Bob Humphries

From Waste to Water Quality

Bob Humphries
(with Tom Long, David Allen and Katrina Walton)
Water Corporation of Western Australia, WA

Abstract:
Achieving sustainable outcomes is mostly a matter of good design. The Water Corporation beneficially recycles most of the 100,000 wet tonnes of stabilised biosolids it produces into compost, and on to agricultural land and plantation forests – but at great cost. We wanted to reduce the costs of biosolids management while creating environmental, social and economic benefits for the wider community.

The Ellen Brook project has developed Lime-amended BioClay (LaBC) – a product based on the lime-amended biosolids from the Subiaco treatment plant. LaBC overcomes many of the problems arising from development on acid grey sands, including low water holding capacity, non-wetting soils, acidity, severe nutrient leaching and economically and environmentally marginal agriculture.

The project has been designed to progressively convert about 100 km2 of the Ellen Brook catchment to perennial vegetation, using farm improvement plans secured by common law contract and provision of LaBC to partner farmers as the main mechanisms to achieve change.

Modelling suggests that this landuse change will reduce nitrogen and phosphorus nutrient loads to Ellen Brook by about 20%-50% over 10 years, helping to restore catchment ecosystem services, while improving farm incomes and climate-hardening agriculture. The Corporation will benefit from lower costs, and from the creation of carbon and nutrient offsets.

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