Figure 5-11. Diatomite filter and related parts.
b. Filtration. When precoating is complete, the effluent control valve (see
figure 5-11, circle C) is switched from the RECIRCULATE to the FILTER position and
filtered water begins to flow to the storage tanks. A portion of the filtered water is
diverted to the diatomite slurry compartment in the upper left side of the chemical slurry
feeder (see figures. 5-6, 5-7). A base charge of 7 pounds of diatomite (1/2 Ib per gal) is
added to the diatomite slurry compartment (see para 5-6d) and the rate of feed variator
(see figure 5-9) on the left side of the feeder is set as prescribed in the TM. When there
is no demand for filtered water (or there is insufficient water in the wet well tank), but it
is desired to maintain the coating on the filter.