Transport of viruses and colloids in variably‐saturated soil and groundwater
[February 12-20, 2019]
Venue: Department of Hydrology, IIT Roorkee
Surface water is often used for the recharge of aquifers used in drinking‐water production. Surface water is often contaminated with pathogenic micro‐organisms and viruses. These pathogens have to be removed to produce safe drinking water. Often chlorination is used as the most effective way for disinfection of drinking water. However, the use of chlorination is not permitted in the Netherlands. One effective way is the passage of surface water through soil, as is the case in bank filtration, dune recharge, and deep‐well injection. Dune recharge is widely applied in The Netherlands, where surface water, after some pretreatment, is fed into canals in protected dune sands. Then, water is abstracted after 50 to 60m of passage through the soil.
Aerial View of Castricum Dune Infiltration Area. Surface water, after some pretreatment, is fed into canals. Water is abstracted from a long row of wells between two canals (shown in red dashed lines)
To assure production of safe drinking water from surface water, adequate travel times and travel distances are needed. In this regard, it is important to determine various factors that affect the rate of removal of pathogenic viruses during soil passage. These factors include hydraulic conditions (such as flow velocity and saturation) and geochemical conditions (pH, ionic strength, concentration of calcium, etc.). In some parts of the world, use of grey water (e.g. kitchen/shower wastewater or treated wastewater) for agricultural purpose is practiced or is being considered. In such cases, it is essential to determine whether the infiltrating water will be laden with pathogenic microorganisms when it reaches groundwater. Even when water is produced from groundwater wells, it is important to have protection zones around drinking water wells in order to ensure that no pollution will reach the well. This will have achieved by enforcing a zone of protection around groundwater well. The proper determination of such a protection zone is essential. It should not be unnecessarily large as it will be costly; at the same time, it should be large enough to provide adequate protection.
In this short course, we present basic principles of groundwater flow and transport of dissolved matter, principles of virus and colloid transport, and an overview of all factors affecting fate of viruses. Results of a large number of laboratory and field experiments under both saturated and unsaturated conditions, for the study of movement of bacteriophages and colloids through soil will be presented. The development of a computational tool for fast calculation of protection zones of groundwater wells will be presented.