Environmental Engineering Reference
In-Depth Information
Example 6.7
Problem:
The flow to a secondary clarifier is 1.6 MGD. If the influent
BOD concentration is 200 mg/L and the effluent BOD concentration is
70 mg/L, how many pounds of BOD are removed daily?
Solution:
BOD Removed = 200 mg/L - 70 mg/L = 130 mg/L
After calculating mg/L BOD removed, calculate lb/day BOD removed:
BOD Removed (lb/day) = 130 mg/L × 1.6 MGD × 8.34 lb/gal = 1735 lb/day
6.4 ProbleM analysis
In primary treatment (as is also clear in the operation of other unit
processes), the primary function of the operator is to identify causes
of process malfunctions, develop solutions, and prevent recurrence. In
other words, the operator's goal is to perform problem analysis or trou-
bleshooting on unit processes when required and to restore the unit
processes to optimal operating condition. Obviously, the immediate goal
in problem analysis is to solve the immediate problem. The long-term
goal is to ensure that the problem does not pop up again, causing poor
performance in the future. In this section, we cover a few indicators or
observations of operational problems with the primary treatment pro-
cess. The observations presented are not all inclusive but do highlight
the most frequently confronted problems.
6.4.1 Causal factors for Poor suspended
solids removal (Primary Clarifier)
•
Hydraulic overload
•
Sludge buildup in tanks and decreased volume allowing solids to
scour out tanks
•
Strong recycle flows•
•
Industrial waste concentrations
•
Wind currents
•
Temperature currents
6.4.2 Causal factors for floating sludge
•
Sludge
becoming septic in tank
•
Damaged or worn collection equipment
•
Recycled waste sludge
•
Primary sludge pumps malfunctions
