Such a solution would cost an additional £17 million per year to run, resulting in a 21 per cent increase in customer bills.
The Drinking Water Directive states that individual pesticide levels in drinking water must not exceed 0.1 micrograms per litre. Regulators want to know by 2017 how this limit will be met for metaldehyde.
At present an outright ban on metaldehyde from 2020 is a “real possibility” unless UK policymakers choose to pursue a more bespoke approach.
Anglian Water has called for more support from the agriculture sector, water sector regulators and pesticide manufacturers to find the best solution overall.
The firm’s catchment strategy manager Lucinda Gilfoyle said: “If resolving this issue is then left to water companies alone any solution would likely need to be ‘end-of-pipe’. Not all pesticides can be removed by conventional treatment technology meaning end-of-pipe solutions can’t be relied upon as a panacea.
“Even if a treatment solution is technically possible on such a large scale, our cost estimates show that funding it would be hugely costly and unsustainable for customers’ bills. We strongly believe that domestic customers should not be the financial backstops for this.”
In May, Anglian revealed that its metaldehyde-free farming trial had achieved a 60 per cent drop in levels of the substance detected in reservoir tributaries. Severn Trent and Thames Water have run similar trials.
The results from the three companies found that even removing 100 per cent of metaldehyde from farmland is not sufficient to meet the drinking water legislation.
The reasons for this are being investigated, but it is believed the chemical takes longer to break down than previously thought and could be coming from other sources such as domestic allotments.
Gilfoyle said catchment management involves many different stakeholders, and should not be the sole responsibility of water companies to deliver.
“More organisations need to take responsibility for catchment management as an essential approach, and for regulators to mirror this in the regulation too,” she said.