Wastewater is any water that has been adversely affected in quality by anthropogenic (or human) influence. Wastewater can originate from a combination of domestic, industrial, commercial or agricultural activities, surface runoff or storm water, and from sewer inflow or infiltration. In today’s growing environmental needs force us to process and reclaim all the process water available.
Typical Wastewater Sources:
Washing water (greywater or sludge)
Surplus manufactured liquids
Highway drainage (oil, deicing agents)
Storm drains (may include trash)
Man-made liquids Illegally Disposed Of
There are numerous processes that can be used to clean up wastewater depending on the type and extent of contamination. Wastewater & Municipal Wastewater (sewage) can be treated in wastewater treatment plants which include physical, chemical and biological treatment processes. Agricultural wastewater may be treated for chemicals in fertilizer, pesticides, animal slurry, crop residues or irrigation water.
Primary treatment consists of temporarily holding the sewage in a quiescent basin where heavy solids can settle to the bottom while oil, grease and lighter solids float to the surface. The settled and floating materials are removed and the remaining liquid may be discharged or subjected to secondary treatment. Some sewage treatment plants that are connected to a combined sewer system have a bypass arrangement after the primary treatment unit. This means that during very heavy rainfall events, the secondary and tertiary treatment systems can be bypassed to protect them from hydraulic overloading, and the mixture of sewage and storm water only receives primary treatment.
Secondary treatment removes dissolved and suspended biological matter. Secondary treatment is typically performed by indigenous, water-borne micro-organisms in a managed habitat. Secondary treatment may require a separation process to remove the micro-organisms from the treated water prior to discharge or tertiary treatment.
Tertiary treatment is sometimes defined as anything more than primary and secondary treatment in order to allow rejection into a highly sensitive or fragile ecosystem (estuaries, low-flow rivers, coral reefs,...). Treated water is sometimes disinfected chemically or physically (for example, by lagoons and micro-filtration) prior to discharge into a stream, river, bay, lagoon or wetland, or it can be used for the irrigation of a golf course, green way or park. If it is sufficiently clean, it can also be used for groundwater recharge or agricultural purposes.
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