Sludge treatment facility for pit latrine and septic tank sludge

Technology The technology is based on treatment using vertical flow artificial wetlands followed by irrigation of the effluent on agricultural land. The sludge derived from pit latrines and septic tanks is dried and decomposed in three wetlands of about 20 m3 capacity each and, after some years of accumulation and six months of resting, the resulting humus is removed from the wetland and used on the agricultural land that is irrigated in the 2nd stage.

Capacity The facility is the first of its kind in the region, so that no previous experiences are available to assess the capacity of the facility. As a first very rough assessment, we are anticipating about 40 m3 of sludge every two days.

Investment Costs Total costs of construction have amounted to less than 9 mil. Ugandan Shillings (UGX). One acre of land in the clayish area has cost 1 mil. UGX.

Operation The facility is operated by a local resident who has been trained accordingly. Disposal fees amount to 10 000.- UGX per load, which are utilized for the maintenance of the site by the operator. The operator is also allowed to grow crops for his personal benefit as directed by the town council.

Benefits •proper disposal of latrine and septic tank sludge •use of water, nutrients and waste product on agricultural land

Environmental Threats The facility has been constructed using in situ clay; the threat to ground and surface waters is thus minimal assuming the operation is performed correctly. There is some odor as sludge is being offloaded. This should, however, not be a nuisance because of the isolated location of the facility. The odor fades very quickly as soon as the sludge is offloaded into the facility.

Problems encountered There has been a significant problem with erosion of the clay dams making up the basins. It has been possible to contain this erosion on the outside of the basins by some kind of terracing and by planting drought resistant grass (as used locally in lawns). On the inside, grass has been planted such that the exposed surfaces will be covered. Towards the end of the dry season, fire has repeatedly been set to the plot with varying degree of damage. In the worst incidence, the basins have burnt up completely, destroying the PVC piping that was exposed above ground. The piping has subsequently been repaired. On another occasion, the basins were only marginally affected, but some of the wooden poles of the fence have burnt down, and many of the hedge plants have died. The above ground PVC piping has repeatedly been stolen or vandalized by locals. The local LC1 chairman has been informed accordingly, but the facility is still awaiting repair of the piping. In one incidence, two of the wetlands have accidentally been ‘digged’ by maintenance personnel. The first operator has shown little commitment to perform the maintenance work like slashing grass or growing crops. The new operator, who is also operating a cesspool emptying truck, has shown greater interest in the facility. Goats have intruded into the plot and eaten the plants under cultivation.