Drinking Water 2003

The Regulations

The Water Supply (Water Quality) (Amendment) Regulations 1999 (the 1999 Regulations) came into force on 30 June 1999. These have been incorporated as regulations 27, 28 and 29 in the new Regulations (the Regulations) and came into force on 1 January 2001 in England and 1 January 2002 in Wales.

The Regulations set a treatment standard of an average of less than one oocyst in ten litres of water supplied from a treatment works. The standard does not take into account different species of Cryptosporidium, nor whether any oocysts detected are viable, i.e. alive and potentially able to cause infection.

It is an offence to contravene the standard subject to a defence by the company that it took all reasonable steps and exercised all due diligence to avoid committing the offence.

The Regulations specify continuous sampling of not less than 40 litres per hour of treated water going into supply at all sites where there is a significant risk of the treatment standard being contravened. The Regulations also specify the conditions that have to be met for the collection and analysis of the samples taken, and the reporting of the results, and it is an offence, subject to the same defence as above, if these conditions are not met.

Implementing the Regulations

Water companies were required to carry out a risk assessment for each of their water treatment works by 30 September 1999. New works must be assessed before they can be brought into use. Guidance on the risk assessment was issued with the 1999 Regulations and can be found on the Inspectorate’s website.

The guidance identified factors that contribute towards the assessment of significant risk, i.e. the quality of the source water; the catchment; whether direct abstraction, or abstraction with storage of less than seven days from a river or stream, was involved; any evidence of rapid surface water connection to an aquifer used for groundwater abstraction; the type of treatment provided; and any past history of an unexplained outbreak of drinking waterrelated cryptosporidiosis, where no specific action had been taken to prevent recurrence. All risk assessments were checked by the Inspectorate to establish whether there was a significant risk of contravening the standard.

The significant risk classification does not imply a contravention of the standard but rather that there is potential for a significant number of Cryptosporidiu m oocysts to be present at times in the treated water.

For works identified as at significant risk, water companies must treat the water to ensure that the standard is met. They must also demonstrate compliance by continuously monitoring the water leaving the works and reporting the results of the daily analysis to the Inspectorate. All regulatory monitoring points were audited during 2003.

The initial risk assessments identified 332 sites as being at significant risk. Of these, 158 sites were works treating surface waters and the remaining 174 sites were groundwater abstractions. Water companies may

The Water Supply (Water Quality) Regulations 2001 in Wales.

submit new risk assessments to the Inspectorate if they believe a site is no longer at significant risk, for example when a new treatment process has been installed and is operating successfully.

The treatment processes at sites of significant risk should be operated and maintained at an appropriate level to meet the standard. As an alternative to continuous monitoring, a water company may install a treatment process capable of continuously removing or retaining particles greater than one micron diameter. The company then has to demonstrate to the Inspectorate the efficacy of the process.

In cases where suitable treatment cannot be installed, companies are either abandoning sites of significant risk, or are combining sources for treatment at another works with an appropriate level of treatment.

Improvement programmes

Where a site has been identified as being at significant risk and the current treatment is considered to be inadequate, the Inspectorate agreed an improvement programme with the water company for appropriate treatment to be installed, or for the source to be abandoned or changed.

Until treatment is installed or other action taken, water companies are encouraged to monitor the treated water continuously and report these operational results to the Inspectorate. However, these data are not included in the regulatory results reported below.

At the beginning of 2003, 13 companies had 76 improvement programmes of work in place for the removal of Cryptosporidium oocysts. Fourtyfour of the programmes were due for completion during 2003. Thirtyseven were completed on or close to schedule including a further 11 schemes carried over from preceding years. The remaining seven were subject to significant delays that were outside the company’s control. The Inspectorate continues to monitor progress with delivery of the remaining 39 programmes.

One company also had 11 undertakings in place for Cryptosporidiu m removal schemes at the beginning of 2003. Eight of these schemes were completed by the end of 2003. The other three schemes were delayed for reasons outside the company’s control and the company submitted revised undertakings. One of these schemes is due for completion in April 2004. The remaining two undertakings will be completed by 31 May 2004.

Analysis of samples

The protocol issued with the 1999 Regulations, and subsequently revised, sets out the requirements for the laboratory facilities and analytical method that must be used for compliance testing. Analysis can only be carried out at laboratories approved by the Inspectorate and these are subject to both announced and unannounced inspections. During 2003 each of the approved laboratories had at least one announced and one unannounced audit.

Samples must be analysed within three days of being taken, unless there has been a significant increase in the turbidity of the water being sampled, or there is some other indication that the number of Cryptosporidium oocysts in the water may have increased. In this case, analysis must be completed within a day of the sample being taken.

Strict rules are laid down for all aspects of sampling and analysis. These rules ensure that suitable chains of evidence are available as testimony, if required, in a court of law. Full details of all the approved procedures are available on the Inspectorate’s website.

Sample results for 2003

During 2003, 47,529 regulatory samples were taken from 151 sites. Very low numbers of oocysts were detected in 539 samples taken from 82 sites.

A maximum concentration of 0.08 oocysts per ten litres was found in one sample. However, most positive samples did not exceed 0.02 oocysts per ten litres. The regulatory standard was not contravened at any site during 2003. The Inspectorate is unaware of any outbreaks of cryptosporidiosis associated with the water supplied from those water treatment works identified as being at significant risk.

The monitoring results clearly demonstrate that treated drinking water is not a major source of exposure of the population to Cryptosporidium oocysts.

The treatment standard and continuous monitoring for Cryptosporidium that is in place in England and Wales is unique in the world. The large amount of data that is collected allows the Inspectorate and the water industry to demonstrate, confidently, that welloperated, conventional physicalbarrier water treatment enables drinking water to meet the required treatment standard for Cryptosporidium.

Membrane treatment plants

Water companies must carry out a risk assessment for each of their water treatment works and any designated at significant risk are subject to regulatory sampling. However, any treatment works, in which all water passes through sufficient treatment plant capable of continuously removing or retaining particles greater than one micron diameter (one thousandth of a millimetre) and where this process is subject to continuous monitoring and shutdown or turn out on failure will not require continuous monitoring irrespective of other factors. The cessation of continuous monitoring is subject to approval by the Inspectorate of a revised risk assessment and membrane integrity testing protocol.

Membrane integrity testing

An approved membrane filtration plant will meet the specification. However, an adequate level of integrity monitoring has to be incorporated into the process design in order to demonstrate the membrane is operating at maximum efficiency. The test generally employed is using air pressure and measuring the rate of pressure decay through the membrane. If the pressure does not drop below a specified value after a set period of time the test is satisfactory. At present the Inspectorate requires this to be undertaken on a daily basis and it must be capable of detecting a single fibre membrane break in a filter module.

A total of 52 membrane treatment works are currently in operation in England and Wales. Of these 37 have approved membrane integrity testing procedures.