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  • Writer's pictureDavid Bennett

How to extend the life of your borehole cleaning programme

Mike Deed, MD of water treatment specialists Geoquip Water Solutions, wants to set the record straight around the misunderstanding of Regulation 31 in the UK and its application to drinking water supply sources.

A close-up of the typical iron bacteria residues on a pipe before the cleaning process

Millions of customers in the UK rely on water companies for their potable water and strict criteria are in place to govern both its quality and consumer safety.

Readers in the UK will be familiar with Regulation 31, laid down by the Drinking Water Inspectorate (DWI), which sets approvals on behalf of the Secretary of State for the Environment, Food and Rural Affairs. It covers chemicals and construction products used by water undertakers - from the source of the water up to the point of delivery to the consumer's building.

A lesser-known fact, however, is that since 2015, Regulation 31 is no longer required for products and substances intended for ‘disinfestation, disinfection or cleaning agents' used in waterworks apparatus and distribution systems.

In simple terms, this means if potable water supply boreholes become blocked with residue and biofilm caused by a build-up of bacteria, the problem can be tackled quickly through a combination of a mechanical cleaning programme and a water treatment chemical solution - without the need for Regulation 31 approval.

It is a topic that Mike Deed, MD of Geoquip Water Solutions, says is often misunderstood and he is keen to set the record straight, saying: "The DWI has made it clear that these type of cleaning products, which are intended for use when borehole equipment has been taken offline, are no longer covered by Regulation 31.

"It has handed responsibility to the water companies to take a risk-based approach in determining whether or not such a product presents an acceptable risk.

"We often find, however, that when we are asked to supply our BoreSaver range of water treatment solutions, the first question water companies ask us, is if we have Regulation 31 approval.

"It's important to reassure them that this is no longer necessary and make the point that a combination of a mechanical clean, followed by a treatment solution, is by far and away the best long-term answer in eliminating the bacteria that leads to a build-up of residue and biofilm - and therefore sludge - in a borehole."

Take control

Deed recommends "taking control" of a well by embracing a comprehensive maintenance regime which will help extend the time between cleans and improve future performance.

"A mechanical clean is good, but on its own, it can only do so much. If you don't airlift the bottom of the well, all the sand and slimy biofilm and residue remains there and becomes a breeding ground for bacteria, which is probably one of the most problematic issues within potable boreholes," he says.

"Evidence shows that chemically speaking, if you take control of a well, you are restricting regrowth of the bacteria, enabling you to maintain the cleaning cycle at the very least, and potentially increasing the time required between cleans."

Deed says although some companies will suggest using chemical sterilising agents, these rarely have any long-term impact on bacteria due to the protective biofilm produced during their propagation.

A more effective alternative is Geoquip's range of BoreSaver water treatment solution products that have been designed to tackle a range of bacteria, including iron-related bacteria, iron manganese and calcium carbonate. Completely biodegradable, the treatment contains a marker that gives an instant all clear to demonstrate that any remaining chemical residue has been removed.

Third-party accreditation

Despite having no need for Regulation 31 approval, Deed says he was determined to adopt a benchmark that would demonstrate BoreSaver's credibility and efficacy to potential customers. As a result, the range is approved by the US-based NSF - the first time such a standard has been achieved in the UK market and it is believed to be the only NSF-approved product in the European marketplace.

The NSF/ANSI/CAN 60 standard was developed by a team of scientists, industry experts and key industry stakeholders. 

"While we know that the NSF is not recognised as an accreditation in the UK, our view is that by having our products approved in such a rigorous way, we are providing fact-based third party evidence that our product is safe to use in potable water supplies, providing it is used correctly," adds Deed.

"Given the onus is now on water companies to undertake their own risk assessment for cleaning products, it helps them to see that BoreSaver meets the appropriate criteria to prove their water supplies will be clear of any chemicals before boreholes are put back online and into production."

Combined cleaning approach achieves success

When a large water utility company identified iron bacteria problems with three of its boreholes, it asked two borehole specialists to remediate the issue. It called in borehole maintenance expert Drilcorp, which worked alongside Geoquip, taking a two-pronged approach involving physical and chemical treatment to solve the problems.

A combination of a mechanical clean by jetting and airlifting to clear initial loose sediment and sludge was followed up with acidisation to remove any long-lasting bacteria and help prevent future regrowth.

Mike Bushby, contracts manager within Drilcorp's Borehole Engineering Services division, explains: "These boreholes were part of a key water supply for two large areas of population and understandably the water company was reluctant to take them out of action for any length of time.

"Two recently drilled boreholes were supporting the water demand for the local area while the works were undertaken. However, it was important to complete the works before any increase in supply was needed."

Having removed the 8in riser pipe with flanged connections out of each borehole, a camera inspection identified the condition of the three wells and at what depths the most intense jetting from Drilcorp's Borestorer machine was required. 

A partial collapse of part of one borehole wall meant large pieces of iron, broken stones and pebbles had also been deposited, and the team was faced with a significant build-up of sediment and sludge.

The third borehole had high suspended solids and turbidity requiring intensive airlifting.

The Drilcorp team first performed an airlift operation in each borehole and followed this up with the Borestorer.

Bushby explains: "The Borestorer uses high-pressure jetting technology inside the borehole, injecting water on a spinning wheel to quickly and efficiently remove any material encrusted onto the casing. This technology not only cleans the casing but penetrates the formation opening fractures and pores previously blocked to improve well efficiency.

"The jetting was carried out over an eight-hour period per borehole, after which we performed another airlift to remove remaining debris, gathering it into tanks ready for disposal and safely pumping the wastewater into a nearby stream."

With physical cleaning completed, the next stage was an application of Geoquip's BoreSaver Ultra C Pro, a proven biodegradable well rehabilitation treatment solution that is well-known in the industry for tackling iron contamination

Geoquip's Mike Deed continues: "A professional mechanical cleaning practice, as performed here by Drilcorp, to remove much of the loose debris and sediment from the borehole as possible, is an essential part of a good, cost-effective treatment.

"This can, of course, impact on the amount of chemical required, using the correct methodology is very important in being able to achieve the best lasting results."

The project was an overall success and a series of tests carried out showed that the cleaning had improved the performance of all three boreholes.

Bushby comments: "By using both the Borerestorer and BoreSaver cleaning processes, we were able to provide a good all-round clean and the combination of these processes, together with the partnership between our two companies, worked really well."

Deed concludes: "We were pleased that we were able to work in partnership with Drilcorp to overcome the contamination problems and ensure these boreholes were once again ready to supply both the quality and quantity of water required by the utility company to serve its customers."

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