home Wastewater Wastewater Treatment Plants Busselton

Located in the south-west of Western Australia, Busselton is one of the state’s fastest growing urban areas. The town is located on flat land between the shores of southern Geographe Bay and the Vasse-Wonnerup Estuary system.

New urban subdivisions are required to be serviced by a sewerage system and, in the last eight years thousands of unsewered properties have been connected through the Water Corporation’s Infill Sewerage Program.

The Busselton Wastewater Treatment Plant is located on Queen Elizabeth Avenue approximately
2 km south of the Busselton By-pass and approximately 7 km from the Busselton town centre.
The plant is licensed by the Department of Environment.

History

The development of the current Busselton Wastewater Treatment Plant, and the difficulty of securing environmentally sustainable disposal solutions in the Busselton area, lead to the construction of an advanced technology treatment plant using a process which includes filtration, disinfection, a constructed wetland and a $1 million nutrient-reducing program in the southern Geographe Bay catchment area, known as the Environmental Improvement Initiative (EII).

Treatment Process

The Busselton Wastewater Treatment Plant produces tertiary-quality treated wastewater through an Intermittently Decanted Extended Aeration (IDEA) process. Treated wastewater is additionally filtered and disinfected.

The treatment plant has influent and screening works, two concrete, rectangular treatment tanks, filters, UV disinfection, on site biosolids drying beds, wetlands and a re-use lagoon and pumping facility.

The key components of the treatment process are:

Screening: Raw wastewater is screened using a mechanical, continuous conveyor. Screenings are removed for burial at a local landfill site and the wastewater moves to one of the two treatment tanks.

Aeration: wastewater is vigorously aerated for about two hours in the treatment tank. During this phase nitrogen and phosphorus are taken up by the rapid increase in micro-biological activity.

Settling: When aeration ceases the wastewater is held for a further two hours. During this time the micro-organisms rapidly deplete the available dissolved oxygen so that the wastewater environment becomes anoxic (no available oxygen). The anoxic wastewater causes significant die-off of micro-organisms and subsequent conversion of nitrates to Nitrogen, which escapes to the atmosphere. Phosphates are largely bound into the blanket of biosolids that settle to the bottom of the tank. During each treatment cycle a small proportion of biosolids are removed as Waste Activated Sludge and pumped to the Biosolids Drying Beds. A further small proportion of biosolids are mixed with the raw wastewater entering the tank (Return Activated Sludge) to help provide consistency of micro-organism levels.

Decanting: During the latter part of the settling phase the clear, treated wastewater on the top of the treatment tank is removed by a decanting weir.

Filtration: Treated wastewater from the decanter is passed through a set of pressure filters to remove the low levels of remaining suspended solids.

Disinfection: The treated wastewater is passed through a bank of three UV disinfection units. There are less than 10 micro-organisms per 100 ml of treated wastewater at the end of this process. To put this in context consider that the same volume of raw wastewater may contain 500 million micro-organisms, water in a rural drain may contain up to 4,000 and seawater at a local beach may range from 20 – 150.