What’s behind the tap?

There are 7 key steps involved in the

service cycle for GVW customers. Step 6 - Wastewater Treatment GVW Owns and managers 26 Wastewater Management Facilities (WMF’s). The Treatment process varies at each facility, however the majority use lagoon treatment followed by land based disposal. During the wastewater treatment process a mixture of domestic sewage and industrial effluent is broken down naturally through the action of and other micro-organisms. Optimum conditions

are provided at the WMF to encourage the most efficient bacterial action.

Pre Treatment Includes screening of raw wastewater to remove solids and foreign objects as wastewater comes into the WMF. Magnesium Hydroxide is then added to ensure the acidity level or pH of the raw wastewater is greater than 7. This enables the bacteria and micro-organisms to work at their maximum efficiency.

Biological Treatment After pre-treatment, biological (secondary) treatment begins. It relies on the raw wastewater coming into direct contact with anaerobic and aerobic bacteria living in lagoons. Anaerobic ‘oxygen hating’ bacteria live where there is little or no oxygen present. Aerobic ‘oxygen loving’ bacteria live where there is oxygen present. The bacteria use the wastewater as a food source, converting it to simpler solids, gases and water. A variety of lagoon treatments are used at GVW.

High Rate Anaerobic Lagoon (HRAL) A HRAL lagoon is a zero oxygen environment. To create this environment, a large synthetic rubber cover is placed over the lagoon, making it ideal for anaerobic bacteria to survive. The bacteria break down the raw wastewater into biosolids, water, and other gases. The cover traps the gases and odours that are produced inside. At the Shepparton HRAL the cover is the size of the MCG!

Lagoons Treatments Throughout the biological treatment process the wastewater passes through various lagoons which are characterised by the amount of oxygen present in each.  Anaerobic Lagoons are quite deep with little oxygen present, enabling anaerobic bacteria to survive;  Aerated Lagoons have large aerators or stirrers to mix the water around, allowing oxygen to circulate;  Facultative Lagoons have a combination of both anaerobic and aerobic bacteria present; and  Aerobic and Maturation Lagoons are shallower and provide the right conditions for aerobic bacteria to survive.

Further Information gvwater.vic.gov.au 1800 454 500

What’s behind the tap?

There are 7 key steps involved in the

service cycle for GVW customers. Step 6 - Wastewater Treatment GVW Owns and managers 26 Wastewater Management Facilities (WMF’s). The Treatment process varies at each facility, however the majority use lagoon treatment followed by land based disposal. Mechanical Facilities GVW also operates some mechanical WMFs where trickling filters are used to break down the raw wastewater. In the trickling filters, bacteria grow on a bed of media and the wastewater passes over its surface. Like the lagoons, the bacteria use the wastewater as food.

By-Products During the wastewater treatment process, by-products are produced that include biogas and biosolids. As bacteria break down raw wastewater, they produce smelly odours and gases called biogas. At HRALs the biogas trapped under the cover can be used to generate renewable energy, which is exported to the electricity grid. Local businesses can then source locally generated GreenPower and reduce their use of coal-fired electricity. Biosolids are the solid waste that the bacteria produce when they breakdown the wastewater. These solids settle to the bottom of the lagoon to form a sludge deposit. These solids slowly build up over time and the lagoons need to be cleaned out once every 25 years. The biosolids are left to dry out for a period of time and can then be used as fertiliser or soil conditioner.

Winter Storages After the wastewater is treated in a variety of lagoons at the WMF the recycled water is often stored in a winter storage lagoon until it can be reused in the warmer months to irrigate. This treated wastewater can also be further treated and then released back to the local waterway.

Wastewater Treatment Processes at GVW High Rate Anaerobic Lagoon Anaerobic Lagoon Facultative Lagoons Winter Storage Aerobic/Maturation Lagoons Trickling Filter Northern Central South West South East Cobram Girgarre Avenel Alexandra Nathalia Kyabram Broadford Bonnie Doon Numurkah Mooroopna Euroa Eildon Strathmerton Murchison Kilmore Mansfield Rushworth Nagambie Marysville Shepparton Seymour Yea Stanhope Tatura Further Information gvwater.vic.gov.au 1800 454 500