Settlement Tanks For Wastewater Treatment 

Coagulation / Settlement Tanks are used for a wide variety of applications in wastewater and construction water treatment. Chemicals are sometimes added to the water being treated to form precipitates and settle suspended solids in the raw water.  

Applications include lime to raw water in the cold lime softening process, which also reduces the alkalinity of the raw water. The addition of lime or other alkalis is also used to effect the precipitation of insoluble hydroxides.  

A settlement tank is used on construction sites to allow silt to drop out the water in the tank. Settlement/sedimentation tanks are used as sedimentation water treatment, primary sedimentation tank or settling tank in sludge treatment and water settlement applications. 

High-Performance Settlement Tank 

This rapidly deployable settlement tank (silt traps) give an effective sedimentation tank for suspended solids. These heavy-duty units give a large settlement area for effective settlementation within a small footprint. The water to be treated is often mixed with the chemicals to decrease the settling time. This water flows through the inlet down to the base of the coagulation vessel via the central chamber. The water then flows up the outside of the chamber where the suspended solids and precipitates settle out.   

The solids (sludge) collected by the unit settle in the cone base or hopper and removed by the opening of a gate valve. This eliminates the need for the unit to be taken offline for emptying thus allowing continuous operation. The treated water is collected at the top of the vessel. 

Silt technically refers to a specific grain size applied to fine particles of soil. Silt carried by water is what gives it water a muddy or dirty discolouration. The most common source of silt pollution is the result of rainwater runoff from topsoil stripped areas of construction sites.  

When washed off into nearby watercourses, silt pollution is highly visible and easily traceable back to the site. Silt can travel a long way causing significant environmental harm. This includes suffocating fish by blocking gills and settling on river beds killing organisms dwelling on the river bed.  

There are legal limits for the concentration of suspended solids in discharged water and is closely monitored by the environment agency. Breaching these is a common reason for construction companies being taken to court and fined.  

What’s a Primary Settlement Tank Used For? 

Primary settlement tanks are used in the initial stages of water treatment. The solid particles simply settle at the bottom of the tank, from where they can be removed.

Primary settlement tanks are used may situations including the treatment of sewage and in aquaculture. Anywhere where there are floating or sinking solids. Primary clarifiers may be used to reduce the number of suspended solids which includes other pollutants such as heavy metals embedded in the suspended solids.

Coagulation Tanks

Chemicals are sometimes added to the water being treated to form precipitates and settle suspended solids in the raw water.  The water to be treated is often mixed with the chemicals to decrease the settling time. This water flows through the inlet down to the base of the coagulation vessel via the central chamber. The water then flows up the outside of the chamber where the suspended solids and precipitates settle out.

Secondary Settlement Tanks or Clarifiers

These are further settlement tanks for use after the water has received its primary treatment. Coagulation and flocculation produce flocs from biological growth which can then be removed as they sink to the bottom of the tank.

Main Menu