Search Results (1,787)

Sludge management is one of the most costly and technically challenging components of municipal wastewater treatment, highlighting the need for sustainable and low-cost stabilization technologies. This study evaluated a pilot-scale vermifiltration system for municipal sewage sludge stabilization under varying hydraulic and organic loading conditions. Three vermifilter pilots incorporating Eisenia andrei earthworms were operated using lightweight expanded clay aggregate (LECA), high-density polyethylene (HDPE) plastic media, and mineral pumice. The systems were tested at hydraulic loading rates (HLRs) of 150, 300, and 450 L/m²·d. Performance was assessed using chemical oxygen demand (COD), total solids (TS), volatile solids (VS), VS/TS ratio, sludge volume index (SVI), and sludge dewaterability indicators, including specific resistance to filtration (SRF) and time to filtration (TTF). Optimal performance occurred at an HLR of 150 L/m²·d, achieving maximum reductions of 49% in COD, 30% in TS, and 40% in VS, along with an SVI reduction of up to 78%. Increasing HLR significantly reduced treatment efficiency due to shorter retention times and biofilm washout. A regression analysis showed the strongest association between COD removal and organic loading rate (R² = 0.63) under the coupled HLR–OLR conditions tested, while weaker correlations were observed for SVI and VS/TS. Dewaterability improved markedly after vermifiltration, particularly in the LECA-based system. Although filter media type did not significantly affect COD or SVI removal, pumice and plastic media provided greater hydraulic stability at higher loadings. These results demonstrate that vermifiltration is an effective and environmentally sustainable option for municipal sludge stabilization when operated under controlled hydraulic conditions. Full article

An integrated field–analytical framework was applied to quantify the impact of two small-settlement treatment facilities (TF1 and TF2) on the Irtysh River (East Kazakhstan). The main objective of this study is to quantify effluent-driven dilution and non-conservative changes in key water-quality indicators downstream of TF1 and TF2 and to evaluate parsimonious models for predicting effluent-outlet BOD and COD from upstream measurements. Paired upstream–downstream control sections are sampled in 2024–2025 for 22 indicators, and plant influent–effluent records are compiled for key wastewater variables. Chloride-based conservative mixing indicated very strong dilution (approximately $D\approx 2.0\times {10}^3$ for TF1 and $D\approx 4.2\times {10}^2$ for TF2). Deviations from the mixing line were summarized using a transformation diagnostic $\theta$. At TF1, several constituents exceeded mixing expectations ($\theta \approx 13$ for COD, $\theta \approx 42$ for ammonium, and $\theta \approx 6$ for phosphates), while nitrate shows net attenuation $\theta <0$. At TF2, $\theta$ values cluster near unity, indicating modest deviations. Under a small-sample regime $\left(\mathrm{N}=10\right)$ and leave-one-out validation, regularized regression provided accurate forecasts of effluent-outlet BOD and COD. Lasso under LOOCV performed best (BOD_after: RMSE = 0.626, MAE = 0.459, and $R^2=0.976$; COD_after: RMSE = 0.795, MAE = 0.634, and $R^2=0.997$). The results reconcile strong reach-scale dilution with constituent-specific local departures and support targeted modernization and operational forecasting for water-quality management in small facilities. Full article

Climate change has exacerbated flood risks for urban infrastructure, rendering sewage treatment facilities (STFs) particularly vulnerable due to their typical low-lying topographic placement. However, conventional flood risk assessment methodologies often rely solely on physical hazard parameters such as inundation depth, neglecting the functional interdependencies and operational criticality of individual treatment units. To address this limitation, this study proposes the Integrated Hydro-Operational Risk Assessment (IHORA) framework. The IHORA framework synthesizes 2D hydrodynamic modeling with a modified Hazard and Operability Study(HAZOP) study to systematically identify unit-specific physical failure thresholds and employs the Analytic Hierarchy Process (AHP) to quantify the relative operational importance of each process based on expert elicitation. The framework was applied to an underground STF under both fluvial flooding and internal structural breach scenarios. The results revealed a significant risk misalignment in traditional assessments; vital assets like electrical facilities were identified as high-risk hotspots despite moderate physical exposure, due to their high operational weight. Furthermore, Cause–Consequence Analysis (CCA) was utilized to trace cascading failure modes, bridging the gap between static risk metrics and dynamic emergency response protocols. This study demonstrates that the IHORA framework provides a robust scientific basis for prioritizing mitigation resources and enhancing the operational resilience of environmental facilities. Full article

Globally, large quantities of animal waste and human sewage sludge are generated annually. Their application as soil amendments can enhance soil quality and support a circular economy. However, these wastes may harbour pathogenic bacteria, posing contamination risks to soil and water and potential transmission to animals and humans. This study investigated the survival of five bacterial pathogens during six months of storage in five types of organic waste and following their subsequent application to soil. During storage, T₉₀ values ranged as follows: Salmonella Typhimurium (2.3–17.7 days), Campylobacter jejuni (0 to 23.9 days), Escherichia coli O157:H7 (4.3 to 57.8 days), and Listeria monocytogenes (1.9 to 170.4 days). In soil, T₉₀ values were S. Typhimurium (4.2 to 17.4 days), C. jejuni (4.8 to 26.8 days), E. coli O157:H7 (4.3 to 52.9 days), and L. monocytogenes (2 to 83.7 days). Clostridium sporogenes remained stable throughout both experiments, preventing T₉₀ calculation. Contrary to our initial hypothesis that soil microbiota would accelerate pathogen decline, T₉₀ values were higher during storage in 11 cases and higher in soil in nine scenarios. These findings highlight the need for pre-treatment strategies for animal waste and biosolids before land spreading to consistently mitigate risks of pathogen transmission and environmental contamination. Full article

The impact of sewage discharge on water quality in reversing rivers has rarely received attention. This study simulated water quality changes in Maoergang River (a water body with counter flow conditions) affected by effluent discharge from Yangjiabu Sewage Treatment Plant. The results revealed that the diffusion patterns of COD, NH₄⁺-N, and TP in the study area were largely consistent; however, different hydrological conditions and discharge scenarios resulted in obvious differences in pollutant distribution. During the dry season, regardless of normal or counter folow conditions, the Maoergang and Xitiaoxi downstream were the primary affected segments. Regulated by hydrodynamic forces, under normal flow conditions, the Xitiaoxi downstream received a higher pollutant load while the Xitiaoxi upstream received minimal inputs. In the wet season, pollutant concentrations were generally lower due to the dilution effect of increased runoff; notably, the primary affected segments shifted to the downstream reaches of Maoergang and Huanchenghe. Under accidental discharge scenarios, excessive sewage release expanded the scope of pollution impacts, with elevated pollutant concentrations causing water quality non-compliance in parts of the upstream and downstream Xitiaoxi—both of which are within the germplasm resource protection zone. Predictive analysis indicated that when the sewage treatment plant’s discharge was reduced to 1.0 × 10⁴ t·d⁻¹, the receiving water bodies could still meet local water quality standards, even under the counter flow hydrological conditions, which pose the greatest threat to water quality during the dry season. Full article

Sewage sludge (SS) management and wastewater (WW) treatment remain among the most critical environmental challenges. The pyrolysis of sewage sludge to produce biochar (BC) represents a sustainable and circular strategy for waste valorization and pollution mitigation. This scoping review provides a comprehensive overview of BC derived from SS (BCxSS), with particular emphasis on how pyrolysis conditions affect key physicochemical characteristics such as yield, ash content, pH, surface area, and functional groups. Although substantial research has focused on the removal of heavy metals and organic pollutants using BCxSS, far less attention has been directed toward its potential for pathogen adsorption and inactivation, revealing a notable research gap. Recent studies highlight BCxSS as a versatile material with considerable promise in adsorption and catalysis. However, its application in pathogen removal remains insufficiently investigated, underscoring the need for further investigation into sorption mechanisms and biochar–microbe interactions. Full article

Sewage sludge is increasingly recognized as a major reservoir for pharmaceuticals and emerging contaminants that are only partially removed by conventional wastewater treatment. This study provides the first comprehensive assessment of these contaminants in biosolids generated from ten major wastewater treatment plants (WWTPs) across Jordan. Different pharmaceuticals were quantified in the sludge samples generated. The results revealed concentrations ranging from 10 to over 2000 µg kg⁻¹, with antibiotics typically showing the highest enrichment (e.g., ciprofloxacin up to 2165 µg kg⁻¹, ofloxacin up to 303 µg kg⁻¹). Anti-inflammatory compounds such as diclofenac reached 196 µg kg⁻¹, while the antimicrobial triclosan exceeded 4700 µg kg⁻¹ in some sludge samples. Carbamazepine, a recalcitrant antiepileptic drug, ranged between 50 and 223 µg kg⁻¹, reflecting both widespread use and strong persistence. Elevated levels of quaternary ammonium compounds (QACs) were also detected. The highest levels were generally associated with large urban WWTPs and plants receiving industrial discharges. Environmental risk assessment (ERA) indicated that the risk for soil biota was acceptable for most cases for low application doses (5–10 t/ha) except for WWTP6-MD, WWTP8-S, and WWTP9-IC, where the risk was non-acceptable. Severe limitations in the risk assessment were noted: reliable toxicity endpoints in terrestrial soil organisms such as microbiota, collembola, and earthworms are few, while deriving endpoints via aquatic available data is not always reliable. Overall, the findings demonstrate that Jordanian sewage sludge contains environmentally relevant levels of pharmaceuticals and QACs and that risk assessment is, therefore, pertinent before any stabilization and realistic land application scenarios are chosen. Full article

The management of landfill leachate remains a persistent environmental issue for municipalities globally. Although dedicated treatment in engineered landfills mitigates environmental contamination, it is often cost-prohibitive. Co-treatment of landfill leachates in sewage treatment plants has been broadly studied, but there are a lot of issues associated with it. Sewage treatment plants apply physical, chemical, and biological processes, and the co-treatment of leachates—contaminated with metals, pesticides, emerging contaminants, and other toxic compounds—can impair the biological equilibrium of the system and compromise the quality of effluents and sludges. In the present research, the processes leading to the formation of landfill leachates and the processes that promote the removal of contaminants in sewage treatment plants were discussed. A theoretical, early screening level mixing model, incorporating removal rates and leachate concentrations from the literature, was employed to simulate effluent concentrations from a co-treatment process involving sequential decantation and an upflow anaerobic sludge blanket (UASB). Under a conservative worst-case scenario obtained from the literature, the model predicts that adsorption of contaminants onto the particulate phase enables removal of metals from the solution. However, considering the volumes of sludge involved, the predictions indicate that concentrations should be lower than naturally occurring in the sediments. It is proposed that continuous monitoring follow-up is a mandatory safeguard for any co-treatment operation. Full article

Confronting severe water scarcity challenges, China’s industrial water circularity demands robust efficiency evaluation frameworks. This research pioneers a two-stage network model integrating undesirable outputs and feedback mechanisms to assess 30 provincial systems. The methodology captures interconnected processes where production generates wastewater, which is then treated to yield reusable water fed back into production. Comprehensive efficiency gaps were quantified using weighted optimization, enabling tailored provincial enhancement paths: wastewater volume reduction and reclaimed water augmentation strategies. Results reveal striking regional disparities, with only two regions initially achieving full efficiency while coastal manufacturing hubs exhibited paradoxical inefficiency despite high output. Implementation demonstrated reclaimed water enhancement’s superior efficacy—enabling over half of regions to reach full efficiency—while wastewater reduction alone proved insufficient for most provinces. Crucially, ecologically fragile regions achieved optimal performance through minimal precision interventions. The study establishes that effective water circularity requires coordinated optimization of both production and treatment stages, with region-specific sequencing strategies. This approach delivers policymakers a diagnostic toolkit for spatially differentiated resource transition planning, balancing economic output with environmental sustainability. Full article

The urgent need for effective food waste management, coupled with the scarcity of carbon sources for sewage treatment, highlights the potential of producing carbon sources from food waste as a mutually beneficial solution. This study investigated the production of carbon sources through anaerobic fermentation using the liquid phase of food waste three-phase separation. Compared with previous studies using raw food waste or mixed substrates, the liquid phase derived from three-phase separation is richer in soluble organic matter and has been pre-heated (80 °C), which facilitates subsequent fermentation and offers easier integration into existing food waste treatment plants. A series of lab-scale batch fermentation experiments were carried out at different temperatures, including ambient, mesophilic, and thermophilic conditions, as well as varying initial pH levels (uncontrolled, neutral, and alkaline). The experimental results indicated that optimal production parameters involve a 4-day mesophilic fermentation at 35 °C with an initial alkaline pH, which increased the total VFAs yield by 252.5% to 40.26 g/L and raised the acetic acid fraction to 45.5% of total VFAs. Under these conditions, there was an observed increase in the relative abundance of acidogenic bacteria and a decrease in that of methanogen archaea. Furthermore, the denitrification performance of the produced carbon source was evaluated in short-term tests, and near-complete nitrate removal was achieved within approximately 2 h. These findings suggest the fermented liquid phase of food waste is a promising partial substitute for conventional external carbon sources. Full article

In this study, we investigated the impact of varying iron (Fe) and aluminum (Al) contents on the adsorption of phosphonates to activated sludge. Phosphonates originating from household applications account for up to 40% of the non-reactive dissolved phosphorus in domestic sewage treatment plants and thus can contribute to the eutrophication of water bodies. Although these substances are not readily degradable, substantial quantities, ranging from 40% to more than 90%, are removed by sludge adsorption. The results demonstrate a strong correlation between the adsorption of aminophosphonates and the Fe³⁺ content of the sludge. The maximum phosphonate loadings were 5.94 mmol g⁻¹ Fe³⁺ for ATMP, 4.94 mmol g⁻¹ Fe³⁺ for EDTMP, 4.74 mmol g⁻¹ Fe³⁺ for DTPMP, and 2.25 mmol g⁻¹ Fe³⁺ for glyphosate. In contrast to pure ferric hydride flocs, the adsorption of phosphonates was approximately threefold higher when the hydroxides were located within activated sludge flocs. It is concluded that native sludge flocs provide larger iron surfaces than ferric hydroxide alone. Based on the weight of the adsorbents, aluminum salts were four times less efficient than ferric salts. In sludge without ferric or aluminum hydroxides, phosphonate adsorption was negligible. Full article

Rapid urbanization has intensified nitrate pollution in megacity rivers, posing severe challenges to urban water governance and sustainable nitrate management. This study presents nitrate dual-isotope signatures (δ¹⁵N-NO₃⁻ and δ¹⁸O-NO₃⁻) from surface water samples collected during the wet season from the Yongding River (YDR) and Chaobai River (CBR) in the Beijing–Tianjin–Hebei megacity region of North China. Average concentrations of nitrate (as NO₃⁻) were 8.5 mg/L in YDR and 12.7 mg/L in CBR. The δ¹⁵N-NO₃⁻ and δ¹⁸O-NO₃⁻ values varied from 6.1‰ to 19.1‰ and −1.1‰ to 10.6‰, respectively. The spatial distribution of NO₃⁻/Cl⁻ ratios and isotopic data indicated mixed sources, primarily sewage and manure in downstream sections and agricultural inputs in upstream areas. Isotopic evidence revealed widespread nitrification processes and could have potentially localized denitrification under low-oxygen conditions in the lower YDR. Bayesian mixing model (MixSIAR) results indicated that sewage and manure constituted the main nitrate sources (49.4%), followed by soil nitrogen (23.7%), chemical fertilizers (19.2%), and atmospheric deposition from rainfall (7.7%). The self-organizing map (SOM) further revealed three nitrate regimes, including natural and agricultural, mixed, and sewage dominated conditions, indicating a clear downstream gradient of increasing anthropogenic influence. The results suggest that efficient nitrogen management in megacity rivers requires improving biological nutrient removal in wastewater treatment, regulating fertilizer application in upstream areas, and maintaining ecological base flow for natural denitrification. This integrated framework provides a quantitative basis for nitrate control and supports sustainable water governance in highly urbanized watersheds. Full article

In the review, the collection of population genetics papers from 1973 to 2025 comprises 400 publications, 81 of which were significant and consulted with representatives from water and sewage companies. Reviewed Proteobacteria (mean H_S = 0.42), Firmicutes (mean H_S = 0.43), Actinobacteria (mean H_S = 0.33), and Spirochaetes (mean H_S = 0.54) represent the 60 species under investigation through the lens of “h” coefficients related to gene diversity and expected heterozygosity. The research also included ESKAPE, emerging pathogens, bacterial indicators of wastewater treatment efficiency, environmental sanitary surveillance and public health. The restoration of the expected heterozygosity for haploids “h” was proposed in wastewater-based epidemiology as an innovative tool for public health. The unique “h” coefficient allows for the comparison of genetic variability in various organisms, regardless of their ploidy, using multiple markers and traits. The parameter represents a noble character for both the variability of phenotypes (proteins) and genotypes (nucleic acids). Leveraging the genetic diversity highlighted by the “h” coefficient can support wastewater-based epidemiology, offering the ability to predict the stages and trajectories of disease outbreaks. Full article

Sewage sludge production is increasing rapidly, yet current sludge treatment capacity and technology remain insufficient. The thermochemical process has been widely adopted for sewage sludge disposal; its solid product (bio/hydro-char) shows considerable potential to improve soil quality by enriching soil nutrient contents. However, limited heavy metals are volatilized during the thermochemical process, and the majority is concentrated in the derived bio/hydro-char. Therefore, it is essential to ensure the environmental safety of sewage sludge-derived bio/hydro-char and avoid heavy metal risk, and thus appropriate heavy metal removal technology is required prior to land application. This review provides an overview of the major sewage sludge treatment approaches focusing on the heavy metal removal and phosphorus recovery, along with emerging challenges and future perspectives for the sustainable utilization of sewage sludge. Notably, the combination of electrokinetic treatment with thermochemical treatments emerges as a promising strategy to simultaneously treat sewage sludge and achieve P reclamation. Full article

Anaerobic digestion of sewage sludge generates large volumes of liquid digestate, which is often returned to wastewater treatment plants (WWTPs) due to the presence of pathogens and pollutants, limiting its safe reuse in agriculture. This study evaluated plasma-based post-treatment as a method to improve the sanitary quality of digestate. The liquid phase from mesophilic digesters at WWTP “Ravda” was treated for 5 min using two plasma sources, the β-device and the Surfaguide WR340 (SAIREM, Décines-Charpieu, France). Disinfection effectiveness was assessed for aerobic and anaerobic heterotrophs, fecal and total coliforms, Escherichia coli, Salmonella sp., and Clostridium sp. Physicochemical parameters measured included pH, COD, NH₄⁺, NO₂⁻, NO₃⁻, and PO₄³⁻. The β-device achieved partial disinfection, with reductions ranging from 16.3% to 89.8% for different microbial groups, whereas coliforms persisted and Clostridium sp. reappeared. The Surfaguide produced near-complete disinfection, eliminating coliforms, E. coli, Salmonella sp., and Clostridium sp., and markedly reduced microbial diversity. Both treatments caused slight pH increases, COD decreases, release of NH₄⁺ and PO₄³⁻, and rises in NO₂⁻ and NO₃⁻. Plasma-based disinfection, particularly with the Surfaguide, effectively improves the sanitary quality of the digestate and modifies its chemical properties, supporting the potential for sustainable digestate valorization and its safe reuse in agriculture. Full article