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IntroductionSimultaneous chemical phosphorus removal process using iron salts (Fe(III)) has been widely utilized in wastewater treatment to meet increasingly stringent discharge standards. However, the inhibitory effect of Fe(III) on the biological phosphorus removal system remains a topic of debate, with its precise mechanism yet to be fully understood.MethodsBatch and long-term exposure experiments were conducted in six sequencing batch reactors (SBRs) operating for 155 days. Synthetic wastewater containing various Fe/P ratios (i.e., Fe/P = 1, 1.2, 1.5, 1.8, and 2) was slowly poured into the SBRs during the experimental period to assess the effects of acute and chronic Fe(III) exposure on polyphosphate-accumulating organism (PAO) growth and phosphorus metabolism.ResultsExperimental results revealed that prolonged Fe(III) exposure induced a transition in the dominant phosphorus removal mechanism within activated sludge, resulting in a diminished availability of phosphorus for bio-metabolism. In Fe(III)-treated groups, intracellular phosphorus storage ranged from 3.11 to 7.67 mg/g VSS, representing only 26.01 to 64.13% of the control. Although the abundance of widely reported PAOs (Candidatus Accumulibacter) was 30.15% in the experimental group, phosphorus release and uptake were strongly inhibited by high dosage of Fe(III). Furthermore, the abundance of functional genes associated with key enzymes in the glycogen metabolism pathway increased while those related to the polyphosphate metabolism pathway decreased under chronic Fe(III) stress.DiscussionThese findings collectively suggest that the energy generated from polyhydroxyalkanoates oxidation in PAOs primarily facilitated glycogen metabolism rather than promoting phosphorus uptake. Consequently, the dominant metabolic pathway of communities shifted from polyphosphate-accumulating metabolism to glycogen-accumulating metabolism as the major contributor to the decreased biological phosphorus removal performance.

Anaerobic membrane bioreactor (AnMBR) for wastewater treatment has attracted much interest due to its efficacy in providing high-quality effluent with minimal energy costs. However, membrane biofouling represents the main bottleneck for AnMBR because it diminishes flux and necessitates frequent replacement of membranes. In this study, we assessed the feasibility of combining bacteriophages and UV-C irradiation to provide a chemical-free approach to remove biofoulants on the membrane. The combination of bacteriophage and UV-C resulted in better log cells removal and ca. 2× higher extracellular polymeric substance (EPS) concentration reduction in mature biofoulants compared to either UV-C or bacteriophage alone. The cleaningmechanism behind this combined approach is by 1) reducing the relative abundance of Acinetobacter spp. and selected bacteria (e.g., Paludibacter, Pseudomonas, Cloacibacterium, and gram-positive Firmicutes) associated with the membrane biofilm and 2) forming cavities in the biofilm to maintain water flux through the membrane. When the combined treatment was further compared with the common chemical cleaning procedure, a similar reduction on the cell numbers was observed (1.4 log). However, the combined treatment was less effective in removing EPS compared with chemical cleaning. These results suggest that the combination of UV-C and bacteriophage have an additive effect in biofouling reduction, representing a potential chemical-free method to remove reversible biofoulants on membrane fitted to an AnMBR. [ABSTRACT FROM AUTHOR]

• SSCF-CW effectively improves N and P removal in low C/N wastewater. • Electrons resupply mode of S and Fe cycle enhance denitrification efficiency. • SSCF improves the iron plaque formation of root. • Fe2+/Fe3+ cycle can improve phosphorus removal by co-precipitation and adsorption. The urgent need to achieve sustainable development goals and address global climate change calls for innovative solutions in advanced low-carbon water treatment technologies. In this study, constructed wetlands (CWs), a sustainable and multifunctional wastewater treatment technology known for its low cost and energy efficiency, was focused. It was presented a novel approach that employs a sulfur-siderite composite filler in the constructed wetland (SSCF-CW), which demonstrated remarkable removal efficiencies for total phosphorus (TP) ranging from 81.14 % to 98.87 %, nitrate nitrogen (NO 3 −-N) ranging from 85.23 % to 99.82 %, and total nitrogen (TN) ranging from 91.65 % to 97.01 % in low C/N wastewater treatment. The electron resupply mode of the sulfur and iron cycles plays a pivotal role in enhancing denitrification efficiency. Furthermore, SSCF enhances the resilience of SSCF-CW against shock loadings, providing increased stability and performance with TN removal rate of 2.96 ∼ 3.42 g N·m−3·d−1 while HRT decreased from 48 h to 10 h. Notably, the majority of NO 3 −-N elimination occurs within the SSCF layer, where Thiobacillus species dominate the denitrification process in SSCF-CW. The introduction of SSCF promotes carbon fixation with the higher relative abundance of DLD gene (5.52 %) in SSCF-CW, benefiting microbial growth and accelerating electron transfer process. Co-precipitation and adsorption pathways in the SSCF layer primarily contribute to TP removal, while iron leaching from SSCF facilitates the formation of iron plaque on roots, establishing an iron reservoir and ensuring bioavailability. These findings highlight the significant potential of SSCF in constructed wetland systems, offering a cost-effective and sustainable low-carbon technology for municipal wastewater treatment. [ABSTRACT FROM AUTHOR]

The electrodes spacing would exert a pronounced effect on bio-electrochemical systems (BESs) performance, especially for the scaling-up of reactors and practical applications. In this study, we traced the effect of electrode spacing on wastewater treatment performances from the aspects of hydrodynamics and electrochemical characteristics. Three series of folded stainless steel mesh ( f -SSM) electrodes with electrode spacing of 2, 4 and 8 mm were designed for azo dye (acid orange 7 (AO7)) wastewater treatment. Results showed that BES with electrode spacing of 2 mm (R S2 ) obtained the highest efficiencies of AO7 decolorization (90.9 ± 0.4%) and COD removal (36.8 ± 3.8%) at HRT of 8 h, which was 30.7% and 15.2% higher than that in BES with electrode spacing of 8 mm (R S8 ), respectively. Moreover, the relationship between pollutants removal, internal resistance and hydrodynamics of BESs with different electrode spacing supported the hydrodynamics was significantly influence the pollutants removal performance. [ABSTRACT FROM AUTHOR]

In this study, a novel scaled-up hybrid acidogenic bioreactor (HAB) was designed and adopted to evaluate the performance of azo dye (acid red G, ARG) containing wastewater treatment. Principally, HAB is an acidogenic bioreactor coupled with a biocatalyzed electrolysis module. The effects of hydraulic retention time (HRT) and ARG loading rate on the performance of HAB were investigated. In addition, the influent was switched from synthetic wastewater to domestic wastewater to examine the key parameters for the application of HAB. The results showed that the introduction of the biocatalyzed electrolysis module could enhance anoxic decolorization and COD (chemical oxygen demand) removal. The combined process of HAB-CASS presented superior performance compared to a control system without biocatalyzed electrolysis (AB-CASS). When the influent was switched to domestic wastewater, with an environment having more balanced nutrients and diverse organic matters, the ARG, COD and nitrogen removal efficiencies of HAB-CASS were further improved, reaching 73.3% ± 2.5%, 86.2% ± 3.8% and 93.5% ± 1.6% at HRT of 6 hr, respectively, which were much higher than those of AB-CASS (61.1% ± 4.7%, 75.4% ± 5.0% and 82.1% ± 2.1%, respectively). Moreover, larger TCV/TV (total cathode volume/total volume) for HAB led to higher current and ARG removal. The ARG removal efficiency and current at TCV/TV of 0.15 were 39.2% ± 3.7% and 28.30 ± 1.48 mA, respectively. They were significantly increased to 62.1% ± 2.0% and 34.55 ± 0.83 mA at TCV/TV of 0.25. These results show that HAB system could be used to effectively treat real wastewater. [ABSTRACT FROM AUTHOR]

Wastewater treatment plants (WWTPs) play an important role within the urban water cycle in preventing the natural water environment and human health from being negatively affected by human activities. However, wastewater treatment processes such as the discharge of effluent and indirect emissions resulting from energy or chemical production, also negatively affect the environment. Footprints have been used to track human influence on the environment through different areas of concern and have been applied in assessing the sustainability of WWTPs. A comprehensive review of footprint assessment for evaluating the wastewater treatment process in WWTPs was investigated in this article. The review showed that the carbon footprint and the water footprint were the two of the most popular footprints for evaluating the sustainability of WWTPs, and other footprint (such as nitrogen and phosphorus footprints) assessment applications were also introduced to assess the eutrophication of water bodies. To promote the application of footprint assessment on WWTP, this article regulated the study goals, frameworks, system boundary, data treatment methods, resultant interpretation process. The pros and cons of footprint assessments were discussed and investigated in detail, several suggestions were come up with for the improvement of footprint assessments. The analyzation of footprint assessments under different WWTPs revealed that wastewater treatment technologies and scales significantly impacted the footprints. Moreover, the research hotspots identified by way of a keyword network diagram showed that researchers tended to propose new indicators and models for the grey water footprint and the carbon footprint respectively, and water-carbon-energy nexus was a promising direction for future studies. Finally, two possible application scenarios, element tracing through modified footprints and management improvement through mathematical optimization, were proposed to optimize the operation strategies of WWTPs. Overall, footprint assessment research for WWTPs is still at the initial stage and needs further exploration and improvement, e.g. introducing new tools, exploring system variation under various scenarios, combining other footprints, and implementing the nexus assessment. Image 1 • First comprehensive review of footprint evaluations for WWTP. • Relationship between footprint and LCA was distinguished. • Two purposes of footprint application were clarified. • Future applications of footprint analysis in wastewater management were introduced. [ABSTRACT FROM AUTHOR]

The Nernst-Monod model is used to describe bio-anode performance with respect to the effect of the electron donor and anode potential. However, electron competition is not considered in the model, limiting its application in wastewater treatment systems. In this work, nitrate was employed to describe the influence of a competitive electron acceptor on bio-anode performance. A new dynamic model of microbial anode respiration and nitrate respiration was developed for the removal of nitrogen oxides. The competitive relationship between microbial anode respiration and nitrate respiration was investigated based on electron transfer as described by the kinetics of Nernst-Monod electron transfer and nitrate reduction. The experimental results showed that nitrate had a significant influence on microbial anode respiration. The model parameters were estimated with the experimental results obtained in a continuous-flow bioelectrochemical system (BES) fed with acetate. The simulated results revealed that nitrate respiration could indirectly affect the microbial anode respiration by altering the available substrate concentration. In addition, bacterial community analysis indicated that there were two dominant functional microorganisms coexisting in the anode chamber. The first microorganism was represented by Geobacter , which has extracellular electron-transfer abilities. The second was denitrifying bacteria, which can use the carbon sources in the anodic chamber and electrons from the electrode for nitrate reduction. This is the first time that mathematical modelling of nitrate reduction has been applied to BESs. [ABSTRACT FROM AUTHOR]

[Display omitted] • Biochar-amended CWs can enhance SMX and nitrogen removal with a low C/N ratio. • Biochar-amended CWs can reduce ARGs absolute and relative abundance in wastewater. • Slightly acidic and neutral states can stimulate DOC release from biochar. • Possible removal mechanism of pollutants in biochar-amended CWs was revealed. Constructed wetlands (CWs) amended with biochar to stimulate antibiotic and antibiotic resistance genes (ARGs) removal from carbon restricts wastewater holds particular application prospect due to high efficiency and good stability. In this study, we conducted biochar amended constructed wetland (BCW) and non-biochar amended constructed wetland (NCW) to explore the feasibility and mechanisms for sulfamethoxazole (SMX) and ARGs removal from low C/N wastewater. Results showed that biochar-amended considerably stimulated the biological oxidation and reduction process in CW, as evidenced by higher chemical oxygen demand (COD), nitrogen, and SMX removal performance (7.1 ± 2.6 %, 19.8 ± 3.6 %, 36.8 ± 6.2 %) than that in NCW. The accumulation of ARGs was negatively associated with SMX removal efficiency, where the int and sul genes performed lower concentration in BCW due to the higher SMX removal efficiency. The biochar's dissolved organic carbon release in CWs indicated that water and alkaline media portray the optimum conditions for SMX and ARGs removal. Microbial community analysis exposed that more functional consortia capable of SMX metabolism (e.g., Arthrobacter , Ramlibacter , Flavobacterium , and norank_f_JG30-KF-CM45) were enriched in BCW. This study demonstrated the feasibility and mechanism of biochar-amended CWs for regulated SMX removal and ARGs accumulation, which provides new insights for enhancing the depuration ability of CWs. [ABSTRACT FROM AUTHOR]

[Display omitted] • The mechanism of CW and BES-CWs degradation of organic matter is summarized. • The effects of electrodes, co-substrates, and HRT on BES-CWs operation were reviewed. • BES-CWs removes most antibiotics by more than 95 % and reduces methane emissions by 14–72 %. • Based on economic analysis and LCA, BES-CWs has great application potential for future development. Recent advances in the integrated bioelectrochemical-constructed wetland systems (BES-CWs) for antibiotics removal are gaining momentum due to having electrode bio-carrier and electro-active bacteria (EAB) that could stimulate degradation via extracellular electron transfer. BES-CWs system performs well in removing antibiotics, and it is proven more competitive in environmental friendly than physicochemical methods. Hence, understanding the reaction features, operation manners, economic and ecological benefits of BES-CWs can provide valuable information for further technological development. In contrast, the successful application of BES-CWs to antibiotics-containing wastewater remediation requires a deeper evaluation of its performance, mechanism, typical attributes and a comprehensive potential evaluation of BES-CWs' practical application in terms of environmental and economic analysis. In this review, the degradation mechanism, abiotic transformations of antibiotics and involved functional microorganisms in BES-CWs were comprehensively analyzed to draw critical suggestions and new insights. Furthermore, the device configurations, operational conditions, environmental impact, and economic evaluation of the BES-CWs was addressed as follows the principle for practical applications. Overall, this review would provide useful information for developing BES-CW technologies to abate antibiotics in wastewater. [ABSTRACT FROM AUTHOR]

Abstract: The results of the use of an expert system (ES) to control a novel multi-stage loop membrane bioreactor (MLMBR) for the simultaneous removal of organic substances and nutrients are reported. The study was conducted at a bench-scale plant for the purpose of meeting new discharge standards (GB21904-2008) for the treatment of chemical synthesis-based pharmaceutical wastewater (1200–9600 mg/L COD, 500–2500 mg/L BOD5, 50–200 mg/L NH4 +-N and 105–400 mg/L TN in the influent water) by developing a distributed control system. The system allows various expert operational approaches to be deployed with the goal of minimizing organic substances and nitrogen levels in the outlet while using the minimum amount of energy. The proposed distributed control system, which is supervised by a Knowledge-Based Expert System (KBES) constructed with G2 (a tool for expert system development) and a back propagation BP artificial neural network, permits the on-line implementation of every operating strategy of the experimental system. A support vector machine (SVM) is applied to achieve pattern recognition. A set of experiments involving variable sludge retention time (SRT), hydraulic retention time (HRT) and dissolved oxygen (DO) was carried out. Using the proposed system, the amounts of COD, TN and NH4 +-N in the effluent decreased by 55%, 62% and 38%, respectively, compared to the usual operating conditions. These improvements were achieved with little energy cost because the performance of the treatment plant was optimized using operating rules implemented in real time. [Copyright &y& Elsevier]

Abstract: The aim of this study was to implement central-composite design (CCD) and response surface methodology (RSM) to optimize the operational parameters for hybrid anaerobic baffled microbial reactor (HABMR) remedying mixed printing and dyeing wastewater (MPDW). The individual and interactive effects of three variables, hydraulic retention time (HRT), pH, sludge loading rate (SLR) on the COD and color removal rates were evaluated. In the area of HRT: 12.5–13.9h, pH: 9.0–9.5 and SLR: 0.27–0.33kgCOD/(kgMLVSSd), COD and color removal rates of HABMR exceeded 40% and 60%, simultaneously. The check experiment revealed that the amount of COD and color in the effluent could be decreased by 9.97% and 10.12% compared to the usual operating conditions, respectively. The results verified that the RSM was useful for optimizing the operational parameters of HABMR in treating MPDW. [Copyright &y& Elsevier]

Polycyclic aromatic hydrocarbons (PAHs) are regarded as priority pollutants owing to their toxic, mutagenic and carcinogenic characteristics. Perylene is a kind of 5-ring PAH with biological toxicity, and classified as a class III carcinogen by the World Health Organization (WHO). Nowadays, some of its derivatives are often used as industrial pigments. Hence, urgent attention is highly needed to develop new and improved techniques for PAHs and their derivatives removal from the environment. In this study, Fenton oxidation process was hybridized with the biological (anaerobic and aerobic) treatments for the removal of perylene pigment from wastewater. The experiments were carried out by setting Fenton treatment system before and between the biological treatments. The biological results showed that COD removal efficiency reached 60% during 24 h HRT with an effluent COD concentration of 1567.78 mg/L. After the HRT increased to 48 h, the COD removal efficiency was slightly increased (67.9%). However, after combining Fenton treatment with biological treatment (Anaerobic-Fenton-Aerobic), the results revealed over 85% COD removal efficiency and the effluent concentration less than 600 mg/L which was selected as the better treatment configuration for the biological and chemical combined system. The microbial community analysis of activated sludge was carried out with high-throughput Illumina sequencing platform and results showed that Pseudomonas , Citrobacter and Methylocapsa were found to be the dominant genera detected in aerobic and anaerobic reactors. These dominant bacteria depicted that the community composition of the reactors for treating perylene pigments wastewater were similar to that of the soil contaminated by PAHs and the activated sludge from treating PAHs wastewater. Economic analysis results revealed that the reagent cost was relatively cheap, amounting to 10.64 yuan per kilogram COD. This study vividly demonstrated that combining Fenton treatment with biological treatment was efficient and cost-effective. • A Biological-Fenton combined process for perylene pigments wastewater treatment was proposed. • Fenton process can enhance the immediately subsequent biological process. • The bio-degradation of perylene diimides was promoted by the co-substrate system. • The community of the reactors for perylene pigments was reported. [ABSTRACT FROM AUTHOR]