Wastewater is an inclusive term referring to water made unsuitable for repeated use either due to the service itself or outside contamination. Recycled water from an automatic car wash needs at least some minimum treatment to remove grit, dirt, oils, and chemicals that could damage the next car in line. Water used in a dentist's office to rinse out your mouth during a root canal shouldn't be channeled directly to the water fountain out in the hall. On another scale, water used to extract oil from underground shouldn't be transported immediately to a nearby reservoir. In each of these cases, the water must be filtered and treated to remove impurities and then, if possible, either reused in the same process or directed back into the supply of safe, clean water.
This broad definition means that wastewater is produced by almost any possible use, but the degree of contamination and the necessary treatment varies. Keep in mind that numerous statutes cover the containment, treatment, and eventual disposal of wastewater. It's critical to consult with experts who can verify your compliance with applicable legislation.
Residential Wastewater
Residential wastewater can come from showering and bathing, laundry, dishwashing, and toilet flushing. Some of these processes, like toilet flushing, produce "black water," which isn't black at all - it just means that the water needs extensive treatment before using it again. Gray water comes from showers, washing machines, and other relatively benign sources. In a few states, gray water can be redirected for watering crops.
Industrial Wastewater
Industrial wastewater can include chemicals such as those from a hair salon or a pharmaceuticals plant. Hospitals produce hazardous liquid waste, and some mining operations generate wastewater loaded with acids and radioactive materials. Even winemakers produce wastewater full of sugar and fruit pulp that can be very difficult to store and treat.
Municipal Wastewater
Municipal wastewater generally refers to the water that flows through sewers and stormwater systems but also includes oil, gas, and other contaminants washed by rain from rooftops and parking lots, fertilizers from yards, and products used to clean facilities and equipment in local businesses. Some cities use combined sewer systems to collect and combine rainwater runoff, domestic sewage, and industrial wastewater. In heavy rainfall, these sewers can become overwhelmed and overflow, expelling not only rainwater runoff but untreated human and industrial waste, toxic materials, and debris. Both operational and closed municipal landfills can produce wastewater with a host of dangerous contaminants. Because municipal wastewater is subject to many variables, treatment processes must be both flexible and comprehensive.
