Since 1998, the ASCE has prepared a comprehensive assessment of the nation’s major infrastructure systems using letter grades for each category and a concise but replicable methodology to analyse all aspects of system performance.

In terms of water infrastructure, the report assesses dams (D+), drinking water (C-), inland waterways (C-), levees (D+), stormwater (D) and wastewater (D+).
This year’s report finds nearly 50% of the grades increasing for the 18 categories assessed, crediting this to recent federal investments to improve US infrastructure.
The report recommends a comprehensive agenda over the next four years to sustain investment, prioritise resilience, and advance forward-thinking policies and innovations.

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What is the Expert Committee for China’s Concept Wastewater Treatment Plants (CCWC) and what are its aims and objectives?

In early 2014, six prominent Chinese environmental experts, Jiuhui Qu, Kaijun Wang, Hongchen Wang, Gang Yu, Bing Ke, and Hanqing Yu, proposed constructing a futuristic urban wastewater treatment concept plant for China. Aimed at 2030-2040, their goal was to incorporate global best practices and advanced technologies to achieve ‘sustainable water quality, energy self-sufficiency, resource recovery, and environmental friendliness’. To support this vision, they formed the ‘Concept Plant Expert Committee’, which expanded to include nine members: Jiuhui Qu (Chair), Hongqiang Ren, Hanqing Yu, Gang Yu, Kaijun Wang, Hongchen Wang, Bing Ke, Xingcan Zheng, and Ji Li. Their mission is to create a concept plant surpassing current global standards by 20 years, transitioning China from a follower to a leader in wastewater treatment.

What are the key challenges for the Chinese water and wastewater sectors?

China has a large total water volume, yet per capita availability is low, at only about a quarter of the global average. Northern regions, in particular, face severe water scarcity. With rapid urbanisation and industrialisation China’s wastewater output has surged, giving it the world’s highest wastewater treatment volume, straining facilities near their operational limits.

A further challenge is the uniformity of national wastewater standards, which limit flexibility, particularly for economically underdeveloped regions, imposing high operational costs and resource waste in areas not sensitive to water issues.

Facilities face significant technical and financial challenges in upgrading to meet stricter standards, especially with the emergence of pollutants like pharmaceuticals and microplastics. In addition, many plants focus solely on pollutant removal, overlooking the potential to recover valuable resources from wastewater and sludge.

Wastewater treatment plants, particularly those using traditional processes, consume a large amount of energy and produce significant carbon emissions. There is a need for urgent energy and carbon reduction solutions if China is to meet its ‘dual carbon’ goals.

What are the most noteworthy aspects of the Yixing Concept Water Resource Reclamation Facility?

The Yixing plant uses anaerobic digestion to produce 3000 m3 of biogas daily, converted into 6000 kWh of electricity, reducing external energy dependency and lowering emissions.

Advanced purification technologies, such as ozone-UV disinfection for emerging pollutants, allow flexible upgrades, including mainstream Anammox (anaerobic ammonium oxidation) technology, for future water quality requirements.

Unlike traditional plants, Yixing transforms organic waste into products like nutrient-rich organic soil, reducing disposal pressure and supporting sustainable agriculture.

Innovative odour control, eco-friendly building designs, and community integration, minimise pollution and enhance biodiversity. In addition, the plant has engaged more than 50,000 community members in environmental education, raising awareness of sustainable water management, and its architectural design won an international award in 2023 for innovative health design.

What have been the key outcomes of the project?

Based on the water-energy-material recycling relationship in wastewater treatment, the concept plant redefines the mission of future wastewater treatment facilities, transforming the public’s perception and understanding of these plants. It conveys the message that wastewater is a resource, and wastewater treatment plants are resource plants.

The concept plant initiative has built five key technical systems to achieve water-energy-material regeneration:

• A Water Quality Safety System focusing on extreme nitrogen and phosphorus removal and the elimination of emerging pollutants.
• A Low-Carbon Technology System centred on processes such as fine filtration and sulphur-based autotrophy.
• A Regional Resource Synergy System using advanced dry anaerobic processing equipment.
• A Smart Management System based on digital twins and intelligent decision-making.
• An Eco-Complex Technology System that integrates elements of water quality, energy, resources and ecology.

The concept plant marks a milestone in China’s wastewater treatment industry, receiving recognition and support from industry stakeholders and spurring ongoing exploration and collaboration among government, industry, academia, and research sectors.

The Three Gorges Group plans to replicate the concept plant model along the Yangtze River over the next five years, implementing a chain-network model to create a series of innovative plants that will serve as effective tools for ecological management in the Yangtze region.

This project is supported by national key research and development funding, with the first implementation under way at the Fenghuangqiao Water Purification Plant in Lu’an, Anhui Province.

What are the future ambitions of the CCWC?

China’s concept plants will aim to meet stricter environmental requirements, focusing on new pollutants such as microplastics and pharmaceuticals. Further expansion of resource recovery will transform plants into resource producers rather than focusing solely on pollution control, and by advancing biomass energy technologies and reducing emissions, Yixing aims to support China’s ‘carbon peak’ and ‘carbon neutrality’ goals.

Future plants will increasingly rely on intelligent digital technologies to optimise resource use and energy efficiency. Our ambition is for China’s concept plant model and expertise to extend globally, aiding other regions in managing water resources and environmental protection challenges.

Future plants will integrate with their surroundings, incorporating eco-friendly architecture, green infrastructure, and community interaction, creating high-acceptance and environmentally friendly facilities.

Centred on a production-based R&D hub, it will bring together leading research talent to drive breakthroughs in core technologies, establishing itself as an incubator and prime site for cutting-edge applications, and through the demonstration of innovative technologies, the concept plant will continually enhance its treatment efficiency and resource recovery capabilities while also exporting advanced technological achievements across China and globally. This will further solidify its role as a benchmark technology demonstration base leading the future development of the industry.

Responses provided by Yifei Zhang, chairman of CSD Water Service Co, Changmin Wu, general manager of the Yixing Concept Plant, and Jifang Zhang, vice-general manager of the Yixing Concept Plant.

Read more about the IWA Project Innovation Awards at:

Global best in water projects announced at IWA 2024 Project Innovation Awards

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One is the article on p14 exploring the reuse of wastewater – or, more accurately, used water – in agriculture. Concerns about the pressures on water resources are forever increasing, not least because of climate change. Planned reuse of wastewater then becomes a policy option to pursue in response, with a need to find agriculture’s place in that planned reuse.

The potential here is clear. As the article highlights, less than 20% of wastewater is treated to a usable level. Of this treated water, 2-15% is reused for irrigation.

At the same time, this issue’s article on the ‘slow pandemic’ of antimicrobial resistance (AMR) highlights the dilemmas of trying to provide solutions. On the one hand, wastewater in this instance is the interface where microbes are exposed to antimicrobials – so is seemingly part of the problem. But the article signals that wastewater treatment tends to improve prospects around dealing with AMR – and so is also seemingly part of the solution.

Climate change is compounding the challenges of balancing multiple interests and factors around water. The Analysis article opposite summarises the findings of a report drawing attention to the plight of the most vulnerable section of global society – refugees.

Climate change is just part of the fragility that underpins this vulnerability. Conflict and, within that wider picture, forcible displacement have complex roots. But the climate dimension is there – in terms of the fact that a very high proportion of people fleeing their homes do so in countries where there is exposure to climate-related hazards, and also in terms of the more specific evidence for climate-related hazards being a driver for displacement.

A more recent report, The Global Threat of Drying Lands: Regional and global aridity trends and future projections, published by the UN Convention to Combat Desertification for its COP16 meeting in December, raises a wider-reaching concern. The report states that 77.6% of Earth’s land experienced drier conditions during the three decades leading up to 2020 compared with the previous 30-year period. Drylands expanded by about 4.3 million km2 and, as the planet continues to warm, the report’s worst-case scenario projections suggest up to 5 billion people could live in drylands by the end of the century.

This all emphasises the need for cohesive water sector strategies that have the buy-in of stakeholders.

In the article on p25, we see how Fiji, one of IWA’s newer Governing Members, is embarking on implementation of its 2050 water sector strategy. The strategy is built on a national collective planning exercise and we can see that IWA’s scope is of clear relevance to priorities highlighted. This includes core concerns such as addressing non-revenue water and regulatory matters such as tariffs. So too for the task of combining use of both centralised and decentralised approaches to wastewater treatment.

The water community around the world faces challenges in advancing sector strategies, especially given the scale of the task of balancing multiple interests and factors. Given such prospects, the need for solidarity and sharing of experiences is greater than ever.

Keith Hayward, Editor

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The day was structured into three sessions, covering industry best practices, collaboration with regulators and research institutes, and strategies to overcome long returns on investments in water technologies. A common theme emerged: the critical importance of collaboration across sectors to address current and future water challenges.

Innovation in industrial water management

Several innovative technologies and approaches were highlighted during the forum, demonstrating the potential for significant improvements in industrial water efficiency:

PFAS remediation: Dr Mohamed Ateia Ibrahim, from Rice University, USA, emphasised that there is no one-size-fits-all solution for PFAS remediation. With more than 10,000 chemicals containing PFAS on the market, new technologies are being explored to meet increasingly stringent regulations. The path forward requires collaboration between academia, start-ups, solution providers, and end-users to develop effective strategies for addressing current issues and transitioning to fluorine-free alternatives.

Energy conservation in cooling systems: Alain Silverwood, from Xylem, presented a two-year study on the energy impact of microsand filtration in open cooling water systems. The collaborative effort between academia, solution providers and end-users demonstrated that proper filtration could reduce biofilms and energy consumption by up to 13%, resulting in significant cost savings for industrial facilities.

Resource recovery from waste streams:

Dr Christopher Lawson, from the University of Toronto, Canada, shared insights into a new technology that ‘retools’ anaerobic digestion for waste-to-chemical biomanufacturing. This innovative approach converts food waste into medium chain fatty acids, potentially reducing carbon footprints by recycling chemicals and materials.

Collaboration: The key to success

The forum emphasised that collaboration is crucial for addressing water challenges effectively. This was evident in the organising committee itself, which included representatives from Xylem, Veolia and Grundfos. Throughout the sessions, speakers highlighted successful partnerships between industry, academia and regulatory bodies.

Industry-academia partnerships: The cooling water filtration study and the waste-to-chemical biomanufacturing project both demonstrated the value of collaboration between universities and industry partners. These partnerships allow for rigorous scientific research to be applied to real-world industrial challenges.

Regulatory collaboration: Mohamed Ateia Ibrahim’s presentation on PFAS remediation highlighted the need for cooperation between regulators, researchers and industry, to develop effective solutions that meet increasingly stringent environmental standards.

Cross-sector initiatives: Jason Morrison, President of the Pacific Institute and Head of the UN Global Compact CEO Water Mandate, discussed engagement opportunities that bring together corporate leaders to address water management challenges collectively.

Overcoming barriers to innovation

The forum also addressed the challenges of implementing new water technologies, particularly regarding the ‘valleys of death’ that can occur when transferring solutions from research to industry. The panel discussion in the third session explored strategies to overcome these barriers:

Technology readiness levels: Panellists discussed the importance of understanding and supporting the various stages of technology development, from basic research (Level 1) to successful application (Level 9).

Funding and guidance: Seth Darling, from Argonne National Laboratory, USA, explained how national laboratories provide crucial support to help researchers scale up their investigations.

Regulatory incentives: Regulatory agencies play a role in encouraging technology development by identifying critical water quality issues and promoting energy reduction and resource recovery.

Corporate leadership: The CEO Water Mandate provides a platform for corporate decision-makers to collaborate on finding innovative water management solutions.

Industry investment: Representatives from Veolia, Grundfos and Dow Chemical shared examples of how their companies invest in, and refine, new water treatment technologies for their clients.

The future outlook

The Industrial Water Forum highlighted the growing pressure to accelerate the development and implementation of water-efficient technologies. Despite the challenges, participants expressed optimism about future breakthroughs in industrial water management. Key areas for future focus include:

• Continued development of PFAS remediation technologies and alternatives to ‘forever chemicals’.
• Further exploration of energy-saving technologies in industrial water systems.
• Advancement of resource recovery techniques from waste streams.
• Expansion of nature-based solutions for industrial water management.
• Improved communication and collaboration between researchers, technology developers, regulators, and end-users to streamline the innovation process.

Conclusion

The Industrial Water Forum served as a vital platform for knowledge sharing and collaboration in the face of growing water challenges. By bringing together diverse stakeholders, the event fostered discussions on cutting-edge technologies, best practices, and strategies for overcoming barriers to innovation. As industrial water use continues to increase globally, the insights and connections made during this forum will play a crucial role in shaping a more sustainable and water-efficient industrial future.

Moving forward, continued collaboration across sectors will be essential to drive innovation, overcome implementation challenges, and achieve significant improvements in industrial water efficiency. By building on the momentum generated at this forum, stakeholders in the industrial water sector can work together to develop and implement solutions that address current and future water challenges, ensuring a more sustainable and resilient future for industry and the environment alike.

The authors: Lærke Nørgaard Madsen is a water treatment application specialist at Grundfos; Michael Skovgaard is Business Development Regional Director, Americas, at Grundfos; Walt Kozlowski is Senior Director Industrial Sustainability Solutions at Xylem; and Youngseck Hong is Principal Engineer at Veolia Water Technologies & Solutions

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Water scarcity is becoming a major issue in many regions, including the southwestern United States and Mexico, northern and eastern Africa, the Arabian Peninsula, and the North China Plain. These areas are already experiencing severe water imbalances that are expected to intensify under climate change, causing catastrophic losses to human life and infrastructure, and substantial economic impacts.

The UN Intergovernmental Panel on Climate Change has projected that extreme weather events will increase in both frequency and severity, and that temperatures globally will continue to rise. Extreme weather events, such as the 2023 extended heatwaves in Europe, western North America and Asia, and floods in Pakistan, Bangladesh, Australia and Libya, are occurring at increased frequency and severity, causing further disturbances to the hydrological cycle, demonstrating the need for urgent action.

Ensuring the effective management of water resources is of utmost importance for global food security and sustainable development. A recent review paper published in Nature Reviews Earth and Environment, titled ‘Sustainable wastewater reuse of agriculture’, takes a close look at the many potential benefits and the possible difficulties that using treated urban wastewater for irrigation might entail.

Right now, the world produces about 400 km3 of wastewater every year. However, less than 20% of this is treated to a useable level. Of that treated wastewater, only 2–15% is reused for irrigation, depending on its country of origin.

The primary concern of using treated wastewater for irrigation is that current treatment technologies cannot fully eliminate all micropollutants, and some of these substances could affect crops, the environment and human health. Nonetheless, it is possible to ensure a stable water supply for agriculture, even in arid regions, by using advanced water treatment and reuse systems. These systems can provide treated wastewater that is safe for use on crops – a reality that has been demonstrated with years of experience in the United States and Israel.

Net gains

Such systems could potentially provide a net positive energy output, as the energy embedded in wastewater far exceeds what is needed for treatment by a factor of nine to 10. Agriculturally useful nutrients, such as nitrogen, phosphorus and potassium, could also be recovered and reused.

Reusing treated wastewater for irrigation can significantly contribute to a circular economy and sustainable development. However, the initial steps towards making this a reality – funding and implementing advanced, sustainable treatment technologies, and gaining social acceptance – are crucial and must be prioritised.

The current mindset that sees wastewater as merely a waste to be discarded must shift. Most wastewater treatment systems today follow a linear, energy intensive approach that is not only inefficient, but also ineffective in terms of resource recovery. There is great potential, however, for these systems to evolve into something much better – a system that is fully circular and efficient at recovering resources and delivering them back into the system.

The reuse of treated wastewater for agricultural irrigation has become a vital strategy for countries facing water scarcity and requiring sustainable water management. Many regions across the globe have adopted treated water reuse schemes to enhance agricultural productivity while preserving freshwater resources.

Transferable international examples

Israel is a pioneer of treated wastewater reuse for agricultural irrigation. Because of the region’s chronic water scarcity, more than 85% of produced effluents are reused, supplying more than half of agricultural irrigation needs. Around 160,000 hectares (~45% of cultivated land) is irrigated with treated wastewater, contributing significantly to agricultural output. Key drivers include a centralised water system (where all water is state property), financial incentives (loans and grants for wastewater treatment plants, pipelines and irrigation equipment), and research assessing treated wastewater’s long-term impact on soil and crops. Strict regulations govern the health and agronomic quality of treated wastewater, ensuring sustainable usage.

Cyprus, with the highest water exploitation index in Europe (124% in 2019), reuses nearly 80% of its tertiary treated wastewater. In other European countries, treated wastewater irrigation is practised on a smaller scale. For example, treated wastewater is used for rice and vegetable irrigation in Valencia, Barcelona and Murcia, Spain, and in Milan, Italy.

In the USA, treated wastewater reuse schemes are based on comprehensive regulations. In Florida, treated wastewater is mainly reused for landscape irrigation, while in California’s Monterey County, disinfected tertiary treated wastewater plays a critical role in the ‘One Water’ management scheme. This involves treated wastewater reuse for aquifer recharge (to manage seawater intrusion) and irrigation of high-value crops such as artichokes, broccoli, cauliflower, celery, and lettuce. Additionally, it supports indirect potable reuse systems.

China has a long history of using treated wastewater in the southeastern suburbs of Beijing for irrigation, providing substantial food supplies to the city.

Australia is also increasingly adopting treated wastewater reuse in agriculture, to secure ‘climate-independent’ water supplies. In the period 2019–2020, 6,500 hm3 of water was used for agriculture, of which 124 hm3 (1.9%) was reclaimed from off-farm sources. The utilisation of treated wastewater from wastewater treatment plants located near vegetable growing areas has been particularly successful.

Using treated wastewater for crop irrigation has pros and cons. On the plus side, treated wastewater is a stable water source that enriches crops with nutrients, thus reducing the need for commercial fertilisers. But it does come with potential problems. Soil salinity could be an issue, and so could the presence of many kinds of organic chemicals in the water, including pharmaceuticals and determinants of antibiotic resistance. Careful monitoring and adherence to water quality standards are necessary to ensure the many agronomic benefits of treated wastewater do not come at too high a price.

Risk reduction

Priority should also be given to upstream measures that prevent water pollution at its source – through restrictions and the development of greener alternatives – which are more effective than traditional end-of-pipe treatments. It is crucial to implement both ‘upstream’ and ‘downstream’ measures to secure public health and the quality of the environment.

Legal and regulatory frameworks for treated wastewater reuse in irrigation vary globally, with several organisations and countries implementing standards to ensure public health, environmental protection, and sustainable agricultural practices. Below is a summary of key regulations and guidelines across various regions. Across these regions, treated wastewater reuse regulations focus on ensuring water quality, mitigating health risks, and balancing agricultural viability with environmental protection. These frameworks emphasise tailored risk assessments and comprehensive monitoring for sustainable water reuse in agriculture.

• International Organization for Standardization (ISO) Guidelines
  ISO 16075:2020 provides technical standards for the reuse of treated wastewater in irrigation. It defines permissible levels of E. coli, biological oxygen demand (BOD5), total suspended solids (TSS), and turbidity, depending on water treatment levels. It also includes recommendations for agronomic parameters such as nutrient levels, salinity, and heavy metals, to protect soil and crops.
  ISO 20426:2018 outlines an approach for health risk assessment and management for non-potable treated wastewater applications, ensuring that treated wastewater reuse is safe for users and the environment.
  The World Health Organization guidelines also offer a global methodology for safe treated wastewater reuse, including frameworks to assess and minimise health risks.
• European Union Water Reuse Regulation
  The EU Regulation 2020/741 sets out minimum harmonised water quality standards and monitoring requirements for treated wastewater, categorised into four classes (A, B, C and D) based on crop type and irrigation methods. These include strict limits for E. coli, BOD5, TSS, and turbidity.
  The regulation mandates the creation of a risk management plan for treated wastewater reuse systems, which addresses additional water quality issues, such as micropollutants, depending on the outcome of specific system risk assessments. Permits for treated wastewater production and supply are issued by national authorities, which can impose further conditions depending on local requirements.
• US Regulatory Framework
  There is no federal standard for treated wastewater reuse in the USA. Instead, individual states regulate the practice. Standards vary depending on the crop type, irrigation method, and treatment levels. For example, California’s Title 22 imposes strict criteria for total coliform bacteria, turbidity, and viruses such as F-specific bacteriophages MS-2 or poliovirus when using disinfected tertiary treated wastewater for irrigating edible crops. The US EPA Guidelines for Water Reuse provide non-binding national guidance based on risk management principles, helping states develop their own regulations.
• Israeli Water Reuse Law
  Israel’s 2010 water reuse law governs the unrestricted use of treated wastewater for agricultural irrigation. The law, approved by the Ministry of Health, provides a permitting process for treated wastewater irrigation, ensuring public health and environmental protection.
• Australian Guidelines
  Australia’s 2006 Guidelines for Water Recycling provide recommendations for the safe reuse of treated wastewater, though they are not mandatory. These guidelines are based on a health and environmental risk management approach, offering flexibility to set water quality standards depending on the intended use of treated wastewater.

The global opportunity

At the global level, especially in developing countries, there is incredible potential to transform wastewater reuse into a viable and valuable practice. This transformation can occur through effective management practices that are enforced by suitable legal and regulatory frameworks. These frameworks must be adapted to local conditions, sufficiently implemented, and empowered by political, institutional and financial support. They also need to be transparent and involve citizens in decision-making. In addition, regulations should encourage circularity in wastewater management by permitting recovered resources, such as nutrient fertilisers, to enter the market. l

The author:

Professor Despo Fatta-Kassinos is Head of the Laboratory of Environmental and Engineered Water Processes and Systems at the Department of Civil and Environmental Engineering, Nireas International Water Research Center, University of Cyprus

More information

www.nature.com/articles/s43017-024-00560-y

Key highlights of the review paper ‘Sustainable wastewater reuse of agriculture’, published in Nature Reviews Earth and Environment

• More than 80% of the world’s wastewater is released untreated, where it can infiltrate groundwater and flow into rivers and lakes. Sometimes this untreated water is used – either directly or indirectly – in the production of food and can pose the risk of contamination.
• The implementation of advanced water treatment and reuse systems can ensure a reliable and safe supply of water for agriculture, potentially replacing an equal amount of fresh water that could be used for drinking or other essential purposes.
• Reusing treated wastewater for irrigation can counteract the water imbalances that plague agriculture in many regions. Expanding this practice, particularly in areas that are already short of water, has the potential to keep food production levels up and even boost them. In places where treated wastewater is available, and systems are in place to deliver it to farms, this resource can make a considerable difference.
• Ongoing research and site-specific assessments are essential for making advanced wastewater treatment processes cost effective and sustainable.
• Wastewater treatment plants (WWTPs) have the potential to become facilities for recovering water, energy, and nutrients. This transformation can
• occur because technological opportunities exist to implement the kinds of changes needed to achieve this new management of WWTPs. One significant prospect is that these technological changes can lead not only to a transformation of the role of WWTPs, but also enable them to become energy-carbon neutral.
• A detailed and all-encompassing regulatory framework is needed to ensure the smooth operation and sustainability of treated wastewater reuse systems. These frameworks are necessary not only for public health and environmental protection, but also to reassure the public.

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With increasing demand for fresh water, wastewater reuse will be one of the most significant solutions to provide sufficient clean water. However, the presence and persistence of waterborne viruses has long been one of the largest challenges that must be addressed for the safety of non-potable and potable reuse.

In June 2024, California’s State Water Resources Control Board, USA, approved new direct potable reuse regulations, requiring at least a 20-log10 reduction of enteric viruses. These heightened standards underscore the need for more effective virus removal technologies in wastewater reuse.

Environmental engineers, in academia and industry, are now focused on understanding the environmental behaviour of viruses and developing advanced treatment processes to ensure the safety of reclaimed water, thereby meeting these stringent regulatory requirements.

History of environmental virology

The roots of environmental virology originated in the 1930s with the detection of polioviruses in wastewater. By the 1970s, virus testing included downstream applications (removal by treatment prior to discharges), as well as upstream public health uses, to understand the epidemiology of infectious diseases in the community. During the COVID-19 pandemic, the field of environmental virology expanded significantly, with the rapid adoption of wastewater-based environmental surveillance (WBES) providing crucial early evidence of viral spread.

Advancing knowledge

The scope of WBES has now broadened beyond SARS-CoV-2 to include enteric viruses, other respiratory viruses, and even arboviruses, offering valuable insights into the epidemiology of viral diseases and guiding public health strategies.

Significant advancements in environmental virology methodologies are directly linked to the rapid expansion of WBES, not only for concentration and extraction methods, but also the use of the digital polymerase chain reaction (dPCR) and high-throughput sequencing to quantify and analyse the viral community in wastewater. These methods have advanced knowledge of virus types and concentrations in wastewater that will also influence reuse applications.

Assessing risk to human health

While molecular techniques are revolutionising virus monitoring, the assessment of infectivity is still important, particularly if the goal is virus inactivation rather than complete elimination. Culturing viruses for their infectivity offers a more accurate assessment of the potential human health risks posed by these pathogens, unlike the polymerase chain reaction (PCR), which only quantifies viral genomes.

Researchers at the University of Arizona have successfully cultured infectious adenoviruses in reuse treatment chains in large volumes through serial passages. This allows the assessment of up to 10-log10 removals. While many important waterborne viruses, such as human noroviruses, remain difficult to culture, new model systems such as enteroids, zebrafish and immortalised human salivary cells have been employed and successfully used to propagate human noroviruses (Hayashi et al., 2024).

Industrial practitioners have also conducted field studies to assess the efficacy of wastewater treatment processes in mitigating health risks from waterborne viruses. A team from H2O Molecular carried out a year-long sampling campaign across nine wastewater treatment plants, analysing bacteriophages as indicators of human viruses (Worley-Morse et al., 2019).

Their findings suggest that facilities employing biological nutrient removal (BNR), tertiary treatment, and UV or ozone disinfection demonstrated superior performance in removing human viral indicators. BNR secondary processes typically achieved greater than 2-log10 removal of viral indicators, and BNR plus UV and BNR plus ozone were able to reach more than 4- and 5-log10 reduction of the viral indicators respectively.

Virus persistence

The aggregative state of viruses can affect their persistence in wastewater. Viruses were initially believed to exist as free, independent particles during transmission and infection. However, in complex environments such as wastewater, viruses rarely act alone. Instead, they tend to clump together to form aggregates or attach to other substances present in the water. Viruses can, for example, latch onto particles such as organic matter, bacteria, and other impurities found in wastewater, forming what we call particle-associated viruses.

The degree of the aggregative state of viruses also depends on water chemistry and treatment processes. Recent discoveries have shown that some viruses can use the host cell’s secretion pathways to exit the cell in protective extracellular vesicles. These particle-associated viruses are known as vesicle-cloaked virus clusters, or referred to as viral vesicles, where multiple virus particles are enclosed in a fluid-filled sac made of a lipid membrane (see Figure 1).

Figure 1

The discovery of particle-associated viruses enhances our understanding of viral behaviour in wastewater environments, as these viruses can be more persistent during treatment processes and may pose increased risks to human health (Zhang et al., 2021 and 2022).

Tiong Gim Aw analysed particle-associated viruses in secondary effluents collected from five wastewater treatment plants across the USA by using particle-size fractionation through a series of membrane filtration. Many enteric viruses were found to associate with particles, as well as viral indicators such as CrAssphage and pepper mild mottle virus.

What is particularly interesting is that the abundance of a specific virus in a specific fraction of particles with defined sizes is different. For example, adenoviruses were evenly associated with particles across a broad range of sizes of 0.45-100µm, and they were also prevalent in the filtrate (< 0.45µm). In contrast, human noroviruses and enteroviruses were reluctant to bind to particles and were most abundant in the filtrate (< 0.45µm).

Yun Shen conducted the environmental surveillance of vesicle-cloaked virus clusters in wastewater. She identified human norovirus vesicles in both municipal and hospital wastewater and, surprisingly, these viral vesicles contributed to 17-45% of total human noroviruses. Metagenomic sequencing (analysing genetic material from environmental samples) of the vesicles elucidated that many common human enteric viruses were associated with vesicles, including norovirus, rotavirus, astrovirus, and Sapporo virus.

Industrial practitioners also found that particle-association promoted the persistence of viruses in wastewater. A team from Trussell Technologies characterised free chlorine disinfection of bacteriophage MS2, a human virus indicator, in recycled water at a pilot-scale study. MS2 showed a biphasic inactivation profile, exhibiting rapid disinfection kinetics at lower free chlorine CT values, followed by significantly slower disinfection kinetics at higher free chlorine CT values. The particle-association of viruses, as indicated by the turbidity of recycled water, contributed to the reduction in disinfection effectiveness.

Conclusions and recommendations

Environmental virology has made steady progress over the years, particularly driven by methodological advancements. The effective treatment of viruses is critical to meet the stringent safety standards for direct potable water reuse. Assessing viral infectivity through culturing and understanding virus aggregative states and removal throughout wastewater treatment processes are essential. Particle-associated viruses, including vesicle-cloaked virus clusters, exhibit increased persistence during treatment, but not all viruses associate with particles or vesicles in the same way.

Critical questions must be addressed to ensure the future safety of water reuse. The authors offer recommendations from both research and practice perspectives to guide future advancements in this field. First, we need to further advance methodologies to facilitate tracking of viral removal up to 20-log10. This includes improving sample concentration techniques for viruses in wastewater, as upstream sample processing often affects downstream analytical methods.

Moreover, viruses are not ‘lone wolves’, and complex wastewater environments impact virus behaviour and removal through treatment. The association of viruses with particles and the presence of viral vesicles in wastewater have significant implications on treatment processes and virus enumeration for estimating log10 reduction values. A better understanding of the mechanisms of this association in complex wastewater matrices is warranted. Additionally, we must consider how treatment and detection methods may impact the aggregative state of viruses, as this could influence the accuracy of removal and inactivation assessments.

The authors:

Danmeng Shuai is Professor, Civil and Environmental Engineering, George Washington University, USA; Tiong Gim Aw is Associate Professor, Environmental Health Sciences, Tulane University, USA; Yun Shen is Assistant Professor, Civil and Environmental Engineering, George Washington University, USA; Joan B. Rose is Professor, Homer Nowlin Chair in Water Research, Fisheries and Wildlife, Michigan State University, USA; and John Scott Meschke is Professor, Environmental & Occupational Health Sciences, University of Washington, USA.

More information

1. Hayashi, T.; Kobayashi, S.; Hirano, J.; Murakami, K., Human norovirus cultivation systems and their use in antiviral research. Journal of Virology (2024), 98, (4), e01663-23.
2. Worley-Morse, T.; Mann, M.; Khunjar, W.; Olabode, L.; Gonzalez, R., Evaluating the fate of bacterial indicators, viral indicators, and viruses in water resource recovery facilities. Water Environment Research (2019), 91, (9), 830-842.
3. Zhang, M.; Ghosh, S.; Kumar, M.; Santiana, M.; Bleck, C. K. E.; Chaimongkol, N.; Altan-Bonnet, N.; Shuai, D., Emerging pathogenic unit of vesicle-cloaked murine norovirus clusters is resistant to environmental stresses and UV254 disinfection. Environ. Sci. Technol. (2021), 55, (9), 6197-6205.
4. Zhang, M.; Ghosh, S.; Li, M.; Altan-Bonnet, N.; Shuai, D., Vesicle-Cloaked Rotavirus Clusters are Environmentally Persistent and Resistant to Free Chlorine Disinfection. Environmental Science & Technology (2022), 56, (12), 8475-8484.

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By investigating dirty pipes to clean up city living, water professionals have begun to help health and law enforcement officials track the dangerous abuse of controlled substances in near real time, opening a promising new front in the domestic ‘war on drugs.’

The effort has enlisted trained researchers in more than a hundred cities from Brisbane and Berlin to Boston and Barcelona. Chemists collect samples from wastewater treatment plants (WWTPs), then analyse them for traces of opioids, amphetamines, cocaine, MDMA (ecstasy) and crystal meth.

In university labs, and in some cases within private companies, researchers are studying strains broken down into parts per million, and dividing the result along demographic areas of the population served. They can then discern levels of concentration, yielding rich and remarkably granular data that help officials more effectively focus on preventative steps.

“We measure human health in sewage,” explains Newsha Ghaeli, co-founder of Biobot Analytics, a small team of MIT engineers-turned entrepreneurs who leverage their combined expertise in urban science, computational biology and spatial epidemiology.

Each effort zeros in on a place-specific issue. The Biobot team has developed proprietary, automated sensors and analytic systems to help cities map and visualise America’s current deadliest health epidemic. The firm’s Opioid Consumption Monitoring (OCM) Program “reveals a democratized assessment of opioid use, providing aggregated, anonymised, and unbiased insights into the health of communities.”

Biobot claims to have ‘cutting edge’ intellectual property and seeks first mover advantage for what Ghaeli calls the “untouched US$400 million market.” The technology to detect, isolate and analyse microbial strains in sewage was once a specialized and rarefied field. But in recent years it has grown to be more affordable and accessible. Yet as this private venture seeks to attract clients who run cities above 100,000 people, it is facing competition from wastewater professionals in universities and urban government itself.

The EU drugs agency, for example, has funded a large consortium of laboratories (SCORE group) to compile illicit drug estimates working with more than 50 European cities. Released in early 2018, the study’s findings found methamphetamine usage highest in Cyprus, eastern Germany, Finland and Norway. Cocaine, on the other hand, was both on the rise and most concentrated in cities in Belgium, the Netherlands, Spain and the UK.

Surprising almost no one, wastewater epidemiologists confirmed “cocaine and psychedelic MDMA (ecstasy) levels rose sharply at weekends in most cities, while amphetamine use appeared to be more evenly distributed throughout the week.”

A third parallel effort is unfolding down under. The Australian Criminal Intelligence Commission has funded a joint UniSA and University of Queensland (UQ) programme to monitor and report community consumption findings on drug use by 14 million people, in 50 different wastewater treatment sites nationwide.

Their analysis did more than confirm crystal ‘meth’ or ‘ice,’ to be the country’s most prevalent illicit drug, smoked or injected. It showed Adelaide residents reportedly use about 80 doses per 1,000 people a day, three times higher than average.

Behind the pithy headlines, notes UQ research leader Jochen Mueller, is serious labour that demands painstaking detail. Wastewater analysis requires skills in liquid chromatography and mass spectrometry in order to measure and interpret the concentrated residues. Research teams in Australia had to gather and ship (at high courier prices) some 4,000 bottles of wastewater, holding untreated, acidified, and biocide-treated influent and effluent. Private and public water professionals form a cornerstone for such coordinated analysis.

“This kind of work requires close collaboration with wastewater treatment authorities to allow us
to sample wastewater influent and provide us with the necessary information about the catchment in order to more accurately calculate our estimates,” says Dr. Ben Tscharke, a postdoctorate researcher at UQ.

Tscharke’s group has detected multiple classes of compounds. These include “herbicides and pesticides, personal care products and pharmaceuticals, illicit drugs, poly-fluorinated alkyl substances, health markers such as vitamins and food biomarkers and plasticisers (phthalates and their metabolites).”
It’s a cocktail of chemicals, which – thanks to innovative technology – also yields rich data.

Logistical challenges emerge as each continent’s team collects samples from distant urban corners. Each jurisdiction has its own unique water chemistry, content, demographics, infrastructure, and political issues. Collaboration between police, health, governance, and water professionals helps improve interpretations of what’s happening between sites across time.

Three roadblocks inhibit the analysis of drugs in wastewater. First, drugs are often, almost by definition, unstable. “If it degrades quickly it will be difficult to detect,” says Tscharke.

To mitigate the risk, his team adds preservative to prevent degradation post-sampling, and is pioneering “real in-sewer degradation experiments where we spike drugs into a pilot sewer and test the degradation rate to ensure our estimates are the most accurate.”

A second issue is concentrated volume. The drug or metabolite has to be excreted at a high enough rate in urine to be detectable and soluble in water. Low doses of a drug, or few users in the population, may effectively dilute the sample to a level where detection is impossible. The technology applies less readily to raw cannabis than pure, refined chemicals.

Third, the certified reference material has to be commercially available. “Our methods are very specific to each drug,” Tscharke explains. “To have the highest confidence in the data, we require the analytical pure reference standard which allows us to accurately identify the drug and its concentration.”

The unlikely alliance began a decade ago. It grew by necessity and came through the back door, after the traditional front entrance appeared slammed shut. A man’s private home is his castle, so authorities struggled to map the extent of drug abuse within cities unless armed with broad search warrants or random drug tests.

Lacking these, cities were often flying blind. Public ignorance, combined with private stigma,
helped the US opioid epidemic, for example, quickly metastasise, while no one knew who abused which drugs where – until it was too late and the casualties piled up.

In recent years, wastewater chemists and engineers have started to highlight the extent of potentially risky drug use through a powerful new petri dish: the flush toilet.

When a drug user conducts their business in a bathroom, his or her confidential waste becomes external public property – captured by municipal sewerage and delivered to water professionals who can break down the chemical-rich contents and reveal what was going on behind closed doors.

This budding, strategic alliance between drug agents and water professionals holds out promise for gains to each side yet it has not escaped controversy from outside or within the water profession.

Some see wastewater epidemiology offering breakthrough research that creates new jobs, saves money, and protects public health. But following a recent story in Water Online, critics fear it could be a slippery slope to social engineering. “I can envision utilities being required to cooperate with criminal investigations by sampling individual building sewers,” warned E. Brown. “Utilities should stick to their mission.”

Right now, Tscharke explains how “samples are completely anonymous and there is no risk of identifying individuals, so privacy is respected.”

The biggest bang per buck is looking at metadata population surveys. He does acknowledge that moving further “up-stream” to sub-pump stations that connect far fewer people in neighbourhoods, “the ethics on this become hazier.”

Few wastewater epidemiologists can envision their data being used in court and for officials grappling with urban drug epidemics like Adelaide, or Cary, North Carolina, the innovative advances are welcome. Any future risk to society’s collective privacy, they say, is far outweighed by the enhanced ability to map and reach out to vulnerable citizens.

So in the near term water professionals will keep helping cities expose tail-end chemicals coursing down sewers underground, hoping to stop these substances from spreading above the surface.

But as technology inevitably gets smaller, cheaper, faster, and more widely available, the spatial mapping data could reveal sharper trends and more granular patterns. At that point decisions may come down to urban ethics.

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Developed by the Pacific Northwest National Laboratory as part of the US Department of Energy, the system could add the treatment of wastewater to the circular economy using what is known as hydrothermal processing. This processing method combines temperature, pressure and water to convert organic matter into forms of energy normally extracted through intense geological drilling techniques.

The system has been tested with more than 100 materials that include wastewater solids, food processing wastes, brewery wastes, animal wastes, and algae.

James Oyler, president of Genifuel, said hydrothermal processing (HTP) mimics the process by which fossil fuels are formed under Earth’s surface, meaning it has the ability to produce resources such as oil and gas in a fraction of the time without using heavy infrastructure or leaving a large carbon footprint.

“Fossil fuels are created when you have geological time and you have organic matter settling down into swamps and shallow lakes. After millions of years it builds up temperature and pressure and of course it’s wet and that starts the conversion into fossil petroleum and natural gas,” he said.

“In HTP the reactions and the products are similar, but we do it in an hour instead of millions of years.”

Oyler added that the fuels created through HTP can be used and mixed as effectively as their natural counterparts. Their production via the method also avoids excess residue, he said, a result typically very expensive to manage. He said the point of the system is not to increase the energy industry’s reliance on fossil fuels but to decrease the need to seek such resources while adding no further greenhouse gases to the atmosphere.

Having trialed the system successfully with the help of its sponsor, the Water Research Foundation (WRF), Genifuel will demonstrate the system to delegates at next month’s forum with Oyler as its formal representative.

BlueTech Research convenes investors, water companies, researchers and regulators, and provides information including analysis of emerging water technology markets.

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Inhabited for 6,000 years, Aqaba sits at the point where Jordan reaches the Red Sea. Its beach resorts are popular for sunbathing and windsurfing, while the Yamanieh coral reef attracts scuba divers from around the world. Booming growth put these magnets at risk.

So to protect the quality of its marine environment and preserve the region’s attractiveness for tourism, the port city has committed to making huge investments into collection and treatment of 61,000 cubic metres per day from sewer and wastewater by 2030.

Aqaba’s resource recovery strategy generates US$4 million in income for the city, maintaining green areas and urban landscapes. Above all, it reduces carbon emission through enhanced operation and energy efficiency, as well as through production of carbon neutral power from solar farms and biogas. Ultimately, the city will recover 100 percent of its energy.

Aqaba was profiled at IWA’s Development Congress in Buenos Aires, among eight cities to illustrate the wastewater challenge and reuse opportunity. It demonstrated how transition to a circular economy is not limited to the “usual suspects” of pioneering cities such as Singapore or Stockholm.

Other cities that recover a significant portion of energy from wastewater include Bangkok (62 percent), Beijing (45 percent), Chennai (77 percent), and Kampala (227,000 Kwh/y).

The ‘zero discharge’ targets are ambitious, and policies must be targeted toward industry and backed by meaningful incentives. The global market for wastewater recycling and reuse should reach US$22.3 billion by 2021. New innovations in technology help open opportunities and make the transition affordable.

“Whilst the necessity of wastewater reuse in water scarce places like Aqaba is apparent,” observes the IWA’s soon to be released The Reuse Opportunity report, “cities everywhere are increasingly taking proactive actions to improve their water security. They are given greater autonomy; decision making is decentralised, and systems are being adapted to local drivers and demands.”

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