On-farm wastewater treatment for irrigation using biochar from local agro-residues in Obuasi, Ghana

Abstract

This study evaluated the effectiveness of a decentralized, on-farm wastewater treatment system using locally generated rice husk biochar for safe agricultural irrigation reuse in Diewuoso-Obuasi, Ghana. The system, a two-stage downflow filtration system, treated raw municipal wastewater over 10 days. Results showed significant removal of turbidity (66.92%), total dissolved solids (38.19%), and salinity (22.03%), meeting FAO irrigation limits. However, electrical conductivity increased (26.58%) due to ash-mineral leaching. Microbial analysis indicated substantial log-scale removal efficiencies for E. coli (90.42%), fecal coliforms (98.39%), and total coliforms (99.99%), but final effluent concentrations exceeded WHO and Ghana EPA thresholds for unrestricted irrigation. The study concludes that while the rice husk biochar filter is an efficient pre-treatment component, it requires secondary post-treatment disinfection to eliminate public health risks, offering a scalable model for circular resource recovery in rural farming communities.