Impact of metals bioleaching on the nutrient value of biological nutrient removal biosolids

The biosolids industry in Australia is evolving around the beneficial use o f biosolids as a resource, Phosphorus rich biosolids from biological nutrie nt removal (BNR) facilities are highly desirable for land application. Howe ver, the accumulation of toxic heavy metals and industrial organic contamin ants may render the biosolids unsuitable for land application. The presence of toxic heavy metals has been identified by Local Authorities in Australi a as a major constraint limiting the beneficial use of biosolids. The poten tial of off-site contamination due to the migration of nutrients is also a major concern especially when applying biosolids to acidic agricultural lan d. Accordingly, the relevant environment protection and conservation agenci es are involved in either developing or finalising guidelines to control th e beneficial use of biosolids products. Metals bioleaching is a process achieved through bio-acidification. Bio-aci dification of biosolids prior to land application can be used to dissolve a nd 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 r esults reached 50% for Cr, 79% for Ni, 45% for Zn, 24% for Cu, 30% for Cd, and 82% for Pb, (C) 1999 IAWQ Published by Elsevier Science Ltd. All rights reserved.