Dewatered anaerobically-stabilized primary sewage sludge composting: Metalleachability and uptake by natural clinoptilolite

Environmental problems associated with sewage sludge disposal have prompted strict legislative actions over the past years. At the same time, the upgr ading and expansion of wastewater treatment plants have greatly increased t he volume of sludge generated. The major limitation of land application of sewage sludge compost is the potential high heavy metal content in relation to the metal content of the original sludge. Composting of sewage sludge w ith natural zeolite (Clinoptilolite) can enhance its quality and suitabilit y for agricultural use. Clinoptilolite has the ability to uptake heavy meta ls in satisfactory levels. Finally, in order to estimate the metal leach ab ility of the final product of compost, the Generalized Acid Neutralization Capacity (GANC) procedure was used and was found that by increasing the lea chate pH, the heavy metal concentration decreases.