How to: Reduce or Eliminate Biological Foams in Wastewater Aeration Basin - Video Foam - Chocolate Mousse
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It accumulates on the surface of the aeration basin and may carry over into the final clarifier and effluent discharge.
The use of detergents could also generates foam but the comments below relate solely to biological bacterial foams.
Three types of biological foaming may be observed:
Foam type 1: white, frothy, not particularly stable foam
Foam type 2: white/brown foam, stable and containing fine particles of mixed liquor solids
Foam type 3: A dark, stable, heavy, chocolate mousse foam
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Foam type 1: few or no filaments in the microscopic examination; high Food to Micro-Organism loading or plant start-up situation
Foam type 2: significant – but not necessarily predominant – presence of filaments in the microscopic examination
Foam type 3: likely significant presence of higher life forms such as rotifers in the microscopic examination; low Food to Micro-Organism and long sludge age
Principal causes:
Foam type 1: Proteins that are not biodegraded due to excessively high Food to Microorganism or, in a plant start-up situation, the optimum Mixed Liquor Suspended Solids concentration not yet having been reached
Foam type 2: certain filamentous bacteria produce extracellular polymer substances which are surface active and cause foaming
Foam type 3: Long sludge age systems operating on high nitrogen raw waste water generate high mixed liquor nitrate concentrations due to biological nitrification. In the absence of a dedicated denitrification facility the nitrate may denitrify in the aeration basin and final clarifier. The resulting nitrogen gas may cause the Mixed Liquor Suspended Solids to float in the final clarifier and aeration basin, forming the characteristic dark brown foam or floating sludge.
Correction strategy:
Foam type 1: Reduce Food to Micro-Organism by increasing the Mix Liquor Suspended Solids. Also check that detergent use is not excessive as detergent foam is similar to this type of protein foam.
Foam type 2: Use the same strategy as for sludge bulking.
Foam type 3: Install a dedicated anoxic tank for denitrification.
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J. Scott Shipe produced this video for educational purposes / questions regarding the content please contact jssh2o@aol.com
File Video 1,352 - 2017 REMEMBER WATER MATTERS!
