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17-Dec-2015

Recharging aquifers with treated wastewater cost effective for heavy industry

  

Managed aquifer recharge (MAR) with recycled treated wastewater is a cost-effective option for augmenting non potable water supplies at Kwinana’s heavy industry precinct near Perth according to a new report by the Australian Water Recycling Centre of Excellence.

The project, led by CSIRO, investigated the economic and technical feasibility, and the environmental and social benefits, of recharging aquifers with recycled water at several sites in the region. The Kwinana industrial area proved to have some advantages for evaluating MAR with recycled water. Groundwater is not used for drinking or private irrigation, and there is an opportunity to control access to infiltration ponds, which are cheaper to install and maintain than buried galleries or injection bores.

The project shows that recycled water infiltration ponds are cost effective, as the Kwinana industry’s current main source of non-potable water (shallow groundwater) becomes less secure and industrial demand continues to grow.

The analysis describes options and assumptions about the cost of alternatives, the cost of tapping into the main coastal wastewater pipeline (the Sepia Depression Ocean Outfall Line), the need and cost of pre-treating the water, and managing down-stream discharge. The cost of MAR water ranges between $0.40 and 1.94/kL, with the lower costs being for no pre-treatment and infiltration by ponds close to the Sepia Depression Ocean Outlet Line, and the higher costs being the converse. Pumping distance and the need to remove nitrogen increase costs the most. The proportion of MAR water that can be recovered by industry also affects its cost effectiveness, as some of the MAR water may be required for environmental purposes in the drying climate.

When compared to the price of purchasing recycled water or the price of scheme water, the cost of MAR water is more competitive. This finding is reinforced by results from another independent Centre-funded MAR project the economic benefit of MAR with recycled water.

Although the project focussed primarily on the MAR as a future water supply for heavy industry, it found other stakeholders would benefit from its uptake, especially if carried out in inland and northern areas where water tables respond more, and there are several inter-dunal wetlands and higher demands for irrigation water. For example, the project concluded that discharging treated wastewater to the Superficial Aquifer at the Kwinana Waste Water Treatment Plant appears to have helped save The Spectacles wetlands from drying out. It also found no long-term evidence that recycled water has contaminated the wetlands or the groundwater, which discharges into Cockburn Sound. A related project is underway to assess the relative contribution of groundwater to nitrogen levels in the Sound.

Groundwater modelling also demonstrated that modest additions of water through MAR can reverse coastal zone salt water intrusion by almost a kilometre. The project also found residential properties near wetlands which are influenced by groundwater levels have higher property values. Depending on the number and closeness of the houses, and whether the wetland has recreational and visual appeal, the impact of property prices can be in the order of several hundreds of millions of dollars.

The report demonstrates that managed aquifer recharge, using suitably treated recycled water, has the potential to replace and enhance natural groundwater levels in regions near Perth. In the future, cost-effective underground storage and reuse of recycled water in rural and regional Australia will help provide certainty in water availability and increase industry confidence to invest.

The main project partners with CSIRO were: Western Australia’s Department of Water, Kwinana Industries Council, Water Corporation, Western Trade Coast, and the WA Department of Health.
A copy of the report can be downloaded here