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4.2 Drinking Water Quality in the North West

Treatment Works

Table 4.2-a Samples Taken from Water Treatment Works Supplying the North West

Microbiological compliance in the North West improved dramatically in 2007, probably reflecting the extensive work that is currently underway to modernise treatment facilities. Coliforms were detected in only eight samples in 2007 (Table 4.2-a), compared with 28 in 2006, and E.coli compliance is showing a similar marked improvement. Turbidity failures at treatment works halved in 2007, although two nitrite exceedences occurred at Backies WTW, whereas no failures were recorded in the North West in the previous year.

Table 4.2-b Summary of Disinfection Indices at Treatment Works in the North West

The disinfection index ( DI) is used by the DWQR to track the progress being made by Scottish Water in improving control of its disinfection processes. This is to make sure that all supplies are thoroughly disinfected to keep them safe, whilst at the same time, limiting the extent to which chlorine concentrations fluctuate. Inconsistent chlorine residuals in water leaving treatment works are a major cause of taste and odour complaints from consumers. The higher the DI, the less consistent the chlorine level in water leaving the treatment works. Scottish Water is funded to undertake work to ensure all water treatment works have a DI of less than 100 by 2010. Disinfection indices have continued to improve significantly in 2007 in the North West (Table 4.2-b), with good progress made to achieving the target for 2010, which will undoubtedly have contributed to the improvements in trihalomethane compliance seen in the region, as poor control of chlorination favours the formation of these by-products.

Distribution System

Table 4.2-c Summary of Samples taken from Service Reservoirs in the North West

*95% samples shall not contain coliforms; 100% shall not contain E.coli

Unlike some other regions in Scottish Water, the North West saw a significant improvement in microbiological compliance at service reservoirs. Notably, only four samples contained E.coli (Table 4.2-c), down from 19 in 2006. No storage points in the region failed to meet the required 95% coliform compliance standard.

Table 4.2-d DMI in the North West - Supply Zones not scoring 100%

Table 4.2-d shows DMI for supply zones in the North West not scoring 100%. Many of the supply zones at the top of this list have a low DMI due to one or two failures within a very small dataset. Of the larger zones, Loch Eck in Argyll is becoming a major concern due to persistent failures of the manganese standard. Manganese has recently become a problem in the raw water supplying the treatment works. As there are no processes capable of removing it at the works, it is building up in the distribution system, causing noticeable discolouration of supplies as well as sample failures. DWQR is putting pressure on Scottish Water to commit to making the necessary improvements to treatment, and will take enforcement action if necessary.

Consumer Contacts

Figure 4.2-a Consumer Contacts about Drinking Water Quality in the North West

Scottish Water's North West region generated 3,107 contacts from consumers about water quality, giving a rate of 67.8 per 10,000 population, which is about the average for Scotland as a whole Figure 4.2-a. The majority of these complaints related to discoloured water and many of the areas where these complaints came from also feature in Table 4.2-d, which gives the DMI results. Areas with a low DMI, which also received a high number of complaints, include Assynt, Badentinan and Inverness. Figure 4.2-b relates consumer contacts to DMI in the North West.

Figure 4.2-b DMI and Consumer Discolouration Complaints in the North West

Incidents

In 2007, there were 42 water quality incidents in the North West region. The majority of these failures (69 percent) were due to failures of the disinfection system. To some degree, this is a reflection of the basic nature and geographical remoteness of the treatment facilities in this region as there are many very small water treatment works scattered over a large area. Most of these works provide only simple disinfection with no other form of treatment and although many did not have power or telemetry in the past, this is often no longer the case. The high levels of Cryptosporidium at Inverinate should no longer be an issue, as that area is now supplied by the Kyle treatment works. DWQR is in ongoing discussions with Scottish Water regarding reducing the risk of Cryptosporidium in the supplies at Blairnamarrow and Torrin.

Achmelvich, 12 January 2007 - Disinfection Failure

This disinfection failure was caused by the chlorine-dosing pump failing to receive a signal from the flow meter after a cable shorted out due to adverse weather conditions. Due to the lack of telemetry on the site, the failure was only discovered during a routine visit. Scottish Water had already undertaken to visit this site on a daily basis (including weekends) until mains power and telemetry was installed and commissioned (by 28/03/07).

Scottish Water agreed: (i) to protect the cable between the flow meter and the dosing pump, (ii) to make Operational Team leaders aware of the need to communicate incidents/events directly to the Public Health Team, and (iii) to review task schedules to ensure all appropriate water quality tests are completed.

Kilmuir, 29 January 2007 - Disinfection Failure

This disinfection failure incident was caused by a corroded connection on the battery which provides power for the dosing pump. Due to the lack of any telemetry on the site, this was only noticed during a routine visit, which normally takes place three times a week.

Having discovered the problem, DWQR is content with the actions taken, which include informing Scottish Water's Public Health Team. However, DWQR expects the Public Health Team to be informed immediately there is a problem and not after one hour as was the case in this instance. DWQR is also concerned about the fact that incident samples were not taken "due to the remote location of the works and the limited availability of operations and sampling staff". Samples were taken later but it is of no surprise that these all passed since they were taken after the problem had been fixed.

As a result of this incident, Scottish Water agreed to visit the site on a daily basis until the works is upgraded, to review whether visual checking of battery terminals for evidence of corrosion needs to be added to task schedule for battery sites, install duty/standby auto-changeover system for the disinfection dosing pumps, investigate the feasibility of installing mains power, telemetry and chlorine monitoring at the works, and ensure satisfactory arrangements are in place for adequate sampling following an incident/event.

Invermoriston, 31 January 2007 - Disinfection Failure

This disinfection failure incident was caused by a breach in the signal cable between the flow meter and the disinfection pumps.

The works is on telemetry but the low chlorine alarm had been suppressed, so the failure was only discovered through a sampler taking a routine sample from the works.

The samples taken from the works outlet all failed bacteriologically. Had the alarm not been suppressed, this incident could easily have been averted.

Suppressed alarm reports are available on Scottish Water's Telemetry reporting system. Team Leaders are to be reminded of the existence of this report and to check it regularly to identify unexpected suppressed alarms. Scotland wide training, based on previous incidents and events, will include the appropriate actions to be taken in the event of a disinfection failure.

DWQR expects the suppressed alarm reports to be checked on a Scotland-wide basis and not just in this region.

Dalwhinnie, 5 February 2007 - Disinfection Failure

This disinfection failure incident was caused by an air lock in the disinfection pump. Due to the lack of telemetry on the site, this was only noticed during a twice-weekly routine visit. DWQR is content with Scottish Water's response following discovery of the problem but would expect the Public Health Team to be informed immediately, not after 5 hours as was the case in this instance.

There was a further delay of about 3 hours before samples were taken from the works outlet and from the distribution system. These delays were a recurring theme at the start of 2007 and although Scottish Water said it was informing operational staff of the importance to engage with the Public Health Team immediately, the message did not get through initially. DWQR has noted a recent improvement in such matters.

DWQR was also concerned that the reason for the delay in sampling was that "the operator had to travel to Inverness to get bacteriological bottles". This is unacceptable and such items must be closer to hand in case of incidents.

As a result of this incident, Scottish Water introduced Scotland-wide "Operator Awareness Training", which includes appropriate actions to be taken in the event of a disinfection failure. Site visits were also increased at Dalwhinnie to three times a week, until a more robust chlorination system and telemetry is installed.

Lochinver, 11 February 2007 - Disinfection Failure

This disinfection failure incident was caused by a blockage (believed to be crystallisation of the disinfectant) in the disinfection dosing line.

The initial low chlorine alarm was investigated at 22:30 on 11 February by a Network Service Operator on standby, not a treatment operator. This person did not fully investigate the problem and did not notice that there was no flow to the chlorine monitor. It was only after discussing the matter with the treatment team leader early the next morning that the issue was fully investigated at 09:30 on 12 February.

Scottish Water's Public Health Team were only informed via email at 13:18 on 12 February. This is far too late in the proceedings. The Public Health Team should be informed immediately a problem such as this is discovered and this should be by telephone in the first instance.

Scotland wide 'Operator Event Awareness Training' was introduced by Scottish Water. This training, based upon previous incidents and events, includes appropriate actions to be taken in the event of a low chlorine alarm.

Sallachy, 14 February 2007 - Disinfection Failure

This disinfection failure was caused by heavy rain, which caused a deterioration in the quality of the raw water which then increased the chlorine demand at the works. Due to the lack of a robust residual chlorine dosing system, the disinfection dose would not have been increased automatically in line with the demand. This therefore resulted in a loss of the "normal" disinfection residual.

Residual chlorine dosing should have been installed as a result of a previous incident in August 2006 but such a system needs a reliable and consistent power source, so the preferred option was to main out this site from Kyle water treatment works. Sallachy was subsequently connected to the Kyle water treatment works later in 2007.

Blackpark, 15 February 2007 - Disinfection Failure

This disinfection failure was caused by an airlock in the disinfection dosing pumps due to modifications carried out the day before the incident.

A low chlorine alarm was initiated on the telemetry system but there was a one and a half hour delay between the control room picking this up and relaying it to the local operator. This was partly to "prevent unnecessary call out" and also because the duty controller "would have assumed that the site would have treated water storage available".

There was a one and three quarter hour delay between the operator arriving on the site and a sample of the final water being taken for analysis. Whilst not excessive, any such delay of this type should be reduced to an absolute minimum. Taking of samples should be one of the first actions carried out in incidents of this nature.

As a result of this incident, electrical and mechanical personnel were to undergo Scotland-wide "Operator Event Awareness Training" to make them more aware of the possible consequences of their actions. Instructions were also given to the control centre that all chlorine alarms have to be dispatched within 15 minutes whenever possible.

Scourie, 2 March 2007 - Disinfection Failure

This incident was caused by a failure of the disinfection dosing pump. The pump failure should have been picked up by the telemetry system but it would appear that the telemetry cable may have been damaged when the pump was replaced due to an earlier failure of the pump on 17 February 2007. The DWQR assessment of this earlier event was that prompt action was taken and that it did not therefore warrant an incident report.

Scottish Water's Public Heath Team was promptly informed in this incident to aid appropriate decisions to be taken in relation to sampling and the protection of public health.

Operators are to check telemetry connections when pumps are replaced and pump fail alarms are to be manually generated to check that the telemetry system picks them up.

Sallachy, 17 March 2007 - Disinfection Failure

This incident was caused by a partial blockage of the intake resulting in a reduction of the raw water flow which in turn caused the disinfection dosing pump to stop.

The site is on telemetry and a low chlorine alarm was sent from the works to Scottish Water's central control room where the staff there say they passed the alarm on to the appropriate local person. However, the local staff contest that they never received an alarm.

The disinfection failure therefore continued for over two days until the next scheduled visit by the operator. Once on site, the operator dealt with the failure efficiently and the problem was fixed within 2 hours. However, the operator should have informed Scottish Water's Public Health Team and should have taken or arranged for water samples to be taken immediately for analysis instead of waiting until he had fixed the problem. It is therefore of no surprise that the samples that were taken, passed. Actions are being taken by Scottish Water centrally to address issues such as these more widely within the business and Scottish Water should reap the benefits of these actions in time.

This was the third such disinfection failure at this works in as many months so DWQR issued a draft Enforcement Notice to Scottish Water to address the matter by accelerating its proposal to supply Sallachy from the Kyle works by 1 June 2007. This work was completed before the end of May 2007.

Glenfinnan, 17 March 2007 - Disinfection Failure

This incident was caused by the failure of the chlorine-dosing pump to start in conjunction with the plant start up. There was no information to determine the reason for the pump fails but inadequate and incorrect prioritisation of telemetry alarms associated with the dosed chlorine system resulted in no action being taken.

The incident was exacerbated by issues surrounding the telemetry systems both in terms of the correct response to alarms and the correct prioritising of the alarms themselves. The failure of Scottish Water staff to comply with policies and procedures put in place to protect public health is a cause for serious concern and the continuing training and development of operational staff is an issue that has and will continue to feature in audits of Scottish Water staff undertaken by the DWQR.

Dornie, 21 March 2007 - Disinfection Failure

Evaluation of the Incident Report suggests that had the telemetry alarm for the loss of battery power been correctly assigned as a Priority 2 alarm then the incident may have been avoided. However, a further opportunity to prevent the event escalating to an incident was lost when the Priority 2 communications failure alarm (telling staff that the communications signal from the plant had been lost) was not passed to the appropriate operational staff upon receipt at the control centre. Given the reliance by Scottish Water on such battery back-up systems in these remote locations it is disappointing to note that only following this incident is a weekly battery check test to be included in the schedule of work required to be undertaken by operators. This is not the first time a battery system has failed with the resulting loss of disinfection and it would have been reasonable to assume that Scottish Water would have taken appropriate steps to prevent a recurrence. The incorporation, albeit belatedly, of the risk based maintenance scheduled task for battery condition checks at sites where battery powered dosing systems are in place along with the inclusion of weekly battery tests on the scheduled tasks for operators is welcomed by DWQR.

Dalwhinnie, 6 April 2007 - Disinfection Failure

The incident was caused by air-locked dosing lines in the disinfection system but it is concerning that following the first occurrence of the problem on 6 April 2007 that Scottish Water waited until the second occurrence on 16 April 2007 before instigating daily checks by the operator on the treatment plant. Given that the works at the time of the two incidents did not have telemetry, the level of risk posed by a failure of the disinfection system was substantially higher than for a works where an appropriate telemetry system was installed. While DWQR welcomes the daily site visits by an operator until a telemetry system is installed and operating it is unfortunate that such a risk-sensitive approach was not operating prior to these incidents. To prevent any future occurrence of this type of treatment failure, DWQR required Scottish Water to review the frequency of operator checks on all treatment works where there is no installed and/or operating telemetry systems and report on the outcome of that review. Scottish Water subsequently agreed to visit all water treatment works that did not have telemetry at least three times a week.

Inverinate, 10 April 2007 - Disinfection Failure

This incident was caused by bad weather resulting in poor raw water quality. The poor raw water quality increased the chlorine demand, but since the system can only be adjusted manually, it had to wait for a routine visit from the operator to carry out these adjustments. Scottish Water subsequently agreed to visit the site daily until the works was abandoned and the area supplied by the Kyle works which eventually took place et the end of 2007.

Shieldaig, 23 April 2007 - Disinfection Failure

This disinfection failure was caused by heavy rain resulting in poor raw water quality. Since the chlorine is only dosed proportionate to the volume of flow through the works it had to be adjusted manually to cater for varying qualities of raw water. The site was only visited twice per week and this was insufficient to ensure adequate disinfection at times of poor water quality.

Scottish Water is planning to introduce additional appropriate treatment at the plant before the end of March 2009.

Acharacle, 23 April 2007 - Disinfection Failure

This incident was the result of a catalogue of errors but basically it was caused by a failure of one of the disinfection pumps. A low chlorine alarm was initiated at around midday on Sunday 22 April 2007, but this was not acknowledged due to the operator having suppressed the alarm the previous day. However, the plant shut down automatically as it was designed to because of low chlorine later that day. A low level clear water tank alarm later on resulted in a visit to the site at which time the plant was switched to manual operation. Further low chlorine alarms were initiated but were not acted on properly due to the suppression of the alarm. This suppression was removed early the following day (Monday 23 April) and another low chlorine alarm followed on from this. The site was visited, the disinfection pumps switched over and the two clear water tanks dosed with additional chlorine but this latter operation was not carried out in accordance with procedures. There were further low chlorine alarms during the course of Monday 23 April and the plant continued to be run on manual until 10:00 on Thursday 3 May.

Actions included a review of the operation of the works, a review of the telemetry system (including all alarms), checking the plant to ensure it was fit for purpose (it was still under warranty at the time), communicating the severity of this incident to all operational staff and stressing the importance of complying with procedures, providing additional training for staff and placing the operator concerned on a formal performance review which will be monitored monthly. The procedure for alarm suppression was also to be reviewed.

Assynt, 28 April 2007 - Disinfection Failure

This disinfection failure incident was caused by the operator not filling the ammonium sulphate vat, which is an essential chemical in the chloramination process. A low chlorine dose alarm was received by the Operations Management Centre but the operator was not called out to investigate. It would appear that the final water chlorine alarm at Assynt water treatment works was not on the telemetry system.

In addition to the above, the sample line to the automatic coagulation unit had been switched off. This resulted in too high a dose of polymer being added which affected the coagulation process resulting in highly coloured water which had a high chlorine demand. It would appear that there are no alarms on the automatic coagulation unit which would have given an early warning of a problem with it.

Actions included a full review of the telemetry including alarms, priorities and end to end testing, ensuring that operators fully understand the procedures to follow in the event of a breach of Emergency Action Levels, adding the automatic coagulation unit to telemetry, adding treated and final water chlorine alarms to telemetry and ensuring that all operators receive training in event and incident awareness.

Londornoch, 2 June 2007 - Coagulation Failure

This aluminium failure was essentially caused by the operator adjusting the pH control to deal with an increase in turbidity without first discussing the issue with the local process scientist. The situation was exacerbated by the changes having been made towards the end of the working day and the operator leaving the works without waiting to check the effects of the changes he had made. Furthermore, it appears that high priority alarms were suppressed since the operator claimed not to have received any alarm calls later that night or early the next morning. Even when the operator did acknowledge the aluminium alarm, there was a delay before he arrived on site.

Operators should have been instructed not to make changes to the process without discussing these first with the process scientist and Scottish Water should investigate delays in response to alarms. Operators must understand the importance of reacting to alarms. Scottish Water's due diligence can be brought into question if there is any failure on their part in this area.

Inverasdale, 14 June 2007 - High Turbidity

The elevation in turbidity experienced during this incident was due to the draw down of the system by tanker operations in the area. The loss of the on-line turbidity meter occurred 4 days prior to the tanker operations (on 8 June) but the tanker log shows that no problems were highlighted at the water treatment works or the clear water tank associated with the works. The length of time taken to deal with the inoperative turbidity meter is a cause for concern. Scottish Water noted that there were 41 High Priority jobs and 13 Urgent jobs in the area at the time of the incident. Scottish Water should put measures in place to monitor Urgent and High Priority job requests along with the provision of appropriate resources to ensure that inappropriate delays or backlogs do not occur.

Oykel Bridge, 15 June 2007 - Disinfection Failure

This was caused by a power failure on Monday 11 June 2007 which caused the circuit breaker for the inlet flow meter to trip. When the power came back on the flow restarted but the trip for the inlet flow meter had not been re-set, so the disinfection pump did not detect any flow so did not start to pump. Thus undisinfected water was going into supply. The operator had been out earlier in the day to investigate an earlier power fail and had carried out various tasks to restore the works. However, a second power fail occurred after the operator had left the site and although a low chlorine alarm alerted Scottish Water's Operational Management Centre, it wrongly assumed that the operator was still on site so did not contact him again to investigate this second power fail. A further low chlorine alarm later in the day was generated and passed to the operator, but no action appears to have been taken. Another low chlorine alarm very early the next morning was passed to the operator who took no action assuming that it was another faulty reading as there had been a few in the weeks leading up to the incident. A further low chlorine alarm about an hour later was passed out to the operator who could not recall receiving it. Since the site is only visited twice a week, all of this went without investigation until the next routine visit on the Friday 15 June 2007. Undisinfected water was therefore going into supply for almost 4 days. Furthermore it was not until the situation had been resolved by mid afternoon on the Friday that Scottish Water's Public Health Team was informed and appropriate samples taken. By this time, the works was running properly again and all the samples subsequently passed. However, even the process of taking the samples was not without fault as it was delayed due to sample bottles not being available, with the operator having to go to another site to pick some up.

Scottish Water interviewed staff about the alarm handling errors, reconfigured the telemetry to prevent treated water chlorine alarms occurring when the works is shut down, looked at the feasibility of reconfiguring the works to automatically shut down in the event of a disinfection system failure or flow meter/signal failure and investigated the extent of the problem with power fails.

Blairnamarrow, 23 June 2007 - High levels of Cryptosporidium

Due to high levels of Cryptosporidium being found in this supply, advice was issued to customers to boil their water before consumption. The incident was associated with heavy rainfall and followed a number or previous incidents of a similar nature.

Savalbeg, 1 July 2007 - Disinfection Failure

This incident was caused by crystallisation of the chlorine in the suction line to the chlorine pump. A low chlorine alarm was generated at 21:30 but this was not passed on to Scottish Water's alarm monitoring centre until midnight (00:00), some two and half hours later due to a fault with the remote telemetry unit at the works. The alarm monitoring centre acknowledged the alarm at 00:09, but did not pass this on to the local operator until 01:42 which caused another delay of an hour and a half. There was thus a total delay in response to the alarm of about 4 hours. The operator arrived on site about an hour after the alarm had been dispatched to him, which is not unreasonable given the time of day and the travel time to the works. Once at the works, the operator took appropriate remedial action to resolve the problem but failed to inform his team leader and the Public Health Team. No formal samples were taken as the chlorine residual at the outlet of the clear water tank was always within target levels and did not breach any Emergency Action Level. However, there is no evidence to support this view. Since no samples were taken it is not possible to say if public health was compromised or not.

Scottish Water held an incident report workshop to clarify roles, responsibilities and procedures between functions and to give formal clear written communication to all staff about the handling of alarms, especially those relating to disinfection failures.

Ballachulish, 4 July 2007 - Disinfection Failure

This disinfection failure was caused by the inlet valve on pressure filter no. 1 failing to close during a backwash. The backwash was set to operate when the clear water tank was full and the works was shut down. Since the valve did not close and the works was in shut down mode, raw water was able to pass through the whole process without any disinfection. A low chlorine alarm was initiated but the operator took no action since he considered the 24 hours storage capacity and the chlorine residual levels adequate.

Another low-level chlorine alarm was passed out about an hour later but the operator did not recall receiving it. This was at 06:00 on Wednesday 4 July 2007. A decision was finally made to investigate at 10.00 and when the operator arrived at the works at 13:00 he found the inlet valve to the filter open and undisinfected water going into the clear water tank. The valve was closed manually and the plant reset to backwash daily. The faulty valve was reported to the mechanical and electrical team, disinfection was increased to protect public health and the public health team were contacted. When the valve was investigated the following day, nothing was found wrong with it.

The valve failed again (twice) on 21 July. Low chlorine alarms followed but no action was taken since it was assumed that the plant was shut down. Investigation and remedial work took place on 23 and 24 July. However, the valve failed again on 30 July and again low chlorine alarms were not acted on but work was carried out later in the day.

It took a further week to finally establish a problem with a configuration of the closing signal for the valve which was then changed and checked to ensure it was operating effectively.

Scottish Water agreed to investigate the communication failures between the duty and standby operators, to investigate the feasibility of alarming the valve status and including another alarm to detect flow through the filter when the works is shut down.

DWQR noted the ongoing work being carried out by Scottish Water to improve the robustness of its telemetry system generally and their ability to react to alarms and to fix problems before they pose a risk to public health. Although the systems appear to be getting better, DWQR continues to be concerned about Scottish Water's ability to react to alarms.

Inverinate, 6 July 2007 - High levels of Cryptosporidium

High levels of Cryptosporidium resulted in advice being issued to customers to boil their water before consumption. This works was closed and the area supplied form the Kyle water treatment works before the end of 2007.

Carrick Castle, 6 July 2007 - Disinfection Failure

This incident occurred when a fault with the electronics controlling the works meant that un-disinfected water passed into supply until the problem was discovered during a routine site visit approximately nine hours later. The investigation in response to this incident discovered that the alarm from the treated water chlorine monitor that should have alerted operational staff to the problem had, in fact, been inhibited three years earlier due to a fault. Despite several work orders having been raised to repair the monitor, they were never actioned. Scottish Water was unable to say why this was, and accepts that several opportunities to rectify the fault were missed.

All chlorine analysers and alarms at the site are now fully operational. Scottish Water has committed to reviewing risk based and reactive maintenance and producing regular reports on all suppressed alarms across the company to enable them to be investigated. Operational staff in the area were reminded of the importance of ensuring that alarms and monitors are operating correctly.

Craignure, 6 July 2007 - Disinfection Failure

Disinfection of the plant failed when a high chlorine alarm switched off the dosing pumps midway through a duty/standby changeover of the disinfectant container vessels. The failure lasted longer that it should without investigation because the alarm was not passed on to operations from the alarm handling centre. Scottish Water agreed to carry out an investigation and take action to reduce the risk of a repeat incident of this nature.

Elphin Knockan, 8 July 2007 - Disinfection Failure

This incident was primarily caused by the blockage of the chlorine sample line by organic matter derived from the source which had a cascade effect of shutting down the dosing system and hence triggering a low chlorine alarm condition. DWQR is aware of the emerging issues with respect to Cryptosporidium and is in discussion with Scottish Water and the Water Industry Commission for Scotland regarding the installation of appropriate treatment at this and other similar sites.

Altnaharra, 17 July 2007 - Disinfection Failure

There is telemetry on this site but at the time of the incident it only monitored flow and battery status. It was therefore only through a routine visit to the works that a problem with the disinfection system was noticed. An air lock in the dosing pump was found and rectified. Fortunately, the problem only occurred earlier that morning so there was still a healthy residual chlorine level. A new membrane plant is being planned for this works.

Gorthleck, 22 July 2007 - Disinfection Failure

This disinfection failure was caused by a failure to fill up the disinfectant tank when it was almost empty. This task should have been done by the operator on 19 July but he was called away for personal reasons and it would appear that no other member of staff was asked to carry out his duties in his absence. A low chlorine alarm on 21 July apparently subsequently cleared itself and so was not investigated. A further low chlorine alarm later the same day on 21 July was not passed to the operator as he had confirmed that he was already due to attend the site to investigate a low raw water flow alarm. Having not been told about the low chlorine alarm and with chlorine residuals being adequate, the operator did not think to check the disinfectant levels. It was therefore not until the early evening on 22 July, when the operator was investigating a further low raw water flow alarm, that he noticed the low level of disinfectant. Appropriate remedial action was then taken. It was fortunate that the chlorine residual never fell below the low Emergency Action Level.

Scottish Water agreed to link an appropriate low level alarm for the disinfectant to telemetry and investigate the feasibility of an auto shut down facility for a low treated water chlorine residual.

Torrin, 30 July 2007 - High levels of Cryptosporidium

High levels of Cryptosporidium resulted in advice being issued to customers to boil their water before consuming it. DWQR is concerned about the adequacy of the treatment process to deal with Cryptosporidium at this works so is promoting an improvement project through the investment planning process.

Blairnamarrow, 21 August 2007 - High levels of Cryptosporidium

Due to high levels of Cryptosporidium being found in this supply, advice was issued to customers to boil their water before consuming it. Due to this and the event earlier in the year on 23 June 2007, DWQR investigated Scottish Water's actions to reduce the risk of a recurrence. Some work was carried out in the catchment, at the inlet works and on the filters at the works in an attempt to improve the situation. In the longer term DWQR is working with Scottish Water to introduce more robust treatment at this works.

Tullich, 6 September 2007 - Organisms in the filters

In September 2007, Scottish Water's customers in the Oban area complained about "worm-like organisms" in their drinking water. These were later identified as a species of Chironomid midge larvae. The Soroba area of Oban was worst affected. Whilst these larvae presented no risk to public health, their presence in the water supply caused significant concern to consumers.

The Drinking Water Quality Regulator for Scotland investigated the incident, working closely with Argyll and Bute Council's Environmental Health team and NHS Highland.

Whilst it was not possible to confirm the exact source of the larvae, it was likely that they entered Tullich Water Treatment Works in the raw water coming from the lochs that supply Oban's drinking water. The filtration process was not able to remove all the larvae and some ultimately broke through into supply. Once the problem was detected, increased washing of the filters quickly improved the situation. Scottish Water's own report into the incident highlighted a number of operational changes that were be made to ensure no recurrence of the incident. DWQR also made recommendations, some in connection with the operation of the treatment works and some concerning the way in which Scottish Water responds to consumer concerns and keeps people informed. Although this was an unusual occurrence, DWQR expects Scottish Water to take all possible steps to ensure there is no repetition.

Invermoriston, 11 September 2007 - Telemetry Failure

The DWQR assessment of this "no water" incident is that it was probably caused by a failure of an air valve on the raw water inlet main. It would appear that water came out through the air valve rather than going forward to the water treatment works. This loss of water meant that there was no water going to the chlorine monitors, which resulted in the plant believing that there was no chlorine so it shut down the raw water pumps as it was designed to do, to prevent undisinfected water from going into supply. Water was however still being supplied from the clear water tank and when it reached its low level, an alarm should have been transmitted to Scottish Water's Operational Management Centre. However, no such alarm was generated and consequently, customers were out of water for longer than they would have been had the telemetry alarm worked. In fact it was a customer calling in to say that they had no water which raised the alarm and prompted an investigation.

Scottish Water's ongoing work on its telemetry system and associated alarms should ensure that they are all appropriate and working as intended. Testing of the signals at Invermoriston from the works to the alarm monitoring centre had still to be carried out at the time of this incident.

Scottish Water were also to inspect and service the air valve, add a check on the chlorine sample pumps to the day to day tasks for the site and review the works control to see if anything more could be done to provide an earlier indication of a raw water system failure.

Tobermory, 26 September 2007 - Coagulation Failure

Problems with the aluminium dosing pumps caused high levels of residual aluminium to enter the supply. However, the telemetry system worked, the problems were investigated and remedial work was carried out on the pumps.

Torridon, 27 October 2007 - Disinfection Failure

The disinfection dosing pumps failed but the telemetry system worked and the problem was rectified. The chlorine control system was also adjusted so that the pumps now switch on when the inlet pumps are activated.

Badcaul, 27 October 2007 - Disinfection Failure

This disinfection failure incident was caused by a fault in the power supply to the disinfection pumps. Mains power at the site only charges two 12 volt batteries that operate in series to provide the 24 volts required to power the pumps. The site is visited twice a week and the power/charging system for the pumps is checked once a week.

When the first failure occurred on 27 October, a low chlorine alarm was initiated, the operator was called out and found the pumps were off but the power system appeared to be operating effectively. Samples were taken which subsequently failed as they contained coliforms.

The system failed again very early on 28 October but this time the low chlorine alarm failed to initiate and only came through two hours later. The operator followed a similar procedure as the earlier incident. Again the samples failed.

Following an urgent request issued on 29 October to check for an electrical fault on the system, electrical and mechanical staff went to the site on 30 October to find that one battery had burst and only 5 volts was being produced by the other. The standby set of batteries was found to be fully charged so the system was set to operate on these.

Scottish Water agreed to carry out a full end to end check on the telemetry system to determine the reason for the failure of the alarm on 28 October.

Scottish Water also agreed to install four new batteries for the disinfection pumps and carry out a weekly check on the condition of all 4 batteries, together with the charging system to ensure that it is operating at the correct voltage for sufficient but not excessive charge.

Ardrishaig, 31 October 2007 - Treatment Failure

It is likely that Scottish Water supplied water that exceeded the standard for aluminium to the area served by Ardrishaig works, which includes Lochgilphead. It is not possible to be certain of the levels of aluminium in the distribution system because Scottish Water failed to take adequate samples to establish the impact on water quality, a shortcoming they identified in their report into the incident.

The cause of the failure was a malfunction in the pH correction dosing pump that elevates the pH of the incoming water to enable it to be treated using aluminium sulphate. In response to the failure, an appropriate alarm was generated and an operator attended site. Scottish Water took appropriate action at the treatment works to resolve the problem, however by their own admission it is possible that more could have been done to mitigate the effects of high aluminium concentrations on consumers by utilising water stored on the site and by carrying out flushing in the distribution system. Scottish Water identified this as a learning point from the incident, along with the timely notification of such events to Scottish Water's Public Health Team who are able to offer advice on water quality and protecting consumers.

Shiel Bridge, 1 November 2007 - Telemetry Failure

A faulty electrical relay caused a power failure to the disinfection pumps. A low chlorine alarm was acknowledged by the alarm monitoring centre but it appears that they did not pass this on to operations for them to investigate it. The problem was therefore only discovered through a routine visit by the operator. This works was subsequently abandoned and the area supplied from the Kyle water treatment works around mid December 2007.

Badcaul, 8 November 2007 - Disinfection Failure

Mains power is used for the lights and for charging the batteries which power the disinfection pumps. The mains power failed and the batteries failed to hold their charge so there was no power for the disinfection pumps. However, the telemetry system worked and power was restored within 3 hours of losing it.

Torrin, 13 November 2007 - Disinfection Failure

This is one of a handful of sites that still do not have telemetry so it was only though a routine visit to the works that it was found that the disinfection system had failed. The failure had been caused by a failure of the electronic signal between the flow meter and the chlorine pump. Having discovered the problem it was fixed and disinfection was restored.

Bonar Bridge, 14 November 2007 - Disinfection Failure

Both chlorine dosing pumps tripped causing a low chlorine alarm to be initiated. However, the telemetry system worked and dosing was restored within an hour.

Dores, 10 December 2007 - Failure to comply with procedures in DOMS (Distribution Operation and Maintenance Strategy)

A new water main was being constructed between the treatment works at Inverness and Dores. This was to supply the area previously fed from Dores by the works at Inverness and subsequently close the works at Dores. Although double check valves were used to protect the existing live water main from any possible contamination by back flow, there was inadequate protection against the possibility of fuel for the temporary pumps getting into the excavation. Also, the contractors' Access Transfer Certificate had expired which resulted in the contractor having to leave the site until suitable method statements had been produced to allow a new Access Certificate to be issued.

Staffin, 18 December 2007 - Disinfection Failure

This disinfection failure was caused by a split in the dosing line. However the telemetry system worked and alerted operations to the low chlorine which was promptly investigated and disinfection was restored.

Water Quality in Local Authorities in the North West

Argyll and Bute Council

Water Supply Zones in Area

Quality of Public Water Supply

Summary of Private Water Supplies

148 supplies unclassified at December 2007

Highland Council

Water Supply Zones in Area

Quality of Public Water Supply

Summary of Private Water Supplies

Moray Council

Water Supply Zones in Area

Quality of Public Water Supply

Summary of Private Water Supplies

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