Stabilization of Al-Rustamiya Waste Water Treatment Plant Sludge Using Lime

Abstract

Sewage sludge treatment and discarding is a costly and environmentally sensitive problem. Sludge production will continue to increase as new sewage treatment plants are built and environmental quality standards are becoming stricter. The processes of stabilization using alkaline chemicals operating on a simple principle of raising pH to 12 or higher, with efficient mixing time and a suitable contact time ensured that microorganisms are either inactivated or destroyed. A 0.157 m3 rotating tank was designed to treat Al-Rustemeyia wastewater treatment plant’s sludge. Characteristics of raw sludge were examined through two parameters: pH, and fecal coliform analysis. Different lime doses of (0- 25) g CaO/100 g sludge were introduced to raw sludge. Samples were mixed manually in a rotating tank. Samples were analyzed 2 hours and 24 hours after mixing by rotation. pH and fecal coliform results were compared with EPA and national Iraqi guidelines. Results showed that 120 g of quicklime per 3 kg of sludge is acceptable to meet Class B criteria and 450 g per 3 kg sludge to meet Class A criteria according to EPA’s 40 CFR Part 503.The results indicated that lime treatment to stabilize sludge could be an appropriate solution provided that soil conditions do not deteriorate.