Mycobacteria are waterborne emerging pathogens causing infections in human. Mycobacteria have been previously isolated from wastewater and sludge, but their densities were not estimated due to cultural biases. In order to evaluate the impact of wastewater treatment processes on mycobacteria removal, we used a real time PCR method. First we compared six DNA extraction methods and second we used the more efficient DNA extraction procedure (i.e., enzymatic lysis combined with hexadecyltrimethylammonium bromide-NaCl procedure) in order to quantify Mycobacterium. With the aim to identify parameters that could serve as indicator of mycobacterial behavior, mycobacterial densities were measured in parallel to those of Escherichia coli and enterococci, and to concentrations of chemical parameters usually monitored in wastewater. Mycobacterium reached 5.5 x 105 (3.9 x 105 copies/L in the influent, but was not detected in the effuent after decantation and biofiltration. Most mycobacteria (98.6 (2.7%, i.e. 2.4 (0.7 log10) were removed by the physical-chemical decantation, and the remaining mycobacteria werere moved by biofiltration. Incontrast, enterococci and E.coli were lightly removed by decantation step and mainly removed by biofiltration. Our results showed that Mycobacterium corresponds to a hydrophobic behavior linked to insoluble compound removal, where as enterococci and E. coli refer to hydrophilic behaviors linked to soluble compound removals.
Mycobacterium behaviour in wastewater treatment plant, a bacterial model distinct from Escherichia coli and Enterrococci
Environmental Science and Technology - Volume 45 – Issue 12
2011