ABSTRACT Membrane fouling remains a major bottleneck for seawater reverse osmosis (SWRO) desalination, and microfiltration/ultrafiltration (MF/UF) pretreatment is increasingly adopted to mitigate it. However, the relative importance of membrane material versus pore size has not been clarified through systematic comparison. Here we evaluated three hollow-fiber membranes – MF1 (PVDF, 100 nm), UF1 (PVDF, 150 kDa) and UF2 (PAN, 80 kDa) — operated under matched transmembrane pressure on polluted seawater (Fukuura coast, Japan), quantifying the colloidal fouling potential of permeates by the modified fouling index in ultrafiltration mode (MFI-UF). MFI-UF decreased monotonically with pore size: the largest reduction occurred between the 1 μm cartridge and the 100 nm MF membrane, and tightening pore size further into the UF range lowered it more, indicating pore size as a primary factor and membrane material as secondary – though not negligible – in this range. LC-OCD and ICP-OES revealed strong biopolymer–Ca covariation (R2 = 0.95), suggesting biopolymer–Ca complexes as a principal colloidal foulant, while silica appeared to associate with low-molecular-weight substances. NaOH extraction with EEM fluorescence identified protein-like organic matter as the main NaClO-recoverable foulant of PVDF membranes, whereas HCl-extractable iron was implicated in inorganic fouling. These findings provide a quantitative basis for MF/UF membrane selection in SWRO pretreatment.
ABSTRACT Sequence of text and pictures showing Tanfloc with alum or pH adjustment applied to liquid manure, indicating that combining Tanfloc with alum improves turbidity removal, reduces costs, and increases phosphorus separation. Tannin-based coagulant-flocculants, such as Tanfloc, are proposed as environmentally friendly alternatives to clarify water and recover nutrients from farm dairy effluent. However, cost and dosage requirements limit their use, and their performance when combined with metal salts remains poorly investigated. This study evaluated the performance and cost-effectiveness of combining Tanfloc with aluminium sulphate (alum) for turbidity removal and nutrient separation from manure (0.5–3.0% total solids). We used jar testing and response surface methods to compare performance with Tanfloc alone (pH 4.0–8.0). Although pH influenced turbidity removal (>99%), and separation of TN (77–79%) and TP (63–75%), alum inclusion enhanced turbidity removal at sub-optimal Tanfloc dosages with similar TN separation across treatments, and increased TP separation to 94–97%. Minimizing residual turbidity (6 NTU) using Tanfloc with pH adjustment cost $23.6 AUD/m3, while combining Tanfloc with alum reduced it to $15.6 AUD/m3. Aiming for moderate clarification (∼50 NTU) did not affect nutrient separation and reduced chemical costs to $2.9 AUD/m3. This study provides a cost-effective strategy to improve nutrient recovery and effluent quality, which may support future reuse on dairy farms. Pathogen analysis, field validation, and assessment of long-term alum effects in soil are required before on-farm implementation.
Water eutrophication prediction remains challenging due to poor long-term feature retention, susceptibility to local optima, and difficulties in balancing smooth and abrupt time-series patterns. To address these issues, this study develops a two-stage reinforcement-learning forecasting framework in which Transformer-based temporal representation, auxiliary replay learning, and error-aware Q-value selection are jointly organized for multivariate eutrophication prediction. In the first stage, the TDDPG model replaces the conventional actor representation in DDPG with a Transformer-based temporal feature extractor and uses an auxiliary replay buffer to reduce the effect of strongly correlated sequential samples during policy learning. In the second stage, the DDPG-Double 3Q model treats the outputs and errors of several DDPG-based predictors as decision states, allowing the final prediction policy to select and refine candidate predictions under both gradual and abrupt water-quality variations. Experimental validation using multi-factor water quality monitoring data demonstrates that the proposed framework achieves an average improvement of 35% across key evaluation metrics - Mean Absolute Error (MAE), Root Mean Squared Error (RMSE), and Mean Absolute Percentage Error (MAPE) compared to baseline models such as ADDPG and RDPG. The results indicate that the framework improves prediction accuracy and training stability in the tested dataset, suggesting that reinforcement learning can provide a useful sequential decision-making formulation for multivariate eutrophication forecasting.
ABSTRACT Graphical abstract showing the study workflow for planned treated wastewater reuse in Vietnam. A vertical flowchart on the left moves from 'International literature review' to 'Vietnam assessment (2,511 projects right arrow 118 selected+stakeholders),' then to 'Key drivers and barriers (PESTEL),' and finally to 'Strategic recommendations for planned treated wastewater reuse in Vietnam.' A map of Vietnam appears on the right. A red boxed list highlights the main recommendation areas: policy and standards, institutional coordination, economic and finance, technology, and capacity building. Vietnam faces growing pressure on water resources due to rapid urbanization, industrial expansion, climate change, and declining water quality. Wastewater reuse offers a promising pathway to enhance water security, reduce pollution, and advance circular-economy objectives. This study assessed wastewater reuse potential in Vietnam through a mixed qualitative approach: a systematic review of international experience, targeted review of Vietnamese policies and sectoral evidence, screening of 2,511 wastewater-generating projects reported on the national environmental consultation portal, detailed analysis of 118 selected projects, and validation through stakeholder consultation and questionnaire survey. Results show that wastewater reuse in Vietnam is driven mainly by rising water demand, environmental pressure, and regulatory interest in resource circulation, and emerging market incentives linked to green production and supply chains. However, implementation remains limited and uneven across sectors. Manufacturing and tourism projects show the strongest uptake, while industrial park infrastructure, urban systems, and livestock applications face greater institutional, technical, and economic constraints. Main barriers are the absence of fit-for-purpose reclaimed-water standards, fragmented institutional responsibilities, high treatment and monitoring costs, limited financial incentives, and low implementation confidence. Scale-up will require clearer regulation, stronger inter-agency coordination, targeted incentives, improved technical capacity, and explicit integration into long-term water and urban development strategies.
ABSTRACT To supplement chemical fertilizers with more sustainable nutrient sources, innovative wastewater separation technologies have been developed to recover nutrients from human urine to derive fertilizers. However, microbial health risks associated with wastewater reuse and urine source separation remain a concern when integrating these technologies into existing sanitation systems. Pathogens, particularly those originating from faecal cross-contamination during source separation, can cause severe acute gastrointestinal disease. Following PRISMA guidelines, this systematic review examines microbial hazards of health relevance in human urine and identifies gaps in understanding pathogen inactivation during storage. Thirty-five empirical studies were reviewed, including investigations of bacterial species (20), viral agents (11), and antimicrobial resistance genes (11). Findings reveal that the range of microbial health risks associated with urine has expanded since source separation was introduced in the 1990s. Key knowledge gaps include uncertainties in pathogen concentrations at the source, the efficacy and stability of urea hydrolysis as a single treatment method, and the use of surrogate pathogens to represent inactivation dynamics in hydrolyzed urine. Addressing these uncertainties will strengthen quantitative microbial risk assessments and support regulatory confidence in the safe agricultural application of urine-derived fertilizers.
The growing implementation of indirect and direct potable reuse (IPR and DPR) highlights the need for robust wastewater treatment to strengthen the performance and reliability of downstream advanced water purification facilities (AWPFs). Next-generation secondary waste-water treatment processes are now being considered to enhance compatibility in potable reuse schemes. This perspective analyzes the role of competing next-generation biotechnologies such as integrated fixed-film activated sludge (IFAS) and the moving bed biofilm reactor (MBBR), membrane biofilm reactor (MBfR), Modified Ludzack-Ettinger membrane bioreactor (MLE-MBR) and anaerobic membrane bioreactor (AnMBR) upstream of reverse osmosis (RO)- and activated carbon (AC)-based AWP, and their ability to enhance contaminant removal and improve overall efficiency of AWP. Both MLE-MBR and AnMBR significantly enhance the removal of suspended solids, organics, and microbial contaminants through membrane filtration. AnMBR offers the possibility of net energy-positive operation but does not remove nitrogen, limiting compatibility with AWP. MLE-MBR removes nitrogen but has significantly greater energy demand due to aeration and mixed liquor return pumping. Overall, next-generation biotechnologies provide flexible and effective solutions to enhance secondary effluent quality, supporting safe and regulation-compliant IPR and DPR applications.
Direct potable reuse (DPR) represents a technologically advanced and tightly controlled water supply strategy. However, legacy practices such as the emphasis on log-reduction credits for enteric pathogens and the routine application of secondary disinfection may not be appropriate nor effective for managing opportunistic pathogens (OPs) and antimicrobial resistance (AMR) in DPR systems. This paper critiques the use of disinfectant residuals from the perspective of microbial ecology, biofilm dynamics, growth and persistence of OPs, and AMR mechanisms. A case it presented that secondary disinfection can drive the selective pressure and subsequent enrichment of resistant taxa, destabilise advanced-treated water quality, and undermine the engineered principles underpinning DPR. Alternative approaches that prioritise infrastructure integrity, proactive monitoring, and ecological control may offer a more sustainable and resilient strategy for DPR, providing superior public health protection with a reduced AMR risk.
Potable reuse is a significant component that supports the development of resilient water supplies globally. To protect public health and to support the uptake of potable reuse, treatment barrier performance must be validated for the removal of chemical and microbial contaminants. Currently, there are variations between existing potable reuse regulations, validation guidelines, and validation protocols, as well as considerable gaps in the scientific knowledge needed to develop, extend, and harmonize these guidelines and protocols. The WaterVal framework, originally developed in Australia to streamline the validation of water reuse treatment barriers, has the potential to fill this gap and serve as a universal umbrella program, providing a template for the development of treatment barrier validation protocols. WaterVal specifies nine elements that must be addressed to ensure consistency and uniformity in treatment barrier performance when targeting pathogen and chemical contaminant removal. CalVal, an initiative to develop guidance for potable reuse in the state of California (USA), has built on these efforts to provide best practices for the design, operation, and reporting of various treatment barriers used in potable reuse schemes. Collaborative efforts between CalVal and WaterVal will help identify and address knowledge gaps to inform proposed validation frameworks and operational recommendations.
To clarify how Low Impact Development systems should be optimally configured under urban spatial heterogeneity and varying rainfall intensity, this study proposes a deterministic optimization framework validated using the coupled SWMM-LISFLOOD-FP model. Taking Lianyungang City, China, as a case study, optimal LID layouts are found to adhere to a 'location-specific matching' principle and are evolved with rainfall intensity. Spatially, Commercial Districts prioritize rain gardens. Under low-intensity rainfall, Residential, Educational, and Public-Service Districts, as well as Green spaces, mainly use permeable pavements. As intensity increases (2- to 20-year return periods), Educational and Public Service Districts shift from permeable pavements to rain gardens, while the share of green roofs increases across all zones. The macro-system is evolved from a dual 'infiltration-retention' paradigm to a ternary system integrating 'three-dimensional detention-terminal storage/regulation-source infiltration'. Post-optimization, hydrological performance improves significantly: runoff control rate remains >63.6%, peak runoff reduction >63%, junction overflow volume decreases by 79.3%-88.9%, and medium/deep inundation is substantially reduced. This enhanced resilience can be attributed to the synergy of 'temporal hydrological attenuation' and 'spatial hydrological load redistribution'. The study provides a transferable, deterministic methodology for building stormwater resilience in heterogeneous urban spaces under climate stress.
This study evaluates a hybrid forward osmosis (FO)-ozonation process for the quaternary treatment of municipal wastewater. Laboratory-scale FO experiments with subsequent retentate ozonation were conducted to assess FO membrane rejection, organic micropollutant (OMP) removal, and bromate formation. Experiments were performed at volume reduction factors (VRF) of 2 and 8 using NaCl and MgCl2 as draw solutions (DS), and total power demand was modeled based on the geometry and hydraulics of a large-scale FO module. The FO membrane achieved high OMP rejection (85.9-100%), with MgCl2 enhancing retention of ammonium and ibuprofen. Ozonation efficiency depended on compound reactivity and applied ozone dose. Increased salinity at VRF 8 and with NaCl as DS reduced OMP removal due to enhanced ozone scavenging, while concurrently decreasing bromate formation. Power modeling indicated that the FO-ozonation process can reduce total power demand compared to standalone ozonation if DS regeneration is not required. Incorporating reverse osmosis for DS recovery substantially increases power demand, limiting applicability. The approach is energetically viable when the diluted DS can be directly applied, as in fertilizer-driven FO. Future work should examine recirculation of ozonated retentates to the biological treatment stage to evaluate impacts on activated sludge and OMP removal.
Seawater-augmented potable reuse at an advanced water purification facility can provide additional water supplies without significant increases in infrastructure. Operational flexibility in the reverse osmosis (RO) process was conceptually analyzed using closed-circuit RO simulations. Feedwater-shortage and increased-production scenarios were compared with a baseline scenario with no seawater augmentation. Seawater augmentation increased the feedwater total dissolved solid (TDS) concentrations but diluted the wastewater constituents (organics and nutrients), and thus decreased the likelihood of RO membrane fouling. Maximum recovery rates, determined using pressure and solubility criteria, decreased from 90 in the baseline to 77% when blended with 30% seawater. The reduced recovery rates required increased RO feedwater flowrates and resulted in increased RO concentrate flowrates. With 30% seawater augmentation, the concentrate flowrate is similar to 2.7 times higher, with a TDS similar to 4.5 times higher than the baseline; this may require modifications to outfall infrastructure. On the other hand, nutrients in the concentrate to be discharged were diluted, which could reduce impacts on aquatic life and human health. Specific energy consumption increased from 1.36 in the baseline to 4.20 kWh/m(3) with 30% seawater augmentation; however, low-pressure energy recovery devices can be implemented to mitigate energy penalties. Modifications to piping may also be required to increase corrosion resistance.
Sequence of pictures: starting with manure in the foreground of dairy yards, then diluted manure in a tub, a jar tester with four beakers to which five chemicals are pointed, leading to separated solids and liquids with models for solid separation and turbidity removal .Chemical treatment of farm dairy effluent can recover nutrients, clarify it for reuse, and improve effluent management in grazing systems. However, the comparative performance of coagulants/flocculants, and models adapted to variable total solids (TS) concentrations, is limited for flushed manures from grazing systems. Aluminium sulphate, ferric sulphate, polyferric sulphate, polyacrylamide Zetag 8185 (R), and a tannin-based coagulant-flocculant, Tanfloc (R), were compared using centrifuge-based jar tests on liquid dairy manure (0.5-3.0% TS). Tanfloc achieved the greatest turbidity removal, polyacrylamide displayed the highest TS separation, and metal salts were most effective in separating nutrients. Polynomial models using the dose and either the centrifuged liquid turbidity (459-9,485 NTU) or TS concentration (0.5-3.0% TS) accurately predicted turbidity removal or TS separation (R-2 = 79.3-98.7%, Lin's concordance correlation coefficient >0.98). Models were validated using random-splitting, k-fold, and cluster-aware methods. Limitations include the length of storage and the manure dilution method, which affect ionic strength and colloidal stability; uncontrolled pH and temperature conditions; and centrifuge-derived responses that may not generalize to typical on-farm solid-liquid separators. Our results provide a basis for chemically treating liquid dairy manure. On-farm validation, pathogens, and chemical residue analysis are required before providing recommendations for operational use.
Australia is continuing to experience high population growth. About 82% of its utility water supply is currently met from surface water. Climate change is resulting in declining average rainfall rates, reducing run-off into rivers and storages. Many of Australia's water utilities are identifying a shortfall of water supply either imminently or within the next 20 years, due to a combination of population growth and increasing demand from specific industries such as data centres. Since 2008, purified recycled water (PRW) has grown to become an important water supply strategy in a number of Australian cities. White many Australian cities have embraced seawater desalination to supplement water supply, the high costs of implementation are coming under greater scrutiny. PRW is known to be a safe water source, uses significantly less energy, and is frequently of lower capital and operating cost, as well as providing very significant environmental advantages. This paper reviews the status of PRW implementation in Australia from the viewpoint of an adviser's hands-on planning lens.
Mobile water reuse units can be used in off-grid communities or conflict zones to provide sanitation and drinking water during times of need. In this study, a pilot-scale membrane bioreactor (MBR) - air gap membrane distillation (AGMD) system was installed in a CONEX shipping container, tested at one water reclamation facility, and subsequently transported to a second facility with different infrastructure and water quality. The MBR-AGMD treated approximately 1,000 L/day of municipal wastewater and consistently produced high-quality water with low total dissolved solids and only trace levels of organic contaminants. Non-volatile species were reduced by over 99% (2-log(10)). Total coliforms, Escherichia coli, somatic coliphages, and male-specific (F+) coliphages were reduced to levels below the limit of detection (1 Most Probable Number/100 mL) before reaching the MD system, representing reduction values of approximately 6-log(10) and 5-log(10) for bacteria and viruses, respectively. A co-spike test into the MD system was performed with >4-log(10) removals for each virus tested. At the second site, pretreatment requirements were identified, as clogging from high levels of wastewater solids challenged the MBR unit. Additional components, including an external pre-filter tank, were added to increase flexibility for wastewater streams lacking treatment by screens or primary clarification. HIGHLIGHTS center dot A membrane bioreactor-air gap membrane bioreactor (MBR-AGMD) unit was tested for decentralized potable reuse in representative settings. center dot The MBR removed carbon and nitrogen, while the AGMD polished water to potable quality. center dot Fecal indicator microbes decreased to undetectable levels by MBR and UV treatment alone. center dot AGMD added 4.4 LRV for viruses via thermal deactivation and membrane rejection. center dot Pretreatment was required when moving to a site lacking primary sedimentation.
Catalonia (NE Spain) underwent an unprecedented 41-month drought (2021-2024), which triggered the implementation of an indirect potable reuse (IPR) to ensure drinking water security for Barcelona. This study assesses the human-health and environmental safety of the El Prat IPR system, which releases up to 2 m(3)/s of advanced-treated reclaimed water into the Llobregat River, 16.6 km upstream of the drinking water intake. A comprehensive 28-month monitoring programme quantified 260 regulated and unregulated chemical compounds across four sites, from reclaimed water discharge to final treated drinking water. Human-health and environmental risks were evaluated by comparing measured environmental concentrations with compound-specific quality standards and guide values (GVs) agreed between the Catalan Public Health Authority and the Catalan Water Agency. Pharmaceuticals were dominant in reclaimed water (5-30 mu g/L total) but were reduced to <0.1 mu g/L in drinking water. PFAS, particularly PFOS (6-15 ng/L), and AMPA persisted in the river but remained below GVs after treatment. The findings demonstrate that the Barcelona IPR scheme is safe even when reclaimed water is discharged only a few kilometers upstream of the drinking water intake and under very low dilution conditions, confirming its viability as a drought-resilient potable supply strategy. HIGHLIGHTS center dot Indirect potable reuse (IPR) was implemented in Barcelona city during the severe 2021-2024 drought. center dot A comprehensive chemical surveillance was conducted to ensure safe potable water distribution. center dot Inter-agency and public-private coordination allowed for robust monitoring that ensured safe IPR for urban water supply in a drought-prone region.
This study evaluated a 23-year-old hybrid treatment wetland (HTW) treating greywater from a residential building in Norway using historic monitoring (2001-2014) and recent sampling campaigns (2023-2024), representing one of the longest documented systems operating in a cold-climate setting. The system consisted of an aerobic vertical flow filter with Filtralite (R), and an anaerobic horizontal flow filter with Filtralite (R) P for enhanced phosphorus removal. Recent findings (2023-2024) show improved organic matter removal, with >98% BOD reduction and effluent BOD consistently <2 mg/L. However, nutrient removal declined over time, with effluent total nitrogen of 3.3-5.6 mg/L (59-74%). Total phosphorus increased from 0.02-0.08 mg/L (2001-2008) to 0.15-0.45 mg/L (2014-2024), indicating partial exhaustion of the Filtralite (R) P media. The HTW achieved effective log reductions of 1.6-3.4 for E. coli, 2.1-3.4 for enterococci, 1.6-3.1 for Clostridium perfringens, and 2.0 for Pseudomonas aeruginosa. Legionella spp. remained below detection limits, and Campylobacter was not detected. A quantitative microbial risk assessment (QMRA) showed the annual risk of infection was <10(-4) for E. coli and Clostridium perfringens. The HTW met Norwegian discharge standards of BOD <20 mg/L, phosphorus <1 mg/L, E. coli <100 MPN/100 mL, and complied with EU standards for agricultural water reuse.
Water scarcity due to a changing climate and population growth has led to increasing interest in water reuse. The chemical water quality of purified recycled water (PRW) is typically evaluated using targeted chemical analysis, though effect-based methods (EBM) are also recommended for monitoring PRW quality. In the current study a comprehensive test battery of in vitro bioassays was applied to source water (treated wastewater) and PRW from an advanced water treatment plant (AWTP) on a fortnightly basis over a year. Bacterial toxicity, photosynthesis inhibition, aryl hydrocarbon receptor (AhR) activity, estrogenic activity and oxidative stress response were detected in all source water samples. Chemicals contributing to the effect in source water were identified with iceberg modelling based on chemical concentrations and potency data. The response in PRW was mostly undetectable, with low levels of oxidative stress response and (anti)glucocorticoid activity in some samples. AhR activity was observed in three PRW samples above the human effect-based trigger value (humEBT), though the activity was not linked to any AWTP process issues or detected chemicals. Overall, bioactivity in source water and PRW remained fairly consistent over the year for most bioassays, with quarterly or biannual monitoring suggested for routine monitoring. HIGHLIGHTS center dot Effect-based methods applied to monitor source (treated wastewater) and purified recycled water (PRW) over a year. center dot Source water induced bacterial toxicity, photosynthesis inhibition, AhR activity, estrogenic activity and oxidative stress response. center dot Limited activity in PRW, with AhR activity slightly exceeding the human effect-based trigger value. center dot Advanced water treatment processes able to remove most bioactive chemicals.
The diversity of river morphology is a critical factor in promoting the sustainable development of aquatic ecosystems. However, rapid development in China has led to a simplification of river morphology, resulting in significant water environmental challenges. This study developed a multi-morphology mobile bed river experimental apparatus and designed four sets of comparative simulation experiments based on typical natural river morphology types: 'mild slope - drop structure,' 'high-permeability - low-permeability,' 'high-velocity river - low-velocity shallow lake,' and 'obstructed - unobstructed.' Pollutant reduction experiments were conducted, monitoring the concentrations of TN, NH3-N, NO3-N, and TP during a 96-h water circulation test. The experimental results revealed that the drop structure river, permeable slope river, high-velocity river, and rivers with certain obstructions exhibited average pollutant reduction rates that were 10.5%, 5.4%, 16.8%, and 4.7% higher than their respective control groups. Their steady-state reduction intensities were also higher, by 0.6%/h, 1.5%/h, 2.7%/h, and 1.5%/h, respectively, indicating more sufficient hyporheic exchange and significantly stronger pollutant reduction capacity. The reason is that these morphological elements provide conditions for turbulence and diffusion in water flow. This study provides references for river ecological restoration and sustainable utilization of water resources.
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 (P-tot), but separated only 40-55% of total nitrogen (N-tot) and NH4-N. RO performed better, removing 96% COD, 86% NH4-N and N-tot, while fully retaining P-tot. 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 m(3) of water annually, saving 71,000 & euro;. Combined savings from water reuse and avoided digestate disposal could alone reach 0.2 million & euro; annually. HIGHLIGHTS center dot Reverse osmosis-treated digestate from short-fiber residues largely meets water quality standards for paper recycling. center dot Recovered water can replace up to 6% of freshwater in a model paper mill. center dot Scanning electron microscopic images reveal minimal scaling and fouling, but considerable particle-membrane interactions on the membrane. center dot First study applying natural zeolite to this type of digestate from short-fiber residues. center dot Zeolite adsorption linked to NH4-N concentration in the treated stream.
