A large distillery had observed a reduction in hydraulic performance and deterioration in the quality of water abstracted from one of their borehole supplies.
A borehole condition survey was carried out to look at the condition of the borehole and any evidence in changes in the water chemistry. The survey revealed that the screened section of the borehole was heavily encrusted and results from water sampling suggested the presence of iron related bacteria was a potential cause for the encrustation (likely iron oxide).
A 10 day programme of rehabilitation was carried out to remove the encrustation. Wire tools were specially engineered to scrub the borehole casing and screen. Mechanical scrubbing was carried out together with a Water Regulations Advisory Scheme (WRAS) approved chemical treatment product to assist in the breakdown of the encrustation.
On completion of the works, the borehole was airlifted to remove debris generated from the scrubbing. Airlifting was carried out until the borehole water was clean. Water sampling was carried out if the field and results verified in the field to confirm the water could be brought back into production. A short programme of testing carried out on the borehole after the rehabilitation confirmed a 25% increase in hydraulic performance.
Whilst in this case it was not possible to prevent encrustation from reoccurring in the future, the rehabilitation work resulted in an improvement in the water quality and the hydraulic performance of the borehole. This highlights the importance of routine monitoring and maintenance to optimise borehole performance and minimise running costs.
Image Top Left: Example of encrusted material obtained from the borehole during rehabilitation
Image Below: Specially engineered scrubbing brushes