The future sludge recycled to agricultural land will be subject to tighter controls of microbiological quality to ensure adequate protection of public health. Also, food retailers are anxious to ensure the wholesomeness of crops and produce grown on sludge treated land. The European Commission and the British Retail Consortium have implied that pathogen removals as high as 6 logs must be demonstrated. This was difficult to apply consistently even with sludges that contain relatively high numbers of pathogens. To overcome these difficulties, the project developed a method previously used as a research tool for studying the destruction of round worm eggs.
The objectives were a) to develop environmental containers previously called "germ bags" for assessing the microbial efficiency of sludge treatment processes, and b) to produce a best practice auditing procedure using "germ bags" which is statistically and scientifically robust.
The research, supported by four UK water utilities, made it possible to validate the microbiological removal efficiencies of sludge treatment processes and so demonstrate compliance with future EU legislation or requirements set by food retailers