Sunday, 30 June 2013

Water Recycling Facility in Yarra Park

Water is a precious resource, yet we have traditionally used it once and disposed of it through our sewage treatment plants. There are many activities that do not require drinking quality water and could use recycled water (e.g. irrigation and toilet flushing). By using recycled water that is treated for its intended use, less water from the potable (drinking) system is needed. As part of an integrated water management solution, water recycling is an important way to help preserve our drinking water supplies.

Sewer mining provides a secure rainfall independent supply of water that is fit for a wide range of uses. Sewer mining process normally involves the removal and treatment of sewage from sewer mains before the sewage reaches the treatment plant. The sewage is treated to produce high quality recycled water for use nearby. High reticulation costs, normally associated with recycled water schemes, are avoided as the recycled water is produced at the point of use.

The Melbourne Cricket Club (MCC) with the financial assistance from the State Government of Victoria recently completed the works at Yarra Park as part of a comprehensive Draft Yarra Park Masterplan, designed to greatly improve the parkland.

The project involved renewal and rejuvenation of Yarra Park through implementation of the Masterplan, based on the original design themes within Yarra Park. As part of the plan, an underground water recycling plant has been installed to secure essential non-potable water for use in Yarra Park, the MCG and Punt Road Oval. 

The $24 million project, funded by the MCC ($18 million) and the Victorian Government ($6 million), treats sewage from the local sewerage network to Class A recycled water standards. This water will ensure the park receives sufficient water, regardless of the drought or rainfall situation.

The purpose of the Water Recycling Facility (WRF) is to provide 140 to 180 million litres of Class A water per year, primarily as irrigation water, for Municipal use in the Yarra Park, Richmond Football Club and the MCG grounds (unrestricted access). The water is also being used in a third pipe recycling scheme throughout the MCG grounds toilets, amenities and for wash down (cleaning and maintenance). For comparison purposes, the Class A water produced by the WRF at Yarra Park will replace the volume of potable water sufficient to supply approximately 1150 households in Melbourne for every year of operation.

The Water Recycling Facility (WRF)

The WRF is located underground in the Yarra Park (adjacent to the Gate 2 members’ entrance at the MCG), with the only visible above ground structures being two access structures and three custom designed air vents. 

The underground plant has a trafficable roof, and architecturally designed entry and egress with a box lift and chemical unloading area. 

The MCG WRF takes sewage from City West Water’s (CWW) Wellington Parade South trunk route, where it is diverted and pumped via a dedicated underground supply pipe to the Yarra Park WRF facility. Associated infrastructure on the inlet side includes the sewer connection, diversion structure/chamber, a 12-metre by 4.8-metre (diameter) pumping station and a rising main. Other infrastructure includes the connections into the MCG and to Punt Road storage as well as a pump station and sludge return gravity line downstream of the sewerage take-off. 

The WRF has the capacity to produce 0.6 ML net of Class A water per day to the third pipe system, after allowances for backwash water and any other plant requirements have been met. Wastewater flows and solids removed at the screening stage are combined, macerated and pumped back to CWW sewer. 

The WRF design is strongly influenced by the requirements set down by the VIC Department of Health and the Australian Guidelines for Water Recycling in producing Class A water. The design of WRF in Yarra Park incorporates a combination of pre-validated equipment and best practices to reduce energy and minimise greenhouse gases whilst addressing those issues identified in the Environmental Risk Assessment.

The Treatment Process

The sewage diverted from the CWW sewer is pumped to the WRF where the following key stages of treatment occur:
  1. Primary screening and grit removal
  2. Intermittent Anoxic/Aerobic Activated Sludge Process with submerged MBR
  3. Ultra Filtration Membranes
  4. Disinfection of product water using UV and chlorination
As part of the process the odorous air collected at source from the inlet works and other treatment processes within the WRF are fed through a chemical scrubber and carbon unit prior to discharge into atmosphere via three stacks.

The treatment process selection has been based on achieving desired water quality, energy consumption and water use. The final process choice was based on the triple bottom line assessment and the above options were chosen which met best practice energy consumption and carbon management.

Performance to date 

Since its commissioning and validation in 2012 the WRF at Yarra park has been producing the class A recycled water of consistent quality at the rate of 200 kl to 600 kl per day. The actual daily recycled water production varied, dependant on demands (e.g. match days) and the sewage flows available in the Wellington Parade South CWW sewer. The lowest sewage inflows were experienced during Christmas / New Year period 12/13, which is typical for the residential catchment.