The side-stream enhanced biological phosphorus removal (S2EBPR) process can generate volatile fatty acids through sludge fermentation and enrich functional microorganisms, thereby potentially reducing external carbon demand and improving phosphorus (P) removal. However, nitrogen (N) removal in S2EBPR systems remains suboptimal, and systematic studies on simultaneous N and P removal (SNPR) remain limited. Here, a mainstream step-feed two-stage anoxic/oxic process coupled with S2EBPR (SF-A/O/A/O+S2EBPR) was developed to enhance SNPR. The effects of different step-feed influent ratios (AX1:AX2 = 2:1, 1:1, and 1:2) on system performance and microbial mechanisms were evaluated. Step feeding improved COD and TN removal from 83% to 90% and from 65% to 77%, respectively. Under 2:1 and 1:1 ratios, limited carbon availability for polyphosphate accumulating organisms (PAOs) reduced anaerobic P release rates (16.6-18.0 mg P/(g VSS & sdot;h)) and decreased PAO abundance from 15% to 10%. In contrast, the 1:2 ratio enriched Dechloromonas-related putative denitrifying PAOs, suggesting a higher potential for endogenous denitrifying P uptake and achieving balanced SNPR, with average TN, PO4 3--P, and COD removal efficiencies of 76%, 89%, and 90%, respectively. Prolonged side-stream anaerobic conditions reduced tightly bound extracellular polymeric substances and were accompanied by an approximately 10% decrease in sludge concentration, suggesting a potential sludge-reduction effect. Meanwhile, complete P release was achieved, and fermentation-derived sCOD contributed an additional 10.24-15.25% soluble organic carbon input to the mainstream process. This study demonstrates that optimizing the step-feed influent ratio can improve high-rate SNPR in S2EBPR systems, providing new insights into process performance, metabolic activity, and microbial ecology.

The side-stream enhanced biological phosphorus (P) removal (S2EBPR) process exhibits efficient and stable P removal by anaerobic fermentation of return activated sludge (RAS) in a side-stream reactor, reducing influent carbon demand while enabling microbial selection and sludge reduction. However, the characteristics and impacts of dissolved organic matter (DOM) released under extended anaerobic conditions remain unclear. In this study, an S2EBPR system was constructed to investigate the composition of mainstream and side-stream DOM and their relationships with system performance. Results showed that humic substances (HS), proteins (PN), and polysaccharides (PS) were the primary DOM components in the side-stream reactor (14.3 +/- 3.0 mg g-1 VSS). An intermediate side-stream sludge retention time (SRTSS) of similar to 72 h minimized DOM by efficient utilization of labile PN and PS, while prolonged SRTSS enhanced HS accumulation, humification, and refractory organics. Notably, a significant positive correlation was identified between effluent phosphorus and total DOM concentration, governed by a threshold effect of sludge hydrolysis. While an optimal SRTSS efficiently supplies volatile fatty acids for polyphosphate-accumulating organisms (PAOs) with minimal DOM accumulation, excessive sludge disintegration under prolonged SRTSS conditions releases refractory intracellular organics, which increases total DOM and inhibits PAO activity. Denitrification remained stable at SRTSS of 72-144 h, with the effluent dissolved organic nitrogen reduced to 6-13%. Fluorescence analysis indicated that DOM was dominated by fulvic acid-like and humic acid-like substances; microbial degradation of PN-like compounds promoted DOM humification. Prolonged SRTSS increased refractory and aromatic DOM without impairing nitrogen removal, though potential risks for downstream treatment and water quality warrant further investigation.

The side-stream enhanced biological phosphorus removal (S2EBPR) process enables simultaneous nitrogen and phosphorus (P) removal from carbon-limited wastewater, leveraging polyphosphate accumulating organisms (PAOs) and in situ volatile fatty acid (VFA) generation. However, its reliance on extended side-stream sludge retention time (SRTSS) increases reactor footprint and cost. This study integrated alkaline pretreatment into S2EBPR-P recovery (S2EBPR-PR) process and systematically evaluated its effects on sludge fermentation, microbial activity, and P recovery under varying pH and SRTSS conditions. Results showed that Alkaline pretreatment (pH 9-10) accelerated organic matter solubilization, increasing SCOD by 208-542% and VFAs by 262-515%. Acetic and propionic acids accounted for 50-71% of total VFAs, providing high-quality carbon for PAOs. Moderate alkaline pretreatment (pH 9) induced transient inhibition of PAOs, denitrifying PAOs, and nitrifying/denitrifying bacteria, with fermentation-driven activity recovering to 71-77% of the control by day 5, whereas strong alkaline pretreatment (pH 10) caused persistent inhibition. With respect to phosphorus recovery, pH 9 favored the formation of well-defined struvite crystals, achieving a P recovery efficiency of 66% and demonstrating a favorable balance between product purity and solid-liquid separation. Although pH 10 yielded a higher P recovery efficiency of up to 95%, crystal quality deteriorated due to organic matter chelation. Nitrogen recovery was also enhanced by alkaline pretreatment, with recovery rates ranging from 13% to 22%, exceeding those of the control system. Overall, moderate alkaline pretreatment could enhance carbon supply and P recovery while reducing reactor footprint, offering a promising strategy for low-carbon, high-efficiency nutrient removal and recovery in S2EBPR-PR systems.

The side-stream enhanced biological phosphorus (P) removal (S2EBPR) process enables efficient and stable P removal by generating internal carbon and selecting functional populations via anaerobic sludge fermentation, yet its underlying mechanisms remain unclear. In this study, long-term operation of S2EBPR system combined with simulated side-stream anaerobic batch tests was conducted to elucidate the fermentation process and microbial mechanisms. Results showed that 91.7 % of the active P release, 97.1 % of the glycogen consumption and 95.8 % of the polyhydroxyalkanoates accumulation occurred within the initial 60 h of fermentation, concomitant with enhanced EBPR activity. Single-cell Raman spectroscopy analysis demonstrated the elimination of glycogen accumulating organisms (GAOs) and persistence of polyphosphate (poly-P) accumulating organisms (PAOs), which exhibited staged maintenance-EBPR-maintenance metabolism, driven by availability of volatile fatty acids and energy, with sequential utilization of poly-P and glycogen as primary energy source under extended anaerobic conditions. Fluorescence in situ hybridization-Raman analysis demonstrated that different PAO subgroups (Accumulibacter and Tetrasphaera) exhibit distinct patterns of energy utilization. PAOs' staged-specific metabolism with diverse energy use strategies enable them to outcompete GAOs. This is the first study to systematically investigate the fundamental mechanisms underlying the impact of side-stream sludge retention time (SRTSS) on fermentation and S2EBPR performance and results indicated the optimal SRTSS of 36-60 h for S2EBPR systems operated at 30 degrees C, which will enhance our ability to effectively design and operate these systems for sustainable and stable P removal and recovery.

Aqueous pathogenic microorganisms pose a significant risk to public health, but conventional disinfection methods present numerous drawbacks. By employing bactericidal tests, radical quenching experiments, and quantitative toxicogenomic assay, this study aimed to evaluate the effectiveness and associated cellular mech-anism of a novel disinfection process combining recyclable copper ferrite (CuFe2O4) nanoparticles with sulfite. At the optimal CuFe2O4 (800 mg/L) and sulfite (4 mM) concentrations determined, the CuFe2O4/sulfite system inactivated 4.65-log (>99.99 %) of Escherichia coli cells at an initial concentration of 10(8) colony-forming units (CFU)/mL in 3 h. Meanwhile, the E. coli cells at the initial concentration of 10(4) -10(6) CFU/mL were 100 % inactivated within 1-2 h. Cuprous ions (Cu(I)) rather than sulfate radicals (SO4 center dot-) played the dominant role in the inactivation process, by breaking the cell membrane, damaging intracellular components (such as adenosine triphosphate and nicotinamide adenine dinucleotide), and stimulating increased reactive oxygen species production. Correspondingly, the toxicogenomics-based toxicity assessment indicated the induction of oxidative damage to exposed cells as a dominant molecular-level disinfection mechanism of the CuFe2O4/sulfite system. Moreover, the CuFe2O4/sulfite system exhibited comparable inactivation efficiency against three other bacterial species, while gram-positive strains (Staphylococcus aureus and Bacillus subtilis) were more susceptible to this system than gram-negative ones (Pseudomonas aeruginosa and E. coli). The magnetic recyclable CuFe2O4/sulfite system is a promising water disinfection method owing to its efficacy, convenience, and environmental sustainability.

Dissolved oxygen (DO) plays an important role in the performance of biological wastewater treatment systems. This study investigated the effect of the DO concentration on nutrient removal performance and microbial community structure in side-stream activated sludge hydrolysis (SSH) and conventional anaerobic/anoxic/aerobic (A2O) processes. The results showed that the change in DO had little effect on the removal performance of chemical oxygen demand (COD), and the removal efficiencies were about 90% for both reactors. Compared with the high DO level (4.1–6.9 mg/L), the A2O and SSH reactors had better nitrogen removal performance at low (0.5–2.2 mg/L) and moderate (2.2–3.9 mg/L) DO levels, with ammonia (NH4+-N) removal efficiencies of 88–89% and 89–91%, respectively, and total nitrogen (TN) removal efficiencies of 74–76% and 75–81%, respectively. Directly reducing the DO concentration from high to low reduced the phosphate removal efficiencies of the A2O and SSH reactors from 80.2% and 86.2% to 63.1% and 70.6%, respectively, while re-elevating the DO concentration to moderate levels significantly improved the phosphate removal efficiencies to 94.6% and 96.0%, respectively. Compared to the A2O reactor, the SSH reactor had more stable and better nutrient removal performance under different DO conditions, partly due to the additional carbon sources produced through the sludge fermentation in the side-stream reactor. The decrease in the DO concentration resulted in a decrease in the relative abundance of Acinetobacter but an increase in the relative abundance of Competibacter, potentially leading to the deterioration in phosphorus removal.

It is important to study the stress effects and mechanisms of haloacetamide (HAcAm) disinfection byproducts to reveal their health hazards. In this context, toxicological g was applied to evaluate the effects of four HAcAms, revealing the status of gene expression on Escherichia coli in different stress response types (oxidative, protein, membrane, general, DNA). This study revealed that the main toxic action modes of these HAcAms were general and membrane stresses by high-resolution, real-time gene expression profiling combined with clustering analysis. The results of time-gene evaluation showed that the presence of chloroacetamide (CAcAm) and bromoacetamide (BAcAm) generated more reactive oxygen species, thus activating oxidative stress. Trichloroacetamide (tCAcAm) induced altered expression of glutathione marker genes and membrane stress-related genes, and iodoacetamide (IAcAm) caused severe DNA damage by damaging DNA strands and individual nucleotides mainly through damage to nucleic acids and bases. Furthermore, quantitative structure-activity relationship (QSAR) modelling results indicated that the biological activities of HAcAms were related to their quantum chemical and topological properties.

In this study, a lab-scale continuous flow side-stream enhanced biological phosphorus (P) removal (S2EBPR) reactor was operated for 247 days treating synthetic wastewater with influent carbon to phosphorus (C/P) ratio of 25.0 g COD/g P and influent PO43--P of 7.4 +/- 0.3 mg P/L. The effect of the return activated sludge (RAS) diversion ratio on S2EBPR reactor was investigated by comparing P removal performance, microbial activity, and community structure. The results showed that the RAS diversion ratio of 8.0%, by yielding a side-stream sludge retention time (SRTSS) of similar to 60 h, resulted in the lowest effluent PO43--P concentration of 0.5 +/- 0.3 mg P/L. The results of in situ process profiles and ex situ P release and uptake batch tests under different RAS diversion conditions showed that the more anaerobic P release was obtained in the side-stream reactor, the higher the P removal efficiency and EBPR activity were achieved. The stoichiometric ratios observed in EBPR activity tests indicated a polyphosphate accumulating organisms (PAOs) metabolism mainly dependent on the glycolysis pathway. The results of microbial ecology analysis revealed that the optimized SRTSS would give a competitive advantage to PAOs in the S2EBPR process. By obtaining statistically reliable results, this study would provide guidance for wastewater treatment plants to achieve optimal P removal performance in S2EBPR configuration.

Octogen (HMX) is widely used as a high explosive and constituent in plastic explosives, nuclear devices, and rocket fuel. The direct discharge of wastewater generated during HMX production threatens the environment. In this study, we used the electrochemical oxidation (EO) method with a PbO2-based anode to treat HMX wastewater and investigated its degradation performance, mechanism, and toxicity evolution under different conditions. The results showed that HMX treated by EO could achieve a removal efficiency of 81.2% within 180 min at a current density of 70 mA/cm2, Na2SO4 concentration of 0.25 mol/L, interelectrode distance of 1.0 cm, and pH of 5.0. The degradation followed pseudo-first-order kinetics (R2 > 0.93). The degradation pathways of HMX in the EO system have been proposed, including cathode reduction and indirect oxidation by •OH radicals. The molecular toxicity level (expressed as the transcriptional effect level index) of HMX wastewater first increased to 1.81 and then decreased to a non-toxic level during the degradation process. Protein and oxidative stress were the dominant stress categories, possibly because of the intermediates that evolved during HMX degradation. This study provides new insights into the electrochemical degradation mechanisms and molecular-level toxicity evolution during HMX degradation. It also serves as initial evidence for the potential of the EO-enabled method as an alternative for explosive wastewater treatment with high removal performance, low cost, and low environmental impact.

针对传统生物脱氮除磷工艺性能易受进水条件变化影响的缺点,构建了侧流活性污泥水解(SSH)工艺反应器,比较研究了该反应器与常规厌氧/缺氧/好氧(A2/O)工艺反应器在不同进水条件下的污染物处理性能和微生物群落的变化规律.试验结果表明:A2/O和SSH反应器化学需氧量(COD)去除性能的变化较小,整体COD去除率均维持在90％左右.进水负荷和流量的升高有利于提高脱氮除磷效果.A2/O和SSH反应器的总氮去除率分别从阶段Ⅰ的58％和72％升高到阶段Ⅲ的67％和83％,总磷去除率均从60％左右升高到85％以上.与A2/O反应器相比,进水条件变化对SSH反应器脱氮性能的影响较小.相同进水条件下SSH反应器脱氮性能更好,总氮平均去除率比A2/0反应器高出23％.高通量测序结果表明,SSH反应器中微生物群落的多样性更高,Dechloromonas、Accumulibacter等脱氮除磷功能菌的相对丰度更高,是反应器出水水质良好且稳定的重要原因.研究成果可为SSH工艺的设计与实际应用提供参考依据.

Polycyclic aromatic hydrocarbons (PAHs) are key organic pollutants in the environment that pose threats to the ecosystem and human health. The degradation of high molecular weight (HMW) PAHs by enriched bacterial consortia has been previously studied, while the involved metabolisms and microbial communities are still unclear and warrant further investigations. In this study, five bacterial consortia capable of utilizing different PAHs (naphthalene, anthracene, and pyrene) as the sole carbon and energy sources were enriched from PAH-contaminated soil samples. Among the five consortia, consortium TC exhibited the highest pyrene degradation efficiency (91%) after 19 d of incubation. The degradation efficiency was further enhanced up to 99% by supplementing yeast extract. Besides, consortium TC showed tolerances to high concentrations of pyrene (up to 1000 mg/L) and different heavy metal stresses (including Zn2+, Cd2+, and Pb2+). The dominant genus in consortium TC, GS, and PL showing relatively higher degradation efficiency for anthracene and pyrene was Pseudomonas, whereas consortium PG and GD were predominated by genus Achromobacter and class Enterobacteriaceae, respectively. Consortium TC, as a highly efficient HMW PAH-degrading consortium, could be applied for synergistic biodegradation of HMW PAHs and in situ bioremediation of the sites contaminated with both PAHs and heavy metals.

Complex and high levels of various pollutants in high-strength wastewaters hinder efficient and stable biological nutrient removal. In this study, the changes in pollutant removal performance and microbial community structure in a laboratory-scale anaerobic/aerobic sequencing batch reactor (SBR) treating simulated pre-fermented high-strength wastewater were investigated under different influent loading conditions. The results showed that when the influent chemical oxygen demand (COD), total nitrogen (TN), and orthophosphate (PO43−-P) concentrations in the SBR increased to 983, 56, and 20 mg/L, respectively, the COD removal efficiency was maintained above 85%, the TN removal efficiency was 64.5%, and the PO43−-P removal efficiency increased from 78.3% to 97.5%. Partial nitrification with simultaneous accumulation of ammonia (NH4+-N) and nitrite (NO2−-N) was observed, which may be related to the effect of high influent load on ammonia- and nitrite-oxidising bacteria. The biological phosphorus removal activity was higher when propionate was used as the carbon source instead of acetate. The relative abundance of glycogen accumulating organisms (GAOs) increased significantly with the increase in organic load, while Tetrasphaera was the consistently dominant polyphosphate accumulating organism (PAO) in the reactor. Under high organic loading conditions, there was no significant PAO–GAO competition in the reactor, thus the phosphorus removal performance was not affected.

Bioretention has been considered as an effective management practice for urban stormwater in the removal of pollutants including polycyclic aromatic hydrocarbons (PAHs). However, the accumulation of high-molecular-weight (HMW) PAHs in bioretention systems and their potential impact on the pollutants removal performance and microbial ecology are still not fully understood. In this study, comparisons of treatment effectiveness, enzyme activity and microbial community in bioretention systems with different types of media amendments were carried out at different spiking levels of pyrene (PYR). The results showed that the removal efficiencies of chemical oxygen demand (COD) and total nitrogen in the bioretention systems were negatively impacted by the PYR levels. The relative activities of soil dehydrogenase and urease were increasingly inhibited by the elevated PYR level, indicating the declining microbial activity regarding organic matter decomposition. The spiking of PYR negatively affected microbial diversity, and distinct time- and influent-dependent changes in microbial communities were observed. The relative abundance of PAH-degrading microorganisms increased in PYR-spiked systems, while the abundance of nitrifiers decreased. The addition of media amendments was beneficial for the enrichment of microorganisms that are more resistant to PYR-related stress, therefore elevating the COD concentration removal rate by ∼50%. This study gives new insight into the multifaceted impacts of HMW PAH accumulation on microbial fingerprinting and enzyme activities, which may provide guidance on better stormwater management practices via bioretention in terms of improved system longevity and performance.

通过构建实验室反应器,比较分析侧流活性污泥水解(SSH)工艺和常规厌氧/缺氧/好氧(A2/O)工艺在不同进水负荷下的脱氮性能及功能微生物群落结构的变化规律.结果表明,在相同进水条件下,SS H反应器具有更好且更稳定的脱氮性能,72％的出水可达到《城镇污水处理厂污染物排放标准》(GB 18918—2002)一级A标准.提高进水污泥负荷可提升两种工艺的脱氮性能,而水力条件的改变会造成出水总氮和氨氮浓度的波动.微生物群落结构分析表明,SS H反应器中脱氮功能微生物的多样性和相对丰度均高于A2/O反应器,这可能和其特殊的工艺构型有关.

通过改变传统厌氧/缺氧/好氧(A2/O)反应器和侧流活性污泥水解(SSH)反应器的曝气强度和溶解氧(DO)浓度,考察了曝气条件对脱氮性能的影响,并对比研究了微生物群落结构的变化规律.结果 表明:相较于高DO阶段,两组反应器在中低DO阶段有更好的脱氮效果.在相同进水条件下,SSH反应器的脱氮性能优于A2/O反应器,且出水满足一级A标准.高通量测序结果表明,中低DO浓度更有利于脱氮微生物的生长.相对于A2/O反应器,SSH反应器中反硝化微生物的相对丰度更高.因此,合理控制曝气条件维持中低DO浓度有利于SSH工艺达到良好的脱氮性能及脱氮微生物的生长.

为探究二氯乙腈(DCAN)对大肠杆菌(E.coli)基因表达的影响及相应的毒性作用,采用自组织映射(SOM)聚类及剂量效应关系分析方法考察了E.coli在不同剂量DCAN暴露120min过程中其基因表达状况.结果表明:随时间及浓度改变E.coli基因表达具有动态性;在DCAN浓度为1.429×10-3mg/L时,多个参与应急反应(SOS response)调节、氧化还原应激及普通应激的基因启动子活性发生改变,导致DNA损伤、氧化应激加剧,细胞生物化学和物理稳态可能受到干扰;此外,毒性终点结果表明DNA损伤是DCAN主要的毒性作用模式.