Mr. Lowcock in 1892, filtered the effluent from a chemical precipitation process at Malvern through a gravel filter at the rate of 300,000 gallons per acre per day. He also used a fine surface layer of gravel to distribute the sewage. Hence in order to maintain aerobic conditions, compressed air was forced into the lower layers of the filter through perforated pipes. A satisfactory effluent was produced, but the cost of compressing the air was too high to warrant extensive adoption of this type of filter. Furthermore, a very serious objection to this and to Waring’s filter is the difficulty of securing an even distribution of air throughout the entire filter bed.
- Buswell, A.M. The Depth Of Sewage Filters And. Illinois: Department Of Registration And Education, 1928.