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RAU and Thames Water field work initiative underway
Tom Edwards, postgraduate Royal Agricultural University (RAU) student, has been awarded a Master of Science by Research (MScR) by Thames Water. Tom is currently working at the University’s Harnhill Manor Farm to determine whether concentrations of metaldehyde can be reduced through the use of swale mechanisms.
Metaldehyde is a chemical used as a pesticide in agriculture. It is applied in the form of slug pellets in order to protect crops from slugs and snails. It is mainly applied during the planting of autumn oilseed rape and winter wheat crops via a hopper attached to the back of an ATV. Metaldehyde has been detected in watercourses nationwide due to diffuse pollution.
The Ampney Brook in the Upper Thames catchment has recorded metaldehyde levels up to 40 times the drinking water standard. Thames Water are researching methods of reducing the amount of metaldehyde in water sources, because the chemical properties of metaldehyde makes it very difficult to remove using current water treatment processes.
Swales are designed to collect runoff in shallow ditches in order to provide water treatment via interaction with soil, bacteria, and vegetation. Previous studies have shown that swales are efficient for the reduction of pollutants such as heavy metals and nutrients but they remain unproven for pesticides.
Two experimental swale sites have been set up at the RAU. Water is taken from a pre-existing stream and travels the length of the swale making contact with soil microbes, particles, and native wetland plant species. The more contact with soil and root systems the more chance of seeing a reduction of pesticide over the course of the swale. The water from two swale sites on the University farm eventually feeds into the Ampney Brook, before travelling downstream and being extracted by Thames Water to produce drinking water.
Water samples are collected where the water is extracted from the stream at the beginning of the swale and again at the end of the swale field before it is directed back into the stream. In order to collect representative samples, water is collected in auto-samplers which are programmed to take 500ml of water at set time intervals. The advantage of using an auto sampler is that several samples can be taken per day allowing the researcher to pinpoint periods of heavy rainfall and increased runoff. The samples are transferred to sample bottles before being labelled and transported to the Thames Water laboratory.