World Bank assisted National Agricultural Research Project (NARP) - University of Port Harcourt
Abstract
Environmental specialists classified sewage sludge as a hazardous waste
because of high organic compounds and pathogenic microorganisms.
Therefore sewage sludge should be stabilized before disposal.
Composting is an effective and economical method to stabilize sewage
sludge. The object of this study is determining the optimum conditions
of co- composting of dewatered sewage sludge and sawdust. Pilot scale
study was performed in Isfahan municipal wastewater treatment plant. To
perform this study, the dewatered sewage sludge with humidity between
78-82 percent was mixed with sawdust. Turning over did once a week for
aeration. Temperature was monitored at different depths daily. Other
parameters such as N, C, organic matters, pH, heavy metals, total and
fecal Coliform and Salmonella were determined three times a week. The
results of this study showed that after about 15th days, temperature of
the mixture reached up to 55\ub0C, and was stabled for fifteen days.
Humidity, organic matter, organic carbon and C/N ratio of the mixture
decreased during of the study, due to increasing the temperature. Also
organic matter and humidity mainly decreased in thermophilic phase. The
number of total and fecal coliforms and also Salmonella decreased to A
class standards of U.S. EPA at the end of the operation. The result
indicated that co-composting of sewage sludge with sawdust is a
reliable and simple method to schedule, with high flexibility and low
odor production. Organic compounds and pathogenic microorganisms
reduced and EPA standards were met during this method. @ JASEM