Municipal and industrial water reuse

Globally, people are facing increasing pressure to minimize their environmental impact in a warming climate. Actions taken are usually identified as reducing emissions and air pollution, however, it is just as important to safeguard water resources.

Water is essential for human, animal and plant life. As the world’s population continues to rise, water scarcity concerns continue to rise as well. It is becoming more important to make investments in solutions for safe water sources, healthy ecosystems and ongoing sustainable water yield.

Water reuse has emerged as a critical component over the past few decades to address the issues outlined above. It was once a niche practice, but - fueled by increasingly effective advanced treatment technology - it is becoming routine, especially in densely populated metropolitan regions with limited rainfall and surface water availability. This is transforming water management practices, providing sustainable pathways to preserve natural ecosystems, supplement local municipal water supplies and enhance efficiency for industry.

Along with the environmental need to protect surface and groundwater resources, the business case for water reuse is becoming more compelling. In many locations, traditional water sourcing methods - such as withdrawing water from rivers, lakes or aquifers - now come at higher costs due to stricter regulations and competition from other consumers. With recent advancements in both affordability and effectiveness, treating and reusing water can be a cost-effective alternative in some cases.

This practice enables municipalities and industrial users alike to reduce their reliance on purchased water from external sources, offering protection against future price fluctuations. Additionally, adopting water reuse practices can enhance a water district’s or company's brand image, attracting environmentally conscious stakeholders.

Beyond the varying fiscal impacts, these activities have positive environmental benefits, as many freshwater ecosystems are under immense stress due to over-extraction and pollution.

Water reuse reduces these and other pressures by decreasing the need for freshwater diversion from sensitive ecosystems. Instead by treating wastewater for reuse, manufacturers help mitigate the negative impacts of over-extraction, which include habitat degradation and reduced biodiversity.

Furthermore, treating and reusing wastewater minimizes the discharge of industrial effluents into the environment, protecting aquatic ecosystems. As rising temperatures intensify water scarcity issues, particularly in arid regions, water reuse provides a reliable and drought-resistant water source.

Water reuse can take on a plentitude of diverse approaches, each with varying levels of treatment and suitability for different applications. Process water reuse entails treating and reusing water within industrial processes. For example, water used for rinsing or cooling in manufacturing can be treated and reused multiple times, minimizing freshwater intake and wastewater discharge.

Treating unclean wastewater streams for reuse requires sophisticated advanced water treatment techniques, such as reverse osmosis, ultrafiltration, ultraviolet treatment or advanced oxidation to remove a wide range of contaminants. Modern technological capabilities enable production of high-quality water, suitable for many demanding industrial processes and even potable reuse in approved locations.

In a typical advanced treatment process flow, preliminary treatment deploys physical mechanisms, such as screening and sedimentation, to remove large debris and suspended solids. Secondary treatment typically focuses on biological decontamination, utilizing microorganisms to break down organic matter and remove nutrients, like nitrogen and phosphorus.

At the final stages, advanced treatment processes are used to remove contaminants that remain after after previous treatment. These techniques include:

• Advanced oxidation processes, which utilize agents - such as ozone and ultraviolet light - to break down persistent organic pollutants and disinfect wastewater.
• Filtration through sand, granular activated carbon, or membrane filters to remove smaller suspended solids, organic matter, viruses, bacteria and microorganisms.
• Reverse osmosis, a pressure-driven membrane process, to withdraw a wide range of dissolved salts, minerals and other impurities.

The benefits of industrial water recycling extend beyond facility walls, providing opportunities to create or enhance valuable ecosystems. Treated wastewater can be used to supplement constructed wetlands , which are engineered ecosystems that provide habitats for wildlife, filter pollutants and present recreational opportunities.

For example, treated industrial water discharge into damaged stream or riverbank areas can help restore critical ecosystems with increased flow and improved water quality to revitalize vegetation, boost biodiversity and enhance the ecological integrity of the surrounding areas. Additionally, recharging groundwater aquifers with treated wastewater is a valuable strategy for replenishing depleted sources to enhance water security, particularly in water-deficient regions.

Beyond ecological benefits, industrial water recycling assists municipalities with responsible wastewater management. By treating and reusing wastewater on-site, manufacturers reduce the strain on regional wastewater treatment plants by freeing up their capacity. This decentralized approach to wastewater management can be particularly beneficial in areas where centralized infrastructure is limited or faces capacity constraints.

Regular monitoring and advanced treatment technologies are being deployed to remove contaminants and assure the safety of recycled water for its designated applications. While non-potable reuse for purposes such as irrigation and industrial processes has been common in water-deficient regions for many years, the concept of potable reuse, where treated wastewater is purified to drinking water standards, is gaining momentum.

Water for indirect potable reuse (IPR) is discharged to environmental buffers - such as groundwater aquifers or surface water reservoirs - before being withdrawn for drinking water purposes, while treated water for direct potable reuse (DPR) is introduced directly into potable supply lines.

While DPR is not yet allowed in many locations, considerable technological advancements are propelling permitting progress for both IPR and DPR systems.

Driven by recent advancements in water treatment technology, water reuse is becoming increasingly price-competitive at scale, prompting further adoption by municipalities and industrial users alike.

Water reuse is an investment in both the present and the future because it bolsters operational resilience, conserves freshwater resources, protects fragile ecosystems and promotes sustainable water yield for generations to come.