Sludge Accumulation Rates in Pour-Flush Latrines
- Creator: Stangl, Michael Paul
- Collection: Master's Papers
- File Type: pdf
- | Filesize: 9.8 MB
- Date Deposited: 2016-06-22
- Date Created: 1985-12-01
In 1983 the United Nations Development Programme Technology Advisory Group (UNDP/TAG) decided to sponsor a research project to investigate sludge accumulation rates in pour-flush waterseal latrines. A grant was given to the Department of Environmental Sciences and Engineering, School of Public Health, University of North Carolina at Chapel Hill, to conduct this project. The project objectives were 1) to determine accumulation rates in a number of pour-flush latrines and 2) to try to explain how these rates had been affected by choice of pit design and local socio-cultural and environmental conditions. A field study of pour-flush latrines was conducted in Patna and Singur, India. Sludge accumulation rates in thirty latrines were measured. Soil type, user population size, hydrogeological conditions and other factors thought to affect the accumulation rate were also evaluated. Specific tests were conducted to examine decomposition and drainage processes. A large variation in sludge accumulation rates was observed. The "normal" range of accumulation rates was found to be between 0.010 and 0.060 m/capita-yr. The "average" accumulation rate was found to be 0.025 m/capita-yr. A theoretical model was developed to analyze the relationship between the sludge accumulation rate and design, socio-cultural and environmental factors. The model was designed to describe liquid loading and loss from a latrine. Model evaluation indicated that the sludge accumulation rate is dependent on five factors - per capita loading rate, pit radius, amount of pit lining, soil hydraulic conductivity, and latrine age. Use of model accumulation rates led to better estimations of sludge accumulation than use of an "average" rate when the field data were examined. Based on the conclusions drawn from the data analysis, recommendations have been made concerning latrine design in terms of 1) a practical guide for determination of pit capacity requirements, and 2) suggested changes in pit design in order to reduce sludge accumulation rates.