ETP Plant Operation

1. Screen chamber

Remove relatively large solids to avoid abrasion of mechanical equipments and clogging of hydraulic system.

2. Collection tank

The collection tank collects the effluent water from the screening chamber, stores and then pumps it to the equalization tank.

3. Equalization tank

  • The effluents do not have similar concentrations at all the time; the pH will vary time to time.
  • Effluents are stored from 8 to 12 hours in the equalization tank resulting in a homogenous mixing of effluents and helping in neutralization.
  • It eliminates shock loading on the subsequent treatment system.
  • Continuous mixing also eliminates settling of solids within the equalization tank.
  • Reduces SS, TSS.

4. Flash mixer:

Coagulants were added to the effluents:

  • Lime: (800-1000 ppm) To correct the pH upto 8-9
  • Alum: (200-300 ppm) To remove colour
  • Poly electrolyte: (0.2 ppm) To settle the suspended matters & reduce SS, TSS.

The addition of the above chemicals by efficient rapid mixing facilitates homogeneous combination of flocculates to produce microflocs.

5. Clarriflocculator:

In the clarriflocculator the water is circulated continuously by the stirrer.

  • Overflowed water is taken out to the aeration tank.
  • The solid particles are settled down, and collected separately and dried this reduces SS, TSS.
  • Flocculation provides slow mixing that leads to the formation of macro flocs, which then settles out in the clarifier zone.
  • The settled solids i.e. primary sludge are pumped into sludge drying beds.

6. Aeration tank

  • The water is passed like a thin film over the different arrangements like staircase shape.
  • Dosing of Urea and DAP is done.
  • Water gets direct contact with the air to dissolve the oxygen into water.
  • BOD & COD values of water is reduced up to 90%.

7. Clarifier

  • The clarifier collects the biological sludge.
  • The overflowed water is called as treated effluent and disposed out.
  • The outlet water quality is checked to be within the accepted limit as delineated in the norms of the Bureau of Indian standards.
  • Through pipelines, the treated water is disposed into the environment river water, barren land, etc.
  • ETP Plant Operation

8. Sludge thickener

  • The inlet water consists of 60% water + 40% solids.
  • The effluent is passed through the centrifuge.
  • Due to centrifugal action, the solids and liquids are separated.
  • The sludge thickener reduces the water content in the effluent to 40% water + 60% solids.
  • The effluent is then reprocessed and the sludge collected at the bottom.

9. Drying beds

  • Primary and secondary sludge is dried on the drying beds.


  • Screening is the filtration process for the separation of coarse particles from influent.
  • Stainless steel net with varying pore size can be utilized.
  • Screens are cleaned regularly to avoid clogging.