Microorganisms and sediments in reclaimed water adhere to the inner walls of pipes or water tanks, forming biofilms that support the continuous growth of microorganisms. These biofilms provide a protective barrier, shielding bacteria from disinfectants. This study investigated the impact of biofilms on bacterial growth and reproduction in reclaimed water and the factors limiting bacterial growth in reclaimed graywater (GMR) and reclaimed mixed wastewater (MWR). The results revealed that biofilm biomass gradually increased and reached a maximum value on Days 20–25, and the biomass of organisms continued to decrease after 40 days. Biofilms serve as a source of bacteria, continuously releasing them into reclaimed water systems. The presence of biofilms reduced the biological stability of the reclaimed water, leading to water quality deterioration. The concentration of assimilable organic carbon in the reclaimed water showed a positive correlation with the heterotrophic bacterial count and Escherichia coli levels in both the reclaimed water and biofilms. The threshold value of chlorine for inhibiting biofilms in reclaimed water was no © 2023

Aerobic duration control (ADC), whereby aeration is terminated before nitrite is extremely oxidized during the nitrification process, is an effective strategy to achieve partial nitritation (PN) for blackwater. This study eval-uated the effects of microbial growth type, influent ammonia-oxidizing organisms (AOO), and comammox bacteria from seeding sludge to ADC-based PN. The long-term operation of lab-scale reactors and model simu-lations were implemented to select the best growth type. The biofilm formed on the inner wall of the activated sludge reactor decreased the nitrite accumulation ratio (NAR) from 99.2% to 77.2%. Meanwhile, the NAR of the pure-biofilm reactor decreased from 95.9% to 47.8%. The deteriorated PN of the biofilm-related reactors was due to the extended solid retention time and increased substrate saturation constants of AOOs compared with those of nitrite-oxidizing organisms (NOO). Periodic biofilm carrier regeneration and biofilm thickness control can recover PN performance but are difficult to implement. In contrast, the optimized activated sludge reactor exhibited high (NAR >94%) and stable (>3 months) PN performance when treating real blackwater. Nitrifiers were found in blackwater, and chemically enhanced high-rate activated sludge pretreatment removed more NOOs than AOOs (41.8% vs. 24.3%) and increased the influent AOO/NOO ratio. Interestingly, the influent AOOs supported fast PN start-up in the moving-bed biofilm reactor without the initial inoculation of activated sludge. Moreover, model simulations verified that high and stable PN could also be realized in an activated sludge reactor by the continuous inoculation of influent AOOs, which is a novel PN start-up strategy. Metagenomic analyses showed that the comammox bacteria from the seeding sludge eventually disappeared owing to their intrinsic specific growth rates and free ammonia inhibition. The findings of this study will provide insightful guidelines for PN application in decentralized and semi-centralized wastewater treatment systems.

Heterotrophic denitratation coupled with anammox is a high-efficiency and low-cost process to scavenge residual nitrate and ammonium from the mainstream partial nitritation/anammox process. Fermentate derived from the carbon-concentrated sludge, e.g., chemically enhanced high-rate activated sludge (CEHRAS), is a valuable carbon source for heterotrophic denitratation. However, acetate rather than all volatile fatty acids (VFAs) in the fermentate results in high nitrite accumulation. Micro-aeration may be a promising technology to facilitate VFA production and acetate proportion. This study implemented performance comparison and mechanism analyses on two different micro-aeration modes (i.e., continuous and intermittent micro-aeration) of CEHRAS anaerobic fermentation. Batch fermentation tests showed that the low-intensity micro-aeration (4.62 mL/(L.min)) increased 2.2 times of VFA productions compared with unaerated blank. Higher oxygen dosages (7.69 and 15.4 mL/(L.min)) increased acetate proportion though reduced VFA production, largely due to the elimination of hydrogen inhibition in acetogenesis and the facultative consumption strengthen. Further, the intermittent microaeration effectively limits the aerobic respiration in the later stage. Moreover, model substrate tests elucidated that micro-aeration accelerated all steps of protein degradation. The long-term beneficial effects of microaeration on VFA production (104 vs. 54.3 mg COD/g VSS) and acetate ratio (59.0% vs. 41.0%) were validated by operating sequencing batch reactors with and without micro-aeration, respectively. Additionally, micro-aeration enriched essential functional microorganisms rather than regulated microbial diversity. Model simulations revealed the crucial roles of increasing acetate proportion in fermentate. The intercellular storage process had higher rate constant and substrate affinity based on acetate than other VFAs, which was the main reason for the higher nitrite accumulation of acetate. Thereby, micro-aeration fermentate from CEHRAS is an ideal carbon source in heterotrophic denitratation.

Pharmaceuticals and personal care products (PPCPs) are emerging pollutants that have gradually attracted the attention of researchers. PPCPs in urban sewage treatment plants mainly originate from human excreta, while water that is mainly composed of human excreta and flushing water is referred to as black water. Based on a traditional anaerobic-anoxic-oxic-membrane bioreactor (AAO-MBR) design, we optimized the strategy of prolonging the anaerobic-anoxic section length and tested its effect on the bioreactor's efficiency in removing conventional pollutants and PPCPs from blackwater. We assessed the PPCP removal mechanism and efficiency of the AAO-MBR system and a combined advanced ultraviolet (UV)/chlorine treatment system. Under the condition with a hydraulic retention time of 40 h, reflux ratio of the mixed liquid of 400%, and carbon source addition to the blackwater (chemical oxygen demand = 780 mg/L), the removal of ibuprofen, carbamazepine, and bezafibrate by the improved AAO-MBR process exceeded 90%. The PPCP removal mechanisms in the AAO-MBR system were mainly biodegradation, sludge adsorption, and effluent residue. More than 95% of ibuprofen and bezafibrate were biodegraded, and the remaining portions were adsorbed on sludge or remained in the effluent, whereas only approximately 50% of carbamazepine was biodegraded, and the rest was adsorbed on sludge or remained in the effluent. When the UV intensity was 8.0 W/m2, the pH was 6, and the free chlorine concentration was 18 mg/L in the NaClO system, the target PPCPs were completely removed after 23 min. The effective removal of PPCPs from blackwater is essential for alleviating potential environmental risks. Our research provides technical support for the discharge of conventional pollutants and the coordinated removal of PPCPs using a UV/chlorine treatment process.

Generation of size-segregated aerosols is an important eco-environmental problem in wastewater treatment plants (WWTPs), but the characteristics of potential pathogens and antibiotic resistomes in submicron aerosols (PM1.0) were almost unknown. Here, 16S rRNA gene amplification and shotgun metagenome sequencing were respectively used to study the profiles of potential pathogens and antibiotic resistance genes (ARGs) in PM1.0 from a full-scale WWTP. Acinetobacter and sul1 were respectively the predominant potential pathogens and ARG subtypes in PM1.0 from aeration process. A total of 9 potential pathogens and 147 ARG subtypes, were shared among WWTP-PM1.0, wastewater/sludge, and ambient air. Significant differences of potential pathogens or ARGs were found between WWTP-PM1.0 and wastewater/sludge, however, wastewater/sludge had more crucial source contribution than the ambient air. Moreover, 13 potential pathogens and 40 ARG subtypes were easily aerosolized in PM1.0 from at least one of the treatment units. ARGs were mainly harbored by Proteobacteria, and multidrug resistance genes were the most ARG type carried by potential pathogens. Taken together, this study indicates the prevalence of potential pathogens, ARGs, and ARG-carrying potential pathogens in WWTP-PM1.0, which highlights the potential risk of PM1.0 in spreading potential pathogens and antibiotic resistomes into the air environments. © 2022 Elsevier B.V.

The domestic wastewater collection and treatment rate of Nairobi, Kenya are not high. The wastewater in the Kibera slum on the outskirts of the city that is directly discharged to the environment and pollution of the surrounding water body is a serious problem. This paper takes the domestic wastewater in the slum area as the research objective and researches on the wastewater characteristics, collection, and treatment, therefore providing the reference for the wastewater collection and treatment technology in the region. In this paper, domestic wastewater in the Kibera slum of Nairobi was sampled and investigated to find out the characteristics of wastewater discharged, the way of discharge of the household wastewater, and the management in this area. The study shows that there are differences in the concentration of main pollutants such as nutrients and organic matter in the wastewater from the household discharged to the residential river in the slum area. The domestic wastewater in this slum area contained a high concentration of nutrients such as nitrogen and phosphorus and other organics, total suspended solids (TSS), total coliforms and color, and with no treatment methods. Therefore, economic and feasible treatment technology needs to be developed. A pilot study was conducted on the treatment of domestic wastewater in the slum area by combining the seed extract of the natural plant Moringa oleifera as a coagulant and vertical flow constructed wetland (VFCW) at Tongji University, Shanghai, China. The VFCW system was efficient in chemical oxygen demand (COD), TSS, turbidity, total phosphorus (TP), and phosphates (PO4-P) removal, but the removal efficiency of nitrogen (total nitrogen (TN), ammonium nitrogen (NH4-N), and nitrate (NO3-N)) was poor, and the effluent pH reached the required discharge country's standard of the water. The average removal efficiencies for COD (79.99%), TSS (86.84%), turbidity (87.35%), TP (61.29%), PO4-P (65.66%), TN (14.11%), NH4-N (18.17%), and NO3-N (93%) were achieved by the treatment system. Furthermore, the removal efficiencies of pollutants such as TP, PO4-P, TN, and NH4-N were carried out by using the fruit extract of Moringa oleifera as raw material and zeolite as an auxiliary agent. The comprehensive effect of zeolite combined with VFCW and natural coagulant in the treatment of domestic wastewater was investigated. The COD removal efficiency was increased by (9%). TN by (46%), NH4-N by (67%), TP by (19%), and turbidity improved by (9%). In short, the domestic wastewater in the Kibera slum was collected and pretreated with natural plant coagulant, and then purified by vertical flow constructed wetland, which can not only significantly reduce the pollutant concentration but also basically meet the discharge standards. It is a low-cost sewage treatment technology suitable for poor areas.

Opportunistic pathogens (OPs) are emerging microbial contaminants in engineered water systems, yet their growth potential in rainwater systems has not been evaluated. The purpose of this study was to compare the growth dynamics of bacterial OPs and related genera (Pseudomonas aeruginosa, Legionella spp., L. pneumophila, Mycobacterium spp., and M. avium), two amoebal hosts (Acanthamoeba spp. and Vermamoeba vermiformis), and the fecal indicator Escherichia coli in simulated rainwater and tap water storage systems (SWSSs). Quantitative polymerase chain reaction (q-PCR) analysis of target microorganisms in SWSS influents and effluents demonstrated that P. aeruginosa and Legionella thrived in rainwater, but not in tap water. V. vermiformis proliferated in both rainwater and tap water polyvinyl chloride (PVC) SWSSs, while mycobacteria were largely absent in rainwater SWSSs. Tank materials exerted stronger influence on target microorganisms in rainwater SWSSs relative to tap water SWSSs, with species-specific responses noted in bulk water and biofilm. For instance, P. aeruginosa and V. vermiformis had the highest gene copy numbers in PVC rainwater SWSS effluents and biofilm, while Legionella peaked in stainless steel rainwater SWSS effluents and PVC rainwater SWSS biofilm. These results highlighted the OP contamination risks in rainwater storage systems and provided insights into rainwater system design and operation in terms of OP control. © 2021

Personal care products (PCPs) are contaminants of emerging concern because of their continuous input into the environment. In this study, membrane bioreactor (MBR) and constructed wetland (CW) methods were used to investigate the effect and mechanism of conventional pollutant and PCP removal from greywater. The effluent of both the MBR-and CW-treated greywater met the reclaimed water reuse standard in China. Conventional pollut-ants and five target PCPs had a higher removal efficiency in the MBR than in the CW. The removal rates of the PCPs, including Tuina musk (AHTN), were >80% using MBR and CW methods. The main pathway of removing PCPs in the MBR was sludge adsorption and biodegradation, whereas the contribution of the membrane module was weak. The main pathway of removing PCPs in the CW was the combined action of plant absorption, microbial biodegradation, and substrate adsorption, depending on the PCP type. Ethyl hexyl methoxycinnamate (EHMC) has strong biological oxidizability and was mainly removed by biodegradation, whereas Jiale musk (HHCB) and AHTN were mainly removed by adsorption. Six types of CW substrates were investigated, and perlite showed the best adsorption effect for the five target PCPs. The optimal substrate adsorption pH was 7. This study provides important technical information on the effective removal of conventional pollutants and PCPs in greywater and the preparation of high-quality reclaimed water. (c) 2021 Published by Elsevier B.V.

Current experiences in pilot sanitation projects indicate that the spontaneous precipitation in urine diversion (UD) systems has been one of the main challenges for the implementation of urine source separation on large-scale. As a result of microbial ureolysis, an increased pH leads to the formation of inorganic precipitates, which increases the risk of pipe blockage. Although significant advancements have been made in controlling the spontaneous precipitation in UD systems, experimentation in pilot projects is not enough to provide the feasible and reliable support for technical selection to adapt quickly to changing boundary conditions, such as population size and density. Therefore, established techniques should be constantly reassessed and improved in a broader variety of experimental settings to ensure the wide applicability, economic and environmental benefits, and social acceptance. This work also clarified the importance of establishing standardized evaluation methods, which helps to integrate the knowledge gained from reported specific case studies and provide detailed information that can support the decision makers. On the other hand, the economic assessment indicated that maximizing the value of the urine-derived fertilizers can ensure a favorable rate of return, which is important to attract investors and promote the implementation of urine source separation. Meanwhile, current legislation and government support have provided the opportunities for large-scale implementation of urine source separation. The decision makers should be prepared well to deal with such a paradigm shift. © 2021

As a widely used ampholytic surfactant, cocoamidopropyl betaine (CAPB) has been improved to enhance waste activated sludge (WAS) reduction in the short-time aerobic digestion (STAD) system, but how system pH value affects the synergetic combined process has not been discussed. This research evaluated how alkalinity affects soluble microbial products (SMP) dynamics and WAS reduction in the synergetic system. After adding CAPB, the biodegradation rate constant of VSS (k(VSS)), TCOD (k(TCOD)) and CAPB (k(CAPB)) were much higher than that of without adding CAPB; pH value at 7.0-8.0 showed the maximum specific oxygen uptake rate (SOUR) of WAS, leading to the highest WAS reduction efficiency. Further study indicated that CAPB can significantly improve the release of extracellular polymeric substances (EPS), leading to the increased SMP concentrations and low molecular weight fractions (MWF) proportions in SMP; more SMP with low MWF fraction led to the increased SOUR, thus further accelerate the WAS reduction; increasing pH could improve the foaminess and solubility of CAPB, thus further improve the organics release and SMP accumulation, which could be quickly removed in the system. This findings lay the foundation of the practical application of the synergetic combination system in WAS reduction.