Water Recycling

By TRWA Wastewater Technician Alex Eaves

While recycling is a term generally applied to aluminum cans, glass bottles, and newspapers, water can be recycled as well. The term water recycling is generally used synonymously with water reclamation and water reuse. Through the natural water cycle, the earth has recycled and reused water for millions of years. Water recycling, though, generally refers to projects that use technology to speed up these natural processes.

Water recycling is reusing treated wastewater for safe, beneficial purposes such as agricultural and landscape irrigation, industrial processes, toilet flushing, and replenishing a ground water basin (referred to as ground water recharge or aquifer storage and recovery). Water recycling offers resource conservation and financial savings. Wastewater treatment can be tailored to meet the water quality requirements of a planned reuse. For example, recycled water for landscape irrigation requires less treatment than recycled water for drinking water. In an area of equivalent need, the fiscally responsible choice may be to go the route of landscape irrigation. However, in areas where drinking water is in high demand, spending the extra time and money to produce safe drinking water may be the right choice for a utility.

Recycled water can satisfy most water demands as long as it is adequately treated to ensure water quality appropriate for the use. Recycled water is most commonly used for nonpotable (not for drinking) purposes, such as agriculture, landscape, public parks, and golf course irrigation. Other nonpotable applications include cooling water for power plants and oil refineries, industrial process water for such facilities as paper mills and carpet dyers, toilet flushing, dust control, construction activities, concrete mixing, and artificial lakes.

“Gray water” is reusable wastewater from residential, commercial and industrial bathroom sinks, bathtub shower drains, and clothes-washing equipment drains. Gray water is reused onsite, typically for landscape irrigation. The use of gray water at decentralized sites for landscape irrigation and toilet flushing reduces the amount of potable water distributed to these sites, the amount of fertilizer needed, and the amount of wastewater generated, transported, and treated at wastewater treatment facilities.

Although most water recycling projects have been developed to meet nonpotable water demands, several projects use recycled water for indirect or direct potable purposes. Examples of indirect potable uses include recharging ground water aquifers and augmenting surface water reservoirs with recycled water. In ground water recharge projects, recycled water can be spread or injected into ground water aquifers to augment ground water supplies, and to prevent saltwater intrusion in coastal areas.

Some utilities are considering direct potable reuse or “toilet to tap.” Direct potable reuse is defined in Texas law as the introduction of treated or reclaimed municipal wastewater directly into a public water system, or into a raw water supply immediately before it enters a water treatment plant.

Recycled water can also be used to create or enhance wetlands and riparian habitats. Plants, wildlife, and fish depend on sufficient water flows to their habitats to live and reproduce. The lack of adequate flow, resulting from diversion for agricultural, urban, and industrial purposes, can cause deterioration of water quality and ecosystem health. Those who reuse water can supplement their demands by using a reliable source of recycled water, which can free up considerable amounts of naturally occurring water for the environment and increase flows to vital ecosystems.

Because of water recycling’s status as a tool in conservation efforts, the impetus for some water recycling efforts comes not from a water supply need, but from a need to eliminate or decrease wastewater discharge to the ocean, an estuary, or a stream. Even if the effluent from a wastewater treatment facility meets local permit requirements, the receiving stream or reservoir may be home to an endangered species or at-risk flora or fauna that would benefit from some of the effluent being diverted for reuse elsewhere.

As the demand for water grows, more water is extracted, treated, and transported sometimes over great distances, requiring a large amount of energy. If the local source of water is ground water, the level of ground water becomes lower as more water is displaced, increasing the energy required to pump the water to the surface and possibly requiring installation of more advanced equipment. Recycling water for use on-site or nearby reduces the energy needed to move water longer distances or pump water from deep within an aquifer.

As discussed above, different types of water recycling require different amounts of resources. Tailoring water quality to a specific type of water use may reduce the amount of energy needed by water treatment plants. The water quality required for landscaping is less stringent than the water quality required for drinking water and requires less energy to achieve. Using recycled water that is of lower quality for appropriate uses is therefore an energy-efficient, as well as fiscally responsible, choice.

Before implementing any water recycling or reuse project, be sure to check with the applicable laws and regulations, which TRWA’s legal team can point you to. In 2021, the Texas legislature passed S.B. 905, which requires TCEQ to develop and make available to the public a regulatory guidance manual to explain its rules applying to direct potable reuse.

Water recycling is part of a toolkit water and wastewater providers can use in crafting plans that are fiscally and environmentally responsible. In addition to aiding a dependable, locally controlled water supply, water recycling provides tremendous environmental benefits. By providing an additional source of water, water recycling can help us find ways to decrease the burden on our water systems. Other benefits include decreasing wastewater discharges and reducing and preventing pollution. As a utility makes their long-term plans for sustainable water production and treatment, water recycling and reuse could be one of the right options.