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

ReportNo WSAA 76

April 1994

SYNOPSIS

Thisreport details investigations into a potential solution to two environmentalchallenges. One challenge is the establishment of sound methods of re-use fordewatered sewage sludge, a waste by-product of sewage treatment works. Theother challenge is to find improved methods for the rehabilitation of landdisturbed by opencut mining.

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

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

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

Thetrial investigated and found no significant problems arising from the use ofsewage sludge in respect of heavy metals and organic pollutants.

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

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