Performance evaluation of fecal sludge treatment plants in Uganda

Abstract

With the inevitably increasing urbanization of various cities, there has come an increasing amount of fecal sludge collected in all cities globally. Such an incidence has consequentially led to the increasing need to not only manage but also treat all fecal sludge following cognizance of the effects of poorly treated fecal sludge on public and environmental health. Fecal sludge treatment plants have been and still are being constructed, with engineers coming up with innovative designs for purposes of treating sludge, even in Uganda. However, whereas the plant construction process is much prioritized, there have been gaps in performance of the plants registered, globally. Those gaps are indicated by the persistence of coliforms, and solids in plant effluent, as reported in various countries. The purpose of this study was to evaluate the performance of fecal sludge treatment plants in Uganda with focus on effluent discharge, and what determines it. The assessment of plant design characteristics revealed that all of them had septage/ sludge reception points, coarse screening screens for grit and solid separation from sludge, all of which were manually raked. The majority of the plants had no sedimentation tanks. However, for those which had sedimentation tanks, they were of the settling-thickening type. The majority of the plants did not have anaerobic ponds, but for those that had anaerobic ponds, all had anaerobic baffled reactors. All plants had aerobic ponds that were all facultative. All plants had dewatering beds. All the plants had pathogen removal ponds, with the majority being constructed wetlands. Four fifths of the plants sampled did not have parts/processes for further drying/pathogen reduction. The level of performance of the fecal sludge treatment plants in Uganda is 40%. Optimal fecal sludge treatment performance was twice as likely at plants where the administrative staffs were permanent employees (aPR = 2.757 [1.515 - 6.114], p =0.028). In conclusion, Fecal Sludge Treatment Plants in the Uganda are generally designed with septage/ sludge reception points; they have coarse screening screens for grit and solid separation from sludge, all of which were manually raked. However, the majority of the plants have no sedimentation tanks, yet and neither do they have anaerobic ponds, yet they all have aerobic ponds of all which were facultative in design. All plants have pathogen removal ponds, but without processes for further drying/pathogen reduction. Fecal Sludge Treatment Plants in Uganda sub optimally perform, only 4 in 10 of them discharge effluent with more than 80% of its bio and physicoc-hemical characteristics compliant with national standards in terms of quantity. Staff characteristics are the only ones that are associated with FSTP performance.