Drinking water quality is controlled, among others, by measuring the presence of bacteria of the coli group. However, when these bacteria, which in themselves are not dangerous, grow in the drinking water production process they no longer constitute an indication of the water quality. This project will study whether these bacteria can grow in slow sand filters in the winter.
Bacteria of the coli group as an indicator of faecal contamination
Bacteria of the coli group are used as an indicator of faecal contamination of drinking water. But this bacterial group can also be of natural origin, so that their presence does not always indicate a faecal contamination. In addition, bacteria of the coli group can also possibly grow in sand filters. In this case, they cannot be used as a good indicator of the microbial safety of drinking water. It is therefore important to discover whether, and if so, under what conditions, bacteria of the coli group can grow in the filter medium or the feed water of rapid sand filters.
Growth of bacteria of the coli group in rapid sand filters
The outcomes of previous experiments show that bacteria of the coli group can grow at different temperatures in the filter medium of rapid sand filters. These experiments were carried out in the late summer. Since the composition of the influent water and the conditions in the filter vary between the summer and the winter, we do not know whether, and to what degree, bacteria of the coli group can grow in the winter.
The objective of this project is to test whether differences in the composition of the influent water of rapid sand filters in the winter and the summer have an effect on the growth of bacteria of the coli group. This will involve sampling the water and filter medium of rapid sand filters in the winter, and then measuring whether, and to what extent, five bacterial strains of the coli group grow in this medium. This knowledge will allow for the implementation of measures to counter this growth process in practice.