Utilisation of Sewage Sludge for Minesite Rehabilitation: Rix’s Creek Mine Trial

This report was produced for the Urban Water Research Association of Australia, a now discontinued research program.

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Report no. UWRAA 76

April 1994

Synopsis

This report details investigations into a potential solution to two environmental challenges. One challenge is the establishment of sound methods of re-use for dewatered sewage sludge, a waste by-product of sewage treatment works. The other challenge is to find improved methods for the rehabilitation of land disturbed by open cut mining.

Sewage sludge is extensively used overseas in minesite rehabilitation. Its use in Australia has been hindered by a lack of information on the effects of sewage sludge on Australian soils and environment under differing climatic conditions. A field-work trial was conducted at Rix’s Creek Mine, near Singleton, NSW. The trial used 24 different treatments involving sewage sludge, topsoil and inorganic fertiliser over a total area of 1.44 hectares.

The trial established that sewage sludge could be successfully incorporated into normal minesite rehabilitation practice. The trial also established that all 18treatments that utilised sewage sludge gave superior dry biomass yields to that of non-sludge treatments.

A study of the economics of the Rix’s Creek Mine trial found that, as a result of high transport costs, it was not financially feasible to use sewage sludge as a fertiliser replacement. Sewage sludge proved to be economic if used as a topsoil substitute in circumstances of topsoil being unavailable on a minesite. A potential weed-control benefit may derive from the use of sewage sludge, as it does not contain the weed seeds often present in topsoil.

The trial investigated and found no significant problems arising from the use of sewage sludge in respect of heavy metals and organic pollutants.

Based on these results it is recommended that the use of sewage sludge in minesite rehabilitation be encouraged, especially by the formulation of a simplified andless restrictive regulatory framework.

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