Effect of biomass type and PCE on archea communities of anaerobic reactors

The effect of perchloroethylene (PCE) and the type of biomass (suspended and immobilized) on the diversity of archaea populations by 16S rDNA fragments amplified by PCR (and further separated by DGGE) in two types of laboratory-scale methanogenic reactors (two complete mix reactors with suspended biomass, CM1 and CM2, and one fluidized-bed bioreactor with immobilized bio-mass, AFBBR) were studied. The experimental design consisted of two methanogenic periods: Period 1, without PCE, and Period 2, 20 mg PCE/L for the CM 1 and 40 mg PCE/L for the other two reactors. Comparison between reactor communities in Period 1 showed that archaeal populations diverged in the order AFBBR-CM1 > CM1-CM2 ≅ AFBBR-CM2. Comparison between archaeal reactor populations showed that they diverged in the order AFBBR-CM2 > CM2-CM1 > AFBBR-CM1. The divergence for each reactor between Periods 1 and 2 followed the order CM2 > CM1 ≅ AFBBR, indicating that archaeal community in biofilm was less affected by PCE than suspended growth biomass in reactors, when comparing reactors fed with 40 mg PCE/L (AFBBR and CM2). The CM reactors could steadily remove COD and PCE whereas their archeae populations fluctuated very much; fluctuation increased with the concentration of PCE in the influent for CM reactors. This is an abstract of a paper presented at the proceedings of the 8th International In Situ and On-Site Bioremediation Symposium (Baltimore, MD 6/6-9/2005).