A sewage treatment plant is a combination of separate treatment processes or units designed to produce an effluent of specified quality from a wastewater (influent) of known composition and flow rate. The treatment plant is also usually , required to process the separated solids to suitable condition for disposal. By a suitable combination of these unit processes it is possible to produce a specified final treated water quality from any type of sewage water. While treated wastewater can be used for groundwater recharge , can be recycled , discharged to surface waters , rivers.