Conventional municipal waste- , preliminary steps include, screening to remove large solids. Grit removal to protect mechanical equipment against wear
Flow measuring and pumping to lift the waste water.
Primary treatment is to remove settle able organic matter accounting to percent of suspended solids and scum.
Secondary treatment is by in open with return biological solids or fixed media followed by final setting excess microbial growth settled out in the final clarifier is wasted while the supernatant is disinfected with chlorine prior to discharge to a receiving water course.
Waste ’s from primary settling and biological are thickened and dewatered for preparation to disposal.
Anaerobic bacterial digestion may be used to stabilize the sludge prior to dewatering.
The overall process of conventional waste water treatment` can be viewed as, thickening: to percent depending upon the plant Solvents moved from solution are concentrated in a small volume convenient for final disposal.
The contribution of raw sanitary waste water is gallons per person with a total solid content of 0.1 percent.
240mgs/l suspended solids.
200 mgs of B.O.D
Liquid waste sludge is withdrawn from primary and secondary processing amounts to approximately 2l/persons with a solids content of 5 percent by weight.
This is further concentrated to handle able material by mechanical dewatering, the extracted water is returned for reprocessing. Cake , amounts to about 1/3l/l with a 30 percent solid concentration from vacuum which is used in large plants to extract water directly from raw sludge.
This type of physical -biological scheme is effective in reducing the organic content of waste water and the main objective is maximum reduction of suspended solids and BOD