Comparison of Aerobic and Lime Stabilization Methods for Evaluation of Sewage Sludge Reuse

摘要

The main objective of this research was the examination of effectiveness of lime dose in order to stabilization of sewage sludge and comparison of lime stabilized sludge reuse with aerobic digested sludge reuse. Lime and aerobic stabilization were carried out in two laboratory reactor with 40 L capacity. The sludge samples were taken from the return activated sludge line in four times. Lime was used at various ratios and the mixture was stabilized for 30 days. During the lime hydrated stabilization pH values were significantly increased from 7 to 12.5. Also, aerobic digester was loaded with raw sludge and mixed by sufficient amount of air for 30 days. The results indicate that the lime addition with the dose of 0.4 g Ca(OH)₂ g^-1 DS could completely inactive a high amount of fecal coliforms within 1 h and in all of the times was lower than 1000 MPN g^-1 DS after 30 days (p<0.01). But after 30 days, fecal coliforms density in aerobic digested sludge could not achieve to Class A of USEPA category. In two stabilization methods, density of viable helminths ova could not reduce to 1 ova/4 g DS and could not achieve to Class A of USEPA category. Therefore, these methods could be achieved the reduction requirement set by USEPA for class B (p<0.01) and the products could be well used as a landfill cover or a soil conditioner. Finally, our study confirmed that lime sludge stabilization has a higher hygienic effect and more cost-effective than aerobic stabilization, specially, when such sludge is used to dung and modify acid soils.