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Getting to the root of the pollution problem

SUSTAINABILITY: Yorkshire Water is seeking out the sources of pollution in an exercise that has major cost as well as environmental implications. Diarmaid Fleming reports.

Sustainability may at times seem more aspirational than physical, but in Yorkshire, work has been forging ahead on a project which it is hoped will save money and help the environment.

Yorkshire Water has engaged consultant Montgomery Watson Hazra (MWH) to conduct a series of 'urban pollution management studies'. These aim to find out how much river pollution comes from sewerage systems and how much is from other 'background' sources, such as run off from agricultural land. The rationale is simple. Without knowing the source of pollution, treating the cause is a hit-and-miss affair.

'There's no point in addressing problems in the drainage network if the cause of intermittent discharges is something else. If there is a problem, we have to find an optimal solution; if not, then there is no point in expending resources on it, ' says MHW senior principal engineer David Balmforth.

The water industry has agreed under its AMP3 capital works programme to reduce pollution from principal sources including combined sewer and emergency overflows, and storm tanks from sewage treatment works. Minimising work required to drainage or sewerage structures is a major thrust of the work. The aim it to keep cost, inconvenience to the public and impact on the environment as low as possible, says Balmforth.

While measuring contamination in a water course might be relatively straightforward, finding its source is considerably more complex.

'We are dealing with large urban areas, with complex drainage and river systems, and need to model these so we can ascertain discharges. This involves a huge collection of data, upgrading existing records, then building computer models of drainage networks and receiving waters. Data collection is just as complex as the modelling, and accounts for around the same cost, ' Balmforth adds.

Field surveying work is needed to measure flows, suspended solids, biological oxygen demand and ammonia content. Variations between dry and wet conditions are measured. The effects of pollution are worst during dry summer spells, when plant growth in rivers is at its maximum and oxygen is at its lowest, and heavy rain after a prolonged dry spell, which flushes out concentrated accumulations of pollution.

Leeds-based Integrated Environmental Technology Group (IETG) has carried out much of the data collection for Yorkshire Water's catchment studies. Business development manager Jim Grandison says crews are on 24 hour alert for the right weather conditions, monitored with the aid of Met Office forecasting tools.

IETG's core data is fed into drainage area models constructed by MWH. 'There are very complex drainage network and river models, ' says Balmforth. Once the models have been refined to match existing conditions, solutions can be devised.' This involves gauging whether alterations to the drainage network will reduce pollution. The social and environmental effects of different solutions are also assessed.

Analysis of the cause and effect of pollution is under way for the Bradford and Leeds catchments, while work along the Calder catchment is in the data collection phase, reports Yorkshire Water drainage area supply manager Peter Myerscough.

INFOPLUS IETG: www. Contact business development manager Jim Grandison, tel 01302 802000, e-mail jim.

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