Pressure Sewers and Vacuum Sewers

A Pressure Sewer System is different from other conventional gravity sewers and small-diameter variable slope, as it has a centralized collection point whereby wastewater is pumped from a holding tank to a pressure main before being fed to the treatment plant. Usually the collection point will consist of either a septic tank or just a normal holding vessel, which will be located underground beneath every household.

Use of the system offers several advantages and the main reason why it is widely employed is because, it does not need to rely on gravity flow to transport wastewater and thus offers more flexibility. However, as with all other collection systems, buildup of solid materials will always pose a problem that leads to clogged up pipeline. Basically, there are two different types of pressure sewer systems. If the collection point is made of up septic tank, which can remove solid from the wastewater, then a grinder pump is not needed to be present to transfer the wastewater. In this case, a normal effluent pump is sufficient and this is known as a septic tank effluent pumping (STEP) system. Otherwise if only a normal holding vessel is used instead, then there will not be any separation to get rid of the solid waste and therefore a grinder pump is needed in order to breakup the solids from forming huge lumps that would clog up the pipeline.

Besides that, advantages of using the system also relate to the fact that larger sized piping can be used to transport huge amount of wastewater. However, all these come at the expense of higher maintenance and installation cost just to setup the pump but it can actually be offset if proper planning is done so that several households can share one underground vessel and pump collectively as a single unit.

Vacuum Sewers System is another alternative to wastewater collection that can serve similar purpose as well. In these setups, wastewater is first transferred to a holding tank that will be sealed off from the main transfer line, which will be under vacuum isolated using a valve. The vacuum condition that exist in the pipeline is actually generated using a vacuum pump located at the main station and once the holding tank reaches a certain level, the self-regulating valve will automatically open to release the wastewater that will travel through the system going to the main station. Since the vacuum condition generates a suction force, wastewater will flow at high speed often avoiding curve and bents. The only disadvantage towards the use of the system is the high operational cost mostly related to maintenance of the vacuum pump.

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