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Types of Wastewater
Wastewater is classified by source and level of contamination. The source of the wastewater determines what contaminants are present in the wastewater. Wastewater from a home contains human waste, soaps, cleaning fluids and food waste. Wastewater from a farm or feed lot may contain fertilizers, pesticides, herbicides and animal waste. Industrial wastewater may contain toxic chemicals and solids that are harmful to the environment. A hospital̵7;s wastewater is likely high in medications, blood and body fluids, and disease-causing bacteria and viruses. Most wastewater requires some form of treatment before reuse.
Treatment is Required First
The degree of treatment required depends on the wastewater type. Wastewater must go through up to three stages of treatment. The first is settling of solids, called primary treatment. Secondary treatment uses biological and disinfection treatment. The third or tertiary step uses filtration, more disinfection and advanced methods to produce high-quality water. The US EPA recommends choosing the treatment level and method based on the intended use for the treated wastewater, and local regulations.
Untreated wastewater with minimal contaminants, such as grey water, may be reusable for irrigation in certain situations. Grey water comes from sinks, shower drains and washing machines. It may contain high levels of sodium from soaps and shampoos which could affect plant growth and drinking water quality. Human contact should be avoided -- grey water is not suitable for reuse in your home or by animals. US EPA guidelines for grey water reuse require its application away from drinking water wells and populated areas. Grey water reuse may not be allowed under your local regulations.
Urban and Agricultural Uses
Treated wastewater can be used by cities to irrigate golf courses, football fields and landscapes. This is its most common use. Some cities also use it to supply water to fire hydrants and toilets. In rural areas, farmers and ranchers can reuse treated wastewater to irrigate crops and orchards as well as non-food vegetation. Usually, a minimum of secondary treatment is required to protect public health and prevent environmental damage. If used for food crops, tertiary treatment may be required.
Wetland Habitat Creation
Wastewater can be used to create new wetlands or to replenish existing natural wetlands. These wetlands provide habitat for wildlife and aquatic organisms and may form part of the local water supply. Water added to natural wetlands has usually been treated, but constructed wetlands are the treatment system. Constructed wetlands are highly effective biological treatment systems which remove organic contaminants through action of soils, plants and beneficial bacteria and micro-organisms.
Recreation and Reclamation
Lakes, streams and ponds can be created by reusing treated wastewater. This technique has been used in new developments and to reclaim former industrial sites such as abandoned gravel pits. The new bodies of water could be used for boating or even swimming. Reclaimed water is also useful for snowmaking at ski hills, and some states like Nevada and California have specific regulations for this purpose.
Drinking Water
You may not realize it, but many cities and towns are reusing wastewater every day by cleaning it in treatment plants. Tertiary treatment is needed to produce water that is safe for use in the home for drinking, cooking and bathing. The treated water is also safe to discharge into streams, rivers, lakes and aquifers. Federal and state authorities enforce regulations to uphold high standards of treatment.