Sustainability Report 2006/07Recycling west of Melbourne
Recycling schemes
Recycled water from the Western Treatment Plant was supplied to the Werribee Technology Precinct from June 2007. A new pipeline, commissioned by City West Water, connected the precinct with our Werribee Irrigation District transfer main. At full development this project has the potential to use about 1000 million litres a year for industrial and commercial processes and for irrigation of open spaces.
Melbourne Water’s Hoppers Crossing pumping station will be the largest customer in the Werribee Technology Precinct, using 100 million litres of recycled water a year for pump lubrication and motor cooling. Work has begun on updating the pumping station infrastructure, with commissioning and operation expected later in 2007/08.
More customers from the Werribee Tourist Precinct signed up with Southern Rural Water to take recycled water from the Western Treatment Plant.
An environment improvement plan was developed to enable Werribee Park and the Werribee Open Range Zoo to join existing customers from the precinct, the National Equestrian Centre and Werribee Park Golf Club. The new customers used the recycled water for irrigation of gardens and open spaces. The Werribee Tourist Precinct was supplied with 220 million litres of recycled water during 2006/07.
Sports fields and other outdoor areas at MacKillop College in Werribee used 13 million litres of recycled water this year. The water was supplied via City West Water, and replaced the use of groundwater and drinking water. The recycling scheme began after City West Water constructed a connection to our Werribee Irrigation District recycled water supply main.
During the year, a public tender was held for projects that could use an additional 35 million litres of recycled water from the Western Treatment Plant during winter. However, lower inflows to the plant due to water conservation measures meant that the water was not available and the tender had to be cancelled.
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Supporting agriculture
The Werribee Irrigation District recycled water scheme continues to support local agriculture by providing an alternative water supply.
The full year volume of 10,946 million litres was more than three times the amount delivered last year and significantly exceeded the 2006/07 expectations of 3000 million litres. As of 30 June 2007, 173 recycled water customers had signed up as part of the scheme.
Recycled water provided the main water source in the district for many growers who faced severe restrictions on their river water and groundwater entitlements.
The drought has increased demand for recycled water as an alternative water source, creating demand management challenges.
Managing demand
To improve our management of competing demands and limited availability of recycled water, a hierarchy was developed to prioritise allocation of recycled water to customers.
In order of priority, recycled water from the Western Treatment Plant will be available for:
- Conservation (biodiversity) flows at Western Treatment Plant and in-plant use
- Committed supply contracts
- New uses to substitute for drinking quality water
- Onsite irrigation (Werribee Agricultural Group) for agricultural operations
- Offsite ‘new uses’ (no substitution)
To manage the additional demand from offsite customers we have also upgraded the capacity of our Class A recycled water pumping system at the Western Treatment Plant.
Since January 2007, some 88 million litres of Class A recycled water was supplied to businesses and organisations from a standpipe at the Western Treatment Plant, primarily as a drought relief measure. Under a process managed by City West Water, recycled water is transported by tankers and used for open space watering, and dust suppression for road construction.
Algal blooms in lagoons
A long spell of dry, warm weather this year coupled with water restrictions and conservation strategies resulted in low inflows to the Western Treatment Plant and increased the risk of blue-green algal blooms in the plant’s lagoons.
In March 2007, a bloom developed in the 25 West lagoon requiring the lagoon to be withdrawn from recycled water supply for three months.
Supply to recycled water customers was maintained with recycled water from the 55 East lagoon. This lagoon developed elevated blue-green algae levels during April 2007 but with intensive monitoring and customer and stakeholder consultation, recycled water supply continued within agreed safety limits.
Werribee Irrigation District lettuce crop incident
In September and October 2006, stunted growth was observed on several lettuce crops in the Werribee Irrigation District. This area is supplied with Werribee River water and Class A recycled water from the Western Treatment Plant. A Department of Primary Industries investigation reported that no single causal agent could be identified.
The problem affected about 5% of the market garden area. Crops planted subsequently in the same location have grown well and have been continually harvested.
The department’s investigation report recommended Southern Rural Water and Melbourne Water consider a range of management actions that are being advanced, including: an increased water quality monitoring regime; establishing a land on-farm management committee to improve farm sustainability and productivity through better management of soils and water; and, undertaking further risk assessment work on potential contaminants that may be introduced into the Western Treatment Plant.
Managing salinity
Reducing salt in recycled water from the Western Treatment Plant is important for its sustainable use. We continued to work with the retail water businesses to investigate options to reduce and manage salt in recycled water from the Western Treatment Plant.
Discussions are continuing with City West Water regarding salt reduction needs for current and future recycled water customers.
Melbourne Water reviewed all options for building a reverse osmosis salt reduction plant at Werribee but the cost of building and operating such a plant meant that water costs would be higher than the growers and other customers were prepared to pay.
To provide recycled water at a cost that growers would be prepared to pay would require a substantial subsidy. Southern Rural Water and the Department of Sustainability and Environment, in consultation with Melbourne Water, will continue to talk with growers about other options to reduce the salinity levels in the irrigation water.
We are also working with Southern Rural Water and growers to manage salt onsite by reviewing irrigation management procedures, updating river water ‘shandy’ rules and through information sharing.
Consultation is also continuing with key industrial customers to understand and explore ways to manage salt in trade waste, which can help reduce salt in recycled water.
Improving recycled water management
During the year, the range of water quality parameters in the recycled water monitoring program at the Western Treatment Plant was expanded to include chemical contaminants such as synthetic organic compounds. These are not traditionally monitored in recycled water supplies.
The extensive monitoring program forms part of a year-long quantitative risk assessment investigation being managed by Melbourne Water, which will improve our understanding of potential contaminants and risks associated with recycled water from a human and environmental health perspective.
Melbourne Water developed and introduced a quality management framework for the supply of Class A recycled water from the Western Treatment Plant to meet emerging requirements of customers and government authorities.
The HACCP (Hazard Analysis and Critical Control Point) system identifies hazards to recycled water quality and the critical points at which these hazards must be controlled.
The system, which covers all aspects of the sewage and recycled water treatment process, provides assurance by transparently assessing, monitoring and verifying control points and validating limits. This is supported by reporting, review and continuous improvement. A similar system was introduced at the Eastern Treatment Plant in 2004/05.
We continued working with the National Health and Medical Research Council to develop the Australian Guidelines for Water Recycling. We are represented on the working group for two of the three new guideline modules: stormwater and augmentation of drinking water supplies (indirect and direct potable recycling) and aquifer storage and recovery.