DGGE-based monitoring of bacterial diversity in activated sludge dealing with wastewater contaminated by organic petroleum compounds

Polycyclic aromatic hydrocarbons (PAHs) belong to t he group of recalcitrants that on reaching wastewater can irreversibly inhibit som e sensitive biological processes in activated sludge such as nitrification. This situat on leads to wastewater treatment failure due to the influence of these substances on bacteria re sponsible for important biochemical processes. Observation of the changes in bacterial diversity using molecular tools, such as denaturing gradient gel electrophore sis (DGGE), could be the first step in finding a way of preventing wastewater treatment fa ilure. The aim of this experiment was to monitor bacterial biodiversity in a membrane biorea ctor (MBR) dealing with synthetic wastewater contaminated with high concentration of petroleum organic compounds (POCs) and to study the influence of POCs contamination on bacterial changeability in activated sludge. COD removal in investigated me mbrane bioreactors was at a level of 93%. The organics removal efficiency was not affect ed by the maximal tested dose of petroleum contamination (1000 μl POCs/l of wastewater) and the MBRs wastewater tre atm nt performance was undisturbed. DGGE analysis revealed that the biodiversity fluctuated slightly in control MBR, while in experimental MBR the biodiversity index decreased drastically after adding the highes t experimental concentration of POCs. These results suggest that concentrations of POCs a t levels from 50 μl/l to 500 μl/l stimulate biodiversity growth, while the concentration 1000 μl POCs/l of wastewater seems to inhibit the most sensitive processes in wastewater treatmen t by i fluencing the bacterial biocenosis.

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