lower apparent ammonia affinity (14.9 ± 1.9 mg N/L), and a heightened sensitivity to FNA and pH variations, compared with counterparts determined by flocculant acid-tolerant AOB. Beyond supporting the potential application of shortcut nitrogen removal in mainstream wastewater, this study also offers the attractive prospect of intensifying wastewater treatment by markedly reducing the HRT of the aerobic unit. [Display omitted] [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]

• Low DO can initiate NOB suppression in MABRs. • Low DO cannot suppress active NOB in MABRs once prevail. • The presence of anammox increases the DO threshold to suppress NOB. • NOB suppression is more challenging in counter-diffusion biofilms than in co-diffusion biofilms. Membrane aerated biofilm reactor (MABR) and shortcut nitrogen removal are two types of solutions to reduce energy consumption in wastewater treatment, with the former improving the aeration efficiency and the latter reducing the oxygen demand. However, integrating these two solutions, i.e., achieving shortcut nitrogen removal in MABR, is challenging due to the difficulty in suppressing nitrite-oxidizing bacteria (NOB). In this study, four MABRs were established to demonstrate the feasibility of initiating, maintaining, and restoring NOB suppression using low dissolved oxygen (DO) control, in the presence and absence of anammox bacteria, respectively. Long-term results revealed that the strict low DO (< 0.1 mg/L) in MABR could initiate and maintain stable NOB suppression for more than five months with nitrite accumulation ratio above 90 %, but it was unable to re-suppress NOB once they prevailed. Moreover, the presence of anammox bacteria increased the threshold of DO level to maintain NOB suppression in MABRs, but it was still incapable to restore the deteriorated NOB suppression in conjunction with low DO control. Mathematical modelling confirmed the experimental results and further explored the differences of NOB suppression in conventional biofilms and MABR biofilms. Simulation results showed that it is more challenging to maintain stable NOB suppression in MABRs compared to conventional biofilms, regardless of biofilm thickness or influent nitrogen concentration. Kinetic mechanisms for NOB suppression in different types of biofilms were proposed, suggesting that it is difficult to wash out NOB developed in the innermost layer of MABR biofilms because of the high oxygen level and low sludge wasting rate. In summary, this study systematically demonstrated the challenges of NOB suppression in MABRs through both experiments and mathematical modelling. These findings provide valuable insights into the applications of MABRs and call for more studies in developing effective strategies to achieve stable shortcut nitrogen removal in this energy-efficient configuration. [Display omitted] [ABSTRACT FROM AUTHOR]

Three TiO 2 and Zn-Al-layered double hydroxide composites, denoted LDH-TiO 2 composites, were prepared using the sol–gel method and characterized utilizing scanning and transmission electron microscopy with energy dispersive spectroscopy, ultraviolet–visible diffuse reflectance spectroscopy, X-ray diffraction, N 2 adsorption–desorption, X-ray photoelectron spectroscopy, photocurrent, photoluminescence and electrochemical impedance spectroscopy techniques. The characterization results illustrated that TiO 2 was attached onto the surface of LDH and the sizes of both TiO 2 and LDH particles were in the nanoscale range. The combination of LDH and TiO 2 promoted the photogenerated electron–hole transfer and separation. The removal abilities of the LDH-TiO 2 composites for Cr(VI) were evaluated using the synergistic adsorption and photocatalytic method. The adsorption percentages of the three LDH-TiO 2 composites for 20.0 mg/L Cr(VI) solutions ranged between 26% and 75%, and upon ultraviolet irradiation, the total removal percentages rapidly increased to approximately 100%. The removal efficiency for Cr(VI) depended on the TiO 2 contents of the LDH-TiO 2 composites. Increasing the TiO 2 percentage resulted in decrease in the adsorption capacities and increase in the photocatalytic removal ratios. The kinetic and isothermal data well fitted the pseudo-second-order and Langmuir equations, respectively. The high removal efficiencies suggested that the composites were suitable for the treatment of Cr(VI)-containing wastewater. Unlabelled Image • The removal percentage of LDH-TiO 2 composites for 20 mg/L Cr(VI) approached 100%. • The combination of Zn-Al-LDH and TiO 2 promoted photoinduced charge transport. • Cr(VI) was removed using LDH-TiO 2 via synergistic adsorption and photocatalysis. [ABSTRACT FROM AUTHOR]

Sidestream sludge treatment approaches have been developed in recent years to achieve mainstream nitrite shunt or partial nitritation, where NOB are selectively inactivated by biocidal factors such as free nitrous acid (FNA) or free ammonium (FA) in a sidestream reactor. The existence of NOB in raw wastewater has been increasingly realized and could pose critical challenge to stable NOB suppressions in those systems. This study, for the first time, evaluated the impact of influent NOB on the NOB suppressions in a mainstream nitrite shunt system achieved through sidestream sludge treatment. An over 500-day sequential batch reactor operation with six experimental phases rigorously demonstrated the negative effects of influent NOB on mainstream NOB control. Continuously seeding of NOB contained in influent stimulated NOB community shifts, leading to different extents of ineffective NOB suppression. The role of primary wastewater treatment in NOB removal from raw wastewater was also investigated. Results suggest primary settling and High Rate Activated Sludge system could remove a large part of NOB contained in raw wastewater. Primary treatment for raw wastewater is necessary for ensuring stable mainstream NOB suppressions. Image 1 • Influent NOB challenge NOB suppression by stimulating community shift and resistance. • Primary settling substantially reduces NOB in raw wastewater. • High-rate activated sludge treatment substantially reduces NOB in raw wastewater. • This study expanded the current knowledge of mainstream NOB suppression. [ABSTRACT FROM AUTHOR]

Starvation and antibiotics pollution are two frequent perturbations during breeding wastewater treatment process. Supplying magnetite into anaerobic system has been proved efficient to accelerate microbial aggregates and alleviate the adverse effect caused by process disturbance. Nevertheless, whether these magnetite-based granules are still superior over normal granules after a long-term starvation period remains unknown, the responsiveness of these granules to antibiotics stress is also ambiguous. In current study, we investigated the resilience of magnetite-based anaerobic granular sludge (AnGS) to starvation and oxytetracycline (OTC) stress, by unravelling the variations of reactor performance, sludge properties, ARGs dissemination and microbial community. Compared with the AnGS formed without magnetite, the magnetite assisted AnGS appeared more robust defense to starvation and OTC stress. With magnetite supplement, the average methane yield after starvation recovery, 50 mg/L and 200 mg/L OTC stress was enhanced by 48.95%, 115.87% and 488.41%, respectively, accompanied with less VFAs accumulation, improved tetracycline removal rate (76.3–86.6% vs. 51.0–53.5%) and higher ARGs reduction. Meanwhile, magnetite supplement effectively ameliorated the potential sludge breakage by triggering more large granules formation. Trichococcus was considered an important impetus in maintaining the stability of magnetite-based AnGS process. By inducing more syntrophic methanogenesis partnerships, especially for hydrogenotrophic methanogenesis, magnetite ensured the improved reactor performance and stronger resilience at stress conditions. [Display omitted] • Magnetite-based AnGS showed strong resistance to starvation and OTC stress. • Magnetite supplement particularly enhanced the methane yield at stress conditions. • Magnetite ameliorated the risk of sludge breakage and induced more large granules. • More syntrophic methanogenesis partnerships were established with magnetite. [ABSTRACT FROM AUTHOR]

• A biofilm-based anammox process was set up to treat acidic nitritation effluent. • Over 80% nitrogen removal at a rate of 149.7 ± 3.9 mg N/L/day was achieved. • Higher than 95% of activity of anammox biofilms can be retained at pH 5. • FNA rather than pH and nitrite plays a key role in anammox activity suppression. • Biofilm plays a key role in protecting anammox bacteria from acidic environment. Acidic partial nitritation (PN) has emerged to be a promisingly stable process in wastewater treatment, which can simultaneously achieve nitrite accumulation and about half of ammonium reduction. However, directly applying anaerobic ammonium oxidation (anammox) process to treat the acidic PN effluent (pH 4−5) is susceptible to the inhibition of anammox bacteria. Here, this study demonstrated the adaptation of anammox process to acidic pH in a moving bed biofilm reactor (MBBR). By feeding the laboratory-scale MBBR with acidic PN effluent (pH = 4.6 ± 0.2), the pH of an anammox reactor was self-sustained in the range of pH 5 − 6. Yet, a high total nitrogen removal efficiency of over 80% at a practical loading rate of up to 149.7 ± 3.9 mg N/L/d was achieved. Comprehensive microbial assessment, including amplicon sequencing, metagenomics, cryosection-FISH, and qPCR, identified that Candidatus Brocadia, close to known neutrophilic members, was the dominant anammox bacteria. Anammox bacteria were found present in the inner layer of thick biofilms but barely present in the surface layer of thick biofilms and in thin biofilms. Results from batch tests also showed that the activity of anammox biofilms could be maintained when subjected to pH 5 at a nitrite concentration of 10 mg N/L, whereas the activity was completely inhibited after disturbing the biofilm structure. These results collectively indicate that the anammox bacteria enriched in the present acidic MBBR could not be inherently acid-tolerant. Instead, the achieved stable anammox performance under the acidic condition is likely due to biofilm stratification and protection. This result highlights the biofilm configuration as a useful solution to address nitrogen removal from acidic PN effluent, and also suggests that biofilm may play a critical role in protecting anammox bacteria found in many acidic nature environments. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract Inline sludge treatment using free nitrous acid (FNA) was recently shown to be effective in establishing the nitrite pathway in a biological nitrogen removal system. However, the effects of FNA treatment conditions on the nitrite pathway performance remained to be investigated. In this study, three different FNA treatment frequencies (daily sludge treatment ratios of 0.22, 0.31 and 0.38, respectively), two FNA concentrations (1.35 mgN/L and 4.23 mgN/L, respectively) and two influent feeding regimes (one- and two-step feeding) were investigated in four laboratory-scale sequencing batch reactors. The nitrite accumulation ratio was positively correlated to the FNA treatment frequency. However, when a high treatment frequency was used e.g., daily sludge treatment ratio of 0.38, a significant reduction in ammonia oxidizing bacteria (AOB) activity occurred, leading to poor ammonium oxidation. AOB were able to acclimatise to FNA concentrations up to of 4.23 mgN/L, whereas nitrite oxidizing bacteria (NOB) were limited by an FNA concentration of 1.35 mgN/L over the duration of the study (up to 120 days). This difference in sensitivity to FNA could be used to further enhance nitrite accumulation, with 90% accumulation achieved at an FNA concentration of 4.23 mgN/L and a daily sludge treatment ratio of 0.31 in this study. However, this high level of nitrite accumulation led to increased N 2 O emission, with emission factors of up to 3.9% observed. The N 2 O emission was mitigated (reduced to 1.3%) by applying two-step feeding resulting in a nitrite accumulation ratio of 45.1%. Economic analysis showed that choosing the optimal FNA treatment conditions depends on a combination of the wastewater characteristics, the nitrogen discharge standards, and the operational costs. This study provides important information for the optimisation and practical application of FNA-based sludge treatment technology for achieving the mainstream stable nitrite pathway. Graphical abstract Unlabelled Image Highlights • Study result and analysis guide free nitrous acid treatment condition determination • Stable mainstream nitrite pathway reached with nitrite accumulation ratio over 90%. • Distinct nitrifying bacteria acclimation behaviours to high treatment concentration • Treatment frequency negatively related to in-reactor nitrifying bacteria activities. • N 2 O emission mainly from nitrifier denitrification, can be reduced by multi-feeding. [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]

Photosynthetic bacteria (PSB) were reported to have great potential for nitrogen removal when treating high-ammonia wastewater. Light-oxygen conditions are the most important parameter; however, the role of the microbial community composition for PSB nitrogen removal remains unclear. This study focussed on the effects of three light-oxygen conditions on PSB performance and the microbial community during high-ammonia wastewater treatment. The results showed that light-oxygen conditions had a significant impact on nitrogen removal efficiency, microbial community diversity and composition. PSB under light-aerobic condition had the highest biomass, highest COD, NH 4 + -N, and NO 3 − -N removal efficiency, and the highest community diversity; these results have not been reported before. The dominant genus in samples under light-aerobic condition was Pseudomonas (with a proportion of 58.23%). The correlation analysis showed that Pseudomonas was positively correlated with NH 4 + -N and NO 3 − -N removal, with high correlation coefficients of 0.9. These results further revealed the underlying nitrogen removal mechanism of PSB in high-ammonia wastewater treatment. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Ordered mesoporous carbons are proposed as adsorbent for treatment of the CGW. • The pore sizes of OMCs can be controlled by varying the synthesis conditions. • The adsorption process of OMC is a spontaneous and endothermic process. • It is proved that physical adsorption takes place during the adsorption process. • The adsorption of samples on phenol from CGW has reached an ideal level. Abstract Coal gasification wastewater (CGW) possess a high phenolics content, how to remove phenols is the crux of the environmental problems. In this work, we report the design and synthesis of a several highly graphitized ordered mesoporous carbons (OMCs) by carbonization of precursors from phenol and formalin. The obtained porous OMCs have uniform structures with the pore size, order degree, and surface areas being controllable by varying the synthesis conditions. In depth study of the prepared materials reveals that the OMCs carbonized at 923.15 K exhibit ordered 2D hexagonal mesoporous structures with high degree of graphitization, high surface area (590.6 m2 · g−1), appropriate pore size (mean diameter about 10 nm) and large mesoporous pore volume (0.512 cm3 · g−1). The prepared OMCs are applied as adsorbent for treatment of the CGW collected directly from the biochemical effluent of coal chemical enterprise in Inner Mongolia Autonomous region, China. The OMCs show excellent adsorption properties for phenol effluent with the removal efficiency of phenols being up to 92.3%. The adsorption experiment data demonstrates that the adsorption is a multi-molecular layer adsorption process, during which the physical adsorption takes place. In addition, the study of adsorption thermodynamics indicates that the adsorption process is spontaneous and endothermic. The adsorption of samples on phenol from CGW has reached an ideal level. [ABSTRACT FROM AUTHOR]

In order to achieve simple pollutant removal and simultaneous resource recovery in high-COD-non-toxic wastewater treatment, a one-step photosynthetic bacteria (PSB) method was established using batch study experiment. The effluent COD met the national discharge standard, and biomass with rich protein and high-value substances was efficiently produced. It eliminated the demand of post-treatment for conventional PSB treatment. Results showed that Rhodopseudomonas effectively treated brewery wastewater and achieved biomass proliferation. Yeast extract was the best additive for PSB growth and the effluent COD was below 80 mg/L with 400 mg/L yeast extract, meeting the national discharge standard. In addition, the PSB biomass increased by 2.6 times, and the cells were rich in protein, polysaccharide, carotenoids, bacteriochlorophyll and coenzyme Q10, reaching 420.9, 177.6, 2.53, 10.75 and 38.6 mg/g respectively. This work demonstrated the great potential of PSB for high-COD non-toxic wastewater treatment in one-step process. [ABSTRACT FROM AUTHOR]

Reliable modelling of sulfide and methane production in sewer systems is required for efficient sewer emission management. Wastewater compositions affect sulfide and methane production kinetics through both its short-term variation influencing the substrate availability to sewer biofilms, and its long-term variation affecting the sewer biofilm structure. While the short-term effect is well considered in existing sewer models with the use of Monod or half-order equations, the long-term effect has not been explicitly considered in current sewer models suitable for network modelling. In this study, the long-term effect of wastewater compositions on sulfide and methane production activities in rising main sewers was investigated. A detailed biofilm model was firstly developed, and then calibrated and validated using experimental data measured during the entire biofilm development period of a laboratory sewer reactor. Based on scenario simulations using the detailed biofilm model, empirical equations describing the long-term effect of sulfate and sCOD (soluble chemical oxygen demand) concentrations on k H2S (the maximum sulfide production rate of sewer biofilm) and k CH4 (the maximum methane production rate of sewer biofilm) were proposed. These equations require further verification in future studies before their potential integration into network-wide sewer models. [ABSTRACT FROM AUTHOR]

Nitrous oxide (N 2 O) is an important greenhouse gas and an ozone-depleting substance which can be emitted from wastewater treatment systems (WWTS) causing significant environmental impacts. Understanding the N 2 O production pathways and their contribution to total emissions is the key to effective mitigation. Isotope technology is a promising method that has been applied to WWTS for quantifying the N 2 O production pathways. Within the scope of WWTS, this article reviews the current status of different isotope approaches, including both natural abundance and labelled isotope approaches, to N 2 O production pathways quantification. It identifies the limitations and potential problems with these approaches, as well as improvement opportunities. We conclude that, while the capabilities of isotope technology have been largely recognized, the quantification of N 2 O production pathways with isotope technology in WWTS require further improvement, particularly in relation to its accuracy and reliability. [ABSTRACT FROM AUTHOR]

• The degradation system could effectively remove BHA-metal complexes. • Acidic conditions were conducive to the removal of TOC, As (V) and Cr (VI). • Alkaline conditions promoted the immobilization of metal cations. • ΔG values of various BHA-metal complexes played key roles in TOC removal. • C–C, C O and Fe–O sites participated in the metals immobilization process. The organometal complexes pollution in beneficiation wastewater has aroused increasing attentions because they were difficult to remove by traditional technologies. In this study, eleven kind of benzohydroxamic acid (BHA)-metal (Pb2+, Cu2+, Mg2+, Ca2+, Zn2+, Cd2+, Fe3+, Fe2+, Sb3+, Cr(Ⅵ) and As(V)) complexes were chosen to investigate their removal performance and mechanism in heterogeneous persulphate degradation system. The metal-biochar/peroxymonosulfate (PMS) system showed the highest and worst total organic carbon (TOC) removal efficiency for BHA-Fe2+ (68.4%) and BHA-As(V) (22.8%), respectively. Meanwhile, the metal-biochar composite had different immobilization abilities toward multiple metal ions. Density functional theory (DFT) revealed that ΔG values of various BHA-metal complexes played key roles for TOC removal. While, metal adsorption was mainly depended on the functional groups on the catalyst surface. After the reaction, Cu, Pb, Fe, Sb, Cr and As mainly existed as residuals. Overall, this study has provided valuable and novel insights into the removal of BHA-metal complexes and broadened the practical applicability of the waste solid-based metal-biochar catalyst coupled with persulphate in beneficiation wastewater treatment. [ABSTRACT FROM AUTHOR]

• Significant loss of total nitrogen is observed in an acidic aerobic sludge digester. • Nitrite is mainly reduced to NO and N 2 O under the acidic aerobic condition. • Rate of aerobic nitrite reduction is comparable to that of aerobic ammonia oxidation. • Controlling the nitrite reduction is critical to development of acidic sludge treatment. The acidic (i.e., pH ∼5) activated sludge process is attracting attention because it enables stable nitrite accumulation and enhances sludge reduction and stabilization, compared to the conventional process at neutral pH. Here, this study examined the production and potential pathways of nitric oxide (NO) and nitrous oxide (N 2 O) during acidic sludge digestion. With continuous operation of a laboratory-scale aerobic digester at high dissolved oxygen concentration (DO>4 mg O 2 L−1) and low pH (4.7±0.6), a significant amount of total nitrogen (TN) loss (i.e., 18.6±1.5% of TN in feed sludge) was detected. Notably, ∼40% of the removed TN was emitted as NO, with ∼8% as N 2 O. A series of batch assays were then designed to explain the observed TN loss under aerobic conditions. All assays were conducted with a low concentration of volatile solids (VS), i.e., VS<4.5 g L−1. This VS concentration is commensurate with the values commonly found in the aeration tanks of full-scale wastewater treatment systems, and thus no significant nitrogen loss should be expected when DO is controlled above 4 mg O 2 L−1. However, nitrite disappeared at a significant rate (with the chemical decomposition of nitrite excluded), leading to NO production in the batch assays at pH 5. The nitrite reduction could be associated with endogenous microbial activities, e.g., nitrite detoxification. The significant NO production illustrates the importance of aerobic nitrite reduction during acidic aerobic sludge digestion, suggesting this process cannot be neglected in developing acidic activated sludge technology. [Display omitted] [ABSTRACT FROM AUTHOR]

In Australia, recycled water schemes have been implemented in residential developments to contribute to sustainable urban development, improve water supply security and reduce pollutant discharges to the environment. A proportion of these schemes, however, have been decommissioned well before the end of their design life which raises questions about the adequacy of the risk assessment and management practices adopted for recycled water schemes. Through a detailed literature review, an investigation of 21 residential recycled water schemes and in-depth interviews with nine scheme stakeholders, we identified 34 risk factors arising from six sources which have the potential to impact the long-term viability of residential recycled water schemes. Of the 34 risk factors identified, 17 were reported to have occurred during the development and implementation of the 21 schemes investigated. The overall risk rating of the 17 factors was qualitatively defined on the basis of the likelihood of occurrence and the impact of the risk factors on the scheme objectives. The outcomes of the assessment indicate that the critical risks to the long-term viability of residential recycled water schemes are 1. unanticipated operational costs, 2. legal and contractual arrangements, 3. regulatory requirements and approval process and 4. customer complaints and expectations not met. To date, public health risks associated with the provision of recycled water have been of primary concern, though the outcomes of this study indicate that the impact to public health has been low. Evidently there is a need for improved assessment and management practices which address the range of critical risk factors, in addition to the routine consideration of public health risks. [ABSTRACT FROM AUTHOR]

• Electrochemical Fe-dosing decreases TSS, COD, dissolved S2−, and P concentrations. • Electrochemical Fe-dosing also decreases H 2 S and CO 2 contents in biogas. • Electrochemical Fe-dosing can mitigate organic fouling of membrane filtration. • The in-situ electrochemical Fe-dosing can generate more benefits than the ex-situ. • Electrochemically generated iron is cost-effective compared to use of iron chemicals. Although iron salts such as iron(III) chloride (FeCl 3) have widespread application in wastewater treatment, safety concerns limit their use, due to the corrosive nature of concentrated solutions. This study demonstrates that local, electrochemical generation of iron is a viable alternative to the use of iron salts. Three laboratory systems with anaerobic membrane processes were set up to treat real wastewater; two systems used the production of either in-situ or ex-situ electrochemical iron (as Fe2+ and Fe2+(Fe3+) 2 O 4 , respectively), while the other system served as a control. These systems were operated for over one year to assess the impact of electrochemically produced iron on system performance. The results showed that dosing of electrochemical iron significantly reduced sulfide concentration in effluent and hydrogen sulfide content in biogas, and mitigated organics-based membrane fouling, all of which are critical issues inherently related to sustainability of anaerobic wastewater treatment. The electrochemical iron strategy can generate multiple benefits for wastewater management including increased removal efficiencies for total and volatile suspended solids, chemical oxygen demand and phosphorus. The rate of methane production also increased with electrochemically produced iron. Economic analysis revealed the viability of electrochemical iron with total cost reduced by one quarter to a third compared with using FeCl 3. These benefits indicate that electrochemical iron dosing can greatly enhance the overall operation and performance of anaerobic membrane processes, and this particularly facilitates wastewater management in a decentralized scenario. [Display omitted] [ABSTRACT FROM AUTHOR]

Several mathematical models have been proposed to describe nitrous oxide (N 2 O) production by ammonia oxidizing bacteria (AOB) under varying operational conditions. However, none of these N 2 O models are able to capture N 2 O dynamics caused by the variation of inorganic carbon (IC) concentration, which has recently been demonstrated to be a significant factor influencing N 2 O production by AOB. In this work, a mathematical model that describes the effect of IC on N 2 O production by AOB is developed and experimentally validated. The IC effect is considered by explicitly including the AOB anabolic process in the model, which is coupled to the catabolic process with the use of the Adenosine triphosphate (ATP) and Adenosine diphosphate (ADP) pools. The calibration and validation of the model were conducted using experimental data obtained with two independent cultures, including a full nitrification culture and a partial nitritation culture. The model satisfactorily describes the N 2 O data from both systems at varying IC concentrations. This new model enhances our ability to predict N 2 O production by AOB in wastewater treatment systems under varying IC conditions. [ABSTRACT FROM AUTHOR]

"Sludge-drying lagoons" are a preferred sludge treatment and drying method in tropical and subtropical areas due to the low construction and operational costs. However, this method may be a potential significant source of methane (CH4) because some of the organic matter would be microbially metabolized under anaerobic conditions in the lagoon. The quantification of CH4 emissions from lagoons is difficult due to the expected temporal and spatial variations over a lagoon maturing cycle of several years. Sporadic ebullition of CH4, which cannot be easily quantified by conventional methods such as floating hoods, is also expected. In this study, a novel method based on mass balances was developed to estimate the CH4 emissions and was applied to a full-scale sludge-drying lagoon over a three year operational cycle. The results revealed that processes in a sludge-drying lagoon would emit 6.5 kg CO2-e per megaliter of treated sewage. This would represent a quarter to two-thirds of the overall greenhouse gas (GHG) emissions from wastewater-treatment plants (WWTPs). This work highlights the fact that sludge-drying lagoons are a significant source of CH4 that adds substantially to the overall GHG footprint of WWTPs despite being recognized as a cheap and energy-efficient means of drying sludge. [ABSTRACT FROM AUTHOR]

The presence of a high level of dissolved methane (e.g., 20–26 g m −3 ) in the anaerobic sludge digestion liquor represents a major challenge to the treatment of this stream, as its emission to the atmosphere contributes significantly to the carbon footprint of wastewater treatment. Here we propose a new approach to simultaneous ammonium and dissolved methane removal from the anaerobic digestion liquor through integrating partial nitritation-Anammox and denitrifying anaerobic methane oxidation (DAMO) processes in a single-stage membrane biofilm reactor (MBfR). In such an MBfR, the anaerobic digestion liquor is provided in the bulk liquid, while oxygen is supplied through gas-permeable membranes to avoid dissolved methane stripping. A previously developed model with appropriate extensions was applied to assess the system performance under different operational conditions and the corresponding microbial interactions. Both influent surface loading (or hydraulic retention time) and oxygen surface loading are found to significantly influence the total nitrogen (TN) and dissolved methane removal, which jointly determine the overall system performance. The counter diffusion and concentration gradients of substrates cause microbial stratification in the biofilm, where ammonia-oxidizing bacteria (AOB) attach close to the membrane surface (biofilm base) where oxygen and ammonium are available, while Anammox and DAMO microorganisms jointly grow in the biofilm layer close to the bulk liquid where methane, ammonium, and nitrite are available with the latter produced by AOB. These results provide first insights and useful information for the design and operation of this new technology for simultaneous ammonium and dissolved methane removal in its potential future applications. [ABSTRACT FROM AUTHOR]

Recent studies have shown that sewer systems produce and emit a significant amount of methane. Methanogens produce methane under anaerobic conditions in sewer biofilms and sediments, and the stratification of methanogens and sulfate-reducing bacteria may explain the simultaneous production of methane and sulfide in sewers. No significant methane sinks or methanotrophic activities have been identified in sewers to date. Therefore, most of the methane would be emitted at the interface between sewage and atmosphere in gravity sewers, pumping stations, and inlets of wastewater treatment plants, although oxidation of methane in the aeration basin of a wastewater treatment plant has been reported recently. Online measurements have also revealed highly dynamic temporal and spatial variations in methane production caused by factors such as hydraulic retention time, area-to-volume ratio, temperature, and concentration of organic matter in sewage. Both mechanistic and empirical models have been proposed to predict methane production in sewers. Due to the sensitivity of methanogens to environmental conditions, most of the chemicals effective in controlling sulfide in sewers also suppress or diminish methane production. In this paper, we review the recent studies on methane emission from sewers, including the production mechanisms, quantification, modeling, and mitigation. [ABSTRACT FROM AUTHOR]

• Mass balance of 11 PFAAs in a laboratory wastewater system was investigated. • Total mass of PFAAs increased by 112% in the system. • Mass increase of PFAAs: activated sludge > sewer process > anaerobic digestion. • Mass of 11 PFAAs in the effluent was 5 times higher than that in digested sludge. The fate and formation of perfluoroalkyl acids (PFAAs) have been investigated during wastewater treatment processes but studies for the entire urban wastewater system comprising the sewage transport and wastewater and sludge treatment processes are scarce. This work performs an integrated assessment of the formation and fate of PFAAs in the urban wastewater system together with their behavior in separate components of the system. To achieve this, PFAAs were monitored over five weeks in a laboratory-scale urban wastewater system comprising sewer reactors, a wastewater treatment reactor, and an anaerobic sludge digester. The system was fed with real domestic wastewater. The total mass of 11 PFAAs flowing out of the laboratory wastewater system significantly (p < 0.05) increased by 112 ± 14 (mean ± standard error)% compared to that entering the system. Formation of PFAAs was observed in all three biological processes of the system. In anaerobic sewer process, perfluoropentanoic acid (PFPeA), perfluoroheptanoic acid (PFHpA), and perfluorooctane sulfonate (PFOS) exhibited significant formation (p < 0.05) with the mass flow increased by 79 ± 24%, 109 ± 31%, and 57 ± 17%, respectively. During the wastewater treatment process, perfluorohexanoic acid (PFHxA), perfluorooctanoic acid (PFOA), and perfluorododecanoic acid (PFDoDA) demonstrated significant increase (p < 0.05) in their mass flows by 176 ± 56%, 92 ± 21%, and 516 ± 184%, respectively. In contrast, only PFHxA was found to significantly (p < 0.05) increase by 130 ± 40% during anaerobic digestion process. The total mass of 11 PFAAs discharged through the effluent (201 ± 24 ng day−1) was 5 times higher than that through the digested sludge (29 ± 6 ng day−1). [Display omitted] [ABSTRACT FROM AUTHOR]