Microbial dynamics in an extractive membrane bioreactor exposed to an alternating sequence of organic compounds

Wastewaters containing organic compounds have been treated using extractive membrane bioreactors (EMBs). During treatment, a biofilm normally develops on the surface of the membrane, on the biological side. This study investi gates the dynamics of biofilm growth in an EMB exposed to an alternating se quence of organic compounds. Microbial dynamics of both suspended and attac hed cultures were investigated experimentally in a single-tube extractive m embrane bioreactor (STEMB), which comprised a continuous stirred-tank biore actor (CSTB) coupled to eight single-tube extractive membrane modules (STEM Ms) via a recirculating biomedium. A model microbial culture consisting of a Burk-holderia sp, strain JS150 (ATCC No. 51283), able to degrade monochlo robenzene, and a Xanthobacter autotrophicus sp. strain GJ10 (ATCC No. 43050 ), able to degrade 1,2-dichloroethane, was used. Both microbial strains exh ibited exclusive degradative capabilities. The CSTB was monitored by quanti fication of individual strains and by product and organic compound evolutio n. To investigate the biofilm growth dynamics, eight STEMMs were run in par allel with the same operating conditions. Every week, STEMMs were stopped f or biofilm analysis and the organic compound in the wastewater was changed. Biofilm growth was investigated by quantification of individual strains, b y evaluation of the;overall biofilm growth, and by microscopic analysis. A biofilm composed of both strains was developed and maintained during the wh ole experiment in the STEMMs. The biofilm that developed on the membrane im proved the response of the system to changes in the wastewater. (C) 2000 Jo hn Wiley & Sons, Inc.