ABSTRACT Flowchart of a model paper recycling mill water circuit, highlighting recycling, recovery, and discharge pathways. Icons indicate each unit (from http://www.flaticon.com). This study investigates nanofiltration (NF) and reverse osmosis (RO) treatment of the liquid fraction from digestate of short-fiber residues from paper recycling mills, focusing on water reuse and ammonium (NH4-N) recovery. NF removed up to 86% chemical oxygen demand (COD) and fully retained phosphorus (Ptot), but separated only 40–55% of total nitrogen (Ntot) and NH4-N. RO performed better, removing 96% COD, 86% NH4-N and Ntot, while fully retaining Ptot. RO permeate met the freshwater quality for paper recycling, with small NH4-N remaining. To improve NH4-N recovery, natural zeolite was tested with RO in three scenarios: treating the liquid fraction of digestate, RO retentate, and RO permeate. The highest NH4-N adsorption (79%, 7.8 mg/g) occurred with RO retentate, and the highest desorption (53%, 2.9 mg/g) with RO permeate. Adsorption performance varied with NH4-N concentration and pretreatment, with higher NH4-N levels leading to greater adsorption. COD was also reduced by up to 70% during adsorption. RO treatment of digestate in a model paper mill (0.7 Mt/year production capacity) could recover about 38,000 m3 of water annually, saving 71,000 €. Combined savings from water reuse and avoided digestate disposal could alone reach 0.2 million € annually.

ABSTRACT Disinfection byproducts (DBPs) resulting from reactions between dissolved organic matter (DOM) and disinfectants following wastewater treatment pose risks to humans and aquatic environments. While enhanced coagulation and ozonation are widely used to reduce DOM and DBP formation, performance of ultrafiltration (UF) following these treatments is less understood, despite its potential to improve overall effluent quality and ensure safe water reuse. This study investigated DOM removal during enhanced coagulation and ozonation pretreatment, and its impact on DBP formation and associated toxicities during pretreated-UF processes. The results showed 41 and 34% reduction in haloacetonitrile formation potential (HANFP) and haloacetamide formation potential (HAMFP) with 120 mg/L polyaluminum chloride (PACl), respectively, and 48 and 41% reduction with 120 mg/L ferric chloride (FC). Trihalomethane formation potential (THMFP) reduced by 36 and 53% with 120 mg/L of PACl and FC, respectively. Ozonation increased brominated DBP concentrations and combining enhanced coagulation with ozonation achieved similar DBP reductions as enhanced coagulation alone. Ultrafiltration altered the DOM optical properties, as reflected by SUVA254 changes, but contributed minimally to overall DOM and DBP precursor removal. Excitation–emission matrix (EEM) spectroscopy revealed that ozonation generates soluble microbial product (SMP)-like organics and proteinaceous compounds that are ineffectively removed during subsequent UF treatment.

ABSTRACT The Naqu River Basin (NRB) is a crucial water conservation and ecological barrier area in the Nujiang River. Climate change has significantly altered its hydrological cycle, affecting water source composition. To investigate recharge dynamics in alpine regions, precipitation, surface water, and groundwater samples were collected from the NRB in Tibet, China, and analyzed for hydrogen and oxygen isotopes. Precipitation isotopes showed strong seasonal fluctuations, with the lowest values in winter and the highest in summer. The local meteoric water line (LMWL) had a lower slope and intercept than the global counterpart, indicating notable sub-cloud evaporation. Along the Naqu River, isotopic values varied spatially, becoming more enriched downstream. Lacustrine water had a higher isotopic composition than river water, reflecting intense evaporation in Cuona Lake. The river's main recharge sources include precipitation, glacial meltwater, groundwater, and lake water, with variations between freeze-thaw periods and along different sections. Meltwater and groundwater dominated recharge in upstream tributaries, particularly during the freeze ignition period, while lake water became a key source downstream.

ABSTRACT Water reuse can contribute to climate-resilient water management because wastewater is available throughout the year. This can mitigate water stress and potential competition between drinking water supply, industry and agricultural irrigation. In rural areas, decentralized approaches may be advantageous compared with transporting wastewater to centralized treatment plants via diesel-powered trucks. The ‘Point-of-Use Re-Use’ (PU2R) approach proposes a mobile, small-scale wastewater treatment plant consisting of a membrane bioreactor (MBR) with UV disinfection for decentralized water reuse in agriculture. In this paper, the sustainability of the PU2R approach is evaluated, with focus on the following points: The capacity of flexible wastewater treatment from single-household cesspits in an MBR with activated carbon dosage and UV disinfection in combination with a H2O2-based advanced oxidation process is assessed.The fate of persistent and mobile organic micropollutants on the pathways from soil to plant and from soil to groundwater is analyzed. To support this, an open-source tool for a 50-year prognosis was developed.A cost assessment is carried out for the decentralized PU2R approach vs. the current wastewater disposal by truck transport and centralized treatment.A life cycle assessment of the potential environmental impact of the PU2R approach is examined for five impact categories.

ABSTRACT Climate change and industrialization necessitate a reassessment of water management strategies, particularly in agriculture, where reclaimed water supply often fails to meet irrigation needs. Storage can bridge supply gaps but raises concerns about water quality deterioration due to microbial changes and pathogen regrowth. This study examined microbial dynamics and regrowth during reclaimed water storage from a municipal wastewater treatment plant in Germany. The treatment train included ozonation, filtration and UV disinfection, and samples were analyzed using traditional culture methods for indicator organisms (e.g., Escherichia coli, Clostridium perfringens spores, and somatic coliphages) and 16S rRNA gene amplicon sequencing. Samples were collected throughout the treatment train and stored at 22 °C in the dark for up to 15 days. Results showed effective microbial reduction by treatment, with storage alone achieving similar declines in many cases. While treatment reduced bacterial diversity, storage gradually restored it, forming distinct microbial profiles from the original water quality. Bacterial communities converged during storage, suggesting a succession-like stabilization process. The findings highlight the dynamic nature of reclaimed water microbiomes and the importance of stimulating stable microbial communities to preserve water quality during storage. Advanced treatment should remove contaminants while supporting microbiomes that protect public health and the environment.

ABSTRACT Water scarcity is a growing global challenge and agricultural water reuse offers a viable solution. However, microbial safety concerns persist, particularly regarding pathogens and antibiotic resistance genes (ARGs). This study assessed microbial contamination of crops irrigated with three water qualities: tap water, reclaimed water from Treatment Train A (conventional activated sludge [CAS] + filtration + UV disinfection), and from Train B (CAS + ceramic ultrafiltration + ozonation + biological activated carbon [BAC] + UV), using overhead and drip irrigation. Culture-based methods, MALDI-TOF-MS, and PCR were used to analyze microbial parameters, including E. coli, coliforms, and ARGs. Results showed no significant differences in E. coli and coliform levels between irrigation types, indicating that water quality did not impact microbial crop safety. MALDI-TOF-MS revealed no major shifts in bacterial communities. While bacterial regrowth occurred in some irrigation water samples, pathogenic and fecal bacteria were not detected on crops. ARGs were present in irrigation water, particularly in Train A effluent, but their transfer to crops was limited. Overall, irrigation water quality and method had little influence on crop contamination, whereas crop type, growing practices, and environmental conditions played a more prominent role. Long-term impacts of ARG dissemination in agriculture warrant further study.

ABSTRACT This study addresses the potential of combining phosphorus biostimulation and phytoremediation as a sustainable strategy for wastewater treatment. Various physico-chemical analyses and microbiological parameters were assessed in different treatments: biostimulation, phytoremediation, and a combined method. These assessments were conducted for both treated (STWW) and untreated wastewater (SWW) categories. The alfalfa plots were then irrigated with the treated wastewater (TWW), followed by enzymatic activity analyses, microbiology, physico-chemical properties, and plant growth. The results show that the selected strain, identified as Aspergillus flavus OQ269829, increased the assimilable phosphorus content of the SWW, raising it to about 3.25 mg/L in the irrigated soil. The TWW presents a neutral pH of less than 8 and a chemical oxygen demand value below 120 mg O2.L−1, together with an increased phosphorus transformation. Dehydrogenase activity in soil irrigated with STWW supplemented with fungi and phosphorus rose from 4.5 to 10.5-μg TPF g−1·h−1 by the end of the incubation period. The plant exhibited significant growth and earlier flowering. Concurrent with this, there was an increase in plant nutrient content when irrigated with a combined application of K+ and Na+, ranging from 104.36 to 189.59 mg·g−1 dry weight for K+ and 15.3–29.9 mg.g−1 dry weight for Na+.

ABSTRACT The sustainability and resilience of a city rely on its capacity to utilize its environmental resources while maintaining social, environmental, and economic balance. Practising urban agriculture (UA) is a sustainable solution that can offset this balance. Treated wastewater (TWW) generated in urban areas can be used to reduce stress on available water resources. However, the extent of its significance remains unclear. This study used bibliometric analysis to explore the trends in publication and thematic evolution between 2008 and 2024 from the Scopus database. The bibliometrics R-package and VOSviewer software were used for bibliometric analysis and science mapping. A total of 1,208 articles were retrieved from the database, from which 960 were used for analysis after data cleansing. The analysis of the results shows that wastewater (WW) reclamation and treatment were found to have the weakest strength and the least number of occurrences. This suggests that researchers did not seriously investigate the use of TWW for UA, thus suggesting a potential gap in the literature that needs to be addressed. Risk reduction strategies for WW reuse in UA were also discussed. This paper argues that reusing TWW for UA can strengthen urban resilience while protecting environmental resources.

ABSTRACT The reuse of domestic treated wastewater in agriculture poses a significant challenge as a result of the incomplete removal of micropollutants, with considerable public health, economic, and environmental consequences. Post-treatment of the treated wastewater by sorption-based technologies using biochar can mitigate these micropollutant-related concerns. Therefore, this study aims to evaluate the efficacy of various biochar types in eliminating micropollutants from treated wastewater to ensure safe reuse practices. The biochar utilised in this study was made from softwood and hygienized sewage sludge. Five indicator micropollutants were used to assess the removal efficiency of the different biochars. The experimental campaign consisted of two steps, starting with a preliminary assessment of the removal efficiency of various biochar types under constant operational conditions. This approach identified the biochar type that achieved the highest removal efficiency. Second, a response surface methodology study was then carried out to explore the interactive impacts of operational variables on the removal of selected micropollutants using the selected biochar type, softwood-biochar. This study showed that softwood-biochar can remove benzotriazole, carbamazepine, diclofenac, irbesartan, and metformin with 98, 92, 94, 90, and 99% efficiency, respectively. These findings pave the way for the development of a low-cost sorption-based micropollutant removal technique for safe reuse.

ABSTRACT Fluoride levels in drinking water pose a significant environmental threat, and adsorption is a common technique. However, many adsorbent materials have drawbacks such as poor adsorption capabilities, extended contact times, high pH levels, and large dosages. A biochar-based magnetic composite adsorbent has been developed for water defluoridation using a chemical co-precipitation process to immobilize iron particles on the biochar surface. X-ray diffraction analysis, Fourier transformed infrared spectroscopy, Brunauer–Emmett–Teller, and scanning electron microscopy were used to analyse the composite. The central composite design was used to design laboratory tests, which included four input variables: solution pH, dosage, contact time, and initial concentration. The adsorbent dosage was 5.92 g/L, the aqueous pH was 5.79, the contact time was 66.48 min, and the initial fluoride concentration was 12.38 mg/L. The removal efficiency was predicted to be 98.61%, with a 98.55% removal efficiency at optimum conditions. The study concluded that the composite adsorbent can be a reliable and sustainable solution for fluoride removal from water.