TM 5-814-3/AFM 88-11, Volume III
TRICKLING FILTER PLANTS
12-1. General considerations.
Trickling filter plants have been justified by their low initial cost, low operating and maintenance costs, and
relative simplicity of operation. Although the effluent from trickling filter plants of earlier design was of
poorer quality than that from activated sludge plants, the performance of trickling filters designed more
recently is comparable to that of activated sludge plants. Both processes offer certain advantages, with
trickling filters providing good performance with minimal operator care and few, if any, energy requirements.
(See Howland, 1957.)
12-2. Design basis and criteria.
The designer will provide preliminary and primary treatment ahead of the filters, and circular or rectangular
settling tanks with mechanical sludge removal equipment following the filters. Design criteria for settling
tanks are in paragraph 12-4 below. Chapter 4 of EPA*s process design manual, Upgrading Existing
Wastewater Treatment Plants, provides design theory for trickling filters, as do published reports EPA-R-
2-73-199. Table 12-1 gives design data for the trickling filter process. The designer normally will use the
average of the hydraulic or organic loading ranges presented in table 12-1 for the design of each filter class
unless special conditions warrant the use of values other than the average.