Hi Sin Tian, I have faced ...

Hi Sin Tian,

I have faced similar issues with textile waste as well. Foaming was generally observed during cooler temperatures and during night. The way I approached was:

1. Built an equalization tank to avoid shock loads and high variance 

2. Reduced the pH to almost neutral levels or just below  (6 to 6.5) by adding ferric chloride and polymers before aeration

3. Recommissioned the aeration tank for the biomass to acclimatize with the process

4. Maintain a DO level of around 1 to 1.5 mg/l

5. Used coconut shell charcoal powder as defoamer in the initial stages and once the system was stabilized, coconut shell powder was not required.

Your BOD levels are in the lower side, this may influence your MLSS in the system which will also impact return activated sludge. Can you provide your biological characteristics at each stage including TDS?

Foaming can occur in nutrient limited state. Hence, it is essential to investigate the type of chemicals or surfactants that you are using and look at alternatives if the foaming continues.