Waste treatment and energy production from small-scale wastewater digesters

Three tubular anaerobic digestion (AD) systems were installed in Haiti to treat black water (toilet-based wastewater), including a three cell 36m³ clinic digester (CD), a two cell 2m³ hotel digester (HD), and a three-cell 3m³ farm digester (FD) for worker use. During digestion, total coliforms were reduced by 99.1%, E. coli by 98.5%, and chemical oxygen demand (COD) by 93.6%. Nutrients in the effluent averaged 99.4mg/L NH₄⁺ and 10.6mg/L PO₄^2-, producing an effective organic fertilizer. Average biogas production in CD was 108L/d, with 65.4% CH₄. Survey participants (n=573) were willing to pay $0.10-0.30 per use for sanitation facilities. Seventy-two percent of the rural population surveyed in Cange, Haiti lacked access to improved sanitation due to financial constraints. The economic analysis calculated an investment cost for a shared toilet AD systems of $16-$47 (USD) per person based on daily use at design capacity.