Removal of MS2 bacteriophages, E. coli and Cryptosporidium through slow sand filtration, column experiments De Punt 2018 - Executive Summary

Slow sand filtration is a good option for sufficient removal of pathogenic microorganisms such as viruses, bacteria and protozoa in drinking water production. To determine the specific efficiency of slow sand filtration for different production locations and process conditions in practice, column experiments were carried out as was done previously in 2016. In addition to the removal of Cryptosporidium (a protozoan), the removal of E. coli bacteria and MS2 bacteriophages (viruses) was also investigated. The results confirmed the extensive removal of Cryptosporidium, by 3.9 to 4.9 log units. E. coli and MS2 bacteriophages were removed less effectively, with average removal of 2.4 and 1.7 log, respectively. The conduct of the experiments in duplicate demonstrated that results can be reproduced. Waterbedrijf Groningen can use the resulting validated process model to determine the removal for the legally required Quantitative Microbial Risk Assessment (QMRA, Dutch abbreviation: AMVD).
Interest: secured safe drinking water. Surface water is contaminated with pathogenic microorganisms that must be removed during drinking water production. Drinking water utilities are required to demonstrate, through a Quantitative Microbial Risk Assessment (QMRA, in Dutch: AMVD), that their water is sufficiently safe. They must therefore have a clear understanding of how effectively their production methods remove various types of pathogens, such as bacteria, viruses and protozoa.
Approach: column tests in duplicate. An experimental set-up with two filter columns was filled with sand from the De Punt production location. The filters were run under identical conditions with feed water from De Punt, in order to simulate the real operational conditions as much as possible. The filter column was run in precisely the same manner as it was in an earlier experiment, which only involved Cryptosporidium. This made it possible to compare the results of all the columns, and to translate them to practice. High concentrations of microorganisms were added to the feed water for the experiment. Then, over a period of 48 hours, all the filtered water was collected and studied in the laboratory to determine the microorganism concentrations. In this way, the removal of viruses, bacteria and protozoa in the column set-up could be established.
Report: This research is described in the report Verwijdering MS2 bacteriofagen, E. coli en Cryptosporidium door langzame zandfiltratie, kolomexperimenten De Punt 2018 (BTO 2019.026).