Collection Tank
Raw sewage transfer pump
The inlet of Collection tank inlet is fitted with a primary bar screen. This is used to separate plastics and larger non-biodegradable solids from entering the collection tank.
1 The sewage is dozed with microorganisms which are introduced by dozing to breakdown the sludge content. This process effectively nullifies the requirement of specialized sludge handling systems. The tank is also kept aerated to prevent formation of septicity to control odour.
Raw Sewage Lift Pumps
- There are two identical pumps. Controls ensure that only one pump can run at a time.
Each pump delivers sewage at a rate that is slightly higher than the actual flow rate of the STP. - Both pumps have independent suction pipes. The inlet pipes extend almost to the bottom of the tank, and must not have foot-valves.
- The delivery pipes from both pumps are combined in a TT-shaped header.
- The bypass pipeline returns the excess sewage back to the tank.
- Valves fitted on all three pipelines serve different purposes:
The valve on the bypass line is adjusted to “waste” the excess capacity of the working pump. (The delivery pipeline (3) always carries sewage at the designed flow rate) The valve on the delivery pipe is closed off when the corresponding pump is removed for repairs. This prevents sewage delivered by the other pump from coming out.