The biosolids industry in Australia is evolving around the beneficial use of biosolids as a resource. Phosphorus rich biosolids from biological nutrient removal (BNR) facilities are highly desirable for land application. However, the accumulation of toxic heavy metals and industrial organic contaminants may render the biosolids unsuitable for land application. The presence of toxic heavy metals has been identified by Local Authorities in Australia as a major constraint limiting the beneficial use of biosolids. The potential of off-site contamination due to the migration of nutrients is also a major concern especially when applying biosolids to acidic agricultural land. Accordingly, the relevant environment protection and conservation agencies are involved in either developing or finalising guidelines to control the beneficial use of biosolids products.
Metals bioleaching is a process achieved through bio-acidification. Bio-acidification of biosolids prior to land application can be used to dissolve and remove a significant fraction of the heavy metals content of the product. However, the process also reduces the nutrients content of the resource. Bio-acidification of Loganholme (Queensland) BNR biosolids dissolved 76% of the total phosphorus and 38% of the TKN. The heavy metals solubilisation results reached 50% for Cr, 79% for Ni, 45% for Zn, 24% for Cu, 30% for Cd, and 82% for Pb.