Screen Filter: The screen filter mesh is fitted on the first tank near the entrance of the sewage to the STP. It helps in removing the non-sewage adulteration component such as; toilet paper, plastic paper, other solids, etc, which can clog the complete system if gone inside.


Biofilter: The biofilter is also part of the aeration chamber which treats the sewage passing from the screen filter. The biofilter reactor, with the help of fine air bubbles supplied by the blower, will disperse the contaminated substance by diffusing and breaking down the organic matter by the aerobic microorganism.


The fine bubble passing through the diffuser will increase the oxygen transmission rate.  


Sewage treament plant parts


‘Settling/ Sedimentation Chamber: The treated sewage water from the biofilter reactor will come to the next chamber which is used for settling purposes. The mixture will be further separated into high-grade water and sediment after being settled in a Sedimentation tank.


The clarification compartment is usually of the hopper type with sloping sides which prevent the sticking and accumulating of sludge and sends it to the suction side of the air lift tube. The untreated sludge settled in the bottom of the sedimentation tank returns to the Biofilter reactor to break up by microorganisms again.


Activated Carbon: The activated carbon is fitted post the settling chamber to remove  Chemical Oxygen Demand (COD) by filtering and absorption. It also helps in treating the Biological Oxygen Demand (BOD) and Suspended Solids.


Chlorinator: The chlorinator is fitted in the last chamber to treat the final stage water for discharging overboard. The chlorinator can be of tablet dosing type or chemical injection type.


Inside the tablet-based chlorinator, clean water comes directly in contact with the chlorine tablets, making a chlorine solution. The chlorinator comprises cylinders for filling the chlorinator with tablets. In the chemical pump type, a measured set quantity of NaOCl is injected into the sterilization/chlorination tank using the diaphragm-type reciprocating pump.


Air Blower: There are usually 2 air blowers installed, which one acts as standby, to supply air (via air bubbles) helping in forming the microorganism in the biofilter reactor. It also helps in transferring the sludge from the sedimentation tank, supplying air to the activated carbon tank, and backflushing the sludge.


Discharge Pump: The discharge pump is provided in a duplex and they are mounted on the last compartment of the STP. They are centrifugal pumps of the non-clog type which are coupled to their respective motors. 


The pump is run in auto mode controlled by the level switches installed in the sterilization tank. The pump is usually run in manual mode when taking out the sludge from the compartments after cleaning the tank insides.



  • The inlet pipe carrying the sewage to the plant is installed with the proper slope to prevent clotting and condensation.
  • The sewage pipe is arranged so that the inside holes are accessible for cleaning during maintenance.
  • The overboard discharging outlet should be placed 200~300mm lower than L.W.L and the discharge pipe is provided with a Non-return valve.

Floats and Level Switches:

  • Usually, Three float switches, namely – high-level, low-level, and high-alarm-level switches are fitted on the chlorination/sterilization chamber.
  • This chamber is also fitted with level switches to control the start-stop of the discharge pump.

Log in

Log in with Google

Log in with LinkedIn


Don’t have an account? Register Now