Wastewater Reuse Research Articles

Assessment of public knowledge, perception and willingness towards treated hospital wastewater reuse in peri-urban agriculture in Ibadan, Nigeria

Assessment of public knowledge, perception and willingness towards treated hospital wastewater reuse in peri-urban agriculture in Ibadan, Nigeria

Modelling the impacts generated by reclaimed wastewater reuse in agriculture: From literature gaps to an integrated risk assessment in a One Health perspective

The reuse of reclaimed wastewater is increasingly recognized as a viable alternative water source for irrigation. Its application, whether direct or indirect, impacts several interconnected compartments, including groundwater, surface water, soil, crops, and humans. Reclaimed wastewater provides essential resources for crops, like water and nutrients. However, it also introduces pathogens, and contaminants of emerging concern (CECs), defined as chemicals that may pose risks to human health and ecosystems but are not yet fully regulated, such as pharmaceuticals and personal care products, among others. Additionally, reclaimed wastewater may contain antibiotic-resistant bacteria (ARBs) and disinfection by-products (DBPs), all of which present potential health and environmental risks. Therefore, regulatory bodies stress the need for preventive risk assessments to ensure safe reuse.This paper critically reviews available models for assessing the impacts of reclaimed wastewater reuse in agriculture. It identifies gaps in current modelling approaches and outlines future research directions. Key areas requiring further investigation include the fate and transfer of CECs, ARBs and DBPs, and the co-occurrence of multiple risks in such interconnected systems, especially in the indirect reuse. To address these gaps, we proposed a simplified approach to integrate three types of risk associated with CECs in indirect reuse, focusing on risks posed by antibiotics and other pharmaceuticals: human health risk, environmental risk and risk from antibiotic resistance development. This approach aids in identifying the most critical endpoints within the One Health approach, supporting (i) CECs prioritization in regulations based on their critical endpoints and (ii) the adoption of CEC-specific mitigation measures.

Evaluation of the Impact of Recycled Distillery Effluent on the Cultivation of Wheat and Sorghum

With increasing global water scarcity, the reuse of treated wastewater for agricultural irrigation offers a promising solution, particularly in arid regions. This study evaluates the impact of distillery wastewater from Kinmen Kaoliang Liquor Inc. (KKL) on the growth of wheat and sorghum in the Kinmen region. The field experiment applied varying proportions of KKL wastewater to assess its effects on soil properties, nutrient distribution, and crop performance. The results showed that wastewater irrigation increased soil concentrations of key nutrients, such as potassium (K), sodium (Na), magnesium (Mg), and phosphorus (P), but also raised the electrical conductivity (EC) and sodium adsorption ratio (SAR) beyond acceptable irrigation standards. K, Mg, Ca, and P primarily accumulated in the stems and grains, while Na was concentrated in the roots. However, higher wastewater concentrations negatively affected soil permeability due to Na accumulation, and elevated salinity levels led to reduced plant biomass. This study concludes that although wastewater irrigation improves nutrient availability, careful management is essential to mitigate salinity risks and ensure sustainable agricultural practices. These findings offer valuable insights into the potential of wastewater reuse in water-scarce regions and provide practical recommendations for managing associated risks.

Resource Nexus for decision-making: an industry-community synergistic approach for textile wastewater management

ABSTRACT Although the textile industry is crucial to economic development, it is a significant polluter of global water sources through its wastewater discharge, which endangers aquatic ecosystems and neighboring communities. This study focuses on stakeholder perceptions from farming and fishing communities related to wastewater management in the Bangladesh textile industry. Using focus group discussions with stakeholders that focused on sustainability values and a Resource Nexus framing, the results emphasise the adverse effects of textile wastewater on neighbouring communities, spanning agriculture, livestock, and ecological resources. The findings also underscore a significant need for collaboration between the textile industry and neighbouring communities, emphasising the ongoing obligation of governance resources, such as monitoring, regulations, and proactive measures and advocates for engaging different stakeholders in the formulation of robust policies, stringent regulations, and concerted efforts across industry, government, and communities to deliver improved governmental monitoring, enforcement of regulations and transparency in wastewater management practices in the textile industry of Bangladesh. The study suggests that a Water-Energy-Ecosystems-Food (WEEF) Resource Nexus approach can enhance decision-making, promoting sustainable energy infrastructure, encourage increased treated wastewater reuse, and facilitate effective management for environmental resilience and socio-ecological systems sustainability. This study contributes valuable insights elicited from a WEEF Resource Nexus approach, offering guidance for policymakers, industry practitioners, and researchers in the textile industry and beyond, aiding in the understanding of resilient industry-community ecosystems.

European approaches to wastewater reuse regulation: A comparison between Spain, Malta and the Netherlands

AbstractWastewater reuse is encouraged and facilitated by legislation and policy across the EU. A recent example is the EU Regulation 2020/741 on minimum requirements for water reuse. This and other regulatory developments have gone hand in hand with an increase in research in technological innovations that facilitate wastewater reuse, including advanced water treatment technologies. Despite these harmonised developments at the EU level, there appear to be large differences across Member States in the volume of reused water, its sources and the purposes of wastewater reuse. These differences are mirrored in the differences in the regulation of wastewater reuse across the European Union. The present paper has two goals. The first is to provide an overview of the regulation of wastewater reuse in three EU Member States, namely, Spain, Malta and the Netherlands. The comparative analysis reveals evidence of variability in the division of roles and responsibilities, substantive provisions on water reuse, and the allocation of costs. The second objective of the paper is to highlight how, even within the boundaries of the theoretical best practices, national regulation can be heterogenous.

Assessing De Facto Wastewater Reuse and Its Implications for Water Quality in Yangtze Basin (2014-2021)

De facto wastewater reuse is the incidental presence of treated wastewater in a water supply source. Unplanned indirect wastewater reuse, which is also called de facto reuse, occurs when wastewater is discharged into surface water upstream of the intakes of suitable drinking water treatment plants. Although this discharged wastewater may increase the water quality risks for downstream water supplies, they contribute to the water supply source as an additional in-stream flow. Therefore, proper wastewater management is crucial to ensure access to safe water and address the challenges due to urbanization and population growth. There are detailed data on the infrastructure and river flows in some countries, but this study examined the use of a more limited dataset in other countries and specifically assessed the de facto reuse in the Yangtze River Basin in China. GIS modelling was used to calculate the streamflow of Yangtze River from the DEM, while macro water consumption data was used to estimate the wastewater discharges, and this methodology solved the problem that the outcome was limited by the lack of gauging stations at more locations and lack of precise geospatial location of drinking water intakes or wastewater discharges. Under an average-flow condition, Chongqing in the upper reaches had de facto reuses that increased from 0.57% in 2014 to 0.60% in 2021; Wuhan in the middle reaches had de facto reuses, which increased from 1.56% in 2014 to 1.64% in 2021; Shanghai, which is located in the estuary of the Yangtze River, increased its de facto reuse from 2.35% in 2014 to 2.51% in 2021. Under low-flow conditions, the de facto reuse of Chongqing, Wuhan, and Shanghai in 2021 was 1.7%, 4.9%, and 7.4%, respectively. This relatively high level of de facto reuse is consistent with the estimation of unintended treated wastewater contributions to streams and growing risk of drinking water quality in the Yangtze River Basin. This research estimated de facto reuse in the Yangtze River Basin and showed the feasibility of using limited infrastructure datasets to assess de facto reuse and the modeling methods allow identification of river reaches most impacted by wastewater, and perhaps suggest prioritization for investments in additional wastewater treatment in reaches with high de facto reuse.

Hydrothermal carbonization of primary sewage sludge in a prototype reactor: Sensitivity analysis of key parameters for hydrochar and liquid phase upscaling and reuse

Hydrothermal carbonization (HTC) of untreated sewage sludge with high water content was evaluated as an alternative to usual wastewater treatment. This bold approach allowed bioproducts useful as biofuel and nutrient sources to be obtained directly from raw sludge. HTC experiments were performed in a scalable arrangement (technology readiness level >4) composed of a 10-liter high-pressure reactor. The influence of the experimental conditions, including temperature (180-220°C), reaction time (60-120min), and pH (6.5-12.0), was evaluated on nutrients and heavy metal distribution through the liquid phase by a 23 central composite design with a triple central point. The bioproducts were characterized by a set of six analytical techniques, and the results were refined by statistical procedures (Principal Component Analysis and Response Surface Methodology). pH is a variable that impacts bioproducts’ characteristics, making it a guiding factor for application. Basic pH promotes transfer of components from solid to liquid phase, while natural pH favors the heating value of hydrochars. Liquid phase is a carbon- and nitrogen-rich source that can be useful for plant nutrition, mainly due to the increase of ammonia nitrogen from 20.6 to 51.7wt.% under pH 6.5, and an expressive decrease of chemical oxygen demand from 32 to 6-16 mgO2L-1. The hydrochar can be considered a renewable solid fuel, reaching up to 12.43 MJ kg-1 under pH 6.5; the basic pH favored an increase in the O/C ratio and lower HHV values. HTC of primary sewage sludge can replace steps of a conventional treatment station and promotes treated wastewater reuse.

Exploring Moringa oleifera: Green Solutions for Sustainable Wastewater Treatment and Agricultural Advancement

Increasing concerns over water pollution have driven the search for sustainable wastewater treatment alternatives. This study evaluates the effectiveness of two coagulants derived from Moringa oleifera seeds–powder and extract–as sustainable solutions for wastewater reuse in agriculture. Comparative experiments were conducted using aluminum sulfate, a conventional coagulant, at various doses under controlled laboratory conditions. The results demonstrated that both M. oleifera-based coagulants were highly effective, achieving turbidity reductions of 97% and 99%, respectively. Notably, the powder form required lower doses than the extract but had longer sedimentation times. Further detailed analyses at optimized doses (500 mg/500 mL for powder and 12.5 mL/500 mL for extract) met international standards for wastewater quality in agricultural irrigation. Comprehensive analyses encompassing pH, turbidity, COD, BOD5, TSS, DO, conductivity, NO2−, NO3−, SO42−, PO43−, and fecal and total coliforms consistently adhered to stringent criteria, confirming the effectiveness of M. oleifera-derived coagulants. These findings highlight the potential of M. oleifera in wastewater treatment, offering sustainable solutions to environmental challenges and enhancing food security in resource-limited regions. Our research supports the broader adoption of these eco-friendly alternatives, which could significantly reduce water scarcity and promote sustainable agricultural practices, addressing critical environmental concerns.

Toward circular greenhouse wastewater reuse: advancements in cation exchange membranes for selective Na+/K+ separation using electrodialysis systems

ABSTRACT Driven by the growing need for alternative water sources and forthcoming stringent nutrient discharge regulations, there is growing interest in developing selective membrane solutions to facilitate circular greenhouse wastewater reuse (as emphasized in the European Union's Horizon 2020 ULTIMATE project). For electrodialysis systems, sodium (Na+) over potassium (K+) selective membranes are essential to achieve minimal liquid discharge. This study addresses the challenge of developing selective, efficient, and scalable Na+/K+ cation exchange membranes. State-of-the-art cation exchange membrane developments were reviewed and the functionalization of commercial membranes with crown ethers was identified as a promising approach. Two crown ether–modified membranes (15-crown-5 (15C5) and 18-crown-6 (18C6)) were developed, characterized, and tested in equimolar and greenhouse wastewater binary feed ratios. While the results demonstrated low overall selectivity, the 15C5-modified membrane showed a marginal enhancement in K+ selectivity, suggesting the need for further optimization. The study concludes with recommendations for the future development of Na+/K+ selective membranes, highlighting the potential of machine learning approaches to expedite progress. This research provides a foundational step toward practical and scalable Na+/K+ ion separation solutions, for achieving minimal liquid discharge in greenhouse horticulture.

The effects of headspace volume reactor on the microbial community structure during fermentation processes for volatile fatty acid production.

The transition from traditional wastewater treatment plants to biorefineries represents an environmentally and economically sustainable approach to extracting valuable compounds from waste. Sewage sludge produced from wastewater treatment is incinerated or disposed of in specific landfills. Repurposing this waste material to recover valuable resources could help lower disposal costs and reduce environmental impact by producing other beneficial polymers. Microorganisms present in the sewage sludge can ferment organic pollutants, producing volatile fatty acids (VFA), precursors for biopolymers that could be used as an alternative to petroleum-derived plastics. To boost VFA production during sewage sludge fermentation, it is necessary to understand the operating microbial community and its metabolic capacities in anaerobic conditions. This study presents the influence of the headspace volume on the microbial community and the VFA production to define the best operational parameters in a 225 L pilot plant fermenter. The wasted sewage sludge was withdrawn from an oxic-settling-anaerobic plant that collected wastewater from the canteen and dormitory of the UNIPA Campus (Palermo University, Italy) and incubated using a 40% and a 60% headspace volume. The microbial community was analysed before and after the fermentation process through metataxonomic analysis, and VFA yields were determined by gas chromatography analysis. Our results showed that the 40% headspace volume induced a tenfold higher VFA production than the 60% headspace volume, modulating the microbial community's efforts to establish a VFA-producing factory. Notably, at 40% headspace, the relative abundance of bacteria, like Proteobacteria, Firmicutes, Actinobacteria, and Chloroflexi, significantly increased, as well as the relative abundance of Bacteroidetes and Verrucomicrobia decreased during the fermentation process. This result is consistent with the selection of efficient VFA-producing bacteria that lead to increased VFA yields that are not obtained at 60% headspace. Thus, reducing headspace is a promising strategy that can be implemented, even in full-scale plants, to optimise the wastewater reuse process and maximise VFA production to produce bioplastics, like polyhydroxyalkanoate, for the transition from linear wastewater treatment plants to circular biorefineries.

A novel integrated material flow cost accounting (MFCA)- IoT-lean management system approach to improving water use efficiency and reducing costs in the beverage industry

The purpose of this study is to present a novel approach of integrating Material Flow Cost Accounting (MFCA), Internet of Things (IoT) and lean management systems to improve water use efficiency and reduce costs in the beverage industry. The positive and negative product costs of water purification, syrup manufacture, concentrate mixing, and packing were analyzed. The MFCA analysis showed 78.5% positive and 21.5% negative product costs. The use of the Power BI application to display real-time positive and negative costs in each process, scenario modeling and simulation was able to promote water savings and cost reductions, as well as supporting factory team ideation for choosing one of three improvement plans: 1) RO flushing water recovery in water purification; 2) water conservation with automated pH correction at packaging warmer; or 3) wastewater treatment and reuse of the rejected RO brine. According to our two-scenario water conservation testing, an automation process could improve pH adjustment in the packaging process, while MFCA, IoT, and lean management systems could be applied to improve industrial water use efficiency, demonstrating the potential for sustainable water use. The beverage-industry case in the present study validated this approach, resulting in a 24.1% production rate increase and a 4.5% cost reduction of 71,010 THB savings per year.

Fouling of Reverse Osmosis (RO) and Nanofiltration (NF) Membranes by Low Molecular Weight Organic Compounds (LMWOCs), Part 1: Fundamentals and Mechanism.

Reverse osmosis (RO) and nanofiltration (NF) are ubiquitous technologies in modern water treatment, finding applications across various sectors. However, the availability of high-quality water suitable for RO/NF feed is diminishing due to droughts caused by global warming, increasing demand, and water pollution. As concerns grow over the depletion of precious freshwater resources, a global movement is gaining momentum to utilize previously overlooked or challenging water sources, collectively known as "marginal water". Fouling is a serious concern when treating marginal water. In RO/NF, biofouling, organic and colloidal fouling, and scaling are particularly problematic. Of these, organic fouling, along with biofouling, has been considered difficult to manage. The major organic foulants studied are natural organic matter (NOM) for surface water and groundwater and effluent organic matter (EfOM) for municipal wastewater reuse. Polymeric substances such as sodium alginate, humic acid, and proteins have been used as model substances of EfOM. Fouling by low molecular weight organic compounds (LMWOCs) such as surfactants, phenolics, and plasticizers is known, but there have been few comprehensive reports. This review aims to shed light on fouling behavior by LMWOCs and its mechanism. LMWOC foulants reported so far are summarized, and the role of LMWOCs is also outlined for other polymeric membranes, e.g., UF, gas separation membranes, etc. Regarding the mechanism of fouling, it is explained that the fouling is caused by the strong interaction between LMWOC and the membrane, which causes the water permeation to be hindered by LMWOCs adsorbed on the membrane surface (surface fouling) and sorbed inside the membrane pores (internal fouling). Adsorption amounts and flow loss caused by the LMWOC fouling were well correlated with the octanol-water partition coefficient (log P). In part 2, countermeasures to solve this problem and applications using the LMWOCs will be outlined.

Increased diversity of macroinvertebrates, but not fish, near wastewater outfalls in the Red River Basin, Oklahoma

The reuse of wastewater for beneficial purposes (e.g. irrigation) can boost water sustainability, but may have positive or negative impacts on the environment. In some drought-prone or over-allocated river basins, wastewater is an important component of stream flows and may buffer river ecosystems from drought. In these locations, wastewater may have a net positive impact on river ecosystems and its capture and reuse would be harmful to these ecosystems. In other locations, wastewater may have a net negative impact if the quality of the wastewater (i.e. concentrations of contaminants and nutrients) is lower than that of the receiving water body. In this study, we quantified the effects of wastewater on fish and macroinvertebrate communities in the Red River, Oklahoma. We investigated two competing hypotheses. First, we hypothesized that if wastewater flows buffer aquatic communities from drought, then measures of biodiversity should be higher at sampling sites near wastewater outfalls than at sites not near wastewater outfalls. Second, we hypothesized that if wastewater outfalls negatively impact water quality or homogenize the flow regime, then measures of biodiversity should be lower at sites near wastewater outfalls. To test these competing hypotheses, we calculated a suite of biodiversity indices at 320 biological sampling sites in the Red River Basin and analyzed for significant differences in communities based on proximity to wastewater outfalls. We found that proximity to upstream wastewater outfalls had significant positive impacts on macroinvertebrate community biodiversity, but we did not find any significant relationships with fish community diversity. Findings from this study provide insight to management decisions on wastewater reuse initiatives in beneficial subbasins while minimizing harmful ecological impacts.

Fluorescence sensor enabled control of contaminants of emerging concern in reclaimed wastewater using ozone-based treatment processes

Contaminants of emerging concern (CEC) pose significant challenges to environmental and human health. The development of the wastewater reuse sector, coupled with progressively stringent regulations, needs innovative systems that integrate advanced treatment processes with in-situ and real-time monitoring of CEC. This study investigates the use of a tryptophan-like fluorescence sensor for real-time and online monitoring of CEC within a pilot plant employing O3-based advanced oxidation processes (AOPs). Two tertiary wastewater effluents (WW-1 and WW-2) were tested, placing the pilot system downstream of two different wastewater treatment plants (WWTPs). Priority substances and micropollutants detected in the investigated water matrixes such as pharmaceuticals, per- and polyfluoroalkyl substances (PFAS) were selected as targeted compounds in this study. Fluorescence degradation was detected in real-time by the sensor, showing a high capability to detect fast changes in water quality induced by oxidation. Furthermore, the real-time fluorescence showed better sensitivity than lab-scale fluorescence in detecting the fast action of hydroxyl radicals (·OH) during the O3/H2O2 process, highlighting the importance of online monitoring. Selected CEC were degraded by AOPs with different percentages of removal efficiency (RE) (0%<RE<100% in WW-1 and 15%<RE<90% in WW-2) depending on oxidant doses and the reactivity of compounds with O3 and ·OH. Fluorescence data by online sensor enabled accurate prediction of the removal of a wide spectrum of CEC during O3 and O3/H2O2 processes (R2≥0.93). Furthermore, real-time fluorescence data were successfully used to predict observed pseudo-first-order rate constants of CEC with O3 or O3/H2O2. Obtained results suggest that real-time fluorescence monitoring is an excellent tool to control CEC removal during O3-based AOPs and monitor the transferred ozone in wastewater (R2≥0.94), contributing to the optimization of reagent dose, energy and costs.

Pre-ozonation coupled with forward osmosis with fertilizer as draw solution for simultaneous wastewater treatment and agricultural irrigation

Membrane-based processes have emerged as effective solutions for treating tannery wastewater. Persistent membrane fouling remains a significant obstacle to long-term operational sustainability, and residual pollutants often persist in the treated effluent. To address these challenges, we investigated an integrated ozone-forward osmosis (O3-FO) process, with a focus on evaluating the efficacy of pre-ozonation in alleviating membrane fouling, as well as exploring the possibilities of this integrated process for the reuse of tannery wastewater. Fertilizer, specifically 2 M Ca(NO3)2, served as the draw solution (DS) in this process. The findings reveal that the integrated system demonstrated remarkable pollutant retention capabilities. Notably, no metal was detected in the fertilizer. Therefore, the integrated process not only dilutes the fertilizer but also minimizes the risk of heavy metal contamination to both crops and soil. Furthermore, pre-ozonation effectively mitigated membrane fouling, resulting in an increase in membrane flux with a maximum increase of 20.98 % at 0.6 L/min. Orthogonal partial least squares-discriminant analysis (OPLS-DA) revealed pre-ozonation has the most significant impact on four parameters: water flux (Jw), chemical oxygen demand (COD), fouling resistance (Rf) and oxidation reduction potential (ORP). Meanwhile, ammonium nitrogen (NH4-N) variation, dissolved organic carbon (DOC) variation and ORP played an important role in the four systems. Multi-criteria decision analysis (MCDA) showed that the 0.2 L/min O3-FO system achieved the highest score (0.66), followed by 0.6 L/min (0.53), 0.4 L/min (0.41) and 0 L/min (0.29). This research offers a theoretical framework for the synergistic integration of advanced oxidation and membrane technology in the treatment of industrial wastewater.

Exploring expert perceptions towards emerging pollutants and their impacts in reused wastewater and agriculture

Water sustainability involves several natural and human spheres conditioning the availability and quality of water resources and life conservation. Regarding water quality, currently emerging pollutants (EPs) are a key topic at global scale since they are difficult to remove by traditional water treatment systems. In this context, this work aims to evaluate experts’ perception of several EPs issues with a special focus on semi-arid Mediterranean areas where EPs are negatively impacting water, environmental, and agricultural systems as, in these areas, effluents from water treatment plants are widely reused in the irrigation of crops, urban gardens, and golf courses or directly discharged on natural streams. Particularly, a detailed survey composed of questions about EPs regulation, risk insight, equipment, social and economic impacts, was performed collecting 437 responses. Main results suggested that EPs existence may pose a significant risk and a destabilizing factor in wastewater reuse, with negative impacts to crop irrigation, being managers the class with more concern followed by scientifics and administratives. New EPs regulations raises uncertainty amongst experts since 29 % considered positive its creation, while 20 % estimated this fact as regular and 14 % as negative. As well, although the combination of technologies to improve EPs removal generated agreement, aspects like the treatment charges at water treatment plants or the price/bill of EPs-free water were features of ambiguity. Within EPs elimination, the three expert groups highlighted that technologies impacts in the sustainability spheres will be positive on public health (87 % of responses), social trust (75 %), and environmental sustainability (76 %). Likewise, 88 % of experts concurred that the future of wastewater reuse relies on a combination of technologies. These findings offer valuable information to water legislators and policymakers to manage water resources, especially in semi-arid areas due to the final use of treated effluents and, therefore, the great implications for agriculture, environment and human health.

Using Treated Wastewater for Non-Potable Household Uses in Peri-Urban India: Is It Affordable for the Users?

Reuse of wastewater is a promising response to water scarcity. For peri-urban areas served by decentralized wastewater treatment plants, the delivery of treated wastewater to the households may be a viable option to promote reuse on a larger scale. Based on a case study in Eastern India, this paper explores if households would accept recycled water for non-potable purposes and if they would pay for it. While the respondents to household surveys had very positive views about recycling, they were not willing to pay much, even if they were from a middle-income class and could afford more. A closer analysis of the attitudes towards recycling indicated knowledge gaps about the risks and advantages of using recycled water.

Sustainable Water Conservation Techniques for an Office Building

The research paper titled "Sustainable Water Conservation Techniques for an Office Building" explores methods to reduce water consumption and promote sustainable practices in office buildings. The study focuses on the rising global water crisis due to population growth and increasing urbanization, advocating for the reuse of rainwater and wastewater as alternatives to conventional water sources. Key objectives include assessing current water distribution systems, comparing existing water management techniques, and proposing sustainable water-saving measures. By integrating solutions such as water-efficient fixtures, greywater recycling, and rainwater harvesting, the study aims to significantly reduce water demand and operational costs, contributing to long-term sustainability​.

Prevalence of antibiotic-resistant enterobacteriaceae in domestic wastewater and associated health risks in reuse practices

The use of wastewater for non-potable purposes is an important alternative for addressing water scarcity, especially in developing regions. However, minimizing the risks, particularly those associated with emerging contaminants that may induce resistance among pathogens in wastewater, is crucial. This study assessed the occurrence of antibiotic-resistant bacteria in untreated wastewater used for agricultural purposes and evaluated the quantifiable health risks associated with this practice in Tamale, Ghana. The resistance of some Enterobacteriaceae, such as E. coli, Klebsiella, and Salmonella-Shigella, to four commonly used antibiotics in Ghana was assessed using a conventional microbiological culture approach and the Kirby Bauer disk diffusion method. A Quantitative Microbial Risk Assessment (QMRA) was performed to estimate the health risks associated with two distinct scenarios of wastewater reuse: (1) accidental ingestion of contaminated wastewater and soil, and (2) consumption of vegetables irrigated with wastewater. This approach applied a Monte Carlo simulation based on 10,000 interactions and identified E. coli O157:H7 as the reference pathogen. Among Enterobacteriaceae, Klebsiella pneumoniae, Salmonella-Shigella and E. coli were isolated, in concentrations exceeding the limit recommended by the World Health Organization (103 CFU/100 ml). All the isolated bacteria were resistant to metronidazole (5 μg). Thirty-three per cent of Klebsiella pneumoniae isolates were intermediate/moderately susceptible, and all other bacteria were resistant to amoxicillin (30 μg). All Klebsiella pneumoniae and the majority of Salmonella-Shigella (69.8 %) isolates were resistant to trimethoprim-sulfamethoxazole (25 μg) and tetracycline (30 μg). When assessing health risks, the mean annual probability of infection associated with consuming vegetables irrigated with wastewater varied between 5.14 × 10−2 and 9.79 × 10−1 per person per year. Conversely, for the accidental ingestion scenario, the probability was 1.00 per person per year. In these scenarios, the probability of illness ranged from 1.29 × 10−2 to 2.4 × 10−1 and 2.5 × 10−1 per person per year. The health risks posed by these findings surpass the maximum threshold prescribed by the World Health Organization, thereby emphasizing the need for prompt mitigation strategies.

Treated wastewater reuse for irrigation: A feasibility study in Portugal

In an increasing water scarcity and climate-vulnerable global context, treated wastewater represents a vital alternative water source, thereby enhancing resource sustainability. Despite its potential, only roughly 2.5 % of the treated wastewater is reused in the European Union, with Portugal's reuse rate being only 1.2 % in 2022. Considering this framework, this study evaluates the feasibility of increasing wastewater reuse in Portugal by focusing on the Tagus River and Ribeiras do Oeste Basins. The regional assessment identified eight key wastewater treatment plants (WWTP) with significant potential for irrigation reuse in the agriculture and tourism sectors. Analysing costs, quality requirements, and technological options, this study considered five treatment lines, incorporating filtration and disinfection methods. The findings indicate that reclaimed water costs may range from 0.02€/m3 to 0.83€/m3, being competitive with other water sources and significantly lower than desalination processes (up to 1.66€/m3). Distribution investments and energy consumption are primary cost drivers, suggesting a relocation of WWTP closer to end-users as a cost-saving strategy. The proposed reuse projects could quadruple regional reuse rates and double the national rate, mitigating water needs for over 2000 ha of agricultural land and golf courses. This study underscores the importance of treated wastewater reuse in addressing water scarcity, advocating for WWTP decentralisation, strategic investments and policy interventions to achieve cost-effective goals. The methodologies and insights presented offer valuable guidance for other regions facing similar challenges, promoting a paradigm shift towards circular water resource management.