Adequacy of vacuum and non-vacuum technologies for emptying faecal sludge from informal settlements of Kampala City

Abstract

Over 90% of the population in Kampala Informal settlements is served by onsite sanitation facilities (septic tanks and pit latrines). These fill up fast, leaving emptying as the most viable option for their sustained reuse. This study fills the gap for the limited information about different emptying technologies suitable for informal settlements and limitations they face while carrying out operations. The study compared adequacy of vacuum and non-vacuum emptying technologies used in informal settlements of Kampala. 111 questionnaires (78 for vacuum and 33 for non-vacuum) were administered to obtain data about faecal sludge (FS) source and time estimates, while an additional 37 samples were used in characterising emptied FS. The results showed that FS emptied by vacuum trucks was 43.6% from lined pits, of which 28.2% are from informal settlements. 56.4% is emptied from septic tanks by vacuum technology, where informal settlements contribute 12.8%. FS emptied by non-vacuum technologies was 9.1% from lined pit latrines, 30.3% septic tanks and 60.6% unlined pit latrines (42.4% from informal settlements). Vacuum trucks of capacity 3.6 m3 were the mostly used in informal settlements, while large vacuum trucks (7.2–14 m3) exclusively operated outside informal settlements. The most critical event is the time spent during containment emptying, where non-vacuum can take up to 3 h and less than an hour for vacuum technologies. Such longer emptying times by non-vacuum technologies can be reduced through enforcing minimum standards of containment facilities and preventing dumping of solid wastes in pits. In addition, there is a need to sanction non-compliant operators in observation of PPEs and SOPs in order to improve their safety.