Microbial profiling: short-circuit flows around water wells

Leakages from the casings and clay seals of water wells can cause short circuits between the aquifers. This applies in particular to small, unnoticed leakages resulting from the faulty installation of clay plugs and from soil subsidence. The leakages present a significant risk of contamination to drinking and process water by pathogenic microorganisms and organic micropollutants.

Through the application of short-circuit detection methods, commercial water laboratories and consultancies can advise well users (like drinking water companies, irrigators, ATES operators, industrial water users) about short-circuit flows, and thus about the condition (vulnerability-robustness) of their wells. Market introduction by the players concerned depends on the availability of short-circuit flow detection methods that are faster and cheaper than current ones.

Technology

The technique essentially involves acquiring a clear picture of the natural bacterial populations in the different aquifers, through the analysis of piezometer water samples taken at different depths and in different wells. If the DNA population profile in one well is anomalous and/or shows similarities with that from shallower piezometers, this probably indicates the presence of a short-circuit flow.

Challenge

The project is being conducted in phases. (1) The first phase involves the development of sampling equipment which can directly sample water from an operating well. The measurement strategy will be tested in a single wellfield, with the aim of characterising the bacterial populations in the different aquifers and wells. (2) Validation of the method through sampling and NGS analysis of the bacterial population of a number of wellfields (ATES and industrial abstraction fields), at which it is known whether short circuits occur or not. A market study will also be carried out.

Solution

Last year, equipment was developed to take water samples in a targeted manner at specific well depths. The equipment was tested by WMD in Drenthe and proved to be very suitable for the detection of small leakage flows on the basis of water-quality samples. Work is also being done on a sampling protocol for DNA material from monitoring wells.

The project should ultimately deliver a proof-of-principle for a toolbox to determine a well’s vulnerability-robustness. The toolbox will include (i) equipment to sample wells on-site and (ii) a measurement strategy using NGS analysis of the bacterial population to detect short-circuit flows.

Initial measurements using WellSampler in WMD’s groundwater wells.