Main pumping stations
Main pumping stations are often large concrete constructions with three to six pumps. The pumps partly work in parallel and as standby pumps so they are capable of coping with large volumes of wastewater or floodwater at all times. Main pumping stations are often the last pumping station for sewage on its way to the inlet pumping station at the wastewater treatment plant.
The pumps are installed either submerged or dry for the same reasons as for network pumping stations. The trend is, however, for larger pumps to be dry installed. It is also becoming increasingly common to operate the pumps in main pumping stations via frequency drives due to the energy-savings potential.
Main pumping stations are typically designed to accommodate the pumps for which they are intended. It is important to ensure a proper design that is large enough to prevent overflow and which can handle many pump starts/stops per hour. The station should be self-cleaning to avoid the settlement of sludge and debris as this may lead to the clogging of pumps, valves and pipes, and could create odour problems due to the generation of hydrogen sulphide in septic sludge.
When designing the pumping station, it is important to take into account whether the pumping station is servicing an area with separate or combined sewer systems.
In a separate sewer system, rainwater and sewage are piped in different parallel systems. One system carries sewage from households, industrial premises and commercial buildings, while the other carries rainwater, flood water and run-off water from car parks and low-lying areas.