Secondary Treatment - Wastewater Operators - page 284

• Gray, shaggy slime growth indicates normal operation.

• Reddish-brown or golden shaggy growth indicates nitrification.

• A white, chalky appearance indicates high sulfur concentrations.

• No slime indicates severe temperature or pH changes.

Sampling and testing should be conducted daily for dissolved oxygen
content and pH. BOD 5 and suspended solids testing should also be per-
formed to aid in assessing performance.

7.4.3 rbC expected Performance

The RBC normally produces a high-quality effluent with BOD 5
removal at 85 to 95% and suspended solids removal at 85 to 95%. The
RBC treatment process may also significantly reduce (if designed for
this purpose) the levels of organic nitrogen and ammonia nitrogen.

7.4.4 operator observations

Rotating biological filter operation requires routine observation, pro-
cess control sampling and testing, troubleshooting, and process control
calculations. Comparison of daily results with expected normal ranges is
the key to identifying problems and appropriate corrective actions.

Note: If the RBC is covered, observations may be limited to the portion
of the media that can be viewed through the access door.

• rotation —The operator routinely checks the operation of the RBC

to ensure that smooth, uniform rotation is occurring (normal opera-
tion). Erratic, nonuniform rotation indicates a mechanical problem
or uneven slime growth. If no movement is observed, mechanical
problems or extreme excess of slime growth are indicated.

• Slime color and appearance —Gray, shaggy slime growth on the

RBC indicates normal operation. Reddish-brown or golden-brown
shaggy growth indicates normal operation during nitrification. A
very dark brown, shaggy growth (with worms present) indicates a
very old slime. White chalky growth indicates high influent sulfur/
sulfide levels. No visible slime growth on the RBC indicates a severe
pH or temperature change.

7.4.5 rbC Process Control sampling and Testing

For process control, the RBC process does not require large
amounts of sampling and testing to provide the necessary information.
The frequency for performing suggested testing depends on available
resources and variability of process. Frequency may be lower during
normal operation and higher during abnormal conditions. The following
routine sampling points and types of tests will permit the operator to
identify normal and abnormal operating conditions.