BIOLOGICAL FOAMS - THE CAUSE-EFFECT RELATIONSHIP, TEST-RESULTS AND COMBAT STRATEGY

Over 75% of French activated sludge (AS) WWTP, 20% are reported to be affected by foaming. 60% of these are linked with Microthrix and only 14 % with Nocardioforms. Few factors conducive to foaming were statistically proved. Experiments run on more than 40 AS WWTP helped us to identify cause-effect relationships and useful methods to reduce foaming, varying with the type of dominant hydrophobic filamentous microorganisms. The finer points related to design and operation are identified in order to be effective against foaming. Depending on the type and degree of urgency of each case, different combat strategies are proposed.