Proceedings

Quicklime is established as an agent to affect stabilisation of raw sewage sludge cake, providing the pathogen kill required to meet the conventional treatment standards as defined by the new Sludge (Use in Agriculture) Regulations. The exothermal reaction that occurs is not critical to the pathogen kill, rather the rise in pH and associated release of ammonia would appear to give an adequate pathogen kill alone. This paper examines whether calcium hydroxide can be successfully used as a substitute for Quicklime. Preliminary work and an investigation of the minimum dose requirement has been completed. Pathogen kill, well above that required for HACCP, and long-term stability was achieved at high dose rates. Applications at lower doses, analogous to those used for Quicklime, gave very promising results and the remaining work will verify these findings and investigate further the mechanisms involved in alkaline stabilisation and its flexibility as a treatment at full-scale.

KEY WORDS Alkaline Stabilisation, Sludge, HACCP, Biosolids, calcium hydroxide paste, Escherichia coli, Pathogen Kill, Agricultural Recycling, Ammonia.