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How Results are determined
Interpretation of Results and Requirements for Monitoring Programmes
The Annex to the EC Bathing Water Directive contains information on the requirements for monitoring programmes. It lists the 19 parameters and values which apply to identified bathing waters and states how results should be interpreted. These requirements have been implemented in Scotland by the Bathing Waters (Classification) (Scotland) Regulations 1991.
The Directive contains information on two main types of values for water quality standards: mandatory standards which Member States must observe, and stricter guideline values which Member States should endeavour to observe.
Mandatory Standards
Mandatory standards apply to 10 parameters: total coliforms, faecal coliforms, salmonella, enteroviruses, pH, colour, mineral oils, detergents, phenols and transparency. Compliance with the Directive's mandatory standards is based on the counts of total coliforms and faecal coliforms. 95% of samples must comply with the Directive's mandatory standards for both parameters for the site to achieve a pass at this level.
Guideline Values
In addition to the mandatory standards set by the Directive, there are guideline values for some of the parameters, including the two coliform groups and faecal streptococci. These guideline values are stricter than the mandatory standards and, if achieved, indicate excellent bathing water quality.
Compliance with the Directive's guideline values is based on the counts of total coliforms, faecal coliforms and faecal streptococci. All three parameters must comply with the Directive's guideline values for the site to achieve a pass at this level.
Under Article 5.2 of the Directive, deviations from these mandatory and guideline values are allowed in the case of floods, other natural disasters and abnormal weather conditions. The guidance that SEPA received from The Scottish Office was that exceptional weather conditions are defined as a storm with a return frequency of one in five years or more. If a waiver is applied, then a replacement sample is taken after an appropriate period to allow the storm effects to dissipate.
Under Article 8 of the Directive, the requirements of the Directive may be waived because of exceptional geographical conditions in respect of the colour and transparency parameters. For example, Sandyhills has a waiver for the transparency parameter because tidal action can lead to high levels of suspended sediment entering the bathing water. At Nairn (East Beach), a waiver has been granted for both the transparency and colour parameters because the River Nairn, when in spate, discharges peaty coloured water into the sea near the sampling point.
In 2008, six identified bathing waters in Scotland have waivers for colour, while 39 identified waters have waivers for transparency.
Sampling Frequency
The minimum frequency of sampling is also set out in the Annex to the Directive. Checks must be made at least once a fortnight during the bathing season for total and faecal coliforms, transparency, colour, mineral oil, surface-active substances reacting with methylene blue and phenols. For the remaining parameters with mandatory standards (salmonella, enteroviruses and pH), and for other parameters where inspection is prescribed, concentrations should be checked whenever inspections show that the substance may be present or where the quality of the bathing water has deteriorated.
Under the Bathing Waters (Classification) (Scotland) Regulations 2008, the bathing water season in Scotland is specified as the period from 1 June to 15 September inclusive. At least 20 samples have been taken at each identified water between 1998 and 2003, in addition to one pre-season sample. From 2004 onwards reduced sampling has been instigated at some sites, further information is available in the results section.
This report includes results of SEPA's microbiological monitoring, as compliance with the Directive’s standards is based on these parameters alone. Owing to space limitations, it is not possible to include all of the results of SEPA's analysis, however, sampling results for the other parameters monitored by SEPA are placed on the public register and are available on request.
Interpretation of Microbiological Values
The microbiological organisms listed in the Directive are all natural inhabitants of the guts of humans and other warm-blooded animals, and are used as indicators of faecal pollution. Their presence, in excess of the values in the Directive, identifies waters which may have received volumes of sewage that have not been given adequate treatment or dilution. Equally, large concentrations of sea-birds or agricultural run-off may also give rise to these microbiological indicators in bathing waters. Livestock slurries and manure, if applied to agricultural land inappropriately, can enter inland watercourses and be transported to coastal areas. The bacteria and viruses present in sewage and animal excreta may cause illness, especially as a result of ingestion or infection through wounds or cuts.
Article 5 of the Directive specifies how the results of faecal coliform, total coliform and faecal streptococci monitoring are to be interpreted. These are summarised in Table 1. Details on interpreting the results obtained from 20 and 5 samples are provided in this Table, as this is the minimum number of samples which should be taken from each identified bathing water in Scotland during the bathing season.
Table 1: Interpretation of Microbiological Values for Bathing Waters Where 20 or 5 Samples Have Been Taken
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Level of pass
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Symbols used
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Interpretations
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Total Coliforms
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Faecal Coliforms
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Faecal streptococci
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| Pass-Guideline |
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G
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Directive states: |
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80% of samples should not exceed 500 total coliforms per 100 ml |
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80% of samples should not exceed 100 faecal coliforms per 100 ml |
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90% of samples should not exceed 100 faecal streptococci per 100 ml |
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Based on 20 samples: |
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Must have at least 16 samples with less than, or equal to, 500 total coliforms per 100 ml |
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Must have at least 16 samples with less than, or equal to, 100 faecal coliforms per 100 ml |
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Must have at least 18 samples with less than, or equal to, 100 streptococci per 100 ml |
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Based on 5 samples: |
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Must have at least 4 samples with less than, or equal to, 500 total coliforms per 100 ml |
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Must have at least 4 samples with less than, or equal to, 100 faecal coliforms per 100 ml |
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Must have 5 samples with less than, or equal to, 100 streptococci per 100 ml |
| Pass-Mandatory |
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M |
Directive states:
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95% of samples should not exceed 10,000 total coliforms per 100 ml |
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95% of samples should not exceed 2,000 faecal coliforms per 100 ml |
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The Directive contains no mandatory standard for faecal streptococci |
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Based on 20 samples:
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Can only have 1 sample with greater than 10,000 total coliforms per 100 ml |
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Can only have 1 sample with greater than 2,000 faecal coliforms per 100 ml |
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The Directive contains no mandatory standard for faecal streptococci |
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Based on 5 samples: |
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Must have no samples with greater than 10,000 total coliforms per 100 ml |
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Must have no samples with greater than 2,000 faecal coliforms per 100 ml |
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The Directive contains no mandatory standard for faecal streptococci |
Bacteriological Analysis
Bacteriological analysis is carried out in SEPA’s specialist microbiological laboratories at East Kilbride, Dingwall, Aberdeen and Edinburgh. All of these laboratories operate to United Kingdom Accreditation Service (UKAS) quality systems for their analytical work and they participate in external inter-laboratory testing schemes such as those run by the Public Health Laboratory and Aquacheck. The inter-laboratory testing has demonstrated consistent high accuracy of SEPA's bacteriological test results.
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