A financial comparison of a parallel sewer based (SB)
system with
activated sludge, and a fecal sludge management (FSM) system with
onsite septic tanks, collection and transport (C&T) trucks, and
drying beds was conducted. The annualized capital for the SB ($42.66
capita–1 year–1) was ten times
higher than the FSM ($4.05 capita–1 year–1), the annual operating cost for the SB ($11.98 capita–1 year–1) was 1.5 times higher than the FSM ($7.58
capita–1 year–1), and the combined
capital and operating for the SB ($54.64 capita–1 year–1) was five times higher than FSM ($11.63
capita–1 year–1). In Dakar, costs
for SB are almost entirely borne by the sanitation utility, with only
6% of the annualized cost borne by users of the system. In addition
to costing less overall, FSM operates with a different business model,
with costs spread among households, private companies, and the utility.
Hence, SB was 40 times more expensive to implement for the utility
than FSM. However, the majority of FSM costs are borne at the household
level and are inequitable. The results of the study illustrate that
in low-income countries, vast improvements in sanitation can be affordable
when employing FSM, whereas SB systems are prohibitively expensive.
In urban Sub-Saharan Africa, the collection and transport of faecal sludge (FS) typically ends up with FS directly dumped into the urban environment, as safe treatment and disposal options are too expensive or non-existent. Resource recovery from FS treatment, such as dried FS as an industrial fuel, could provide a financial incentive to increase access to FS management services. In Dakar, Senegal, enhanced drying to reduce the footprint of drying beds for fuel production was evaluated.Greenhouses did not increase drying rates over uncovered beds, however, daily mixing of FS on the surface of the beds resulted in a 6 day reduction to achieve 90% total solids (TS). FS was dried to 90%
This research tested the viability of using faecal sludge (FS) as solid fuel -an end use that could unlock an environmentally and financially beneficial replacement for disposal-oriented FS management, while replacing fossil energy. FS samples were collected from pit latrines, septic tanks, drying beds and stabilization ponds in three cities, Kumasi, Dakar and Kampala. For each sample, the average calorific value, solids and water content, and their variation with source and age were determined. The average calorific value of untreated FS across the three cities was 17.3 MJ/kg total solids (TS), which compares well with other biomass fuels. The age of FS did not affect its calorific value, nor did the reduction in chemical oxygen demand (COD) that occurred while it was in drying beds. The TS content of FS depended on its source but ranged from 1 to 6% for sludge from septic tanks and pit latrines, respectively. Harnessing net energy from FS requires partial drying. The results indicate that sufficient drying occurs within two weeks in open-air drying beds, or in a matter of days with simple drying bed innovations.
The National Utility for Water and Sanitation in Burkina Faso (ONEA) has recognized the difficulty in providing sewered sanitation to the entire urban population and has opted for a strategy involving Lessons learned are transferable nationally and internationally.
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