STABILIZATION OF DEWATERED SEWAGE SLUDGE BY AEROBIC COMPOSTING METHOD: USING SAWDUST AS BULKING AGENTS

• Main Authors: A PARVARESH, H MOVAHEDIAN, E BAZR AFSHAN
• Format: Article
• Language: English
• Published: Wolters Kluwer Medknow Publications 2002-12-01
• Series: Journal of Research in Medical Sciences
• Subjects: Sludge, Stabilization, Sewage sludge, Aerobic composting, Isfahan, Environmental Health
• Online Access: http://journals.mui.ac.ir/jrms/article/view/3296

Introduction. Sludge production from municipal wastewater treatment plants should have quality standards before disposal in to the environment. Environmental specialists classified sewage sludge as a hazardous waste because of high organic compounds and pathogenic microorganisms. They belive that sewage should be stabilized before disposal and so composting of sewage sludge is an effective and economical method to stabilize. Sewage sludge compost could be used to improve soil structure and enrich the soil with nutrients.
 Methods. To evaluate the optimum conditions of aerobic compost, the mixture of dewatered sewage sludge from Isfahan municipal waste water treatment plant and sawdust as bulking agent were used. Pilot scale study were performed in Isfahan municipal waste water treatment plant. To perform this research project, the dewatered sewage sludge with humidity between 78 to 82 percent were mixed with sawdust. Turning over method of the piles with one week interval were applied to aerate the mixture. Temperature of the piles were monitored at different depths daily. Other parameters such as N, G, organic matters and pH were determined weekly. Total and fecal coli form, and salmonella were determined at the beginning and end of the composting process, also heavy metals were measured at the same time.
 Results. The results of this study showed that after days, temperature of the mixture reached up to 55 G, and were stabled for 15 days. Humidity, organic matter, organic carbon and GIN ratio of the mixture decreased over the period of the study, due to increasing the temperature. Also organic matter and humidity mainly decreased in thermofilic phase. The number of total and fecal coliform and also salmonella decreased to A class standards of US.EPA at the end of the operation.
 Discussion. The results of the study also showed that, this type of composting method is reliable, and simple to schedule, with high flexibility and low odor production. Organic compounds and pathogenic microorganisms reduced and EPA standards were reached during this project.