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 36 m(3) clinic digester (CD), a two cell 2 m(3) hotel digester (HD), and a three-cell 3 m3 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 99.4 mg/L NH4+ and 10.6 mg/L PO42-, producing an effective organic fertilizer. Average biogas production in CD was 108 L/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.