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3. Drinking Water Quality Across Scotland
3A Public Water Supplies in Scotland
Table 3A Key Facts - A Summary of Drinking Water Assets in Scotland
Public water supplies in Scotland are the responsibility of Scottish Water. The majority are derived from surface water sources, although an increasing number of groundwater sources are being used. Water from all of these sources is treated at 307 treatment works before being distributed through 1,088 service reservoirs and over 47,000km of mains. On average, about 2,530 Megalitres (Ml) of potable water is supplied each day to about 97% of the resident population. The remainder of the population are served by private supplies, which are described in section 3B of this report.
The area served by the public water supply system is split into water supply zones. In 2007 there were 354 public water supply zones in Scotland. The number of treatment works and supply zones in Scotland has been steadily decreasing as Scottish Water and its predecessors have developed regional schemes to replace many of the smaller supplies, improving efficiency and the quality of water supplied. Notably, in 2007 the small treatment works on the shores of Loch Alsh and Loch Duich were closed, and the population previously served by these works became part of a larger single supply zone supplied from the modern works at Kyle of Lochalsh. The maximum population allowed in a single water supply zone is 100,000.
Assessment of Water Quality Compliance
The Water Supply (Water Quality) (Scotland) Regulations 2001 set out the number of samples that have to be taken by Scottish Water from each water treatment works, service reservoir and water supply zone every year. The majority of samples in water supply zones are taken from randomly selected consumer taps. The Drinking Water Quality Regulator expects full compliance with the sampling frequencies specified in the 2001 Regulations. Circumstances outwith Scottish Water's control can occasionally prevent samples from being taken, but over-sampling is not allowed. In practice, each sample may be tested for several parameters so the text and the tables relate to the number of determinations (tests) made for each individual parameter rather than to the number of samples taken.
Schedule 1 of the 2001 Regulations sets a prescribed concentration or value ( PCV) for 40 parameters. In general, to be wholesome, water must not contain a parameter in excess of a PCV; in the case of the Hydrogen Ion parameter (pH) the value must lie in a range defined by a maximum and minimum prescribed value. Schedule 2 of the Regulations sets values for a further 11 "indicator" parameters. These are not part of the definition of wholesomeness unless a breach of the standard constitutes a risk to health. Scottish Water is required to investigate any exceedences of Schedule 1 or Schedule 2 parameters.
Ten key drinking water quality standards have been identified from the 2001 Regulations that are of particular significance when considering the quality of drinking water in Scotland. Definitions of these Ten Key Parameters may be found on the fold out flap at the back of this report.
In contrast to the 1990 Regulations that they replaced, the 2001 Regulations do not enable Scottish Ministers to authorise the relaxation of a PCV. However, where a non-trivial exceedence of a Schedule 1 parameter occurs, Scottish Water can apply for an Authorised Departure. This allows for a temporary departure from the standard while work is undertaken to secure compliance with the Regulations. This process is described in full in Annex C.
It is important to note that the PCV's for parameters that are of health significance are based on World Health Organisation ( WHO) guidelines and that they are set with a wide margin of safety. For parameters that are of aesthetic significance, the standards are generally set well below the level at which water would become unacceptable to consumers. A contravention of a standard therefore is not necessarily indicative that the water is unfit to drink or represents a risk to health.
However, a contravention of a PCV is of significance because it means that the water supplied at the time the sample was taken cannot be regarded as wholesome as defined by the Regulations. When a contravention is considered in conjunction with other monitoring results, it may indicate that work is necessary in order to meet the high standards set in the Regulations. When interpreting some contraventions of samples taken from a consumer's tap, especially those for lead and microbiological parameters, it is important to remember that the result may reflect the condition of the tap or plumbing in the property rather than the water in the public supply. The circumstances under which water is stored within a building can also greatly affect its quality.
The general rule that any individual contravention of a PCV constitutes a breach of Schedule 1 of the Regulations and thus causes the water to be regarded as unwholesome, does not apply to the coliform standard at service reservoirs. Regulation 4(6) requires that 95% or more of tests from a Service Reservoir, carried out over the preceding year, meet the coliform standard.
In addition to absolute PCVs for nitrite and nitrate, Regulation 4(d) specifies an additional requirement reflecting the combined concentration of the two parameters, namely that the water satisfies the formula:
[nitrate]/50 +[nitrite]/3 <1
where the square brackets refer to the concentration of the two compounds in milligrammes per litre (mg/l). An assessment of compliance with this formula shows that this standard was not breached in 2007.
Overall Compliance
The drinking water quality results reported by Scottish Water for 2007 show that 363,451 tests were carried out on samples taken from water treatment works, service reservoirs and consumer taps. Of the 160,601 tests on samples taken from consumers' taps, 99.76% complied with the requirements for which there is a numerical standard. A total of 393 tests gave results which did not meet the standard set out in the 2001 Regulations. As in previous years, the largest number of failing samples was for the total coliform and trihalomethane parameters. Further details may be found in Section 3.4.
3.1 Quality of Drinking Water Sources
Table 3.1-a Summary of Data from Sampling of Water Sources
The 2001 Regulations do not require Scottish Water to sample its water sources, although in 2007 sampling did take place for operational reasons and to comply with the EU Surface Water Abstraction Directive ( SWAD). Table 3.1-a shows a summary of selected results from tests carried out on samples taken during 2007 from water sources used for public drinking water supplies. The data is a combined summary of all the sources that were sampled (mainly reservoirs and lochs). It provides an indication of the range of waters Scottish Water normally has to treat in order to comply with the standards set down in the 2001 Regulations.
Water quality can vary considerably between sources but quality can also vary with time, especially during severe weather. Scottish Water must therefore ensure that its treatment works have the processes necessary to reliably produce clean, safe drinking water from the range of raw water quality likely to be encountered by that works.
Some substances, such as manganese, are naturally occurring, while others, like nitrate and pesticides are present because of agricultural activity. It can be expensive to remove nitrate and pesticide from the water - fortunately they are not present in many Scottish sources because most sources in Scotland are derived from upland catchments where agricultural activity is limited.
Many raw sources contain significant numbers of bacteria, which serves to demonstrate the importance of adequate treatment, including disinfection, in order to make the water safe to drink.
The EU Surface Water Abstraction Directive has now been repealed and arrangements have been put in place with Scottish Water to ensure that sampling of raw waters continues under the Water Framework Directive.
Table 3.1-b Source Water Cryptosporidium Data
The Cryptosporidium (Scottish Water) Directions 2003 require Scottish Water to sample all drinking water sources that have been designated as high risk for Cryptosporidium. In 2007, a total of 78 drinking water sources were sampled across Scotland. Positive Cryptosporidium samples were found at all but 19 of these sites. In 2007, 27.4% of raw water samples contained oocysts - the corresponding figure for 2006 was 24%; the increasing percentage perhaps reflecting the wetter Summer weather in 2007. Table 3.1-b shows a summary of the data for the whole of Scotland and lists the ten sites with the highest average count of Cryptosporidium oocysts in source water samples. As in 2006, Dodburn near Hawick and Forehill supplying Peterhead contained the highest average oocyst count in raw samples. An appropriate, well-optimised treatment process should minimise the risk of Cryptosporidium oocysts being present in the final water.
3.2 Drinking Water Quality at Treatment Works
Table 3.2-a Microbiological Tests on Samples taken at Water Treatment Works and Comparison with Previous Years
The Regulations require that samples are taken from treatment works and tested for a number of parameters. These include microbiological parameters, in order to confirm the effectiveness of the disinfection process, and turbidity and nitrite, to demonstrate control of this and other treatment processes. Table 3.2-a shows summary results for tests carried out for coliforms and E.coli on samples taken at treatment works in 2007. Thirty-three (0.10%) of the samples taken at treatment works contained coliforms. This is a significant reduction on the preceding year and represents the best compliance since regulatory sampling was introduced. To put this achievement in perspective, 10 years ago, the percentage of samples taken from treatment works (1997) that contained coliforms was 1.8%. Sixteen of the 33 failures occurred in the Summer months of June, July and August.
In 2006, a number of large treatment works experienced more than one failure but in 2007, there was no particular geographical pattern, although Alnwickhill treatment works, which supplies parts of Edinburgh, generated four of the failures.
In 2007, 10 samples taken from treatment works contained E.coli, a failure rate of 0.03% - less than half the rate of failure seen in 2006. Invercannie WTW, serving Aberdeen, saw one sample containing E.coli in 2007, compared with 5 in 2006. Scottish Water has investigated the failures at Invercannie and concluded that they were due to the location of the sample tap rather than the quality of the water leaving the works. Arrangements have been put in place to move the sample point.
Table 3.2-b Summary of Nitrite Tests on Samples taken at Water Treatment Works
Nitrite is a compound that can form when there is an excess of ammonia in a supply. It is an indicator parameter in treated water, and the standard was introduced in order to monitor the effectiveness of the disinfection process, particularly where chloramination is used.
Table 3.2-b shows that in 2007, 3 samples failed to meet the required standard for nitrite at treatment works of 0.1mg/l, representing a failure rate of 0.09%. This is an improvement on 2006. Two of the failures occurred at Backies in Highland, the other was at Kirkmichael in Perthshire.
Table 3.2-c Summary of Turbidity Tests on Samples Taken at Water Treatment Works
Turbidity (cloudiness) of treated water is an important measurement because it can provide an indication of how well the treatment process is removing particulate matter (including Cryptosporidium). It also indicates the effectiveness of disinfection because it is difficult to adequately disinfect turbid waters.
Table 3.2-c shows that in 2007, 71 samples exceeded the turbidity standard at water treatment works, representing 0.83% of samples tested. A number of these failures are undoubtedly due to the location of the sample tap at the treatment works and the influence of lime added during the treatment process to control the pH of the water. It is disappointing that Scottish Water has not taken action to ensure that all sample points are located sufficiently far downstream of any treatment process to ensure that the samples taken are representative of the water leaving the treatment works and not impacted upon by the treatment process itself.
Table 3.2-d Summary of Sample Data for Cryptosporidium in Final Water
Cryptosporidium is a microscopic protozoan parasite that can live in the gut of humans and warm blooded animals. There are a number of species of Cryptosporidium, and not all are thought to be infectious to humans. All species form bodies known as oocysts in which they can survive in the environment for long periods. Once ingested, Cryptosporidium multiplies rapidly in the gut and oocysts are excreted in very large numbers, completing the life-cycle of the organism. In humans, infection can cause stomach cramps and diarrhoea and, in extreme cases, can be fatal to the immuno-compromised or to the very young or old.
Cryptosporidium oocysts can enter a water supply if faecal material is washed into the source (raw) water and if any oocysts present are not removed by the treatment process. Standard chlorine disinfection is not generally effective against oocysts, so removal using a filter barrier is the best option. The Cryptosporidium (Scottish Water) Directions 2003 set out the measures Scottish Water is expected to take to monitor and operate assets to prevent oocysts from contaminating drinking water supplies. Under the requirements of the Cryptosporidium (Scottish Water) Directions 2003, all Scottish Water's treatment works should have at least 12 final water samples taken and tested for Cryptosporidium during the year. The exact sample frequency is determined by the risk assessment process defined in the Cryptosporidium Directions.
In 2007, Scottish Water again improved sampling compliance with the specified sampling frequencies, with 11,393 final water samples being taken; although the total number of works at which samples were collected was slightly lower (Table 3.2-d). Of these samples, 927 contained Cryptosporidium oocysts, meaning 8.1% of final water samples were positive, a significant increase on 2006. Interestingly, the number of works recording a positive result fell in 2007, suggesting that a smaller group of works were recording a larger number of detections. Just under half of all Scottish Water's treatment works recorded at least one positive sample during 2007. The increase in the number of positive samples for Cryptosporidium in the 2007 data is not entirely surprising as during the year there were a number of high profile boil notices issued following positive detections. These included Blairnamarrow, Langholm, North Ronaldsay, Torrin and Ullapool. Further details on these boil notices may be found within the incident section of the regional pages ( Section 4) of this report.
It is possible that the high summer rainfall experienced in 2007 is to blame for the increase. What is clear, is that a number of Scottish Water's treatment works do not constitute an adequate barrier to prevent Cryptosporidium entering the water supply. Following the Summer incidents, DWQR requested that Scottish Water take appropriate measures to protect these supplies. Although the construction of the permanent treatment processes required will take time, a number of operational measures at the works and in the catchment are possible. DWQR has urged Scottish Water to fully investigate and utilise all available measures in order ensure that supplies are protected. DWQR will be monitoring this situation closely.
The maximum oocyst count in treated water in 2007 was 16.21 oocysts per 10 litres at North Ronaldsay in Orkney. Fourteen out of 49 samples taken at this works contained oocysts, with an average oocyst count of 0.45 per 10 litres. The site with the highest proportion of positive samples was Waterstein on Skye, with 83% of samples containing oocysts. This site is due to be de-commissioned and the area supplied from Glendale by the end of 2008. A total of 162 sites did not record any positive samples in 2007, this represents 54% of the sites at which samples were taken.
3.3 Drinking Water Quality in Distribution Systems
The network of water mains, service reservoirs and water towers which carries drinking water from the treatment works to the consumer is known as the distribution system. Regardless of how thoroughly drinking water has been treated, the condition of the distribution system can have a significant effect on the quality of the water passing through it. Cast iron mains can corrode and add particles of iron to the water. Deposits of iron, manganese or aluminium can accumulate in the system, perhaps from inefficient treatment processes, long since replaced. These deposits can be stirred up by changes in the flow causing discoloured supplies. If the integrity of the distribution system is breached, or re-growth of microbiological organisms occurs, bacterial contamination can occur. Careful management of the distribution system is therefore required in order to ensure that the quality of the treated drinking water is not allowed to deteriorate during its journey to consumers.
Service reservoirs and water towers are constructed at points in the distribution system to store water, both for hydraulic reasons and to even out patterns of water demand through the day. Service reservoirs that are not maintained in good structural condition can be prone to inward leakage from contaminated surface water.
Secondary disinfection is installed at some service reservoirs, but this should only be used where chlorine residuals diminish because of long distribution networks. In such cases there may be a need to boost disinfection levels to achieve a disinfection residual at the end of the network. It is important that secondary disinfection does not disguise a more fundamental problem with a service reservoir such as compromised structural integrity. Scottish Water adopts a risk-based approach to cleaning and refurbishing service reservoirs. The DWQR inspects a selection of structures each year in order to ensure that they are being maintained and operated in a way which minimises any risk to water quality.
Table 3.3-a Summary of Microbiological Tests on Samples Taken from Storage Points and Comparison with Previous Years
The Regulations require that Scottish Water sample every storage point once a week for every week it is in operation. Faecal coliforms must not be present in any sample taken from a service reservoir and for coliform bacteria, the requirement is that 95% of samples are free of contamination.
Summary results for storage points in 2007 (Table 3.3-a) compared to those for previous years show that 0.23% of samples contained coliforms. This represents a slight deterioration in compliance on 2006 - disappointing in a year when almost every other compliance measure has improved. Of the failures, 88 occurred during the months of June to September when water temperatures are higher and microbiological activity is correspondingly greater. The high rainfall in the Summer may also have been a factor, although it is vital that the integrity of storage points is maintained and they are not liable to ingress from environmental water. A number of sites recorded more than one failure. Scottish Water investigates each failure and takes action where required, reporting these to DWQR, Local Authorities and Health Boards via the event reporting system. Five samples taken from Kerse service reservoir in South Ayrshire contained coliforms. As a result, this site was audited by DWQR. Although it is likely that the siting of the sample point contributed to the failures, a number of deficiencies were also found and these are being rectified by Scottish Water. Four sites failed to meet the regulatory requirement that 95% of samples will not contain coliforms.
E.coli (faecal coliforms) were found in 16 (0.03%) of samples, half the rate of the previous year. Eleven of these sample failures occurred in July and August. One service reservoir - Holland on North Ronaldsay, Orkney - produced two samples containing E.coli during the year.
Table 3.3-b Distribution Maintenance Index ( DMI) in Scotland
Distribution Maintenance Index, or DMI, (formerly known as OPI( TIM)) is a measure used by all the UK drinking water quality regulators to monitor the performance of distribution systems. DMI looks at regulatory sample data for turbidity, iron and manganese at consumer taps. These are the three parameters that best reflect the performance of the distribution system and its tendency to cause discoloured water incidents.
Turbidity is a measure of the cloudiness of the water, and iron and manganese are the two substances most commonly associated with discoloured supplies. Whilst iron in water supplies is commonly associated with the corrosion of cast iron water mains, it may also originate from a poorly performing water treatment works which is failing to adequately remove naturally occurring iron from the raw water. Elevated levels of manganese always originate from a treatment source. Both iron and manganese may be deposited in distribution systems where low flows enable them to settle out and accumulate. Such deposits may later be disturbed by changing flow patterns causing discoloured supplies. DMI is a measure of the extent to which these substances are accumulating in the distribution system and the effectiveness of the techniques used by Scottish Water to keep the distribution system clean. A full description of DMI, which is derived from the Mean Zonal Compliance for the three parameters, can be found in Annex E.
Table 3.3-b shows that overall DMI for Scotland in 2007 was 99.15, an improvement on the 98.86 index for 2006. In 2006, 62 supply zones had an DMI of less than 100%, meaning there was at least one failure of a test for turbidity, iron or manganese. This figure was 61 in 2007, suggesting that although the number of failures of these parameters has decreased, they are spread over a similar number of supply zones. These may be the same zones as 2006, or failures that are occurring in new zones where water quality has deteriorated over the year, replacing zones where an improvement has been seen. The improvement in the overall index is due to a significant reduction in the number of iron exceedences, as the two other parameters have not seen any improvement. This suggests that, whilst Scottish Water's extensive water mains rehabilitation programme is showing benefits, more work remains to be done to improve treatment processes to ensure efficient manganese removal.
The table also shows the worst performing zones in 2007, reflected by the lowest DMI scores. Many of the supply zones listed are in the North West region. In part, this can be explained by the small populations of many of these zones which means that only a small number of samples require to be taken throughout the year. One failure within a small dataset can have a large impact upon DMI. This also explains why many of the DMI scores are the same. Despite this, there is no doubt that many of these small supplies do allow large amounts of iron to enter the distribution system, usually due to inadequate treatment.
The Authorised Departure process (described in Annex C) provides a formal process by which Scottish Ministers can track failing zones and require Scottish Water to install appropriate remedial measures. Cannich, the zone with the lowest DMI in 2006, has improved since the old supply was replaced by a new borehole source and treatment works at Tomich, such that it no longer appears in the table. A worrying new entrant to the table is Whitehillocks supply zone in the North East which had five iron failures in 2007. DWQR has submitted a list of supply zones to Scottish Water in which it expects full investigations to be undertaken in order to identify sections of main requiring rehabilitation. DMI and consumer discolouration contacts have been used to produce this list to ensure that the work is targeted at areas most in need of quality improvements.
As in previous years, several supply zones which feature on the table are in the same area of Dumfries and Galloway and are supplied by the Penwhirn, Barclye and Palnure water treatment works or a combination of these. The failure of the treatment works to remove iron and manganese and the extremely poor condition of the distribution system are having a serious impact on consumers. A large amount of work to rehabilitate water mains is underway, and consumers should be noticing a gradual improvement in quality, although the extensive nature of the work required means that it does take time to complete. The area immediately around Newton Stewart should experience a noticeable improvement in quality later in 2008 when the two non-compliant treatment works at Palnure and Barclye are replaced by a supply from the existing Penwhirn treatment works.
3.4 Drinking Water Quality at Consumer Taps
Table 3.4-a Summary of Microbiological Tests on Samples Taken at Consumer Taps with Comparison for Previous Years
Microbiological compliance at consumer taps improved significantly in 2007, building on the improvements seen the previous year. Table 3.4-a shows sample data for coliform bacteria and E.coli. Many of the larger water supply zones saw multiple coliform failures in 2007, the most notable being Milngavie M2 supply zone where 6 failures were recorded. The 5 E.coli failures all occurred in different supply zones. Scottish Water is expected to investigate all microbiological failures at consumer taps and take action to protect public health if the failure proves to be due to the water supplied rather than the tap itself.
Figure 3.4-a Year on year Comparison of the Percentage of Tests from Consumer Taps Failing the Regulatory Standard
Most tests to verify compliance with the regulations are undertaken on samples taken from consumers' taps. Sample frequencies are determined by the population of the water supply zone. Sample locations are chosen at random within the zone and it is expected that sampling will be evenly distributed throughout the year.
The ten key parameters that are of most significance for drinking water quality accounted for 90.1% of the 393 failing samples in 2007. Figure 3.4-a shows the year on year change in percentage compliance for these parameters since the introduction of the 2001 Regulations at the start of 2004. The improvement in compliance is striking, especially for colour, iron and total trihalomethanes ( THMs). This undoubtedly reflects the extensive and ongoing investment to bring the numerous small rural supplies with basic treatment up to modern standards.
Table 3.4-b summarises the results of all samples taken from consumers taps in 2007. The ten key parameters are shown first. A description of the significance of these parameters may be found on a fold-out page on the back cover of this report. The remaining parameters are listed alphabetically. The number of Authorised Departures refers to those in force for that parameter at any point during 2007.
The largest number of failing samples was for the THM parameter, with 80 samples not meeting the standard - overtaking Coliform Bacteria, for which compliance has improved significantly. Of the 1,737 samples analysed for THMs, 4.61% did not meet the standard. Although this represents an improvement on previous years, much work clearly remains to be done. This group of substances are by-products of the disinfection process and compliance is best achieved by installing treatment to remove the precursor compounds that react with chlorine to form THMs as well as ensuring tight control of chlorine dosing systems.
Iron compliance has improved markedly this year, probably in response to the extensive programme of mains rehabilitation currently underway in Scotland. Upgraded treatment processes will also be partly responsible for this improvement. The benefit of this work should be noticed by consumers as a reduction in the amount of times they experience discoloured water.
Unfortunately, the manganese parameter, which is also responsible for causing discoloured supplies, has not shown an improvement in compliance in 2007. This is disappointing, especially as there is extensive work nearing completion in North Ayrshire, a former manganese "hotspot". It is likely that the full benefits of this work are yet to be felt, but also, and more worryingly, another location - Loch Eck Supply Zone around Dunoon - is showing a marked deterioration in compliance for this parameter. Scottish Water is examining how it might include the necessary remedial work in its current investment programme. DWQR is of the opinion that such work has now become urgent, and needs to proceed without delay.
Table 3.4-b Summary of all Tests on Consumer Tap Samples during 2007
*Only parameters in Schedule 1 of the Regulations (shaded) are used in the calculation of Overall Compliance
Compliance with the standards for the non-key parameters has also improved. Scottish Water has taken action to resolve local issues that were causing failures of the standards for ammonium, bromate and nitrite. The failures of the nitrite standard in 2006 were an issue in the supply zones supplied by Marchbank WTW to the west of Edinburgh. Scottish Water has taken action to reduce nitrification in the distribution system and improve control of the chloramination process at the treatment works. Results are currently encouraging, although DWQR will continue to watch closely.
Work is underway to improve compliance with the current lead standard of 25µg/l and the revised standard of 10µg/l, which takes effect from 2013. Lead is not present in water leaving the treatment works, but may be dissolved from old lead pipes that are sometimes present in consumer plumbing and communication pipes connecting properties to the water main. Properties constructed after about 1970 do not generally contain lead, although some plumbing after this date contains solder with a high lead content; a practice that has also now been discontinued. Map 3.4 shows exceedences of the current lead standard and the future revised 10µg/l standard in Scotland during 2007. Scottish Water is making progress to install and optimise phosphate dosing at works supplying those zones identified as being at risk of exceeding the lead standard. Phosphate inhibits the tendency of the water to dissolve lead, and DWQR is monitoring this work closely. Where this work is nearing completion, water supply zones are surveyed to establish whether or not they will comply with the 10µg/l standard. These surveys are to be completed by February 2009, at which point a decision will be taken as to the requirement for any future work. The only certain, and sustainable, way of achieving full compliance with the standard is to remove all lead pipework. This will prove a difficult task to achieve as much of it is in privately owned properties, however DWQR will be working with other groups to try to find an appropriate means of progressing towards this ultimate goal.
Map 3.4 Failures of Existing (25µg/l) and Future (10µg/l) Lead Standard in 2007
3.5 Summary of Drinking Water Quality Events and Incidents
Scottish Water must inform DWQR of any event at a water treatment works or in the distribution system that could adversely affect water quality, cause concern to consumers or attract media attention. Each event is assessed by the DWQR and may be classified as an incident, if it was sufficiently serious or had the potential to be serious. Usually, DWQR will request a full report from Scottish Water on the causes and impact of any incident, including details of the remedial action taken and actions by Scottish Water to prevent a recurrence. Where appropriate DWQR will investigate further. All events where a boil notice or alternative supplies are issued are classified as an incident regardless of whether a report is requested by DWQR.
Table 3.5-a Summary of Drinking Water Quality Incidents in 2007
Figure 3.5-a Summary of 2007 Drinking Water Quality Incidents by Type and Waterwatch Scotland Area
In 2007, 1,407 event notifications were received from Scottish Water. Of these, 64 were classified as incidents by DWQR.
Table 3.5-a and Figure 3.5-a summarise the drinking water quality incidents that occurred during 2007. Despite the ongoing improvements to the treatment processes and water quality alarm systems at the many small water treatment works in the North West region, this area still generates the majority of incidents. Many of the incidents involved failures of the disinfection process where chlorine dosing failed for various reasons. However, DWQR has noted that there was an increase in 2007 in the number of events where a water quality alarm resulted in prompt action by operational staff, thus preventing an event becoming a more serious incident. This is encouraging, but more work is needed to ensure that this type of response becomes the norm and the number of incidents reduces.
Failures of the treatment process in the South West area in 2007, often involved the coagulation process where pH control was not as robust as it should have been. The number of incidents reported from the Island region reduced significantly in 2007.
A notable feature of 2007 was the number of incidents involving the detection of Cryptosporidium in treated water. Several communities, including Tomintoul (Blairnamarrow) in Moray, and Langholm in Dumfries and Galloway had multiple boil water notices imposed by the local NHS Board in order to protect public health. The presence of Cryptosporidium in the water supply was partly due to the extremely wet weather last summer, but also because the treatment process at the works serving these communities was not sufficiently robust to deal with the risk presented by the incoming raw water. NHS Boards, politicians and local people have all expressed their concern over the issue. The situation is clearly unacceptable, and DWQR has worked with Scottish Water to ensure that improved treatment is put in place at these sites.
However, temporary solutions remain in place at Blairnamarrow and Langholm because progress with the permanent solution has taken longer than hoped. While DWQR appreciates the complexities of the capital investment framework within which Scottish Water operates, public health must not be put at risk. DWQR is therefore considering taking enforcement action to ensure that a degree of urgency is applied to the improvements. DWQR expects a more proactive approach from Scottish Water in identifying risk posed by inadequacies in its water treatment processes to ensure that, as far as possible, improvements can be planned and public health protected.
3.6 Summary of Contacts about Drinking Water Quality
Scottish Water is required to record details of any complaints or enquiries it receives from consumers concerning drinking water quality. These contacts may be received by telephone, letter or email.
Table 3.6-a and Figure 3.6-a show the number and type of telephone contacts recorded by Scottish Water in 2007. The meaning of the categories used by Scottish Water is described below:
Appearance of the Water
Discoloured Water
Water with a discernable taint or colour caused by suspended or dissolved matter. Two of the most common causes are a yellow taint caused by dissolved organic matter arising from peat in upland sources and more general orange, brown or black discolouration caused by suspended particles of iron (orange/brown) and manganese (black). Iron discolouration may occur through natural iron present in the raw water passing through inadequate treatment or from corrosion of cast iron distribution mains. Manganese is present in some raw waters and may not be removed if treatment is inadequate.
Aerated (Milky or Cloudy) Water
Water which has a milky appearance caused by tiny bubbles of entrained air which dissolve in the water under pressure but come out of solution at the consumer's tap. A number of causes are possible including burst mains, malfunctioning pumps and throttled consumer stop taps. If air is the cause of the milky water, the cloudy appearance will clear in a glass of water from the bottom up.
Stained Washing
Brown or black staining of clothes can occur on clothes inadvertently washed in discoloured water. If clothes are kept damp, the staining can often be removed by gently acidifying with a suitable substance such as citric acid. However, staining may also arise from a fault with the washing machine.
Particles in water
Visible particulate matter in water which is otherwise not discoloured. This can be caused by corrosion of iron mains or deposits of sand, grit or other material present in the main being re-suspended following a change in the flow in the main.
Organisms in water
Complaints of insects or other animals in the water supply. Most complaints arise where an insect has crawled up a tap or is present in the sink. Very occasionally water systems can contain animals which may arise from the raw water, treatment works or within the mains themselves. This is extremely rare, however organisms such as midge larvae ( Chironomid) or water shrimp ( Aesellus) have occasionally been found in domestic supplies.
Taste or Smell of the Water
Chlorine or Phenolic
Excess residual chlorine or the reaction of chlorine with phenolic compounds which may be present in household plumbing can result in taste and smells. Chlorine taste and smells should dissipate if the water is left to stand in the fridge for a few hours. It will also not be present after boiling. Phenolic tastes can be more persistent. Common descriptions used by customers include TCP, medicinal, swimming pool, bitter, and chemical. Common sources of phenol include washing machine hoses, tap washers and kettles. British Standard approved plumbing products which do not contain phenol should be used in all plumbing installations.
Metallic
Metallic tastes may arise from an excess of iron, aluminium or other metal dissolved in the water, although normally there will also be visible discolouration. Occasionally phenolic complaints may be described as metallic.
Musty or Earthy
Musty or Earthy tastes can arise due to naturally occurring compounds present in raw waters that have not been removed by the treatment process. Geosmin is one such compound commonly associated with earthy/musty tastes. Complaints are more common in the summer months when biological activity is highest - algal blooms in raw water sources are common causes of widespread musty tastes.
Figure 3.6-a Categories of Water Quality Contact (Complaint and Enquiry) Received by Scottish Water in 2007
Table 3.6-a Drinking Water Quality Contacts Received by Scottish Water During 2007 - Comparison with 2006
The pie chart and table show the number and type of contacts received by Scottish Water about drinking water quality in 2007. The figures are a sum of what Scottish Water classifies as complaints and enquiries. Having audited Scottish Water's consumer contact handling process with respect to drinking water quality in early 2008, DWQR considers it unhelpful to make the distinction between these types of contact, and consequently has added the two classifications together. In last year's report Drinking Water Quality in Scotland 2006, only those contacts Scottish Water classified as complaints were considered in this section of the report. A category relating to consumer requests for information has been excluded from the figures as it was evident that this contained a significant proportion of contacts unrelated to quality.
In 2007, Scottish Water report that they received 26,702 consumer contacts, representing a reduction of 16% on 2006. As in previous years, by far the largest category of contacts received (70%) related to the discolouration of water supplies. As the benefits of Scottish Water's programme of rehabilitation of cast iron mains begins to realised, DWQR expects the number of discolouration contacts received to fall sharply in future years. Areas that experienced large numbers of contacts in 2006 such as North Ayrshire and Newton Stewart in Dumfries and Galloway were again prominent in the 2007 data. Work is well under way in both of these areas to improve the quality of supplies, and DWQR expects to be able to report a significant reduction in the number of discolouration contacts from both of these areas in 2008.
During the course of 2007, a few other areas have experienced significant numbers of discolouration contacts. Loch Eck Supply Zone in the Cowal Peninsular around Dunoon, Loch Ascog Supply Zone on Bute and Gartcarron Supply Zone in rural Stirlingshire all generated significant numbers of discolouration contacts and contact rates in excess of 200 per 10,000 population. Work is planned at Loch Ascog treatment works in order to install a manganese removal process which should prevent naturally occurring manganese from entering supply and discolouring the water. DWQR is currently pressing Scottish Water to take similar action at Loch Eck treatment works. It is likely that the discolouration in Stirlingshire is due to iron sediment, and Scottish Water is working to identify and address the section of mains causing the issue.
Milky or cloudy water is an occurrence that can be quite alarming to consumers although the usual cause is a simple one - air dissolved in the water. In 2007, 11 % of contacts were due to this, with Camps Supply Zone in Lanarkshire and Castlehill Supply Zone in North Ayrshire reporting a significant number of contacts about milky water. In Castlehill, this may have been the rehabilitation work that was underway during 2007, enabling air to enter the mains. If so, 2008 should see an improvement.
Contacts to Scottish Water about tastes and odours have reduced significantly in 2007. The largest decrease was for chlorine or phenolic tastes and odours, where contacts have more than halved. Many of the contacts in this category in 2006 were from the two Marchbank supply zones covering Western Edinburgh and parts of West Lothian. The majority of these contacts, nearly 800, were received in association with the incident at Marchbank WTW in July 2006, although it seems as though chlorine contacts in these zones have reduced significantly throughout the year, perhaps due to Scottish Water's efforts to control nitrite formation in the distribution system. A notable decrease in chlorine contacts was also seen in Forehill supply zone, covering Peterhead. This area was highlighted by DWQR in last year's annual report.
While this apparent reduction in contacts is to be welcomed, DWQR's perception from contacts received directly by the Regulator and via Waterwatch Scotland is that the taste and smell of the water is becoming more, not less, important to consumers. Two Shetland water supply zones - Lerwick and Eela Water - recorded a particularly high rate of contacts about chlorine tastes. Further details may be found in Chapter 4.
Figure 3.6-b Number of Treatment Works in Each Disinfection Index Category by Year
It is vital that all drinking water supplies are adequately disinfected to ensure that pathogens such as E.coli are not present. Chlorine has been used to disinfect water supplies for over 100 years and is a safe and established technique that is used throughout the world. Some people are very sensitive to the taste of chlorine and find it unpleasant. One way of minimising the impact of chlorine on consumers, as well as reducing the likelihood of chemical by-products forming in the water, is to ensure chlorine dosing is consistent without large fluctuations in concentration.
The DWQR uses a "disinfection index" to assess control of chlorine at treatment works, and has set Scottish Water targets linked to the investment process to ensure improvements are made at the sites in most need of improved control. A higher disinfection index indicates less consistent dosing of chlorine. Scottish Water has been set the target of ensuring all treatment works have a disinfection index below 100 by 2010. The number of treatment works falling within each disinfection index category for each region for the last three years is shown in Figure 3.6-b. It can be seen that the number of treatment works in the poorest performing category (greater than 100) has significantly reduced over the four years that the index has been used.
3B Private Water Supplies in Scotland
It is acknowledged that the quality of water from private supplies is highly variable and when poor can cause significant health problems. This section discusses the situation in Scotland and the regulatory framework that has been developed to facilitate improvements in the quality of drinking water from private water supplies.
It has been estimated that around 150,000 people in Scotland rely on a private water supply for their drinking water with thousands more using them occasionally each year, typically when they are on holiday. Definitive numbers are difficult to obtain as the number of supplies and the use to which they are put constantly changes across Scotland. In the data returns requested from local authorities, the DWQR asked for the population on private water supplies in each local authority area and defined this number as being "the maximum number supplied on any one day". This definition allows a truer picture of the potential exposure to drinking water from private water supplies and from the returns we find that around 3.35% of the population is using private water supplies for drinking water.
This number masks the "transient" population, i.e. those who travel into an area for example on holiday, stay a few days or weeks at most and then move on. A number of studies suggest that this transient population is at greatest risk from illness arising from private water supplies. DWQR, in collaboration with the Scottish Government and agencies such as the Food Standards Agency, is actively engaged in trying to further understand this complex situation and in the 2008 annual report, DWQR will hopefully be able to provide a more robust estimate of the transient population number.
The Private Water Supplies (Scotland) Regulations and associated grant scheme came into force on 3 July 2006. These measures were required to implement the European Drinking Water Directive 98/83/ EC and also incorporate other recommendations on the delivery of safe drinking water, including elements of the latest guidance from the World Health Organisation and Scotland's E.coli O157 Task Force Report. The strengthened Regulations build on earlier Regulations that had been in force since 1992. The principle aim of the strengthened regulatory framework is to ensure that all those who use private water supplies can do so safely.
A private water supply is any supply which is not provided by the statutory water undertaker, which in Scotland is Scottish Water. Private water supplies are classified as Type A or Type B. Type A supplies attract mandatory monitoring and enforcement of water quality standards by local authorities; Type B supplies are subject to a discretionary regime which, in approach, is similar to the previous regulatory regime.
Local authorities are responsible for the enforcement of the strengthened Regulations. The duty (and cost) of ensuring a private water supply meets the requisite standard falls on the "relevant person". The local authority must identify the relevant person for each supply. It will be:
(a) the person providing the supply; or
(b) the person occupying the land from, or on, which the supply is obtained; or
(c) any person who exercises powers of management or control in relation to the supply.
The relevant person could, therefore, be a landowner who has sold or rented properties which rely on a private supply that originates on his land, or a tenant if he occupies the land on which the supply originates. In the case of a failure to comply which is due to the pipework within a property, the owner or person responsible for the pipework in the property (the "responsible person") is stated to be liable for rectifying the deficiency.
Relevant persons on a Type A supply may apply for a temporary departure from the statutory requirements if they believe the supply will fail to meet one or more of the quality standards. A temporary departure may only be authorised if certain conditions are met. There are notification requirements to publicise any temporary departure to those who may be affected. Temporary departures are intended to last for the minimum period necessary to complete the remedial action but they can last for up to three years. In exceptional circumstances an authorised departure can be extended.
Risk Assessments
A core part of the revised regulatory package is the introduction of risk assessments for private water supplies. These risk assessments are designed to highlight any real or potential risks to drinking water quality. For example, the risk assessment requires the source of the private water supply to be examined to ensure that access to animals is denied. If animals can access the source then there is potential for faecal contamination to occur resulting in human illness.
Local authorities were required to complete risk assessments for all Type A supplies in their area as soon as practicable but with a target date of 31 December 2007 set for completion. Despite assurances from local authorities that the vast majority of Type A supplies would be risk assessed by the target date, the data returns for 2007 show that only around 27% of Type A risk assessments had been completed by the due date. While it is for individual local authorities to ensure that they comply with the requirements of the revised Regulations, DWQR is concerned about that apparent lack of progress reported by local authorities. The situation will be monitored closely through 2008 and unless there is a very significant improvement in the completion and reporting of Type A risk assessments, DWQR will undertake a detailed audit of local authority activity in respect of Type A risk assessments and, if necessary, seek additional powers to ensure that local authorities carry out their duties in respect of the Private Water Supplies (Scotland) Regulations 2006.
Information Notices
Any premises served by a private water supply, which is used as part of a commercial or public activity must display an information notice indicating that it is served by such a supply. This requirement fulfils a commitment made by the Scottish Government to implement the recommendations of the E. coli O157 Task Force report.
Grant Scheme
The Scottish Government has funded a grant scheme, available through local authorities, to assist with the one-off costs of works to improve the nature or quality of a private supply. This can include the installation of treatment equipment or the provision of a new private supply or domestic distribution system of up to the value of £800.
While details of the uptake of the Grant Scheme is properly a matter for the Scottish Government to publish, DWQR notes that there has been a slow up take of the Scheme and endorses the efforts of both the Scottish Government and local authorities in trying to encourage greater uptake and also to undertake research into the possible issues that are preventing users and owners of private water supplies from accessing this resource to improve the quality of their drinking water.
Small Community Supply Management Network ( SCSMN), World Health Organisation ( WHO)
In October 2007, DWQR along with the Scottish Government and the Drinking Water Inspectorate for England and Wales hosted the 4th meeting of the World Health Organisation's Small Community Supply Management Network. At the meeting delegates from over 17 countries as diverse as Australia and Uganda, Bangladesh and St Lucia, participated in meetings and seminars that ran over 4 days in Edinburgh. The work being done in Scotland in trying to address the issues associated with drinking water quality from private water supplies (also known as small community supplies) was show-cased to the delegates and the developments being made in Scotland were acknowledged as being at the forefront of such developments across the world.
The DWQR is delighted to be associated with the SCSM Network and is committed to continued participation of the work of the Network. Further details of the Network can be found on the WHO website: ( http://www.who.int/water_sanitation_health/dwq/scwsm_network/en/index.html).
Delegates to the SCSM Network meeting, Edinburgh October 2007
More Information
For more information on private water supplies a website www.privatewatersupplies.gov.uk
has been built specifically to assist the owner and users of private water supplies. A toolkit has also been developed for distribution through local authorities, which provides information designed to support improvements in drinking water quality. Users and owners can also contact their local authority environmental health department directly (their contact details will be in the local telephone directory).
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