Assessment of the suitability of sludge from Dompoase faecal sludge treatment plant as a building material

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May 2016
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Faecal sludge collected from the anaerobic pond at Dompoase Faecal Sludge Treatment Plant (DFSTP) in Kumasi was treated with lime for stabilization. The sludge was characterized by determining its physical, chemical and microbial parameters according to Standard Methods for the Examination of Water and Wastewater. Results showed that 76-79 % and 57-69 % level of stabilization were achieved for BOD and COD respectively. 40% removal of total volatile solids was recorded and up to 75 % removal efficiency of helminth eggs was observed. Optimum stabilization of sludge was achieved at pH 12.3 with a lime dose of 500 g/kg sludge for 120 minutes contact time. Chemical composition analysis of major and minor oxides was carried out on the lime-stabilized sludge and results indicated that the lime stabilized sludge consisted of chemical composition essentially contained in limestone. The lime-stabilized sludge was investigated for its suitability as brick material. The use of the lime-stabilized sludge as brick material provided a viable solution for alleviating disposal problems, closing the sanitation loop, improving economic design of buildings, pollution control and conservation of natural resources. Four different mixing proportions of sludge at 10 %, 20 %, 30 % and 40 % of total weight of sludge-clay and cement-sludge-clay were studied and used as clay supplement in brick making. The hand-moulded bricks were subjected to firing in a heat controlled furnace at high temperatures of 850 oC, 900 oC, 950 oC and 1000 oC for 10 h. Compressive strength, water absorption and shrinkage of the manufactured sludge-clay brick were determined and evaluated according to British Standard Specifications for Clay Bricks (BS 3921, 2003). Performance evaluation of the burnt bricks as construction materials was also carried out according to standards. The results revealed that between 10 % – 20 % of the lime-stabilized sludge addition could be utilized to make good quality brick for various engineering applications in building and construction. It was also observed that firing temperature and sludge percentage were the main factors that determine the quality of bricks. Increasing sludge content resulted in decreased compressive strength and increased water absorption. The results also demonstrated that increasing the sludge content improved workability of sludge-clay mix.
A Thesis Submitted to the Department of Civil Engineering Kwame Nkrumah University of Science and Technology in Partial Fulfillment of the Requirements for Degree of Master of Science Water Supply and Environmental Sanitation