Effect of solarization on pathogen reduction in sewage sludge

Key words: Solarization, Sewage sludge, Inactivation, Thermotolerant coliform, Enterococci, E. coliThe effect of solarization on bacterial inactivation in sewage sludge was studied using thermotolerant coliforms, enterococci and Escherichia coli as the indicator organisms. Solarization significantly increased the sludge temperature. The maximum temperatures were achieved at the beginning of the second week, reaching 65, 58, 55 and 50 ºC at depths of 0?10, 10?20, 20?30 and 30?40 cm, respectively. E. coli was found to be the most sensitive microorganism and was reduced to undetectable levels after 12 days at all monitored sludge depths. Thermotolerant coliforms were rapidly inactivated but were not reduced to below the detection limit. The inactivation curves of enterococci showed both shoulders and tailing, indicating a larger heat resistant fraction than with E. coli and the thermotolerant coliforms. Overall, the results suggest that the temperature regime produced by solarization was sufficient to reduce pathogens to an acceptable level, meeting the pathogen regulation limit, in two weeks.