ABSTRACT
An application of lime in the composting process could highly efficient for the reduction in bioavailability of heavy metals in composting process can be attributed the formation insoluble carbonate salts. Natural zeolite has been widely used to reduce the bioavailability of heavy metals due to its sorption and exchangeable properties towards the heavy metals in the composting of sewage sludge. The addition of the clinoptilolite rock to sewage sludge might change chemical speciation of heavy metals in composts and decrease their mobility and bioavailability. Addition of lime to the composting mixture raised the pH of the mixture and subsequently decreased the bioavailability and eco-toxicity of heavy metals. The addition of lime was very effective for the reduction of the bioavailability of water-soluble and DTPA-extractable metals during the composting of water hyacinth, sawdust, and cattle manure.
