The treatment of wastewater is a fairly simple process that uses physical, biological and chemical processes to remove impurities. Treatment of wastewater includes four main steps:
- Preliminary Treatment is the first step in treating wastewater and usually uses physical barriers to remove objects. Objects can include anything from leaves to plastic bags. This process may occur in several stages, with the water flowing through bar screens that remove large objects to protect the mechanical systems used to pump the water through the rest of the treatment process.
- Primary Treatment begins after the water passes through the bar screens. The flow is slowed and sent into large settling tanks designed to allow particles that are denser than water to separate using gravity. Slowing down the flow allows sand and grit to fall to the bottom of the tanks, while fats, oils and grease rise to the top, where they are skimmed off.
Just these two steps remove as much as 70 percent of the contaminants from wastewater.
- Secondary Treatment uses biological and chemical processes to remove suspended and dissolved particles from the water. The biological process is introduced first using aerobic or anaerobic processes. Either way, micro-organisms present in the water start to do what they do naturally – consume any organic material.
These “bugs” convert organic material into solids, which again settle to the bottom. Both the solids and the micro-organisms are captured and removed from the water later in the process.
Once the micro-organisms have finished their job and pass through another filter system, the water enters a chamber where disinfection methods such as chemicals, ultraviolet radiation or other technology is used to make sure any micro-organisms are removed. If chemicals were used to treat the water, they are now removed, and the water is tested to ensure that it’s clean for its next use.