Gray water is the waste water generated by the use of hand basin, shower, bath, clothes washing machine or laundry tub. The characteristics of gray water are influenced by the number of occupants, the age distribution of occupants, their lifestyle characteristics and water use patterns. Gray water from laundry is most often considered for reuse by individuals with onsite wastewater treatment systems.
Gray water use from laundry can be contaminated in three ways.
– the water is contaminated by microorganisms, many of which can cause disease. Coliform bacteria in laundry wastewater is highest in the wash water and lowest in rinse water. Numbers of coliform bacteria ranged from one million when infant clothes were washed to 25 in the second rinse water (reported in colony forming units/100 ml).
– The water may be polluted chemically by dissolved sodium, nitrogen phosphates and chloride, or by organic chemicals such as soap and detergents. Wash cycle water was found to have concentrations of sodium, phosphate, boron, surfactant, ammonia and nitrogen.
– The water may be physically polluted by particles of dirt, hair, dead skin cells, lint, fabric fibers and fecal matter. Wash cycle water was high in suspended solids including lint, turbidity and other organic material. If applied to land without treatment, laundry water can lead to environmental damage as well as posing a threat to public health.
Some individuals have diverted laundry wastewater and used it in the environment without treatment. Most often it has been used to water the lawn during drought periods, or to “take some pressure off of a septic system.” However, this is an illegal practice. It is not legal in Nebraska to discharge untreated gray water.
People can reuse gray water, such as laundry water, only after it has been treated for protection of public health and the environment, it is discharged at a location and in a manner that does not put the environment or human health at risk, and a permit has been obtained. Treatment systems typically include components that allow for settling of solids, anaerobic digestion, aeration, clarification or filtration, and disinfection.
In addition, the dwelling must be plumbed so that gray water is kept separate from black water. Systems must be designed by an engineer and designs must be approved and permitted by the Nebraska Department of Environmental Quality.
