Anaerobic methanogenesis is a fundamental pathway for resource recovery from municipal wastewater and an effective pretreatment for anaerobic ammonium oxidation. However, its efficiency is frequently constrained by ambient temperature fluctuations and the low organic strength of real municipal wastewater. Here, a Fe3O4-modified volcanic rock anaerobic biofilter was constructed to investigate its phased methanogenic performance and the mechanisms underlying its enhancement under ambient temperature conditions (15.0-19.4 °C) for treating real municipal wastewater. Results showed that Fe3O4 induced a distinct, phase-dependent response, shifting from initial inhibition associated with electron competition to a subsequent 29.7% increase in methane yield, reaching 0.223 L CH4/g TCODre. Mechanistically, Fe3O4 enhanced the activities of the electron transport system and coenzyme F420 while promoting extracellular protein secretion, which facilitated the development of a denser biofilm. With the gradual reduction in dissimilatory iron reduction (DIR) activity during operation, the dominant electron transfer mediators appeared to shift from primarily Fe3O4 to a combined mechanism involving both residual Fe3O4 and humic-like substances. During the initial phase, Fe3O4 promoted the enrichment of hydrolytic-acidogenic and dissimilatory iron-reducing bacteria, thereby accelerating organic degradation. Subsequently, an enrichment of potential syntrophic acetogens (e.g., Christensenellaceae_R-7_group, Smithella, and norank_f__Rikenellaceae) and methanogens (Methanosaeta) coincided with improved methane production. These findings provide a viable strategy to overcome the methanogenic bottleneck in municipal wastewater treatment at ambient temperature and provide insights into the dynamic, phase-specific mechanisms of Fe3O4-mediated enhancement.

Algae not only play a crucial role in carbon sequestration and reduction, but also act as the initiator of water quality deterioration and eutrophication. To date, rare studies have focused on the presence, abundance of microalgae and bacterial - microalgal interactions in reclaimed wastewater treatment plants (RWWTPs). In this study, the bacterial and microalgal community compositions, as well as bacterial - microalgal interactions were investigated in three typical RWWTPs in different seasons. Results showed that not only bacteria but also microalgae were contained in the RWWTP influent, with microalgae exhibiting temporal variations in community. Microalgae, mainly including Bacillariophyta, Cyanobacteria and Chlorophyta existed widely in three RWWTPs. The community compositions of microalgae and bacteria varied with process types, operation parameters, seasons and environmental conditions, etc. Correlation analysis showed that Bacillariophyta, Cyanobacteria and Chlorophyta were commonly positively correlated with Acidobacteriota, Myxococcota, Nitrospirota and Planctomycetota, while Cyanobacteria and Chlorophyta were negatively correlated with Patescibacteria. Notably, Cyclotella, Fragilaria and Synechococcus were detected in RWWTP effluent, which may indicate potential environmental risks such as harmful algal blooms. These results highlight the importance of focusing more on microalgal growth and control in RWWTP monitoring. Moreover, the detection of microalgae in RWWTP and their distribution characteristics across different treatment units suggest the potential feasibility of applying bacterial-microalgal symbiotic system in practical wastewater treatment.

Monovalent-selective cation exchange membranes are crucial for water softening and resource recovery via electrodialysis (ED). However, effective separation of monovalent and divalent ions remains challenging due to small differences in charge and ionic size. This study employed low-temperature plasma grafting to covalently graft polyaniline onto cation exchange membrane substrates. Iodinated linear alkanes with varying carbon chain lengths were used to quaternize the polyaniline layer, modulating surface hydration energy. Increasing the carbon chain length enhanced membrane hydrophobicity, and the Na+/Ca2+ permselectivity of the PANI-C5 CEM increased from 0.70 to 6.06. In mixed-salt systems, Ca2+ experienced stronger electrostatic repulsion and additional migration resistance due to the interception effect of surrounding Na+ ions. This work demonstrates that integrating surface hydration energy regulation with ionic competition effects is an effective strategy for developing high-performance monovalent-selective membranes.

Completely autotrophic nitrogen removal over nitrite (CANON) is widely implemented for treating high-ammonium wastewater. However, nitrous oxide (N2O) emissions may offset its climate benefits, and pathway-level evidence from full-scale systems remains scarce. Here, N2O production, transformation, and underlying pathways were investigated in a full-scale integrated fixed-film activated sludge (IFAS)-CANON system treating sludge digestion supernatant using in situ monitoring, batch tests, biofilm microelectrode profiling, and stable isotope analysis. The N2O emission factor of the full-scale system reached 1.59 ± 0.50% of the total nitrogen removed. Despite similar microbial community structures across different locations, N2O production and associated pathways varied spatially. Ammonia-oxidizing bacteria (AOB)-enriched activated sludge and the biofilm outer layer were identified as the main N2O-producing zones. Driven by the complex wastewater matrix, both biotic and abiotic pathways contributed to N2O production, with biotic processes dominating. Biotic pathways mainly included AOB denitrification and hydroxylamine (NH2OH) oxidation, and heterotrophic denitrification also contributed due to limited biodegradable carbon and low denitrifying community diversity. For abiotic N2O production, NH2OH oxidation by HNO2 was a potentially important pathway. Nitrite accumulation was the key driver across all critical pathways. Correspondingly, in the full-scale system, N2O production was significantly higher at locations where NO2⁻-N concentrations exceeded 25 mg/L than at downstream locations. These findings provide process-level mechanistic insights and identify key targets for reducing N2O emissions in full-scale IFAS-CANON systems.

In natural surface environments, iron (hydroxy) oxides serve as primary scavengers for dissolved chromium (Cr). However, complex environmental conditions often cause Cr re-leaching, especially when organic matter (OM) interacts with Cr-Fe coprecipitates through coprecipitation or post-adsorption. Therefore, we selected the rarely studied alkaline conditions, taking paper wastewater as an example, and its important OM, alkali lignin, was selected as the coexisting OM to explore the stability of Cr-Fe coprecipitates. However, how lignin's formation pathway (coprecipitation vs post-adsorption) specifically controls Cr(III) stability remains unresolved. This study revealed that in the coprecipitation pathway, lignin enhanced average dissolution to 0.51mg/L by causing structural disorder and reductive dissolution, with the Fe/lignin contents playing a significant role. The post-adsorption pathway indicated that low lignin concentrations encouraged Cr release via complexation, while high concentrations promoted colloid formation, resulting in Cr re-immobilization. Under H2O2-induced oxidative stress, lignin triggers the invalid decomposition of H2O2, thereby suppressing the oxidation of solid-phase Cr(III). Moreover, structural disorder in Cr-Fe-lignin coprecipitates further strengthened this inhibitory effect. These findings clarified how OM, through different interaction pathways, regulated the dissolution stability and reoxidation potential of Cr-Fe coprecipitates, and offered a theoretical basis for assessing Cr migration and transformation risks in complex settings.

Microplastics (MPs) in sewer systems can be transported extensively before entering wastewater treatment plants. Sewer systems harbor complex microbial communities under low-oxygen, sulfide-rich conditions that drive key biogeochemical cycles. These conditions drive microplastic aging, whereas these particles concurrently perturb sewer microbial ecology and metabolic functions. However, the underlying mechanisms of in-sewer microplastic aging and their subsequent impacts on sewer microbiomes remain unclear. Here we show that hydroxyl radicals preferentially attack ester bonds (C–O) in polyethylene terephthalate (PET) and polybutylene adipate terephthalate (PBAT) MPs, increasing surface roughness, reducing particle size, promoting surface oxidation, and ultimately inducing polymer chain scission. Exposure to PET and PBAT MPs at 30–500 particles L−1 intensified oxidative stress, disrupted membrane integrity and permeability, impaired microbial activity, and suppressed sulfide production in a dose-dependent manner. These disruptions coincided with weakened microbial co-occurrence networks and a shift from stochastic toward deterministic community assembly. High doses of PET and PBAT MPs reduced hydrolytic/fermentative bacteria and sulfate-reducing bacteria by up to 63.4% and 49.7%, respectively, while enriching hydrogen-producing acetogenic bacteria and methanogenic archaea by 48.4–67.0%, consistent with reduced sulfidogenic potential and enhanced methanogenic potential. Changes in genes related to antioxidant defense, SOS response, quorum sensing (e.g., sodA, katG, lexA, and luxS), and redox signaling suggested potential mechanisms of microbial metabolic perturbations aggravated by PET and PBAT MPs. Our results indicate that sewer systems are not passive conduits but active reactors that promote MP aging, and that MPs reshape microbial functions. Microplastic control may therefore help reduce downstream particle pollution and limit perturbations to urban sewage biogeochemistry.

Most pollutants in the environment exist in complex forms, and exploring the impact of a single pollutant lacks wide applicability. The co-exposure of microplastics (MPs) and NaClO in wastewater treatment plants (WWTPs) is a widespread occurrence. At present, relevant reports on the impact of individual NaClO or MPs on antibiotic resistance genes (ARGs) have been established. Herein, this study investigated the fate of antibiotic-resistant bacteria (ARB) and ARGs after exposure to MPs with or without NaClO stress. In this study, the total ARG abundance increased by 11.83% under MPs stress, and further increases by 17.89% under NaClO stress with MPs co-exposure. The mechanism was that the presence of NaClO promoted the selective enrichment of potential ARB and ARGs on the MPs-biofilm. The surface morphology of the MPs was changed and the attached biofilm became thicker, which provided a suitable environment for the proliferation of ARB and the spread of ARGs. Vertical gene transfer (VGT) and horizontal gene transfer (HGT) of ARGs were facilitated by MPs under NaClO stress. Specifically, the VGT of ARGs was facilitated via enhanced bacterial cell proliferation (by 132.66%), and relevant functional genes are also increased. HGT of ARGs is promoted by the increasing relative abundance of mobile genetic elements (MGEs). ARG-carrying plasmids are also demonstrated that MPs promoted HGT of ARGs in the presence of NaClO. The increase in oxidative stress, cell membrane permeability, and Type IV secretion system (T4SS) collaboration facilitated the HGT of ARGs. In summary, co-exposure to NaClO and MPs promote VGT and HGT of ARGs through the variation in MPs structure and the enhancement of MPs-biofilms. Furthermore, the presence of MPs restrained the disinfection effect of NaClO, with an inhibition rate higher than 50%.

MPs aging/degradation in thermal hydrolysis of sludge (THS) might interfere with organic matter reaction pathways, yet the specific mechanism unclear. This study investigated polyethylene (PE) and polyethylene terephthalate (PET)’s impacts on organic matter transformation and associated molecular mechanism across THS temperatures. It was found that MPs altered organic matter distribution, promoted chain breakage, and induced protein structures change. These enabled MPs to boost clean energy gases production (H2 up 2.45–3.07 times, CH4 up 1.67–2.33 times at 180°C vs. sludge’s maximum yield) and reduce volatile sulfur compounds types. The active species generated by sludge were likely act on MPs, accelerating their aging. At the molecular level, PE/PET bond to proteins through hydrophobic interactions, hydrogen bonds, salt bridges and π-cation interactions. These bindings reduced their stability, enhanced reaction activity, and promoted mutual transformation (i.e., protein dissociation). In summary, MPs in sludge could further promote sludge disintegration and organic matter transformation.

Sludge thickening, the first step in sludge treatment, is a major source of volatile sulfur compounds (VSCs) in wastewater treatment plants. The anaerobic environment within thickened sludge favors VSC formation, leading to their massive accumulation and subsequent release during dewatering, which causes environmental pollution. However, how VSCs are transformed and produced from sulfur-containing substances during sludge thickening is poorly known. This study investigates VSC generation, distribution, and sulfur transformation pathways during sludge thickening. Results indicate that the anaerobic environment during thickening promotes the production of a wide variety of VSCs and a substantial increase in their concentrations (a 1353 % to 4613.2 % increase in thickened sludge relative to influent sludge). Concentration also changes sulfur-containing substances from inorganic (SO42-) to organic forms, leading to a predominance of organic sulfur. Analysis of sulfur-containing precursor metabolism reveals that VSCs generated during concentration mostly originate from degradation of organic sulfur precursors, with methionine degradation rates exceeding those of cysteine, and with SO42- making a limited direct contribution. The main role of SO42- is to promote organic sulfur-containing precursor accumulation through assimilation. Abundances of sulfate-reducing and sulfur-oxidizing bacterial populations in sludge remain low, and key SO42- reduction enzyme activities remain persistently suboptimal, likely explaining the weak dissimilatory sulfate reduction. These insights clarify the mechanisms of sulfur transformation and VSC emission, providing a scientific foundation for optimizing sludge thickening processes and developing targeted odor control strategies.

Overcoming the limitations of single electron donor (ED) in microbial chain elongation (CE) process, such as lactate inefficiency and ethanol overoxidation, is crucial for advancing the commercial viability of CE system. This study investigated the feasibility of a lactate-ethanol ED alternating strategy in enhancing caproate production. Results demonstrated that compared to the single-ethanol control, the ethanol stage after lactate pre-cultivation significantly mitigated ethanol overoxidation and increased the maximum caproate yield by 58%. Mechanistic analysis revealed that this lactate-assisting-ethanol strategy not only better utilized the residual pyruvate (a byproduct of the lactate-stage acrylate pathway) as an additional CE substrate but also promoted acetyl-CoA production, accompanied by an increased microbial electron transport activity and a reduced matrix oxidation-reduction potential. Metagenomic data indicated that the microbial community was adaptable to the ED alternating processes, with lactate-utilizing bacterium (e.g., Pseudomonas) being enriched in the subsequent ethanol stage. Crucially, the increase in the relative abundance of genes encoding the Acrylate pathway-related succinate dehydrogenase and methylmalonyl-CoA mutase during the ethanol stage favored ethanol oxidation and intermediate metabolism, synergistically boosting caproate production. This work provides a novel and efficient ED alternation strategy that leverages microbial metabolic adaptation to improve CE efficiency.

Groundwater nitrate contamination, coupled with long-term overexploitation and intensive anthropogenic perturbations, has become a critical environmental challenge in the northwestern North China Plain, underscoring the urgent need to elucidate groundwater hydrochemical characteristics and their genetic mechanisms. Taking the upper section of the Yongding River alluvial–proluvial fan as the study area, this research aims to quantitatively decipher the hydrochemical characteristic and genetic mechanism of high-nitrate groundwater, identify the sources of nitrate contamination, and assess the associated human health risks. By leveraging over a decade of continuous hydrochemical monitoring data, an integrated analytical approach is adopted, including hydrochemical ionic ratio analysis, Positive Matrix Factorization, and Human Health Risk Assessment. The results indicate that the groundwater is characterized by HCO3-Ca. The pH values range from 7.2 to 8.2 while the total dissolved solids concentrations vary between 695 mg/L and 949 mg/L. Ionic ratio analysis demonstrates that water–rock interaction is the dominant controlling process, involving silicate hydrolysis, dissolution of carbonates, gypsum dissolution, and cation exchange. The Positive Matrix Factorization model quantitatively identifies four key factors controlling the hydrochemical characteristics of groundwater. Factor 1 is dominated by NO3− (76.67%) and associated with exogenous nitrate inputs from nitrogen fertilizer application. Factor 2 is dominated by Na+ (72.26%) and Mg2+ (81.67%), deriving from silicate weathering and dolomite dissolution. Factor 3 is governed by pH (59.62%) and K+ (71.65%), with its driving mechanism being the weathering and dissolution of potassium-bearing silicate minerals. Factor 4 is dominated by SO42− (50.12%) and constitutes a mixed source associated with sulfur-containing fertilizer application and livestock breeding. Groundwater NO3− concentrations range from 4.2 mg/L to 23.3 mg/L, with 69% of dry-season and 77% of wet-season samples exceeding the 10 mg/L threshold, primarily originating from manure and domestic wastewater. HHRA results show that nitrate poses significant non-carcinogenic health risks, with the highest risk observed in children (100% of samples at high risk), followed by adult females (92% at high risk) and adult males (77~92% at high risk). This study provides quantitative insights into the genetic mechanisms of groundwater nitrate contamination and offers a scientific basis for groundwater quality management and health risk mitigation in the NCP and other similar agricultural regions worldwide.

Under the background of China's "dual carbon" goal, developing low-energy-consuming and high-efficiency municipal wastewater treatment technology remains a major challenge. In particular, mainstream partial nitritation/anammox (PN/A) processes are difficult to maintain under low ammonium concentrations and complex substrate conditions, which limits their practical application. To overcome these limitations, this study introduced microalgae to establish a coupled partial nitritation-anammox-microalgae (PN/A-M) system. Its performance in treating municipal wastewater was systematically evaluated, and the underlying nitrogen conversion mechanisms were investigated through metagenomic and metabolic pathway analyses. After 120 days of continuous operation, the PN/A-M system achieved stable and efficient nitrogen removal, with an average total nitrogen (TN) removal efficiency of 85.16% and a maximum of 89.45%, while maintaining stable performance under approximately 30% reduced aeration after microalgae inoculation. Metagenomic analysis revealed significant enrichment of key functional genes: the transcripts per million (TPM) value of the ammonia oxidation amo gene cluster increased from 28.21 to 58.08, while the photosynthesis-related genes psbA and petF increased by 15.73% and 306.02%, respectively. Microalgal introduction increased the abundance of genes related to nitrogen metabolism and photosynthesis in the system. Overall, microalgae improved the stability and nitrogen conversion potential of the mainstream PN/A process, providing a promising strategy for low-energy nitrogen removal from municipal wastewater.

Carbon steel is widely employed in wastewater treatment plants (WWTPs), yet the complex and highly variable wastewater characteristics often lead to severe corrosion and scaling, shortening equipment lifespan and reducing operational efficiency. To address this challenge, carbon steel was selected as the study material, and rotating coupon tests, orthogonal experiments, and additional analytical methods were adopted to systematically elucidate how key water quality parameters (COD, NH4+, HCO3 , Cl , Ca2+, etc.) influence corrosion and scaling processes from physical, chemical, and biological perspectives. The protective performance of scale layers, corrosion inhibitors, and biocides was also evaluated. The results indicated that NH4+, COD, and water hardness are the primary factors accelerating corrosion. Specifically, NH4+ intensifies nitrification, lowering system pH and stimulating microbial growth, thereby significantly exacerbating corrosion. Regarding mitigation strategies, a combined formulation of amino trimethylene phosphonic acid (ATMP) and 2-phosphonobutane-1,2,4-tricarbox-ylic acid (PBTCA) at a 1:3 ratio exhibited strong synergistic scale-inhibition, achieving an inhibition rate of up to 94%. For controlling microbiologically influenced corrosion (MIC), biocide 1277 provided the most effective suppression of biofilm formation. This study offers threshold values for critical water quality indicators and identifies effective chemical formulations to mitigate corrosion and scaling in carbon steel equipment in WWTPs, providing substantial engineering value.

The emerging Fe(Ⅲ) reduction coupled to anaerobic ammonia oxidation (Feammox) process offers a promising approach toward carbon neutrality in wastewater treatment. However, its nitrogen transformation pathway and metabolic mechanism remain unclear. This study established a Feammox-dominant sequencing batch reactor (Fe-SBR) and operated it for 515 days, achieving an ammonia removal efficiency of 97.9 ± 4.5% during the stable phase. Feammox was confirmed as the dominant process for NH4+-N conversion, accounting for 83.2% of ammonia transformation. NH2OH, NO, and N2O were identified as key intermediates in the Feammox nitrogen transformation pathway. By integrating metagenomic analysis of functional gene dynamics with metagenome-assembled genomes (MAGs), a potential coupled iron-nitrogen (Fe-N) metabolic pathway was proposed. This pathway suggested that the Feammox process might be accomplished through multi-species metabolic cooperation, with MtrC-mediated extracellular electron transfer potentially serving as the key link coupling nitrogen transformation to the iron redox cycle. These findings provide novel insights into the Feammox metabolic pathway and lay a theoretical foundation for the future precise control and optimization of this process.

Microplastics (MPs) and NaClO were both prevalent in MBRs, and their coexistence poses a potential threat to nitrogen biotransformation in wastewater treatment systems. However, investigations on how MPs combined with NaClO affect the microbial nitrogen conversion and metabolism of the activated sludge are still scanty. In this study, the MPs or NaClO exposure alone had marginal impacts on the nitrogen removal in MBRs, while the two pollutants' coexistence in MBR, the total nitrogen removal efficiency decreased from 83.59 % to 74.46 % by the suppression of nitrogen transformation processes. Metagenomic analysis revealed that the abundance of functional genes encoded by key enzymes related to nitrogen transformation, including nirK, norB, nosZ and nirS, were also decreased with MPs and NaClO co-exposure. The reason for the above phenomenon may be the biotoxicity of MPs to activated sludge caused by NaClO, the ROS production increased to 128.57 % with MPs and NaClO co-exposure. The increase of intracellular oxidative stress level and virulence factors synthesis confirmed that NaClO can aggravate the toxicity of MPs to activated sludge. The increased toxicity of MPs to activated sludge caused by NaClO may be attributed to the oxidation of MPs, that is, the change of functional groups. This study provides vital insights into the responses of microbial community structure and nitrogen conversion processes to interference MPs combined with NaClO backwash agent residual in MBRs.

While the partial nitrification/anammox-based completely autotrophic nitrogen removal over nitrite (CANON) process offers substantial advantages for treating high-ammonium wastewater, significant nitrous oxide (N2O) emissions pose a challenge to its low-carbon sustainability. In this study, long-term field sampling and stable isotope analysis were conducted in a full-scale CANON process to evaluate N2O dynamics and the contributions of different pathways, as well as to perform a scenario-based carbon footprint assessment. The results showed that N2O emissions were low when hydroxylamine oxidation dominated, whereas free nitrous acid (FNA) accumulation was associated with an increased estimated denitrification-associated contribution and higher N2O emissions. Aeration-enhanced gas-liquid transfer likely contributed to dissolved N2O release into the gas phase. During long-term operation of this process, periods with dissolved oxygen (DO) concentrations below 0.20 mg/L were associated with approximately 65 % lower N2O emissions. Under the adopted system boundaries and parameter values, the calculated carbon footprint and operating cost of the CANON scenario were 42 % and 83 % lower than those of the conventional anaerobic-anoxic-oxic process, mainly owing to lower electricity consumption and the absence of external carbon addition. These findings indicate that maintaining stable pH, limiting FNA accumulation, and avoiding transient DO increases may help preserve the low-carbon performance of CANON under site-specific operating conditions.

Sewers served as primary gateways for microplastics (MPs) into urban drainage systems, yet MP transformation under dark, anaerobic, and sulfide-rich sewer conditions remained poorly understood. This study elucidated the aging characteristics of polyester MPs (polyethylene terephthalate (PET) and polybutylene adipate terephthalate (PBAT)) in sewers and identified the key mechanisms governing sulfide-induced MP aging. Sewer exposure reduced the number-average molecular weight and increased the surface hydrophilicity, carbonyl index, and O/C ratio of PET/PBAT MPs, indicating pronounced oxidative modification. Among representative sewer constituents, sulfide was identified as the crucial driver of MP aging. Hydroxyl radicals and superoxide anions generated via sulfide autoxidation induced oxidation and sulfide-addition reactions in both PET and PBAT MPs, while PBAT MPs likely underwent concurrent reduction and more pronounced physical damage. Sulfide also promoted the leaching of dissolved organic matter (DOM) from polyester MPs, particularly PBAT (up to 12.86mg/L), yielding more humified, predominantly endogenous-like DOM signatures and generating up to 107 nanoplastics/mL. These findings provided mechanistic evidence of sulfide-induced MP aging in sewers, offering essential insights into the ecological risks of MPs in urban drainage systems.

The microplastics (MPs) are often exist as cumulative state in the bioreactor (especially MBR) of wastewater treatment plants (WWTPs). NaClO is a common chemical cleaning agent which will inevitably enter the MBR membrane pool and contact with the accumulated MPs in the membrane pool during membrane cleaning process. Therefore, the focus of this study is the toxicity mechanism of NaClO and MPs co-exposure to activated sludge. In this study, the COD, TN, and TP removal efficiencies decreased at first several cycles, and then gradually recovered without NaClO stress. While the nutrient removal efficiency showed a continuous declination trend with NaClO stress and have no recovery trend. Meanwhile, the key enzymes (such as AMO, NXR, NIR and NAR), which could echo the trend of nutrient metabolism. The dominate bacteria related to nitrogen removal including nitrification (Saccharimonadales) and denitrification (Tessaracoccus, Mobilicoccus, vadinHA17, Mesorhizobium and Hyphomicrobium) were both inhibited with NaClO and PVC-MPs co-exposed. This study also confirmed that NaClO stress could change the types of MPs leachate and enhance the release of main additives (BPA) from MPs. The NaClO and MPs co-exposure could enhance the level of oxidative stress, which led to the broken of cell membrane. The toxicity mechanism of NaClO and MPs co-exposure to activated sludge is as follows: NaClO can increase the oxidative stress level of microplastics, which has nothing to do with the release of trace additives.

The emissions of volatile sulfur compounds (VSCs) from wastewater treatment plants (WWTPs) pose odor nuisances and health risks to workers and surrounding residents, thus becoming a major environmental concern for these facilities. This study investigated the long-term monitoring of emissions of VSCs from an anaerobic/oxic (A/O) WWTP and employed the AERMOD model to simulate the dispersion of VSCs within an area of 5 × 5 km2 for assessing the impact of these emissions on odor and health risks. The obtained results indicated that the emissions of VSCs from the WWTP decreased in the order of summer > autumn > spring > winter. The pretreatment unit accounted for 90.72