Co-composting of organic waste and sewage sludge- a waste management option for Chirano Gold Mines Limited, Western Region

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The study investigated the ratios of organic solid wastes and dewatered sewage sludge that were appropriate for producing a good compost as a management option for reducing waste at Chirano Gold Mines Ltd. Chirano Gold Mines Ltd produces on a daily bases an average of 1300 kg of solid wastes (of which about 65% is compostable). And sewage sludge is produced on a daily bases from a Sewage Treatment Plant (STP) on site. Grab sample of organic solid waste was collected from the dump site. Dewatered Sewage sludge was also collected from the sewage treatment plant (STP). Sanitary pads and other objects were removed from it. The organic wastes were shredded and mixed uniformly using a cutlass and a shovel. Sample was taken to laboratory for physicochemical and biological parameters as well as heavy metals. Based on the results, the feedstock (organic solid waste and dewatered sewage sludge) were mixed according to volume-to-volume ratio and piled in a shape of a cone. These were 1:0; 1:1; 2:1; 3:1 and 0:1 (organic solid waste/ dewatered sewage sludge). Temperature of each pile was measured daily over the entire composting period. At the end of the study, the concentrations of all the heavy metals analyzed were within normal international standards. All the piles produced at the end of the composting period were sanitized for use except the pile with 0:1 ratio (organic solid waste/ dewatered sewage sludge) which could not attain the right thermophilic temperature for the destruction of pathogens present in the composting material due lack of readily degradable carbon and poor aeration. The highest mean temperature was attained by pile 3:1 (organic solid waste/ dewatered sewage sludge) with a temperature of 63oC. Statistically, there were significant differences in all the treatments (compost piles) in the final compost for Nitrogen, Potassium and Phosphorus which are very important in compost. Piles A (1:0), B (1:1), C (2:1), D (3:1) and E (0:1) ended with (1.61±0.07) %, (2.59±0.13) %, (2.03±0.24) %, (2.94±0.45) % and (3.08±0.16) % respectively for Nitrogen.
A thesis submitted to the Department of Theoretical and Applied Biology in partial fulfillment of the requirement for the award of the Master of Science degree in Environmental Science,