MIL-HDBK-1138
them from becoming covered with ice and turning over or sinking.
Remove any baffles as well, or be prepared to repair them in the
spring. Because the ice will affect the depth of the lagoon,
winter operations should be run at the highest liquid levels
possible to increase lagoon volume. Because of the ice coverage,
little to no algae activity will occur under the ice and snow.
Adding the lower water temperature to the situation, lagoon
performance in the winter may be marginal. With the rise in
spring temperatures, the lagoons will have a liquid turnover,
with a possible washout of solids.
7.5
Disinfection. Chlorine gas cylinders need to be
in a heated environment because evaporation chills the contents
when the gas vaporizes in the tank. The EPA recommends keeping
the temperature of the chlorine room no lower than 50F (10C).
External heat sources should not be too high (cylinders should
not be higher than 158F [70C]), but heat should be considered
if it will solve the vaporization problem. Hypochlorite tablets
will dissolve more slowly in cold water. Additional tablets may
be necessary to achieve the proper levels of disinfection. All
lines carrying disinfection chemicals and solutions should be
heat-traced where they are exposed to freezing conditions.
Table 10 lists disinfection freezing problems and remedies.
Table 10
Winter Disinfection Problems
Problem
Solution
Feed lines freeze
Enclose all storage and
pumping facilities in a
heated building.
Hypochlorite solution
Keep in heated room above
65F (18C).
crystallizes in pumps and pipes
Surface contact chamber freezes
Cover and insulate tanks.
Source: Taken in part from U.S. Army CRREL Special Report 85-11.
7.6
Solids Management. Solids digestion is a
biological process that slows down as a result of decreasing
process temperatures. Solids processing equipment exposed to the
elements will be adversely affected by freezing weather.
Table 11 summarizes problems associated with solids management in
winter and offers possible solutions.
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