Environmental Engineering Reference
In-Depth Information
Cause:
Nutrient deficiency
Corrective action:
Add nutrients.
Cause:
Toxicity
Corrective action:
Identify source; implement pretreatment.
Cause:
Overaeration
Corrective action:
Reduce aeration during low low periods.
•
symptom 2.
Solids settled properly in settleability test but large
amounts of solids lost over effluent weir.
Cause:
Billowing solids due to short-circuiting
Corrective action:
Identify short-circuiting cause and eliminate
if possible.
•
symptom 3.
Large amounts of small, pinhead-size solids are leav-
ing settling tank.
Cause:
Old sludge
Corrective action:
Reduce sludge age (gradual change is best);
increase waste rate.
Cause:
Excessive turbulence
Corrective action:
Decrease turbulence (adjust aeration during
low flows).
•
Large amounts of light floc (low BOD
5
and high solids)
are leaving the settling tank.
symptom 4.
Cause:
Extremely old sludge
Corrective action:
Reduce age; increase waste.
•
symptom 5.
Large amounts of small translucent particles (1/16 to
1/8 in.) are leaving the settling tank.
Cause:
Rapid solids growth
Corrective action:
Increase sludge age.
Cause:
Slightly young activated sludge
Corrective action:
Decrease waste.
•
symptom 6.
Solids are settling properly but rise to the surface
within a short time. Many small (1/4 in.) to large (several feet) clumps
of solids are visible on the surface of the settling tank.
Cause:
Denitrification
Corrective action:
Increase the rate of return; adjust the sludge
age to eliminate nitrification.
Cause:
Overaeration
Corrective action:
Reduce aeration.
