Water & Wastewater Treatment

8 | NOVEMBER 2014 | WWT | www.wwtonline.co.uk Comment W ith many modern publications refer- ring to the inexorable rise of nitrate concentrations in groundwater, and the uncertainty of when UK nitrate levels will peak, capital investment required to maintain drinking water quality for nitrate alone is estimated to be between £5M and £12M every year, with the high carbon and operating costs of these plants also of concern. But could engagement and collaboration with those that are inadvertently affecting the water supply be the key to reducing groundwater nitrate concentrations - essentially saving bill-payers mil- lions of pounds? The main cause of nitrate contamination is ar- able farming, as nitrate is the main constituent of many fertilisers used by farmers to encourage crop yield. This means that the compound can enter groundwater when large quantities of fertiliser are added to the soil and, in this guise, nitrate has the capability to infiltrate groundwater sources or surface waters such as rivers, open reservoirs, and essential public water supplies through surface water runoff. Nitrate concentrations in groundwater in- creased steadily between 1975 and 2004, with the Work with farmers can defuse the nitrate 'time bomb' Recent findings suggest that nitrate concentrations in groundwater may not be rising as fast as feared, but dialogue with farmers on the issue remains crucial rise being a direct result of the intensification of farming following World War II. Since 1975, around 50 groundwater sources in the UK have been closed because of high nitrate concentrations, which amounts to 140 million litres a day of public water supply being lost. The UK and European standard for nitrate concentration in drinking water is 50 parts per mil- lion (50mg/l), and water companies with sources above this are required to take remedial action, either blending the water or using specialised water treatment to reduce the concentrations. The process is carbon intensive, with the energy used by the water industry in the UK accounting for around three percent of the country's total energy consumption. For this reason, nitrate in ground- water has cost the UK water industry around £250M to date, with many of these costs passed on to the end consumer. The ongoing trend of rising nitrate concentra- tions in groundwater has been labelled the 'nitrate time bomb' as it's unclear when concentrations will peak and how high the concentrations could get. However, a review of data for the 44 worst affected groundwater sources in the Midlands and North West shows that this isn't actually the case, with many of the concentration trends already levelled out or beginning to decline. Stabilisation in recommended fertiliser applica- tion to arable crops and the reduction to its appli- cation on grasslands, from around 1980 (halving the amount of fertiliser which has been applied to pastures nationwide), have had a major effect on the rising trends in nitrate concentrations. The government and its agencies have also tried to reduce the trend over the years with a succes- sion of schemes, including nitrate sensitive areas (NSA), nitrate vulnerable zones (NVZ), safeguard zones, and environmental stewardship schemes. However, there are still risks as conversion of pasture into arable land releases large quantities of nitrate and this, in particular, has been noted in the north and west of the country, as the econom- ics of livestock farming have declined. Either way, the stabilisation and possible slight declines in nitrate concentrations across some parts of the Midlands and the North in particular are a positive starting point for engaging farmers in discussions on how to reduce nitrate inputs (and impacts) even further – using the meth- ods explored by the government (NSA and NVZ schemes) as a starting point. Essentially, engage- ment and collaborative working may be the key to reducing surface runoff and direct contamination of nitrate into the public water supply. There still is a lot of nitrate in the system and there is still a lot being applied to farmland so any changes will be subtle. But if we can stabilise rising trends, reverse stable trends and accelerate declining trends this may allow water companies to defer or avoid investment in new nitrate treatment plants, which can save water companies' bill payers millions of pounds and reduce carbon emissions. Steve Buss is a catchment management special- ist at ESI Ltd, an independent scientific environ- mental consultancy specialising in water, land and sustainable development Steve BuSS CaTChMENT MaNagEMENT SpEcIaLISt ESI Ltd

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