A review of sludge production in South Africa municipal wastewater treatment plants, analysis of handling cost and potential minimization methods

Abstract

The government of South Africa through the department of water and sanitation has installed numerous activated sludge systems in most of the municipal wastewater treatment plants (MWWTPs) to ensure adequate sanitation. However, secondary sludge generation and handling is a major challenge of the AS process. This work reviews the sludge production potential in selected regions in South Africa including Midvaal, Emfuleni and Lesedi municipalities. Further, the sludge handling cost and potential methods of sludge minimization are discussed. This study found that the selected MWWTPs discharge effluent volume of between 3 and 65 ML/day with average COD of about 350 mg/L leading to sludge production of between 5 and 23 tons/day with an estimated handling cost of €57,000 to €320,000 per year. Some of the technologies reviewed for sludge minimization to cut down plant operation cost include chemical oxidation using ozone and potassium ferrate (K2FeO4), application of oxic-settling-anaerobic (OSA) process, anaerobic/anoxic/oxic (AAO) combined with K2FeO4 oxidation side stream reactor (SSR), SANI® technology and use of anaerobic side stream reactor (ASSR) in the conventional activated sludge (AS) line.