DRINKING WATER QUALITY STANDARDS

 

The descriptions of parameters listed are common to all water companies in England and Wales and have been in force from 1st January 2004.  Due to the nature of Hartlepool water, borehole sourced from the limestone aquifer in the southeast Durham area, it is unnecessary to carry out any special treatments to remove or add elements or compounds to comply with the standards.  We operate a simple disinfection treatment process enhanced only by the addition of a small dose of phosphorous as part of a legal undertaking given by the company to the Drinking Water Inspectorate.

 

 

Parameter

 

Comment

 

Prescribed Concentration or Value (PCV)

 

1,2-Dichloroethane

1,2-Dichloroethane is a chemical intermediate and solvent.  It can contaminate groundwater beneath industrial sites.

3 ug/l

 

 

Aluminium

Occurs naturally in some source waters. Aluminium compounds are not used for water treatment by Hartlepool Water.

 

200 ug/l

 

Ammonium (Ammonia and Ammonium Ions)

Ammonium salts are naturally present in trace amounts in most water sources.  They can indicate possible contamination of sanitary significance and they interfere with disinfection processes.

 

0.5 mg/l

Antimony

Antimony is not normally found in water sources.  Trace concentrations in drinking water can be derived from brass tap fittings and from solders.

 

5 ug/l

Arsenic

Arsenic is naturally present at levels above the standard in a few groundwater sources.

 

10 ug/l

Benzene

Benzene is an organic chemical present in in the environment largely because of it use in petrol.  It is not normally found in water sources or supplies, though it can migrate through plastic underground supply pipes, if petrol is spilt in the vicinity.

 

1.0 ug/l

Benzo(a)pyrene

(a PAH)

One of a group of compounds known as polycyclic aromatic hydrocarbons (PAH) see below. Derived from coal tar linings in old iron mains. A stringent standard has been set for this individual substance based on its toxicity.

 

0.01 ug/l

Boron

Boron in water sources comes from the residues of detergent formulations that are present in treated sewage effluents.  The concentrations present in drinking water are not of public health concern.

 

1 mg/l

Bromate

A disinfection by-product formed by the reaction of naturally occurring bromide with strong oxidants (usually ozone).  A stringent standard has been set based on toxicity and best water treatment practice. Hartlepool Water does not use ozone in its water treatment process.

 

10 ug/l

Cadmium

Cadmium is only found at very low level in drinking water.  These traces can arise from environmental contamination or dissolution of impurities in plumbing fittings.

 

5 ug/l

Chloride

Chloride in drinking water can originate from natural sources. However, it may also be due to local use of de-icing salt and saline intrusion.

 

250 mg/l

Chlorine Free

It is a statutory requirement to disinfect public water supplies and chlorine is most frequently used for this purpose. Sufficient chlorine is added to ensure that the water is free from harmful bacteria as it travels through the mains network until it reaches your kitchen tap. In addition, we aim to avoid high levels in supply in order to minimise associated taste and odour.

 

No specific standard

Chromium

Chromium is not present in water sources and is generally not found in drinking water.

 

50 ug/l

Clostridia Perfringens

E. Coli

Enterococci

These bacteria are found in human and animal gut and are indicators of faecal contamination. They should not be present in drinking water and immediate action is required to identify the source of contamination. Clostridia perfringens is a pore forming bacterium that can survive disinfection.

 

0 per 100ml

0 per 100ml

0 per 100ml

Coliform Total

These bacteria are widely distributed in the environment, often as a result of human or animal activity but some grow on plant matter. They provide a sensitive measure of the microbiological quality. Their presence in water supplies indicates a need to investigate the source of contamination.  Coliform bacteria indicate whether water treatment, especially disinfection, is satisfactory. 

 

0 per 100 ml (95% of samples taken at service reservoirs must have 0 per 100ml)

Colony counts

Colony count measurements detect a wide range of micro-organism, the types and numbers detected depends on the media and temperature used.  The test is of little value as a measure of pathogen risk but is a useful operational tool.

 

No abnormal change

Colour

Colour occurs naturally in water from surface water sources. Hartlepool Water is all under ground water source. The standard is set for aesthetic reasons

20 mg/l

Pt/Co scale

 

Conductivity

This is a measure of the ability of the water to conduct an electric current and is a measure of the mineral salts dissolved in the source water.

 

2500 us/cm

@ 20 °C

Copper

Copper in drinking water arises mostly from copper pipes and fittings in household plumbing. May cause blue staining on sanitary fittings. Excess can cause a metallic taste.

 

 

2 mg/l

Cyanide

Cyanide is generally not present in water sources and it is not found in drinking water.

 

50 ug/l

Fluoride

Fluoride occurs naturally in many water sources, particularly groundwater.  It is not removed by conventional water treatment. Hartlepool water is a naturally fluoridated supply.

 

1.5 mg/l

Iron

Present naturally in many waters. It is not used in Hartlepool Water’s treatment process. Iron in water supplies may also be derived from the corrosion of iron mains. The standard has been set for aesthetic reasons to minimise discoloured water.

 

200 ug/l

 

 

Lead

Lead is only rarely present in water sources but may be present as a result of dissolution after contact with lead service pipes and plumbing particularly in areas with older properties. Hartlepool water has been examined for its potential to dissolve lead and receives marginal phosphate treatment as an effective control.

 

25 ug/l (reduced to 10 mg/l by 2013)

Manganese

Present naturally in many water sources. Black deposits of manganese dioxide cause discoloured water and the standard is set for aesthetic reasons.

 

50 ug/l

 

Mercury

Mercury is not generally present in water sources or drinking water.

 

1 ug/l

Nickel

A few groundwater sites can contain nickel.  Nickel may also be present in coatings on modern taps and other plumbing fittings.

 

20 ug/l

Nitrate

Application of agricultural fertilisers is the main source of nitrate in water supplies. The extent of nitrate contamination can be minimised through good farming practices and appropriate controls in catchment areas.

 

 

 

50 mg/l

Nitrite

Traces of nitrite are produced when chlorine and ammonia are used together in the disinfection process to form chloramines. Hartlepool Water operates a simple chorine disinfection process.

 

 

0.5 mg/l at customer taps and 0.1 mg/l at treatment works

Odour and taste

These standards ares measured by a trained panel of experts who examine the water and assess the dilution ratio to eliminate any taste or odour.  The standard is set for aesthetic reasons.

 

Dilution No of 3 at 25oC

Pesticides

Heptachlor, heptachlor epoxide and (Aldrin, dieldrin)

 

These persistent organo-chlorine compounds are no longer used in the UK and generally they are not found in water sources but a stringent standard has been set on the basis of their toxicity.

0.03 ug/l

Pesticides – other compounds

This group includes organic chemicals with a wide range of uses such as weed-killers, insecticides and fungicides.  Many water sources contain traces of pesticide residues as a result of both agricultural and non-agricultural uses of pesticides on crops and for weed control.

 

0.1 ug/l

Pesticides - total

This parameter represents the sum of the detected concentrations of the individual pesticides.

 

0.5 ug/l

pH (Hydrogen ions)

pH value or hydrogen ion concentration gives an indication of the degree of acidity or alkalinity of the water.  A pH of 7 is neutral and preferably waters should be slightly alkaline i.e. 7.5-8.0 to protect metallic fittings and pipework corrosion. A tighter maximum indicator value of 6.5-9.5 also applies.

 

6.5-10.0 pH units

Polycyclic aromatic hydrocarbons (PAH)

Polycyclic aromatic hydrocarbons are present in coal tar linings, which were used to protect water mains before 1970.  Traces of PAH, at concentrations that are not of significance to health, may be found in drinking water if the  original coal tar lining is still present.  This parameter represents the sum of the concentration of four individual PAHs.

 

0.1 ug/l

Selenium

Selenium is an essential element, concentrations in drinking water sources and supplies are usually very much less than the standard.

 

10 ug/l

Sodium

Occurs naturally in water after passing through certain mineral deposits and rock strata.  Concentrations in drinking water are normally very low but some water softeners can significantly add to the sodium concentration. Always use water from a tap free from the softening process for drinking, cooking and for preparing babies feeds.

 

200 mg/l

Sulphate

This occurs naturally in water from contact with particular mineral deposits and rock strata and is not removed during water treatment.

 

250 mg/l

Tetrachloroethene and Trichloroethene

These solvents can be present at low concentrations in groundwater under industrial areas.  The standard relates to the sum of the detectable concentrations of the two compounds.

 

10 ug/l

Tetrachloromethane

This solvent can be present at low concentrations in groundwater under industrial areas.

 

3 ug/l

Total organic carbon (TOC)

TOC represents the total amount of organic matter present in the water.  Used in the operational control of water supplies as the concentrations present in water donot present any risk to health.

 

No abnormal change

Total indicative dose

Total indicative dose is a measure of the effective dose of radiation the body will receive from consumption of water.  Its calculation is only required when screening values for gross alpha or gross beta are exceeded.

 

 

 

0.10 mSv/year

Trihalomethanes (THMs)

THMs are formed by the reaction between chlorine and mainly naturally occurring organic substances.  The use of chlorine in water treatment is a very important public health safeguard.

 

100 ug/l

Tritrium

Tritrium is a radioactive isotope of hydrogen.  It is not normally found in water sources.  Discharge of radioactivity to the environment is closely regulated by the Environment Agency.

 

100 Bq/1

Turbidity

All source waters can at times become naturally cloudy due to fine particles suspended in the water.  Turbidity is a quantitative measure of cloudiness.  It can also arise from disturbance of sediment within the distribution systems. Sometimes minute air bubbles give the supply a milky appearance but on standing for a few minutes these will clear for the bottom upwards. There is a tighter standard set for treatment works than at consumer taps.

 

4 NTU units at consumer taps

1 NTU unit at treatment works

 

 

Key:

PCV – This means the ”prescribed concentration  or value”, which is the standard set in The Water Supply (Water Quality) Regulations 2000. Some parameters listed do not have a regulatory standard and no value is shown.

 

Units:

Mg/l = milligrammes per litre (or parts per million)

µg/l = microgrammes per litre (or parts per billion)

NTU = nephelometric turbidity units

µS/cm = micro siemens per centimetre

mSv/year = milli sievets per year

Bq/l = becquerels per litre

Pt/Co scale = Platinum Cobalt scale

 

 

 

 

 

 

 

 

               

 

 

 

 

 

 

 

 

 

 

               

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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