Vermicomposting of Sewage Sludge Produced at Camp SIC in Cité-Verte (Yaounde-Cameroon) as an Agricultural Amendment

The aim of this project is to reuse the sewage sludge produced at the Camp SIC Cité-Verte wastewater treatment plant (WWTP) as an agricultural amendment using the vermicomposting process. The methodological approach involved characterising this sludge, producing three types of vermicompost (E1, E2 and E3), characterising them and testing their effectiveness on maize. The WWTP produces a large quantity of sludge, 364.3 kg per day. The sludge is rich in organic matter, mineral elements (Total Carbon: 53.01%, Total Nitrogen: 8%, Total Phosphorus: 2500 mg/kg and Potassium: 2723 mg/kg) and pathogens (faecal streptococci = 128 CFU/100 ml and faecal coliforms= 166 CFU/100 ml). Analysis of the vermicompost obtained after sixty-five days showed a significant increase in the nutrients carbon (E3 :59%), potassium (E1: 2710 mg/kg, S2: 3125 mg/kg, E3: 2985 mg/kg), phosphorus (E1 : 2536 mg/kg, E2: 2836 mg/kg, E3: 3101 mg/kg); then a decrease compared to the initial substrate for carbon (E1: 44.02%, E2: 48%), nitrogen (E1: 2.06%, E2: 2.84%, E3: 3.05%) and a considerable decrease in pathogens in samples E1 and E2, unlike E3 where they are completely absent. The effectiveness of vermicompost showed germination rates of 65% and better results for maize growth and development.