Can numerical computer modelling aid innovation, efficiency and cost reduction in sanitation provision?

Numerical computer modelling techniques have proven to be an invaluable tool in the assessment of water supply and drainage for buildings in a northern, industrialised context, allowing new devices and techniques to be developed leading to improvements in efficiency and reductions in costs. These methods can also be applied to sanitation systems in less developed countries so that similar benefits in both efficiency and cost reductions can be achieved. Analysis of a simplified sewerage installation using the building drainage numerical model ‘DRAINET’ confirms that this sanitation option is best suited to densely populated areas, while it is also shown that its implementation may be expanded to less densely populated areas by a reduction in pipe diameter from 100 mm to 75 mm set at a shallow slope characteristic of simplified sewerage installations.

Numerical computer models have been used to good effect in the developed world to: • • • • highlight inefficiencies, innovate new technologies, reduce costs of the installed drainage network, reduce the complexity of building drainage system networks, and • influence legislation and code authorities on policy matters. The simple network design of simplified sewerage systems has much in common with building drainage systems and it seems only right that a synergy between the two disciplines should bear fruit. The example simulations in this paper confirm that simplified sewerage is best suited to high density housing areas however, by reducing the network pipe diameter it could be possible to expand the number of [1] M. Gormley, Air pressure transient generation as a result of falling solids in building drainage stacks: definition, mechanisms and modelling, Build. Services Eng. Res. Technol., 28(1) 2007 55–70. [2] J.A. Swaffield, D.P. Campbell and M. Gormley, Pressure transient control Part 1: criteria for transient analysis and control, Build. Services Eng. Res. Technol., 26(2) (2005) 99–114. [3] D. Satterwaite, Appropriate Sanitation Technologies for Addressing Deficiencies in Provision in Low- and Middle-income Nations ‘Human Development Report’, Occasional Paper UNDP, 2006. [4] D.D. Mara, Modern engineering interventions to reduce the transmission of diseases caused by inadequate domestic water supplies and sanitation in developing countries, Build. Services Eng. Res. Technol., 27(2) (2006) 75–83. [5] D.D. Mara, Low Cost Sewerage, Promotion through Innovation, WHO Publication, pp. 249–262. [6] http://duncanmarasanitation.blogspot.com/2008/04/ whys-it-called-condominial-sewerage.html. [7] J.A. McDougall, Mathematical modelling of solid transport in defective building drainage systems, Ph.D. Thesis, Heriot-Watt University, UK, 1995. [8] J.A. Swaffield and J.A. McDougall, Simulation of building drainage system operation under water conservation design criteria, Build. Services Eng. Res. Technol., 21(1) (2000) 45–55. [9] J.A. Swaffield and L.S. Galowin, The Engineered Design of Building Drainage Systems, Ashgate Publishing Limited, England, 1992. [10] J.A. McDougall and J.A. Swaffield, The influence of water conservation on drain sizing for building drainage systems, Build. Services Eng. Res. Technol., 24(4) (2003) 229–243. [11] D.D. Mara and A.S.P. Guimaraes, Simplified sewerage: potential applicability in industrialized countries, Urban Water, (1999) 257–259.