Sludge stabilization by composting: a Jordanian case study

Municipal sludge handling is a major problem facing wastewater treatment plants due to the high costs of treatment and disposal. This issue is of special importance in Jordan because of the critical economic situation as well as the lack of financial support for such nonprofit projects. This study investigates the possibility of solving this problem by testing a method of sludge stabilization that requires minimum initial and operating costs. The method tested here is sludge stabilization by composting which is an attempt to transform sludge into a safe, nuisance free, humus like product that can be applied safely to land and can become a source of income that would recover the costs of processing. Two types of composting systems were tested in this study, aerated static pile and windrow. Results obtained indicate that composting of dried sludge was not possible due to the extremely low moisture content; which was overcome by sludge seeding and mixing with amendment and bulking agents. This resulted in efficient stabilization and reduction of the amount of organic matter in the final compost. The experimental results obtained also indicate that both systems (aerated static pile and windrow) are efficient. The organic content of the sludge was reduced in the windrow system by 46% and in the aerated static pile by 66%. In addition, the total volatile solids had decreased in the windrow and the aerated pile by 26 and 73%, respectively. The heavy metals content of the final compost was examined and found to comply with the international standards.