Environmental Engineering Reference
In-Depth Information
• Efluent weirs are not level.
•
Short-circuiting is occurring because of temperature variations.
•
Withdrawal rate or frequency is not correct.
•
Excessive solids loading is occurring due to excessive
sloughing.
Corrective actions
•
Check
hydraulic loading and adjust recirculated flow if the hydrau-
lic loading is too high.
•
Adjust flow to ensure equal distribution.
•
Inspect sludge removal equipment; repair broken equipment.
•
Monitor the
sludge blanket depth and sludge solids concentration;
adjust the withdrawal rate and frequency to maintain aerobic condi-
tions in the settling tank.
•
Adjust the effluent weir to obtain equal flow over all parts of the
weir length.
•
Determine
temperature in the clarifier at various points and depths
throughout the clarifier. If depth temperatures are consistently
1 to 2°F lower than surface readings, a temperature problem exists.
Baffles may be installed to help to break up these currents.
•
Determine whether high sloughing rates caused by biological activ-
ity or temperature changes are creating excessive solids loading.
The addition of 1 to 2 mg/L of cationic polymer may be helpful in
improving solids capture. Remember, if polymer addition is used,
solids withdrawal must be increased.
•
Control high sloughings due to
organic overloading, toxic wastes,
or wide variations in influent flow at their source.
7.3.7.4 Filter Flies
Symptoms
•
The
trickling filter and surrounding area become populated with
large numbers of very small flying insects (
Psychoda
moths).
Causal factors
•
Poor housekeeping
•
Insufficient recirculation
•
Intermittent wet and dry conditions
•
Warm weather
