WASTEWATER or a packaged diesel pump. The Incident Site Manager selects the most appropriate contingency action based on the contingency plan and experience. Previously the most common contingency action for failed SPS pumps or even power failures was using tankers. Similar in size to a large petrol tanker (about 22,000 litres capacity), these
tankers with its on-board pump are used to suck up the sewage from a collection point and then transport it to another sewerage system area for controlled discharge. Unfortunately this has significant limitations, such as sometimes the small on-board tanker pump is unable to overcome static head (generally greater than 5 metres) to lift the sewage for collection. Or due to the large SPS inflow too many tankers are required that create a logistical problem. A mobile diesel pump can be brought in to provide better lifting capability, but again there remains some limitations on ability to lift the sewage (greater than 10 metres). A submersible pump if able to be brought
in and temporarily installed within the SPS wet well is a better proposition to feed the tankers as it has no lift limitations. Better again and now the most preferred contingency action, is to have a temporary installed submersible pump having its discharge pipe connected to a purpose-built plate installed on the SPS or WPS pressure main. This bypass pump fitting plate has a camlock connector,
reflux and stop valves welded in-line and attaches to the pressure main, typically above the pressure main reflux valve. This action can provide bypass pump indefinitely with minimal ongoing monitoring, unlike using tankers. Tankers cannot be used for WPS failures, nor bypass pumps and local rezoning of the water supply network by operators can provide water to affected customers. It remains that the easiest, least expensive, and most reliable method to ensure pumping ability of the pumps at a pumping station is to perform appropriate preventative maintenance (particularly for large pumps), monitor operating performance (to detect partial chokes,
noisy or hot bearings, excessive gland seal leaks) and to effect speedy repairs to reduce the out of service time. For power failures, a suitable mobile generator can be used at the pumping station site with a quick connection box installed at most pumping station sites. It is important to consider both start-up current and running current requirements when selecting the mobile generator. From fairly humble beginnings of locating spare bypass pumps and piping at various sites in its area of operation, Sydney Water now has a much more sophisticated centralised contingency and bypass pump equipment storage at its Potts Hill Centralised Warehouse. There are various sized mobile packaged pump units, starters and generators on trailers complete with correct-sized piping and pipe joiners. It is general protocol to only use these units for a few days when needed in an Incident and then returned to the Warehouse to ensure availability. Equipment hire of this equipment is used if there is need for this type of equipment greater than a few days at the sites. There are also maintained bypass pumps, almost all of the submersible type, of various sizes and pumping duties to match the variances in Sydney Water pumping stations. These are arranged in a numbered grid pattern to facilitate easy identification, enough space for pump movement and to enable regular preventative maintenance. The aim is to ensure rapid access, easy identification, establish equipment suitability and then service reliability once installed in an Incident. As can be seen, there is much preparation to undertake a swift continuation of the pumping function at our pumping stations when faults develop to ensure continuing customer service and to protect the environment.
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