Jointly meeting global challenges Annual report 2012


Size of protection zones around water production areas is sufficient

21 February 2012BTO

Soil passage is an excellent strategy to remove pathogenic micro-organisms from contaminated water. To remove these micro-organisms effectively, a minimum “travel” time of the water to the well is required. Field studies at Waternet’s water supply dunes show that a protection zone of 60 days around the water production areas provides sufficient protection against breakthrough of pathogenic micro-organisms.

A 60-day protection zone is implemented around drinking water production areas – this means that, from the edge of the protection zone, the water must “travel” at least 60 days horizontally through the soil before it reaches the well. During soil passage numbers of pathogenic bacteria and viruses are reduced by attachment and inactivation. Oxygen levels in groundwater are important for the removal of pathogens. Previous research showed that in drinking water production areas with groundwater containing oxygen, these 60 days are enough. In groundwater without oxygen, the removal of bacteria and viruses is less effective. However, considering not only horizontal, but also vertical transport, the protection zones provide sufficient protection. Current research focuses on the removal of pathogens during soil passage in groundwater with only a little oxygen.

Effective removal under low oxygen conditions

Pathogen removal in aquifers containing a very low concentration of oxygen is just as effective as it is in aquifers containing more oxygen. This means that the protection zone of 60 days sufficiently protects drinking water wells against the breakthrough of pathogenic bacteria and viruses, originating from sources like surface water or leaking sewage pipes in the vicinity of the protection zone .

© 2017 KWR Watercycle Research Institute

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