ENHANCING THE DEWATERABILITY AND AMENABILITY OF SLUDGE FOR SUBSEQUENT STABILIZATION PROCESSES BY USING ORGANIC WASTE SOLIDS AS CONDITIONERS

Abstract

Dual-material conditioning of sludge was evaluated using a chemical conditioner (either alum or ferric chloride), followed by a physical conditioner (either wood chips or wheat dregs). The combined effects of the conditioners on the dewaterability of the sludge with vacuum filtration and the amenability of the resulting sludge cake for subsequent stabilization processes were investigated. Results showed that the specific resistance of the conditioned sludge was effectively reduced when the dose of wood chips or wheat dregs was increased in each dual-material combination. From the results of analysis of solids in the cake, the filtered sludge cake with either wood chips or wheat dregs conditioning in higher dosage resulted in lower moisture and higher volatile combustible solids content. Accordingly, sludge conditioning with these two materials substantially increased the heating value of the dewatered sludge. In addition, wood chips are the most widely used bulking agent, and wheat dregs could be suitable to act as amendments in sludge composting. These results indicate that these two organic waste solids could replace a significant portion of the chemicals now used for sludge conditioning to improve the dewaterability of sludge and the amenability of the resulting sludge cake for incineration and composting processes.

Keywords:

• Sludge dewatering
• Conditioning
• Skeleton builders
• Wood chips
• Wheat dregs
• Heating value

ACKNOWLEDGMENTS

We would like to express our appreciation to the National Science Council of the Republic of China (Project Number: NSC-84-2211-E-041-002) for funding support for this project, and to Dr. James P. Kaetz, Associate Professor, Department of English, Auburn University and Editor of National Forum, for help in editing this paper.