Numerical experiments into optimisation of VDR filters

A comprehensive model of the filtration process, that includes the effect of deposition on,head loss and removal efficiency, has been combined with a hydraulic model,of a Variable Declining Rate (VDR) plant. This model has been used to study the behaviour of VDR filters. These results have been compared to the operational rules deduced from an earlier simplified analysis of the hydraulics of VDR filter plants. The new model has confirmed the validity of these rules, in particular that the filter run is longest if simultaneously the head loss and the ratio of maximum to average flow rates are equal to,the highest acceptable values.