Microbiological Diversity of the Anaerobic Sludge During Treatment of Venezuelan Oilfield Produced Waters

In the present investigation the microbial abundances in the granular sludge of two upflow anaerobic sludge blanket reactors (UASB) were compared: the first one fed with production waters of light oil (31.1-39.0° API), from the zuliana region (Venezuela) (APP) and the second one with glucose. To this respect, the populations of glucose fermenting bacteria (BFG), acetogenic bacteria (BAC), metanogens (MET), sulfatereducing bacteria (BSR), nitrate-reducing bacteria (BNR)and heterotrophic bacteria were monitored, using selective culture media. The microbial density was correlated with physicochemical parameters: pH, total alkalinity, COD, SO4 =, NO3-, as well as with the percentages of CH4, CO2 and N2in the biogas. The results exhibit significant differences between the microbial diversity of both reactors, with a proportion of BFG > BSR > MET > BAC > BNR for the glucose reactor and of MET > BNR > BAC > BSR > BFG for the APP. The abundance of bacteria in the glucose reactor was in the order of 108, whereas in the APP reactor was of 105, which ensues from the organic and mineral composition of effluents. The results presented in this study reach evidences on the population dynamics in sludge of UASB reactors, during the treatment of oilfield produced waters.