Performance of Modified Recirculating Sand Filters Using Bottom Ash and Boiler Slag Media

摘要

The research was conducted to evaluate the performance of a novel recirculating sand filter RSF2 treating septic tank effluent. The RSF2 consisted of a column containing filter media underlain by gravel. The gravel served both as a storage and treatment zone. Effluent was removed from a layer which lay between the filter media and the gravel zone. Four different RSF2 columns containing: (1) screened boiler slag or Black Beauty (BB); (2) screened Fort Martin Bottom Ash (FMBA); (3) unscreened Fort Martin Bottom Ash (UFMBA); (4) screened Mitchell Bottom ash (MBA). Loading rates based on forward flow (FFO of 5 to 10 FPD/sq ft and recirculation ratios (RR) of 3:1 and 5:1 were studied. It was found that all columns could be successfully operated at a FF of 5 GPD/sq ft and a RR of 5:1 for long periods without ponding. It was concluded that bottom ashes screened to WV specifications could be operated at a loading rate of 6 GPD/sq ft. However, unscreened bottom Ash filters should be restricted to 5 GPD/sq ft.