Industrial wastewater treatment is the process of treating substantial amounts of wastewater to make it safe for other uses, or for release into the environment as effluent. Along the same lines, any large scale facility handling sewage may be considered an industrial wastewater treatment facility. Some industrial plants pre-treat their wastewater before sending it to a government treatment facility. This may also be considered industrial treatment of wastewater.
A multistep process is required for sewage going through industrial wastewater treatment. Preliminary treatment, primary treatment, secondary treatment, and final treatment all work incrementally to clean the water. Some steps clean those contaminants seen by the naked eye, and other steps focus on renewing or neutralizing the microscopic elements.
The first step in the industrial wastewater treatment process is called the preliminary treatment. At this point, water passes through one or more screens. This filters out larger objects that get washed into the sewer lines, and travel to the treatment facility.
After the water passes through the screens, the next step in the industrial wastewater treatment process further separates some of the suspended particles in the water. During this primary treatment stage, water is held in a holding tank for a number of hours as solids settle to the bottom, and oil and grease rise to the top. The sediments are eventually pumped out, and the grease and oil is skimmed off the top.
After the settling tank, the water begins the secondary treatment step by going into an aeration tank. There, microorganisms feed on the other organic matter left in the water, some of which could be harmful to humans. The water is then sent to a clarifier, which will allow any final solids in the water to settle. Some of the microorganisms used will be sent back to the aeration tank, and others will be discarded.
The final step involves chemical wastewater treatment to remove any harmful organisms left behind. Depending on the final use of the water, different disinfection methods may be used. Water being released into a reservoir or river will not need to be sterilized completely, because the chemicals used to do so could cause great harm to the environment. If the water is being put directly into a drinking water supply, it will require larger amounts of antimicrobial chemicals such as chlorine.
A factory pre-treating its water before sending it to a general use industrial wastewater treatment facility typically does the first two steps in the process on site. This allows the factory to receive a substantial discount on its sewer rates. Furthermore, it does not put as much pressure on the municipal or government facilities during times of high demand.