Potable Reuse: Turning Wastewater to Blue Gold to Solve the Drinking Water Crisis

The story of water reuse is inextricably linked to the story of civilisation. Water reclamation has been practiced since antiquity, and is once more in the spotlight as a means to address shortages brought on by climate change and rapid population growth. Globally, an estimated 1.1 billion people lack adequate water supplies. Singapore, consuming 440 million gallons of water daily, could face doubling demand by 2065. Amidst threats of climate change, other countries are experiencing heightened water stress, and projected global population growth to 9.9 billion by 2050 will further pressure water resources.

This blog will highlight the practice of wastewater recycling to turn into drinking water, otherwise known as Potable Reuse (PR). It will present PR as a viable solution for drinking water scarcity challenges, explore the differences between indirect potable reuse (IPR) and direct potable reuse (DPR) and provide a historical context of water reuse. The article spotlights BW Waters’ expertise that make it a valuable partner for utilities undertaking IPR and DPR projects.

Potable Reuse (PR) – The Future of Drinking Water

PR is the process of treating wastewater to a quality where it is safely drinkable. It has garnered attention as nations look to expand their water resource portfolio. UNESCO posits that 80% of the world's wastewater is released into the environment without treatment, with figures higher in least-developed countries. Typically, untreated wastewater is discharged to rivers or streams where it is diluted and transported downstream or infiltrated into aquifers.

PR is an important niche as it gives wastewater a second life. Experts note that wastewater is no longer viewed as waste, but as a “renewable and recoverable source of drinking water, resources, and energy.”?

A History of Water Recycling

Since the Bronze Age, the Indus Valley and Mesopotamian civilisations used domestic wastewater for irrigation and aquaculture, followed by Ancient Greeks and Romans. Advancements in technology make it an exciting solution for contemporary societies. Uptake of projects has been aided by the widespread use of reliable technology since the 1980s, such as ultra/microfiltration (MF), reverse osmosis (RO), low, medium and high UV disinfection and oxidation treatments. These tools boost the safety of reclaimed water, making PR viable. Parameters for PR projects were finally codified by the WHO in 2017.

Differences between IPR and DPR: IPR and DPR waters are subject to distinctive processes. Knowing the difference between the two is important for gaining public acceptance and for understanding safety parameters.

Indirect potable reuse (IPR) involves blending reclaimed water into a raw water supply, such as a reservoir or a groundwater aquifer. Using the IPR methodology can lead to cost savings, as the reclaimed water is further treated through natural environmental processes, thereby eliminating the need for further advanced treatment.

Before water is released into raw water systems, it must be purified. IPR uses engineered processes such as MF as a pre-treatment to RO. Finally, the water is exposed to UV light to kill any remaining microbial matter. Results have proven effective. Studies show that RO membranes are able to reject most endocrine disrupters, pharmaceuticals and personal care products.

IPR then takes advantage of natural biological processes to make treated water even safer for consumption. Soils provide a layer treatment through natural biodegradation and filtration, before water enters municipal groundwater supplies. Aquifers offer a natural mechanism for storage and subsurface transmission of reclaimed water.

Direct Potable Reuse (DPR) refers to the introduction of disinfected reclaimed water either directly into a potable water supply distribution system downstream of a water treatment plant, or into the raw water intake system immediately upstream of a water treatment plant.

Because of negative public perception, DPR is not common in many parts of the world. Yet, that trend may change soon. The city of Windhoek, Namibia, has used DPR to augment its drinking water supply since 1968. Since the 2010’s, other utilities exclusively using IPR practices began exploring DPR, as eliminating environmental buffers from the process can offer operational advantages and cost savings to a utility.

Health and environmental regulations for potable reuse differ regionally. Guidelines in some countries integrate several approaches using risk management frameworks such as Life Cycle Analysis. The NEWater project in Singapore monitors more than 300 drinking water parameters to meet USEPA and WHO standards.

The Benefits: Self-reliance and Renewable Supplies

Water managers often consider mixed options to maximise water resources. Many municipalities have aging infrastructures requiring expensive upkeep. Long-term groundwater supply can be threatened by intensive food cultivation, expanding industry and urban sprawl.

Singapore is just one nation using advanced treatments to create clean drinking water. The State relies on a mix of four different sources for its potable water. These include freshwater imports from Malaysia, desalination plants, water from local catchments, and recycled water, known as NEWater. There is intensive investment in five IPR NEWater factories in the island state.

The Changi Water Treatment Plant stands out, with its capacity to treat up to 900 million litres of wastewater daily. The system employs IPR practices of MF, RO and UV disinfection to remove impurities on wastewater from sewers. The result is high-grade, drinkable NEWater. The product is mostly used by Singapore’s industry, yet during dry periods, it is blended into reservoirs of raw water, further treated and then supplied to consumers as tap water.

The Obstacles: Public Perception and Trace Toxins

DPR and IPR can support stressed traditional drinking water systems. Yet potential hazards in PR must be recognised and managed.

Often, even proven scientific results cannot counteract inbuilt biases against wastewater. While interest in PR projects has grown, public acceptance remains low. Understanding and addressing stakeholder concerns around wastewater, and involving communities in decision-making process around water treatment can spell success for PR projects.

More importantly, wastewater contains contaminants from domestic, industrial, and agricultural sources, such as endocrine disruptors. RO effectively removes most contaminants, but some micropollutants and disinfection by-products can remain. In IPR, aquifer recharge can lead to metal leaching into groundwater. Success in managing these compounds and continuous monitoring must be proven for PR projects.

The future of PR

The last three decades have seen growing inclusion of reclaimed water in resources management plans. The UN focuses on treated wastewater as a reliable potable source in its World Water Development Report 2024, as does the USEPA.?

PR treatment often exceeds the standards of other water sources. Filtration with a combination of media and membrane along with Chlorination can remove over 99% of fine solids, bacteria, and protozoa, dissolved solids while additional treatments like ozone, UV, and oxidation enhance safety and accuracy in contaminant removal as of different types of water source. DPR practices like engineered storage buffers offer greater controls, as seen in Singapore’s NEWater facilities, where treated water is stored for hours for continuous monitoring and contamination response.

Stricter regulations may also win public acceptance of PR. NEWater is subject to rigorous audit processes annually to comply with national and global regulations detailed by the Singapore Food Agency, the EPA and the WHO.

New technology is also making PR monitoring increasingly accessible and safe. Singapore uses online sensors as an early warning system of illegal discharges of industrial materials, assisting source control.

With significant advancements in technology and regulation, attitudes towards IPR and DPR projects are changing to embrace wastewater recycling as a solution for water-stressed locations. These projects must be considered by municipal authorities in collaboration with capable EPC companies experienced in PR facilitation.

BW Waters is a reliable partner for utilities considering potable water reuse projects. With expertise that encompasses comprehensive process design for water systems, and innovative solutions for surface and groundwater treatment as well as extensive experience in complementary water security projects such as desalination, BW Waters offers end-to-end solutions for the innovative wastewater recycling projects that pave the way for flourishing communities.