Pro-poor sewerage: solids modelling for design optimisation Available to Purchase

More than 2·8 billion people still live without adequate sanitation. ‘Simplified sewerage’ is one possible solution, offering the possibility of an appropriate scale for urban sanitation. Adoption of such systems requires the range of engineering and advocacy tools erstwhile only available in developed countries. The application of small-bore solid transport system models is wholly appropriate for simplified sewerage, but modifications are required to account for the shallow gradients and the likely accumulation of solids due to low water usage. The importance of local water flow depth on drain self-cleansing where large accumulated solids are present has been identified, and the solid movement threshold has been quantified for a range of expected gross accumulated solids. These modifications, together with improved solid deposition predictions, have contributed to the development of a robust model suitable for application to simplified sewerage systems in order to improve efficiency and optimise design.