What is Sewage Treatment Plant ?

It is a normal question that what is STP and How does it works and what are the technologies involved , So the answer is here ……

Sewage Treatment Plant is a facility designed to receive the waste from domestic, commercial and industrial sources and to remove materials that damage water quality and compromise public health and safety when discharged into water receiving systems.

Objective: - The Principal objective of waste water treatment is generally to allow human and industrial effluents to be disposed of without danger to human health or unacceptable damage to the natural environment.

 Conventional wastewater treatment processes

            Conventional wastewater treatment consists of a combination of Physical, chemical, and biological processes and operations to remove solids, organic matter and, sometimes, nutrients from wastewater.

Preliminary treatment

            The objective of preliminary treatment is the removal of coarse solids and other large materials often found in raw wastewater. Removal of these materials is necessary to enhance the operation and maintenance of subsequent treatment units. Preminary treatment   operations typically include coarse screening, grit removal and, in some cases, communication of large objects.

A.     Primary treatment

            The objective of primary treatment is the removal of settleable organic and inorganic solids by sedimentation, and the removal of materials that will float (scum) by skimming. 

B.     Secondary treatment

            The objective of secondary treatment is the further treatment of the effluent from primary treatment to remove the residual organics and suspended solids. In most cases, secondary treatment follows primary treatment and involves the removal of biodegradable dissolved and colloidal organic matter using aerobic biological treatment processes. Aerobic biological treatment is performed in the presence of oxygen by aerobic microorganisms (principally bacteria) that metabolize the organic matter in the waste water, thereby producing more microorganisms and inorganic end-products (principally CO₂, NH₃, and H₂ O). Several aerobic biological processes are used for secondary treatment differing primarily in the manner in which oxygen is supplied to the microorganisms and in the rate at which organisms metabolize the organic matter. Common high-rate processes include the activated sludge processes, trickling filters or bio filters, oxidation ditches, and rotating biological contractors (RBC). A combination of two of these processes in series (e.g. bio filter followed by activated sludge) is sometimes used to treat municipal wastewater containing a high concentration of organic material from industrial sources.