Dear Zyaad, Foaming in ...

Dear Zyaad,

Foaming in activated sludge process is a common operational problem in many wastewater treatment plants.The foam can occur in aeration tank, Followings process to remove scum.

1. Verify that the return sludge is flowing to the aeration tank. Maintain a sufficient return sludge

rate to keep secondary clarifier blanket to normal levels (1ft to 3 ft).

2.  Stop wasting activated sludge for a short time to build the MLSS levels back up and MCRT to

desired range.

3.  Control air flow rates to control DO in the 1.0 to 3.0 mg/l range. Foaming may persist longer

with fine bubble aeration compared to course bubble aeration.

–4. Consider hauling in seed activated sludge if warranted

–5.Actively enforce sewer use ordinances to avoid process upset and deterioration of the

secondary system. Check out the distribution of return sludge, and influent into the basin for

proper flow split.If nitrification is not required, gradually increase the F/M and decrease the MCRT.

6.If the scum is not returned to the aeration tanks, include the volatile solids removed in

the scum in the waste sludge calculations. During normal operation, the amount of

volatile solids removed with the scum is to small to matter. However during periods of

high foam, 10 to 15% of the solids may be removed with the scum.

7. If filaments appear, try to identify the cause. There are several books on the market

that will help you identify the type of filament and how to control it. A microscope is a

must in identification of filaments.