Water Resource Recovery Basics

Water resource recovery refers to using wastewater streams to produce clean water, energy, and other valuable resources. Water and wastewater contain recoverable resources, including metals like lithium, and fertilizer nutrients like nitrogen and phosphorus. All of these resources typically must be removed from water, in any case, before it can be safely used or discharged.

After removal, these materials can be recovered and recycled back into the economy, lowering the life cycle energy and emissions of various products and providing revenue to offset the cost of water treatment.

What Resources Can Be Recovered?

Water resource recovery, or valorization, can refer to the recovery of materials from waste streams, the reuse of wastewater, or the generation of energy from wastewater treatment processes. Valorization technologies include:

Water Reuse

Desalination and water reuse technologies reclaim water from nontraditional sources such as brackish (salty) groundwater and wastewater. With sufficient treatment, water resource recovery facilities can treat water to a standard suitable for certain applications.

For example, toilet water doesn’t need to be treated to drinking water standards. Systems that capture the relatively clean water collected from bathtubs, sinks, and kitchen appliances can reduce the demand for water across communities.

Brine Valorization

Brine is the highly saline by-product left over from desalination. Brine can be collected and used to replace potable water in manufacturing products, like cement, and contains chemicals such as sodium hydroxide and hydrochloric acid, which are widely used across a range of industries from papermaking to metals manufacturing. Desalination facilities can offset the cost of brine disposal by selling its contents to commercial facilities.

Some thermal and electrochemical technologies aim to eliminate the liquid in brine, which are collectively known as zero liquid discharge (ZLD). The remaining solids can include metals such as potassium and minerals such as gypsum, both of which can be sold to fertilizer manufacturers and used to improve agricultural yields. Learn more about desalination.

Creating Energy from Wastewater Treatment

With technology innovation and deployment, wastewater treatment can be used to generate more energy than what is required to treat it. WRRFs utilize bacteria in low-oxygen conditions to safely break down solid organic waste, which releases methane, a potent greenhouse gas. Rather than letting the methane escape into the atmosphere, it can be captured and burned at the plant, providing energy and reducing the facility’s carbon footprint.

Other treatment processes can produce biofuels, which offer low-carbon alternatives to diesel and gasoline. Hydrothermal processing heats organic wastes at elevated pressures to produce an energy-dense liquid fuel. With this technology, sewage sludge or microalgae from wastewater recovery can be used as a feedstock for biofuel.

Extracting Nutrients from Wastewater

Plant nutrients like nitrogen and phosphorous must be removed from wastewater before it is discharged into local waterways. These nutrients stimulate the growth of algae, depleting an ecosystem’s oxygen, potentially leading to massive sea life die-offs.

Instead of stimulating undesirable algal growth, these nutrients can instead be used to encourage crop growth. Commercial fertilizers provide plant nutrients like nitrogen and phosphorus to improve crop yields.

These nutrients can be extracted during wastewater treatment in the form of struvite, a mineral which contains nitrogen, phosphorus, and magnesium–another plant nutrient–and can be applied to crops to achieve yields comparable to those produced by commercial fertilizers.