Evaluating and optimizing Biofil digester technology for sustainable waste management

The alarming rate at which traditional septic tanks accumulate human organic waste due to rapid population growth, has led to environment pollution that poses vital health and ecological risks. The subsequently environment pollution may be attributed to lack of proper investigation of other alternative waste management initiatives that can replace traditional septic tank systems. This dissertation evaluates and optimizes the performance of Biofil digester technology for household and institutional waste management in Buea, Cameroon. Field experiments were conducted on three pilot Biofil digesters (1 m³, 2 m³, and 5 m³ capacity) treating mixed domestic wastewater under varying Hydraulic Retention Times (HRT: 5–15 days) and Organic Loading Rates (OLR: 1–3 kg VS/m³·day). Performance indicators such as Chemical Oxygen Demand (COD) removal, Total Suspended Solids (TSS), and biogas yield were monitored. More so, soil Samples were extracted from several sites and assessed using standard geotechnical. The dissertation addresses the challenges of poor sanitation and increasing organic waste by exploring biofil digesters as a sustainable, low-cost solution. To achieve these objectives, a mixed-method approach was employed. User interviews and household surveys supplemented the technical assessment by providing insight into usage patterns, community perceptions and maintenance habits. The results revealed that biofil digester efficiency is significantly influenced by soil permeability, household user load, maintenance frequency, and system design quality. The optimized HRT of 12 days at OLR of 2 kg VS/m³·day achieved a COD removal efficiency of 80 ± 7%, TSS reduction of 74%, and peak biogas yield of 0.40 m³/kg VS. Comparative analysis with traditional septic tanks revealed superior pathogen reduction (>90% E. coli removal) and lower sludge accumulation. Digesters installed in sandy or silty sand soils (A-2-4 or A-3 classifications) performed effectively with minimal surface effluent, while those located in clayey or poorly drained areas (A-6) experienced frequent failures. Design advancements, such as embedding gravel filtration layers, installing ventilation stacks, and improving systems in flood-prone zones, resulted in 30-45% advancements in infiltration and odour reduction across test sites. The findings demonstrate that Biofil digesters are scalable, cost-effective, and suitable for peri-urban African contexts. Adoption in Buea can significantly improve sanitation, reduce waste volumes, and improve energy recovery.