Many of the water companies have been required to bring forward their pesticide control programmes following an official review of "undertakings" which they gave at the time of privatisation. Many of these set deadlines around the end of the century for pesticide levels in drinking water to be brought within EC standards, but the threat of legal action by both the European Commission and Friends of the Earth forced the Government to advance the timetable.
The review was carried out by the Drinking Water Inspectorate. As a result, 21 water companies have now made revised undertakings. These apply to 152 water treatment plants (see table ) serving some 20 million people.
Most of the treatment plants are due to be upgraded by the end of 1995, but improvements at 24 plants will not be completed until 1997 or later.
The capital costs of the improvement programme given in the table were obtained from a telephone survey. Companies also expect their annual running costs to rise by about 10% of capital expenditure. Only Southern Water refused to reveal figures, but an ENDS estimate based on the technologies and size of plant required has been included.
Roughly equal numbers of surface and groundwater sources are covered by pesticide undertakings, with the herbicides atrazine and simazine being the most common pollutants involved.
Most companies are fitting granular activated carbon (GAC) filters to groundwater sources, although some smaller bore-holes will be closed because it is uneconomic to treat them. Surface waters tend to have higher pesticide peaks than groundwaters, particularly after heavy rain, and for these sources companies are generally opting for GAC and ozonation, and sometimes hydrogen peroxide as well.
Many companies are currently conducting ozone trials, including Anglian, North Surrey, Severn Trent, Thames, Wessex, and York. A few have already installed or are installing ozone or ozone and peroxide systems. Bristol Water already has experience of ozonation, which was installed at its Littleton plant in 1990. The single-stage system has not proved capable of reducing all pesticide peaks to below the EC limit of 0.1µg/l, and the company is now looking to boost oxidation with peroxide. At its second treatment plant, Bristol is planning to install a two-stage ozone treatment plant.
Sutton Water intends to use ozone alone to reduce pesticide levels in its two, otherwise relatively pure, groundwater sources. Another unusual option being tested by Mid Southern Water is a combination of ozone and ultra-violet light.