INVESTIGATING FILTER PERFORMANCE AS A FUNCTION OF THE RATIO OF FILTERSIZE TO MEDIA SIZE

The size of the filters used in a water treatment pilot study has a bi g impact on the cost of the pilot facility itself. It has been shown t hat errors can be avoided by maintaining an adequate ratio between fil ter column diameter and media diameter (D/d). The purpose of this stud y was to investigate the effect of this same scaleup parameter on the filtration process itself. Five pilot-filter columns were operated in parallel with a full-scale filter. In these tests, (D/d) ranged from 2 6:1 for the smallest column to 6,000:1 for the full-scale filter. No s ignificant differences were observed in the mean rate of head loss bui ldup, the effluent turbidity, or the effluent particle count for any o f the filters, although the variance in the estimate of rate of head b uildup was much greater for the smallest filter. A D/d ratio of 50 or greater is recommended for most pilot-filter operations.