Watermark > Spring 2002 > Features: Dewaterability of Thermophilically Digested Biosolids
Features
- Drinking Water Protection: Where are we at?—Rick Corbett, BCWWA President
- Fire Hydrants: Life Safety and Life Threatening?—Doug Dolan, Cross Connection Control Chair
- Dewaterability of Thermophilically Digested Biosolids—Jim Zhou, Don Mavinic, and Harlan Kelly
- Full Cost Pricing, Accounting for Water and Sewage Services Contained in New Safe Water Legislation Introduced in Ontario
- New Arsenic Limit of 10 Parts Per Billion Now Law in USA
- Protection of Drinking Water ‘to increase’—Scott Simpson
- Tenth Anniversary of The Rice Cake Race
Dewaterability of Thermophilically Digested Biosolids
By Jim Zhou, Don Mavinic, and Harlan Kelly
Thermophilic digestion is a hightemperature sludge stabilisation process that produces Class A biosolids. Full-scale experience has revealed that thermophilically digested biosolids often exhibit poor dewaterability and require high amounts of polymers for conditioning. This research work investigated whether or not operating conditions such as feed sludge composition, digestion temperature, and sludge retention time can be optimised for improved dewaterability of thermophilically digested biosolids. This work also searched for factors that have the most significant impact on dewatering properties, and explored mechanisms of solidliquid separation in relation to dewatering. Laboratory-scale, aerobic bioreactors of thermophilic and mesophilic digestion were operated and various digestion temperatures (40-70 degrees C) were tested. This study indicated that digestion temperature, rather than duration, appeared to be a more important factor affecting dewaterability. Current efforts are directed towards identifying more effective means of improving dewaterability of thermophilic biosolids. It is envisioned that valuable information will be obtained from this research to assist in planning and operating more cost-effective, thermophilic sludge digestion as part of secondary waste treatment processes.
