Urban drainage - the alternative approach

The paper presents an alternative drainage philosophy and strategy which mimics nature’s way by slowing down (attenuating) the movement of urban runoff. This approach results in cost-effective, affordable and sustainable drainage schemes. The alternative strategy can be described as one of prevention rather than cure by effecting controls closer to source rather than the traditional approach which results in the transfer of problems downstream, compounding the problem, resulting in its cumulation and, the need for large scale centralised control. The alternative strategy is set in context relating to the evolution of current practice and the implications of fragmented institutional responsibilities. Issues relating to socio-economic factors and appropriate development are discussed and the alternative strategy is shown to incorporate tenets of a holistic approach. The paper concludes by recommending the adoption of the alternative strategy for the provision of urban drainage infrastructure in developing countries. It suggests that this paradigm shift should help developing countries to leap frog the developmental stages in their provision of effective urban drainage infrastructure for their rapidly burgeoning urban centres

Upgrading and uprating of water treatment plants

The paper describes how the contact flocculation-filtra­tion and adsorption system (CFFA) can be used in a staged approach to cost-effectively upgrade existing Water Sup­ply Treatment Works. A case study is presented for modifications to the existing Water Treatment Works at Tokokoe and Befikrom in Ghana. The resulting upgraded plant is designed to be capable of handling a three-fold increase in throughput within the area occupied by the existing works units. The CFFA system has been evaluated and developed from pilot through to full-scale units. Data from operational monitoring of the system modules show consistent per­formance at high throughputs up to three times conven­tional loadings, producing potable water meeting WHO and EC guideline values