Deadly food poisoning bacteria and viruses such as hepatitis A and E.coli 0157 are present in the sewage which is sprayed on fields or pumped into the soil. The sewage is allowed to stand for up to three months before being used as agricultural fertiliser, but scientists fear this may not be long enough to allow bacteria to die off. Frontline Scotland commissioned tests from Edinburgh's Herriot-Watt University to establish what bacteria remained in the soil and water of treated fields. Residents who live close to treated fields in Scotland claim that mysterious outbreaks of illness could be linked to the use of sewage. Already some supermarket chains are reviewing their policy of buying from farms which use sewage and abattoir waste as fertiliser.
Scientists agree that more research is urgently needed.
The UK has to stop the dumping of sewage at sea by the end of the year increasing the need to find acceptable ways of disposing of waste on land. Edinburgh alone will have to find space for enough waste to fill Murrayfield rugby stadium twice over each year. Tune in to your local BBC station to find out more details of their coverage of the BBC's Water Week.