Water Quality and Standards

3. 2 Cryptosporidium Direction

Cryptosporidium parvum is a protozoan parasite known to infect both humans and animals. The disease cryptosporidiosis is an acute, self limiting diarrhoeal illness, commonly of 2-3 weeks duration. There is a background level of cryptosporidiosis in the community which is generally attributed to contact with farm animals, or contact with others who have the disease. From time to time the infection can be spread through drinking water supplies. When viewed nationally, these water borne cases appear to represent only a very small fraction of all cases of diarrhoea. However if public water supplies are contaminated, there is the potential for a large outbreak in the area served by the contaminated supply. It also sets out a timetable for implementing the requirements of the Bouchier and Badenoch reports.

Water authorities already have a duty to prevent cryptosporidium and a Direction will soon be published setting out an approach to risk assessment to allow them to ensure this. The risk assessment protocol provides a very flexible approach. Certain high risk situations could be dealt with in a single step providing a complete solution to a short timescale. Alternatively it may be appropriate to manage the risk in a more incremental way. An early expedient to remove a high risk element would afford the authority more time to implement a more permanent solution. If there is a significant or unacceptable risk of contamination water authorities are then expected to make an assessment of the effectiveness of the installed treatment to remove the organism. These assessments should be reviewed from time to time particularly when there is a change in circumstances potentially affecting the risk. Modifications of existing treatment or installation of additional treatment should only be required where there is a specific additional risk or an unacceptable risk of contamination of a water source and where the installed treatment is not effective in removing cryptosporidium. However, conventional water treatment should provide satisfactory protection.

The Direction should not result in significant additional capital expenditure where the Badenoch and Bouchier reports were already being complied with. However the risk assessment process has revealed a number of situations which will result in capital expenditure. The planning assumption should therefore be that the target times for managing the cryptosporidium risk score downwards to an acceptable level should be respected. Compliance with the Direction may need capital expenditure at some sites and there may be additional operating expenditure as a result of the increased level of analysis required.