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

Abstract

A study was performed to evaluate heavy metals removal from sewage sludge using lime. The processes of stabilization using alkaline chemicals operating on a simple principle of raising pH to 12 or higher, with sufficient mixing and suitable contact time to ensure that immobilization can reduce heavy metals. A 0.157 m3 tank was designed to treat Al-Rustemeyia wastewater treatment plant sludge. Characteristics of raw sludge were examined through two parameters: pH and heavy metal analysis. Different lime doses of (0- 25) g CaO/100 g sludge were mixed manually with raw sludge in a rotating drum. The samples were analyzed two hours after mixing. pH and heavy metals results were compared with EPA and National Iraqi Standard (NIS). Results showed as lime was added, the concentration of heavy metals decreases the higher the dose, the less heavy metals concentrations in the sludge. Although the concentration of heavy metals in the sludge was among the determinants according to the US Environmental Protection Agency, the results showed that 750 g of lime per 3 kg of sludge had reduced the concentration of heavy metals zinc from (662.934) mg/kg sludge to (452.998) mg/kg sludge, copper from (113.101) mg/kg sludge to (64.981) mg/kg sludge, lead from (91.215) mg/kg sludge to (53.307) mg/kg sludge, nickel from 107.257 mg/kg sludge to (50.478) mg/kg sludge, molybdenum from (13.743) mg/kg sludge to (8.724) mg/kg sludge). At the same time, the dose of 450 g lime per 3 kg of sludge had reduced the concentration of chromium from (110.577) mg/kg sludge to (0) mg/kg sludge.

Performance Evaluation of Al-Khadraa' Wastewater Treatment Plant, Mosul-Iraq

“…The range of BOD 5 /COD ratio of effluent wastewater was (0.35 -0.5), It is a high ratio compared with the ratio of (0.1-0.3) table (3) for treated wastewater. The variation between BOD 5 and COD concentrations for effluent wastewater refer to the presence of non-biodegradable organic compounds and this refers to the fact that the effluent needs additional treatment [13]. Mixed liquor suspended solids (MLSS) concentrations was in the range of (1116-2536) mg/l versus (3000-6000) mg/l as designing value for extended aeration process [8], This is attributable to the scarcity of recycling the sludge from the settling basin to the aeration tank, the ratio was 67.92% compared with the design value of 100% and even more during optimal operation for extended aeration system.…”