Wastewater (Sewage) Treatment Process

Lower Murray Water operates ten sewage treatment plants, and associated sewerage systems.The sewerage system is made up of the pipes, pump stations, treatment plant and equipment etc required to collect, transport, treat and dispose of the sewage. The transport system consists of small pipes that join into increasingly larger ones, eventually becoming the 'mains' entering the treatment plant. The treatment plant treats the sewage to a standard whereby it can be reused or recycled in an environmentally safe and sustainable manner, under licence to the Environment Protection Authority.

The wastewater is treated at the treatment plant by two basic processes, pre/primary treatment consisting of the separation of screenable and settleable solids and then secondary treatment whereby microorganisms break down the organic matter in the wastewater to a stage where it can then be disposed of in a environmentally sustainable and beneficial manner. There are many types of treatment plants, some consisting of mechanical operations that supply oxygen to the microorganisms to speed up the breakdown of the organic matter in the wastewater. These types of plants require a relatively small 'foot print' and are used in areas where large areas of land are not available and where environmental conditions may not suit the operation of lagoon based systems.

Lagoon based systems require relatively large areas of land. In this type of treatment the breakdown of the wastewater occurs by natural microbial processes without the need for aerators to supply oxygen mechanically.The process is therefore relatively slow compared to the mechanical types of plants alluded to above, but are more economical and easier to operate and maintain.

Lower Murray Water's ten treatment plants consist of the following:

Mildura WWTP - this is a extended aeration activated sludge plant based on the carrousel system, servicing a population of approximately 17,000. All the treated wastewater is reused on site irrigating both pasture and tree plantations.

Koorlong WWTP - this plant services approximately one third of the Mildura residential area, the township of Irymple, including major trade waste from this area, and trade waste from a fruit and vegetable processing operation in Merbein. Serves a population of approximately 11,000 as well as the trade waste. The treatment process at this plant is quite unique in that there is currently no secondary treatment, the process consisting of pre and primary treatment followed by chemically assisted sedimentation, short term storage in balancing tanks, filtration down to 80 micron particle size then direct irrigation via a dripper system on to 109Ha of tree plantations.

The treatment plant process is undergoing augmentation which will be based on teh Sequencing Batch Reactor activated sludge process, followed by UV disinfection. The class C reclaimed water from the process will be sold to a third party for reuse in the irrigation of high value horticultural crops.
The new plant is expected to be commissioned mid 2010.

Red Cliffs WWTP - the treatment at this plant is based on a high rate trickling filter followed by polishing ponds and storage in a wet weather storage. Treated wastewater from this plant is used to irrigate the fairways at the Red Cliffs Golf Club as well as the treatment plant surrounds and a small on-site tree plantation. The plant services a population of approximately 2,600.

This plant will be decommissioned and the wastewater diverted to the augmented Koorlong WWTP, mid 2010.

Merbein WWTP - is a lagoon based treatment plant, servicing a population of approximately 1,800. The treated wastewater is recycled back into the water cycle by evaporation.

Robinvale WWTP - is a lagoon based treatment plant, servicing a population of approximately 1,800. The treated wastewater is reused on-site irrigating lucerne.

Nyah West WWTP - is a lagoon based treatment plant, servicing the townships of Nyah and Nyah West with a combined population of approximately 885. The treated wastewater is recycled back into the water cycle by evaporation.

Swan Hill WWTP - is a lagoon based treatment plant, servicing a population of approximately 10,000. The treated wastewater is recycled back into the water cycle by evaporation.

Kerang WWTP - is a lagoon based treatment plant, servicing a population of approximately 4,000.The treated wastewater is recycled back into the water cycle by evaporation.

Koondrook WWTP - is a lagoon based treatment plant, servicing a population of approximately 850. The treated wastewater from this plant will be reused on-site for pasture/fodder production.

Lake Boga WWTP- is a lagoon based treatment plant, servicing a population of 700. The treated wastewater is recycled back into the water cycle by evaporation.