Navigating the regulatory landscape of water reuse

Propelled by global population growth, industrialization and warming temperatures, concerns about clean water supplies are growing. As a result, water reuse conversations that were once novel and niche are becoming increasingly mainstream and these practices are proving integral to global and localized strategies for water security.

Advanced wastewater treatment and reuse for agricultural irrigation, industrial processes and potable consumption provides a replenishment answer for dwindling freshwater reserves. However, successfully navigating and implementing water reuse schemes requires interaction among diverse policies, stringent regulations, various agencies, varied public opinion and unique regional geographies and climates.

Public trust in water treatment centers around water quality regulations. These guidelines, customized for specific regions and their unique challenges, establish the permissible levels of a vast array of contaminants across all water classifications, ensuring each category meets the necessary safety standards for its intended use. The public understands this well in the context of conventionally-treated freshwater for potable use, but the topic becomes unclear when applied to wastewater treatment for both non-potable and potable reuse.

To ensure compliance and enable rapid response in the event of deviations, continuous real-time monitoring of water quality is required. Monitoring programs typically require analyzing a wide range of parameters, including:

• Microbial indicators, such as fecal coliforms and other bacterial indicators, which gauge the effectiveness of disinfection processes in eliminating harmful pathogens.
• Chemical contaminants, including heavy metals, pesticides, pharmaceuticals and industrial byproducts.
• Aesthetic parameters, such as turbidity, color, taste and odor. While these characteristics do not directly indicate health risk, they can impact public approval, especially pertaining to reused water.

As water reuse applications and regulations expand, agencies are increasingly relying on advanced technologies - such as microfiltration, ultrafiltration, reverse osmosis, advanced oxidation processes and ultraviolet disinfection - to remove even the most persistent contaminants. The specific combination of technologies employed is dictated by the quality of the source water, the intended treated water use and the regulatory requirements of the region.

International organizations like the World Health Organization and the International Water Association provide guidance and help develop best practices for water reuse. However, translating these guidelines into enforceable directives is typically reserved for national and regional authorities.

Regulations regarding indirect potable reuse (IPR) and direct potable reuse (DPR) are some of the fastest-growing threads in the global water landscape. IPR entails treating wastewater and then injecting it into a natural water containment buffer, such as a surface water reservoir or groundwater aquifer, prior to extraction and potable treatment. DPR, by contrast, requires treatment to drinking water standards because product is introduced directly into the public water supply.

Without the intermediary buffer of IPR, DPR requires more technologically advanced treatment to ensure wastewater meets drinking water standards. And while it provides the highest level of water recovery, DPR often encounters significant public resistance due to the psychological quandary of consuming water directly derived from wastewater. Addressing these and other concerns, countries like the United States - which is ramping up DPR permitting programs - are implementing rigorous multistep treatment systems. These systems typically include a combination of advanced water treatment technologies, along with additional safeguards, such as activated carbon filtration, to remove trace contaminants.

In contrast, IPR takes a more indirect route, requiring intentional and controlled introduction of treated wastewater into an environmental buffer. This allows for natural filtration and biodegradation processes to occur, further purifying the water before it is extracted, treated to drinking water standards and distributed for public consumption. Although IPR encounters fewer public acceptance challenges because of the natural buffer between wastewater and drinking water, it requires robust regulations for wastewater discharge and stringent groundwater management practices.

Regions with naturally arid or semi-arid climates - including Australia, Namibia, Qatar, Israel and parts of the southwestern US - have successfully integrated IPR projects into their water management strategies. These sorts of regions often have well-established water recycling infrastructure and they benefit from natural filtration processes inherent to their geological formations. However, because they are more complex to maintain over the long term, IPR programs are often viewed as gateways to DPR.

The influence of geography and climate extends beyond IPR and DPR regulations, playing a pivotal role in shaping water reuse policies worldwide. Water-scarce regions, particularly those facing chronic drought or limited freshwater resources, often exhibit more proactive approaches towards water reuse out of necessity.

For example, Singapore - an island nation with limited land area and freshwater sources - faces existential water scarcity. Consequently, the country has pioneered highly purified reclaimed wastewater that vastly surpasses drinking water standards found anywhere in the world. While safe for potable consumption immediately after treatment, most of the treated water is blended with surface water sources to maintain natural mineral balances.

Australia is also familiar with the challenges of limited freshwater, and as a result, it has some of the most advanced and comprehensive water reuse regulations worldwide. While each Australian state and territory enforces regional directives, Australia’s National Water Initiative provides an overarching framework that promotes sustainable water management, including reuse. Regulations are tailored to specific applications and potential risks. For instance, reuse for irrigation carries less stringent requirements than potable reuse.

Western Australia's Water Corporation operates several successful IPR projects, injecting highly treated wastewater into aquifers prior to extraction, then treating the water further for potable use. Also recognizing the potential of DPR, Australia has developed rigorous guidelines for its implementation and rollout, requiring advanced treatment technologies and extensive monitoring to ensure potable water quality.

In the United States, water reuse practices vary significantly. While states experiencing water scarcity like California and Arizona - driven by recurring droughts and growing populations - are leading the Western world in IPR, and soon DPR, implementation, other regions are not yet adopting these practices. The development of regulatory frameworks built upon existing guidelines from the US Environmental Protection Agency are therefore fundamental for increasing adoption. Additionally, implementors are quickly learning public education campaigns that highlight the safety and sustainability elements of water reuse are essential for successful program expansion.

Europe, with similarly varied geography and water availability, represents an assortment of water reuse practices. Facing water scarcity due to climate change and agricultural demands, Southern European countries like Spain and Italy are actively exploring and implementing water reuse projects, particularly for irrigation purposes. Among the northern nations with historically abundant water resources, however, there has not been a significant need to change traditional water management approaches. Nevertheless, the European Union's Water Framework Directive, which encourages sustainable water management practices, is gradually driving interest and investment in water reuse technologies across the continent.

While governing bodies are primarily concerned with monitoring water quality for human health and environmental protection, other monitoring objectives have emerged in recent years. Among these, pathogen data collection in wastewater was a helpful tool during the 2020 COVID-19 pandemic to track its spread. In adopting communities, this provided early outbreak warnings and helped identify new variants.

By analyzing wastewater samples for specific pathogens - including viruses, bacteria and protozoa - health officials can gain critical insights into the spread and severity of disease outbreaks. This approach, referred to as wastewater-based epidemiology, helps identify emerging hotspots by tracing the movement of pathogens through communities, helping to inform targeted public health interventions.

The lack of universal regulatory directives for water reuse presents both challenges and opportunities. While international organizations, such as the World Health Organization and the International Water Association, develop best practice guidelines and disseminate scientifically-predicated frameworks that promote water reuse and sustainability, implementation responsibility ultimately falls on individual nation state and regional governments.

Advancing reuse programs - especially for IPR and DPR - requires fostering public approval through transparent communication and comprehensive education campaigns. These efforts must address public concerns, rigorously explain treatment processes and highlight environmental benefits of water reuse to garner support for these increasingly essential water management strategies.

Water security compels adaptive harmony and balance between technological development and robust regulatory frameworks. Effectively navigating the complexities of the emerging water landscape will require collaboration at global and regional levels, along with a collective commitment to water sustainability.