Changes in Microbial Composition of Wastewater During Treatment in a Full-Scale Plant.

The monitoring of wastewater treatment plants is important for their proper functioning as well as for re-use of water and also to avoid possible circulation of human or animal pathogens in our environment. The samples in this study originated from a full-scale wastewater treatment plant where the structure of the bacterial community was monitored using 454-pyrosequencing. The composition differed in different parts of the plant. In the effluent, bacteria belonging to phyla Proteobacteria, Actinobacteria, TM7 and Bacteroidetes were most frequently detected. The presence of Mycobacterium sp., Mycobacterium avium, Norovirus, Hepatitis A and E viruses was examined using quantitative real-time PCR. Mycobacterium sp. was detected in the effluent in quantities of up to 10(4) cells/ml. Mycobacterium avium subsp. paratuberculosis and subsp. hominissuis were detected in amounts of up to 10(3) cells/ml, and Norovirus group 1 and 2 were also detected. Our findings show the importance of monitoring and controlling the occurrence of specific pathogens in effluent, mainly because of the negative impact on human health when the water is reused.