Sludge is a waste water treatment by-product and the generation of methane gas for use as a fuel is a potentially beneficial feature of sludge treatment, in particular anaerobic digestion. Sludge treatment facilities should not release methane into the environment in the course of normal operation, nor should methane gas be released from a well-operated and maintained waste water collection or treatment system. The European Communities (Waste Water Treatment) (Prevention of Odours and Noise) Regulations 2005 require sanitary authorities to ensure that waste water treatment plants in their control are operated and maintained in a manner that does not cause a nuisance through odours or noise emissions. The authorities are also required to maintain records of odour and noise incidences occurring in treatment plants and to provide details of any such incidences in their annual report to the Environmental Protection Agency.