[Influence of different sampling systems on evaluation of bacteriological and virological performance for an...

Various quantitative evaluations of the performance of an activated-sludge treatment plant for viruses and bacteria removal and ameliorating physicochemical characteristics have been performed over a period of 24 hours, using successive and continuous samplings. The performance of the treatment plant evaluated using these two sampling systems shows no difference with the one obtained from punctual sampling. In every case, one can observe at the discharge a reduction amounting to 1 or 2 log. for the bacterial density and from 1/2 to 2 log. for the viral charge. Statistical study shows that whatever the sampling method used - punctual or successive and continuous over 24 hours - there is no fundamental difference between values of viral and bacterial densities. This comparison can only be established if a previous study has been made to determine the most representative hour to effect the punctual sampling.