Contextual investigation of factors affecting sludge accumulation rates in lined pit latrines within Kampala slum areas, Uganda

Ahamada Zziwa,Florence Kyazze,Noble Banadda,Joshua Wanyama,Julia B Kigozi,Peter Tumutegyereize,Yvonne Lugali,Isa Kabenge,Robert Kambugu

doi:10.4314/wsa.v42i3.15

Abstract

Pit latrines in slums areas of Uganda fill up faster than might be expected from some estimates owing to inappropriate use and failure to consider critical factors affecting sludge accumulation rates at the planning, design and construction stages. This study sought to investigate factors affecting filling rates of lined pit latrines in slum areas of Kampala with the goal of contributing to accurate planning, design, construction, emptying and overall maintenance. Fifty-five pit latrines were selected from the five divisions of Kampala city using stratified random sampling. Data collected included: number of users, frequency of emptying, years taken since last emptying, type of non-faecal materials deposited, cross-sectional dimensions of the pit, rate of sludge degradation and geo-physical factors of pit location. Methods used were: field surveys, questionnaires and key informant interviews plus on-site depth measurement. Mass loss tests to investigate the rate of sludge degradation were carried out in the laboratory at moisture content levels similar to those in pit latrines. Sludge accumulation rates were calculated using volume of sludge in the pit, number of users and time taken since last emptying. Statistical analyses included correlation and one-way ANOVA. Results revealed that number of users and type of material deposited in the pit latrines, especially non-faecal matter, had a significant (p < 0.05) effect on sludge accumulation rate. Public pit latrines with a higher number of users had lower sludge accumulation rates and this was attributed to greater degradation taking place and greater restriction on entry of non-faecal matter. The rate of sludge degradation was higher at 90–100% than 80–90% moisture content, due to better degradation conditions. Tighter restrictions on non-faecal material deposition into pit latrines are recommended to reduce filling rates of pit latrines in slum areas. Keywords : sludge accumulation rates, slum areas, faecal matter, degradation, lined pit latrines

Highlights

IntroductionUganda’s capital city, hosts the largest part of the country’s urban population (Kessides, 2005) with 87% of the population having access to pit latrines (UBOS, 2012)
Pit latrine coverage in Uganda is estimated at 85.5% (UBOS, 2010)
Ethics clearance was obtained from the Uganda National Council for Science and Technology (UNCST) and permission was obtained from Kampala Capital City Authority (KCCA) and the local leaders in each of these divisions before the study was carried out

Summary

Introduction

Uganda’s capital city, hosts the largest part of the country’s urban population (Kessides, 2005) with 87% of the population having access to pit latrines (UBOS, 2012). The majority (46%) of pit latrines are in a fair condition but about 35% are in a poor state, either filled up or almost filled up (Zziwa et al, 2014). There can be more than one pit latrine stance per pit latrine site and this is always the case in rental and school pit latrines for multiple users. This accounts for the poor sanitation situation in the slum areas of Kampala (Fig. 1)

Methods

Results

Conclusion