(a) If the coagulated water appears cloudy, it is an indication that more
ferric chloride should be added.
(b) If the coagulated water above the slurry blanket has a reddish
color, it indicates too much ferric chloride.
(c) If the water looks clear, but large particles are rising and the blanket
looks Iight and fluffy, the Iimestone slurry feed rate should be increased.
(d) If a sample of slurry from the bottom of the sludge concentrator
tank contains visible quantities of Iimestone, excessive limestone application is
indicated and the Iimestone slurry rate should be decreased.
b. Operating Controls
(1) Effluent launder. The effluent launder of the erdlator assembly (see
figure 5-10, circle I) must be level at all times. If it is level, water from the erdlator tank
wiII flow into it uniformly around the entire circumference. If the launder is not level, it
may be leveled by turning one or more of the effluent launders adjustable support rods
(see figure 5-10, circle N).
(2) Sight glass. A sight glass is located on the raw water influent Iine (see
figure 5-6) just prior to the point where the water enters the erdlator. The presence of
excessive air bubbles in the sight glass indicates air in the suction Iine. The suction Iine
should be checked for leaks from the strainer (which may not be sufficiently submerged)
to the pump. Foreign matter may also be observed through the sight glass.
(3) Preaeration. The aspirator aeration manifold above the erdlator tank
provides aeration of the raw water entering the influent launder. This manifold is
equipped with two gate valves (see figure 5-10, circle 0) and a pressure gage (see
figure 5-10, circle P). The normal operating pressure with both valves open is 5-7 psi.
If the pressure rises above this reading, it indicates that the aspirators are clogged or
the valves are closed. Cleaning the aspirators or opening the valves, as appropriate,
may remedy this. If numerous air bubbles are observed on the surface of the water in
the erdlator tank, it indicates that the water is supersaturated with dissolved gases. This
may be remedied by partially closing one or both valves, thus increasing the pressure
and obtaining better aeration.
(4) Slurry blanket rotation. The slurry blanket in the erdlator must be kept
rotating. Banking of the slurry blanket on the outer perimeter of the tank indicates too
much rotation. Insufficient rotation is indicated by lack of movement of the slurry
blanket. The rotation is increased or decreased by moving the agitator drive belt (see
figure 5-6) to a larger or smaller groove of the motor pulley.
(5) Slurry level and sludge removal. After several hours of continuous
operation, the amount of slurry in the erdlator tank will increase untiI the slurry blanket