An Approach to the Design of Trickling Filters

Trickling filters are accepted as an efficient means of secondary sewage treatment for wastes amenable to biological treatment. Among the reasons reducing their usefulness are (a) space requirements, (b) seasonal variations in efficiency, (c) clogging and pooling, (d) limitations on hydraulic and organic loading, and (e) limitations on the strength of applied sewage. Many investigators have worked on improvements in filter design in an effort to overcome one or more of the objectionable characteristics of filters. The treatment field has profited from these investigations. Improvements have been made in media, circulation, hydraulic flow rates, and methods of applying sewage to the filter. An entirely new approach to trickling filter design, which has been investigated in the laboratory for a year, will be presented herein. The results of these investigations show that it was possible, at laboratory scale and under controlled conditions, to treat settled domestic sewage efficiently at hydraulic rates as high as those used for rapid sand filtration of water.