The Clara sewage treatment system plant consists of a mechanical pre-treatment and a biological compartment.
The mechanical pre-treatment part is formed of sedimentation tank with a high volume buffer area.
The sewage water enters the Clara unit via the Inlet pipe and flows in the buffer area of the storage tank. Settable solids fall to the bottom of the tank and floating matter is caught by a scum board, thus protecting the raw sewage air lift pump against blockage.
Hydraulic peaks at the inlet of the Clara sewage treatment plants are absorbed in the buffer area. The pre-treated water is the pumped at a uniform flow rate from the buffer area into the biological part of the plant. Hydraulic peak equalising considerably increases the stable purification efficiency.
The biological part of the Clara consists of an activation tank and a built in final sedimentation tank.
The activation tank is aerated by micro-bubble aeration.
The water goes from the activation tank into the final sedimentation tank
The water goes from the activation tank into the final sedimentation tank, which enables treated water to be separated gravitationally from activated sludge. The treated water flows out of the sewage treatment plant through the outlet connection. The activated sludge falls to the bottom of the final sedimentation tank, from where it is pumped back as return sludge and also partly into the storage area as surplus sludge.
The final sedimentation tank is optionally equipped with a skimmer for the automatic collection and removal of floating sludge from the water surface. This device can reduce maintenance work during operation. Surplus sludge is stored in the storage area, which in fully loaded plants is capable of holding about 100 – 150 days’ capacity. The pumping of sewage water and return and surplus sludge is achieved using air lifts in the Clara. These air lifts need no maintenance and are resistant to clogging. The hydraulic capacity of the air lifts is continuously adjustable, even at very low flow rates. This helps to ensure a uniform purification process and thus achieve stable purification efficiency.