Enhanced anaerobic digestion as a sanitation and energy recovery technology : a paper presented at the second conference on developments in faecal s...

In this research, the potential of using an enhanced anaerobic digestion (AD) process as a sanitation and energy recovery technology for communities that lack access to basic sanitation is evaluated. For the enhanced AD system to generate a reliable supply of biogas, so that it can be adopted and self-sustained by the community, the use of algal biomass as a supplementary feedstock to the system is evaluated. In addition, the effects of operational parameters on waste mineralization and biogas production is investigated. The results show that the enhanced AD system has the potential to be developed into an effective waste treatment technology, and it has produced high energy yields and digested waste low in faecal bacteria and high in nutrients. Reductions of 42 to 51% in volatile solids (VS) and 29 to 45% in chemical oxygen demand (COD) were achieved at 35°C. On average, total coliform (TC) and faecal coliform (FC) concentrations of 7.6x105 and 1.4x104 CFU per gram of total solids (TS), respectively, were measured in the digested waste. Thus, the residual meets the EPA requirements for pathogen reduction (FC < 2x106 CFU/g TS) and vector attraction reduction (> 38% reduction in VS) for land application. The total nitrogen and phosphorus content of the residual was determined to be in the range of 9-17% as N and 3-7% as P (7-16% as P2O5), respectively. The biogas yields varied in the range of 470-570 L per kg of VS digested. [authors abstract]