Influence of algal organic matter on Escherichia coli behaviour

This study was undertaken after a report of drinking water industries which suggested the existence of a relation between algal proliferation (algal bloom) in resource water and coliform non-conformity in distribution networks. Our objective was thus to estimate if algal organic matter (AOM) could be used as a substrate by E. coli and explain its resuscitation in drinking water. For this purpose, E. coli was inoculated in sterile dechlorinated drinking water supplemented with organic matter of various origins in order to reach +0.2 (±0.1) mg BDOC L⁻¹ (AOM, glucose or acetate). The results showed that the addition of AOM (naturally secreted by algae or released after a chlorine or ozone stress) in drinking water can represent a risk for water biological stability: indeed, AOM allowed either a higher cellular production, or a better maintenance of cultivability of E. coli than those observed in non-supplemented sterile drinking water, glucose or acetate solutions (in spite of equivalent additions of BDOC). Growth of E. coli was even up to 10 times higher in the presence of AOM coming from ozonated algae.