The EGL Pressure Sewer Solution
Description of the Pressure Sewer System
EGL Pressure Sewers consist of a network of pressure pipe, much like a water pipe network and E/One grinder units, which are installed serving all the properties throughout the collection system. Depending on local factors each unit will serve one residence or several home units or townhouses, or larger facilities. Upstream from the grinder pumps, gravity house drains from within the residence are no different from any other system, except much shorter.
The Street Main Pressure Network
The polyethylene pressure pipe network is usually installed in the road reserve. The network is completely sealed through the use of electrofusion welding techniques for jointing, thus eliminating infiltration and inflow.
The Grinder Pump
The E/One grinder pump grinds the sewage and discharges a finely ground slurry into the small-diameter pressure piping. The semi-positive displacement pump in the grinder pump station is the best type of pump for successful parallel operation of many pumps into a system of common pressure mains. The pumps do not have a single fixed “operating point”, but must operate consistently over a wide range of heads that are continually, and often rapidly, changing. The maximum desirable pumping head is 45m.
The Grinder Pump Unit
A grinder pump unit consists of a grinder pump, tank, alarm panel and connecting cable. The gravity pipework upstream and the pressure pipework downstream connect to the grinder pump unit, with electrical connection also required.
In operation, the grinder pump station will handle sewage and many items that should not, but often do, appear in domestic wastewater. For example, plastic, wood, rubber and light metal objects can be routinely handled without jamming the grinder or clogging the pump or piping system. Transporting sewage several thousand metres to a discharge point at a higher elevation is possible as long as the sum of the static and friction losses does not exceed the desirable design limit of 45m.
Water authorities around Australia are addressing the backlog of unsewered properties in their areas of operation to provide them with sewer service. This septic tank replacement effort has gained considerable momentum in recent years. Accordingly, the standard approach for sewering communities with gravity sewers is increasingly being found to be a more expensive approach.
In addition to backlog sewerage, developers are also beginning to recognise the advantages of pressure sewer for new developments as well.
Where pressure sewer systems are best used
To protect sensitive environmental areas:
- Areas with significant underlying rock formations
- Flat sites
- Hilly or difficult terrain including islands
- Sites with high water table
- Areas remote from existing infrastructure
- Low density housing areas
- Where avoiding infiltration and inflow is critical
- To avoid numerous standard pumping stations