Least Cost Sand Filter Design for Iron Removal

In the optimization of a single-media filter, it is necessary to be able to predict all combinations of filter design variables which will provide equivalent performance and determine their first cost and operating costs. An empirical filter performance prediction model is used in developing a computer program for predicting sets of equivalent sand filter designs and their first and operating costs. The effects on the cost of the filter system of pertinent variables such as sand size, sand depth, terminal head available, flow rate, and run length are evaluated. For all sand sizes studied (0.6 mm to 1.3 mm), the optimum design filtration rate (4.0 gpm per sq ft-5.5 gpm per sq ft), run length (32 hr-42 hr), and terminal head loss (8 ft-11 ft) all closely approximate values used in current practice. The optimization techniques developed to predict both the filter designs providing equivalent performance and their costs have potential application in both the design of new filtration plants and the prediction of the operating conditions, such as run length and effluent quality, of existing sand filtration plants.