Abstract
A microbial substance that lyses filamentous bacteria was purified and characterized. It could not be rendered inactive by various enzyme denaturing treatment. The substance had properties similar to those of a biosurfactant that is often produced by B. subtilis. Lysing of filamentous bacteria with synthetic surfactants was also examined. Several synthetic surfactants were found to be capable of lysing filamentous bacteria. Nonionic synthetic surfactants with an HLB of 14 were found to lyse Spaerotilus natans, Type 1701, Thiothrix, Haliscomenobacter, Type 0961 and Type 021N in activated sludges sampled from wastewater treatment plants. Use of the synthetic surfactant to lyse filamentous bacteria was also demonstrated in a continuous-feed aeration tank, and settleability of sludge was improved. The surfactent did not adversely effect floc-forming microorganisms as evidenced by the high rate of TOC removal. The results indicate that synthetic surfactants can be used to prevent filamentous bulking in the activated sludge process.
