Water Quality Prepared by: Nicola Houlahan, Water Quality Director

Transcription

1 Water Quality 2011 Prepared by: Nicola Houlahan, Water Quality Director March 2012

2 Table of Contents 1.0 Introduction Summary of Water Quality Microbiological Quality Chemical Quality Iron Turbidity Lead Nickel Hardness Metaldehyde Operational Monitoring Improvement Programmes Provision of Information Appendices 11 Appendix 1 Summary of Water Quality, Appendix 2 Annual Water Quality Report, Appendix 3 Overall Drinking Water Quality, Appendix 4 Improvemnet Programmes in force during March 2012 Page 2 of 20

3 1. Introduction Sutton and East Surrey Water supplies drinking water to approximately 655,000 people in East Surrey, parts of West Kent and West Sussex, and the London Boroughs of Sutton, Merton and Croydon, over an area covering 834 square kilometres. 85% of the Company s water supplies come from boreholes in the chalk and lower greensand, and the remainder comes from Bough Beech reservoir. The reservoir is filled by abstracting water from the River Eden in Kent during the autumn and winter months. Water is treated at eight treatment works to ensure any particles, bacteria, metals and trace contaminants are removed before it is distributed to customers, and the hard chalk groundwater also is partially softened before supply. Water is distributed to customers through 32 service reservoirs or water towers and approximately 3,400 kilometres of mains, covering 20 water supply zones. Average daily demand is 160 Ml (160 million litres) of water. Water suppliers must satisfy the requirements of the Water Supply (Water Quality) Regulations 2000 (as amended), which fully incorporate the requirements of the 1998 European Drinking Water Directive on the quality of water intended for human consumption. The Regulations impose standards for drinking water to ensure water is safe to drink, and they also set limits for parameters that ensure that the appearance and taste of the water is acceptable to our customers. The Regulations define how many samples must be analysed to monitor water quality, where the samples must be taken from and at what frequency. Samples are taken from defined points at treatment works, service reservoirs and supply points, and at random from consumers taps, in accordance with an annual programme. Although the primary responsibility for monitoring water quality rests with the water supplier, water quality is also assessed by the Drinking Water Inspectorate (DWI), a division of the Department for Environment, Food and Rural Affairs. The DWI assesses the wholesomeness of water supplies and undertakes annual technical audits of water suppliers. This report relates to water quality supplied by Sutton and East Surrey Water plc for the calendar year March 2012 Page 3 of 20

4 2. Summary of Water Quality Sutton and East Surrey s water supplies are of very good quality and are safe to drink. During 2011, 5560 samples of treated water were taken to satisfy the requirements of the Regulations and approximately 33,000 measurements were made on those samples to assess the extent to which our water supplies met the standards set in the Regulations. The Regulations set Prescribed Concentrations or Values (PCVs) for parameters used to determine the wholesomeness of the water, and Specification Concentrations or Values (SCVs) for parameters that are additional monitoring requirements (otherwise known as indicator parameters), but which do not impact on the determination of the wholesomeness of the water supplied. In 2011, 99.98% of the tests undertaken to determine compliance with the directive and national standards, and 99.99% of the tests taken to determine compliance with the indicator parameters met the standards set. Details of the extent of compliance are given in Appendix 1 of this report. Any contraventions of a standard are investigated in accordance with the guidance issued by the Drinking Water Inspectorate. In some cases further sampling does not confirm the original findings and no further action is required, but in other cases remedial action such as mains flushing or lead pipe replacement may be required. In general, contraventions are associated with local conditions that are not representative of the water quality throughout a zone, and in particular, some contraventions can be associated with poor maintenance of the plumbing within an individual property. Irrespective of the cause of the problem, the affected consumers are advised of what action has been taken to remedy the situation, or what action they can take to ensure the problem does not recur. Details of the numbers of tests carried out on samples from treatment works, service reservoirs, supply points and consumers taps (or water supply zones) is given in Appendix 2. A summary of the key aspects of water quality, including commentary on all parameters where standards were exceeded in 2011, is given in sections 3 and 4. The Chief Inspector of the DWI produces an annual report on drinking water for England, and her report for 2011 will be launched in July The report includes a statistically determined measure for assessing water company performance overall drinking water quality, previously referred to as mean zonal compliance % or MZC%. The overall drinking water quality % for Sutton and East Surrey Water for 2011 has been determined as 99.96%, and a summary of our historical performance in respect of this quality index is shown in Appendix 3. Further details of the Inspectorate s assessments of the Company are available on their website 20 March 2012 Page 4 of 20

5 3. Microbiological Quality The primary aim of microbiological monitoring is to demonstrate that water supplies are safe to drink. Coliforms are bacteria that are widespread in the environment, and whose presence in water may indicate contamination of supplies and the possible presence of harmful organisms that may cause illness. When detected in water, however, they may also be indicative of the poor hygienic condition of the sampling location. In 2011 only four samples contravened the standard set for the coliform parameter; two taken from a treatment works and two taken from consumers taps. All microbiological failures are notified to the relevant local authorities and health protection units. Water leaving treatment works was tested for total coliforms and E.coli. 100% of the 2153 samples taken from our eight treatment works were clear of E.coli and only two samples contained coliform organisms. Investigations identified that the coliform detections (detected at the same treatment works in samples taken two days apart) were due to the growth of coliforms in a treated water pump that had been out of service for an extended period of time for a motor repair. The coliform growth was eliminated by disinfecting the pump in situ, through operating the works to an increased free chlorine final water disinfectant residual, rather than the usual chloraminated disinfectant residual, for a short period of time. All samples taken since the work was carried out have confirmed that coliforms are absent in the treated water at this site. Water leaving service reservoirs was also tested for coliforms and E.coli. 100% of the 1662 samples taken from reservoirs in 2011 were free of coliforms and E.coli. The Regulations include mandatory standards for E.coli and Enterococci in samples collected from consumers taps. All of the 1680 consumer tap samples tested for E.coli and the 161 samples tested for Enterococci were free of these organisms. Samples taken from consumer taps were also tested for coliforms. Two of the 1680 samples taken contained coliforms, and in both cases the investigations confirmed that the cause was the condition of the domestic plumbing arrangements. In the first coliform investigation, a Water Fittings Inspection did not find any particular required improvements to the domestic plumbing, but it was suspected low water usage in the property may have led to the development of a biological film in the pipework. It was suggested to the customer that they may wish to flush and disinfect their pipework to improve the quality, although the coliforms identified were not actually of any concern to the health of those consuming the water. In the second case of coliforms, it was identified that a pressure vessel fitted to the mains supply had not been maintained in accordance with recommended manufacturer s instructions. The replacement of this vessel, together with other minor works on the domestic plumbing, eliminated the coliform contamination of the supply. 20 March 2012 Page 5 of 20

6 Monitoring for Clostridium perfringens is carried out at supply points. The absence of this organism in treated water confirms an efficient treatment process. 100% of the 175 samples tested were free of C.perfringens. 4. Chemical Quality Chemical monitoring includes tests for a great variety of compounds, including organics (such as solvents and pesticides), metals, inorganics (such as chloride and nitrate) and physical properties of the water, such as taste and odour. The majority of substances we check for are invisible to the consumer, but some do impact on the appearance, and therefore the acceptability, of our product to our customers. Whilst it is impossible to comment on all the chemical parameters we monitor for, those detected in exceedance of the standards during 2011, and those generally of particular interest to our customers, are discussed below. There were only two exceedances of the standards set for chemical tests in 2011, one for lead and one for nickel Iron There were no exceedances of the standard set for the iron parameter in The standard set for iron is based on its effect on the appearance of the water, and not on health grounds. Iron may be present in the water due to the disturbance of iron particles, accumulated over time from the corrosion of iron mains Turbidity 4.3. Lead There were no exceedances of the turbidity parameter in 2011, at either treatment works or in water supply zones. Turbidity is a measure of the suspended fine particulate material in a sample and the standard set for turbidity is based on its effect on the appearance of the water, and not on health grounds. Lead in drinking water arises from lead service pipes and fittings; it is not present in the mains water supplied. Whilst lead pipework has not been used for new installations for many years, there are still a large number of lead pipes in existence. The water supplier owns some of this pipework, but the vast majority actually belongs to the customer. Lead can also be introduced by the inappropriate use of lead solder during internal plumbing work. Sutton and East Surrey Water conditions the water supplied to minimise lead pick-up from any lead pipes that may be present in the distribution network, but in some cases this is still not adequate to prevent lead dissolution into standing water. 20 March 2012 Page 6 of 20

7 4.4. Nickel There was a single exceedance of the lead parameter in the 161 compliance samples taken in water supply zones in Our investigations confirmed high lead in further check samples taken at the property, but not at other properties in the same road. We also identified that there had been some recent repair work to internal lead plumbing in the weeks immediately prior to the sample being taken and it is believed that the disturbance of the internal pipework most likely led to the high lead concentrations. The Company replaced its section of the service pipework to the property with an alternative material free of charge and advised the customer to consider replacing their section of the service pipework and any internal lead pipework. The Company also carries out operational testing for lead, and conducts tests in response to customer requests. A low number of these samples exceeded the regulatory limit for lead in 2011 and in these cases there was a full investigation, as there would be for an exceedance of the standard in a compliance sample. If it is found that the Company owned pipework is constructed of lead, then it is replaced by an alternative material free of charge. If the pipework owned by the customer is shown to be lead, or it is identified that the problem is due to the use of lead solder, then the customer is advised to consider replacing their problem pipework. From April 2010, in accordance with the Company s revised lead strategy, Sutton and East Surrey Water have actually replaced Company owned lead pipework at any property where the lead concentration has exceeded the Company standard of 10 µg/l (micrograms per litre, or parts per billion) lead, as well as those where the concentration has exceeded the higher regulatory value of 25 µg/l. The Company standard is equivalent to the revised regulatory standard that will be in place from 25 December In all cases where a customer chooses not to replace their part of the lead service pipework following a failure of the lead standard, or following the detection of lead greater than 10 µg/l, they are advised to thoroughly flush the pipework before taking any water for drinking or food preparation purposes, in order to minimise their exposure to lead. The flushing water can be used for watering plants. More information on lead is available in the Lead in drinking water fact sheet, available on our website, Although nickel may be naturally present in drinking water at low concentrations, high concentrations generally only arise due to contamination from nickel coatings used on some domestic taps and water fittings. In 2011 a single sample exceeded the standard for nickel and our investigations confirmed that the issue was confined to the original property, with neighbouring properties served by the same supply main having low concentrations of nickel as expected. 20 March 2012 Page 7 of 20

8 The customer was advised that they could reduce their exposure to nickel by replacing their kitchen tap or by ensuring that they thoroughly flush the kitchen tap before taking any water for drinking or food preparation purposes. They were also advised that any flushing water could be used for watering plants Hardness Hardness is caused by naturally occurring calcium and magnesium salts dissolved in the water. Although hard water can cause scale build-up on fittings and in pipework, and can leave a scum on the surface of boiled water, it is not harmful to health. Many of Sutton and East Surrey Water s borehole sources are in chalk aquifers that are naturally hard. The Company partially softens the water at five of the larger treatment works to reduce the effects caused by hard water. At our other treatment works, the water is naturally softer. Under the current Regulations there are no requirements to monitor and report on water hardness levels. We continue to monitor hardness levels at our treatment works, however, to ensure the efficient operation of the softening process, and to enable us to provide the information to consumers if required. More information is available in the Hardness and scale fact sheet on our website, Metaldehyde Metaldehyde is a selective pesticide, used by farmers and gardeners to control slugs in a wide variety of crops. The standard for the individual pesticide parameter is a target for treatment, and is not based on the impact to health. Sutton and East Surrey Water is working with other water companies, the Metaldehyde Stewardship Group, the Environment Agency, Natural England, the Campaign for the Farmed Environment, the Chemicals Regulation Directorate, the Drinking Water Inspectorate and farmers (through the Voluntary Initiative) to ensure significant reductions are seen in the levels of metaldehyde in water sources through improved practices of product application. These catchment management activities and the installation of improved treatment at our surface water treatment works resulted in 100% compliance with pesticides in treated water in 2010 and March 2012 Page 8 of 20

9 5. Operational Monitoring In addition to the tests carried out on treated waters for regulatory purposes, Sutton and East Surrey Water takes a number of samples for operational reasons such as monitoring the efficiency of treatment processes and checking the integrity of the distribution network after maintenance work. We are also required to carry out regulatory monitoring of raw water abstraction points and we take samples to confirm source water quality and to verify the risk assessment of sources carried out as part of the Company s Drinking Water Safety Plans. Approximately 73,000 additional tests (operational and regulatory abstraction monitoring) were carried out for these purposes in Improvement Programmes If a water supply exceeds a standard in the Regulations and the investigation concludes that it is likely to recur, the Secretary of State can require a water supplier to put in place a legally binding improvement programme of work to improve drinking water quality. This improvement programme can be in the form of an Undertaking or an Authorised Departure. Sutton and East Surrey Water had no Authorised Departures in force during 2011, but agreed Undertakings with the Drinking Water Inspectorate in respect of the pesticide metaldehyde and lead, in December 2009 and June 2010 respectively. These Undertakings place a legal obligation on the Company to complete a number of agreed steps, aiming to secure or facilitate compliance with the standards for metaldehyde and lead in the period to 31 March A summary of the agreed steps of the Undertakings are shown in Appendix 4, or can be found on the following DWI websites: Provision of Information Water companies are obliged to maintain records and provide details of regulatory water quality analysis within seven days of a request from any person. Customers wishing to see a water quality report for their area can download the latest report from our Company website. Access to reports, other general information and frequently asked questions about water quality can be found on our website at Alternatively customers can contact our Customer Services team by telephone on , or by , customer_services@waterplc.com. 20 March 2012 Page 9 of 20

10 Reports on the results of regulatory sampling and general water quality issues are regularly sent to all Environmental Health Officers and Consultants in Communicable Disease Control covering the Company s area of supply, as well as this annual summary report. Regular meetings are held with representatives of local and health authorities to discuss water quality and a meeting was held at our Cheam Treatment Works in October March 2012 Page 10 of 20

11 8. Appendices 20 March 2012 Page 11 of 20

12 Appendix 1 Summary of Water Quality, 2011 Schedule 1 Mandatory Determinands (Directive and National standards) Asset No. of tests No. of failures % Compliance Treatment Works Service Reservoirs Supply Points Water Supply Zones Total for mandatory dets Schedule 2 Indicator Determinands Asset No. of tests No. of failures % Compliance Treatment Works Service Reservoirs Supply Points Water Supply Zones Total for mandatory dets Schedule 1 & 2, Mandatory & Indicator Determinands Asset No. of tests No. of failures % Compliance Treatment Works Service Reservoirs Supply Points Water Supply Zones Total for mandatory dets Notes: The figures in the tables above do not include tests for parameters that do not have a standard additional tests were carried out for the determination of gross alpha, gross beta and residual disinfectant, as required by the Regulations. Details of the failures are discussed in the main body of the report. 20 March 2012 Page 12 of 20

13 Appendix 2 Annual Water Quality Report, 2011 Quality of Water at Water Treatment Works Number of water treatment works: 8 Parameter Schedule 1 parameters No. samples and Units Samples Water Treatment Works No. % No. % Total coliforms /100ml E.coli /100ml Nitrite mg NO 2 /l Indicator parameters Colony count 48h 37 C Colony count 72h 22 C Residual Disinfectant 2153 (N/A) No./ml (N/A) No./ml (N/A) mg/l Turbidity NTU Quality of Water at Service Reservoirs Number of service reservoirs: 32 Parameter Schedule 1 parameters No. samples and Units Samples Service Reservoirs No. % No. % Total coliforms /100ml E.coli /100ml Indicator parameters Colony count 48h 37 C Colony count 72h 22 C Residual Disinfectant 1662 (N/A) No./ml (N/A) No./ml (N/A) mg/l Note: Compliance with the required standard for total coliforms at a service reservoir is achieved if coliforms are absent in 95% samples taken at any single reservoir. All reservoirs complied with this standard. 20 March 2012 Page 13 of 20

14 Quality of Water at Supply Points Number of Supply Points: 8 Parameter Schedule 1 parameters No. samples and Units Samples Supply Points No. % No. % Bromate µg BrO 3 /l Cyanide µg CN/l Fluoride mg F/l Mercury 61 1 µg Hg/l Pesticides 2,4-D µg/l ,4-Db µg/l Atrazine µg/l Azoxystrobin µg/l Boscalid µg/l Bromoxynil µg/l Carbendazim µg/l Carbetamide µg/l Chlorothalonil µg/l Chlorotoluron µg/l Cyproconazole µg/l Diuron µg/l Epoxiconazole µg/l Flufenacet µg/l Flusilazole µg/l Flutriafol µg/l Glyphosate µg/l Isoproturon µg/l MCPA µg/l Mecoprop µg/l Metaldehyde µg/l Metazachlor µg/l Methabenzthiazuron µg/l Pendimethalin µg/l Propachlor µg/l Propyzamide µg/l Prosulfocarb µg/l Simazine µg/l Tebuconazole µg/l March 2012 Page 14 of 20

15 Quality of Water at Supply Points Number of Supply Points: 8 Parameter No. samples and Units Samples Supply Points No. % No. % Total Pesticides µg/l Triclopyr µg/l Trifluralin µg/l Indicator parameters Clostridium perfringens /100ml Chloride mg Cl/l Conductivity µs/cm Sulphate mg SO 4 /l Total Organic Carbon 61 (N/A) mg C/L Gross alpha activity 8 (N/A) Bq/l Gross beta activity 8 (N/A) Bq/l Note: A supply point is a monitoring point at a water treatment works, service reservoir, blending point or fixed point in distribution where the result of analysis of the water at that point will not change in material respect in its passage to the consumer s tap. Sutton and East Surrey Water monitored for supply point parameters at water treatment works. 20 March 2012 Page 15 of 20

16 Quality of Water in Water Supply Zones (at consumers taps) Number of Water Supply Zones: 20 Parameter Schedule 1 parameters No. samples and Units Samples Water Supply Zones No. % No. % E. coli /100ml Enterococci /100ml ,2-Dichloroethane µg/l Aluminium µg Al/l Antimony µg Sb/l Arsenic µg As/l Benzene µg/l Benzo 3,4 pyrene µg/l Boron mg B/l Cadmium µg Cd/l Chromium µg Cr/l Colour mg/l Pt/Co Copper mg Cu/l Iron µg Fe/l Lead µg Pb/l Manganese µg Mn/l Nickel µg Ni/l Nitrate mg NO 3 /l Nitrite mg NO 2 /l Nitrite/Nitrate formula Odour Dil. Num Selenium µg Se/l Sodium mg Na/l Sum Tetra- and Trichloroethene µg/l Taste Dil. Num Tetrachloromethane µg/l Total PAH (4 substances) Total Trihalomethanes µg/l µg/l Turbidity NTU March 2012 Page 16 of 20

17 Quality of Water in Water Supply Zones (at consumers taps) Number of Water Supply Zones: 20 Parameter Indicator parameters No. samples and Units Samples Water Supply Zones No. % No. % Total coliforms /100ml Colony count 48h 37 C Colony count 72h 22 C Residual Disinfectant Ammonium mg NH4/l Hydrogen Ion (ph) (6.5min) ph units 656 (N/A) No./ml (N/A) No./ml (N/A) mg/l March 2012 Page 17 of 20

18 Appendix 3 Overall Drinking Water Quality, The following chart shows the Company performance in the Overall Drinking Water Quality Index, as defined by the Drinking Water Inspectorate, over the past eight years. The Company performance is compared to that of the published industry average (the result for 2011 to be published in July 2012) Overall Drinking Water Quality Index, SESW Industry average The fluctuations in Company performance, compared to the steady performance of the industry as a whole, shows how very low numbers of exceedances of the standards for some parameters, i.e. those that have a low regulatory monitoring frequency, can have a major impact on the overall index for a small water company. In 2011 just two exceedances of relevant standards, one for lead and one for nickel, resulted in an apparent deterioration in performance compared to 2010 (a reduction from to 99.96), despite there actually being a slightly higher number of contributing exceedances of the standards in March 2012 Page 18 of 20

19 Appendix 4 Improvement Programmes in force during 2011 Undertaking in respect of Metaldehyde, in Water Supply Zones Supplied from Bough Beech TW Water Supply Zones affected L03, L04, L08, L24 & L11 (part) will have had non-trivial breaches of the metaldehyde standard L17 could be at risk of exceeding the standard if receiving an input from Bough Beech TW L01 and L19 are not considered as being at risk of exceeding the standard, but they do receive a small input from Bough Beech TW Agreed steps to be taken Assess metaldehyde as a hazard for the Bough Beech Treatment Works supply system; Submit an action plan that identifies the short, medium and long term mitigating steps; Develop and implement an enhanced monitoring strategy; Confirm the extent of metaldehyde usage in the catchment; Review the abstraction regime from the River Eden; Investigate the effectiveness and feasibility for cost effective optimisation of existing treatment processes at Bough Beech; Provide support to all national, regional and local catchment management initiatives aiming to reduce the amounts of metaldehyde that reaches water sources; Status / Planned Completion date Completed Completed Completed Completed Completed For the duration of the Undertaking For the duration of the Undertaking Support industry investigations into treatment options for metaldehyde; For the duration of the Undertaking Continually appraise the risk of metaldehyde; Ongoing Report to DWI at regular intervals; Provide an interim report to DWI; Provide a final report to DWI. Every six months 31/03/13 31/03/15 20 March 2012 Page 19 of 20

20 Undertaking in respect of Lead, in all Water Supply Zones Water Supply Zones affected All Agreed steps to be taken Assess lead as a hazard for all water supply zones; Submit a strategy for the protection of public health and for compliance with the drinking water standards as far as practicable with respect to lead, identifying the short, medium and long term mitigating measures; Continue to implement an enhanced monitoring strategy for lead at consumers taps; Status / Planned Completion date Completed Completed For the duration of the Undertaking Submit a summary of the investigations carried out to confirm the appropriateness of the remedial measures proposed; Completed Complete planning for the implementation of the remedial measures proposed as part of the agreed programme of work; Completed Complete implementation of the remedial measures proposed as part of the agreed programme of work; Continually appraise the risk of lead; Report to DWI at regular intervals; 31/03/15 Ongoing Every six months Carry out an interim review of the efficacy of the remedial measures to allow for further development of the Company s lead strategy and consideration of future investment requirements to deliver the strategy; Provide a final report to DWI. 31/03/13 30/04/15 20 March 2012 Page 20 of 20