FEASIBILITY OF ANAEROBIC SEWAGE-TREATMENT IN SANITATION STRATEGIES IN DEVELOPING-COUNTRIES

Sanitation strategies in the growing cities may aim at protection of shallow groundwater, public health protection, removal of oxygen consuming substances and removal of nutrients. It is shown that anaerobic treatment of municipal waste water in UASB type reactors has become a feasible treatment option in those strategies. This study investigates the merits of the technology for on-site management of black and grey waste water, and for off-site centralised treatment At on-site scale where effluent is leached into the ground, anaerobic reactors offer no advantage over cheaper leaching pits. At larger centralised scale, anaerobic reactors have performed well and reliably over longer periods. Post-treatment may be required, but the total treatment is financially advantageous in warm climates; if land cost is low long-retention ponds may be more attractive, however. In addition, the technology's characteristics open the possibility to develop ''intermediate'' solutions at township-level based on low-cost (shallow and small-bore) sewerage and reactors for communities of typically 100 up to 1000 households. Sludge, produced in lower quantity, dries easily. Pathogen removal is limited, and biogas production only a minor asset.