Information On Melbourne Sewage Systems Part 3
Sewage passes through two major ‘drop structures’ via spillways from these two mains to enter the Brooklyn Trunk Sewer, which is at a lower level. This movement of sewage results in the emission of high levels of hydrogen sulphide gas. If untreated, the gas can cause corrosion and odour problems. To counteract this, the gas is extracted from the sewer and pumped through odour control plants where it is treated and then released to the atmosphere through a vent stack.
Prior to the commissioning of the Western Trunk Sewer in 1993, sewage was transferred via an open channel that stretched from Newport to Werribee, which had been operational since 1897. The main outfall sewer was replaced because it had reached the end of its service life, there was a need to increase the hydraulic capacity of the sewer for future flows, and there was a need to reduce odour. The Sewer is nearly 23 kilometres long and extends from the Brooklyn Pumping Station to the Western Treatment Plant.
Hoppers Crossing Pumping Station. The Hoppers Crossing Pumping Station, located on six hectares about 20 kilometres west of Melbourne, is one of the largest sewage pumping stations in Australia. The Station was commissioned in 1992 and is the size of a 22-storey building, although only a quarter of it is visible above ground. Hoppers Crossing Pumping Station lifts unscreened sewage from the Western Trunk Sewer and transfers it to the Western Treatment Plant for treatment. The plant is fitted with eight pumps. Each pump stands 4.5 metres high, is four metres across, weighs 45 tonnes and is capable of pumping in excess of 5000 litres a second. The eight pumps are driven by eight 3150 kW variable speed motors that allow the pump to vary the speed depending on the volume of incoming sewage flow. Four motors have systems that enable them to feed power that would otherwise be wasted as heat emission back into the internal power supply system.
