Interpreting water analyses

How to interpret the results of common water studies?

MICROBIOLOGIGAL AND CHEMICAL QUALITY REQUIREMENTS AND RECOMMENDATIONS OF HOUSEHOLD WATER

The Finnish Ministry of Social Affairs and Health’s regulation 401/2001 divides the quality criteria for household water in small units between quality requirements and quality recommendations.

The quality requirements apply to the most damaging materials or bacteria. Exceeding the quality recommendations usually results in only technical and aesthetic damages.

1. Quality requirements for household water in general

Household water must not contain micro-organisms, parasites or any other materials in amounts that could jeopardise human health. Household water must be fit for its application, and it cannot cause harmful corrosion or precipitation inside the water supply equipment.

Individual households are in charge of the quality of the household water they acquire and the system used for the purpose. Improving the quality of drinking water is mostly voluntary.

2. Monitoring the water quality of individual household wells

Municipal health protection authorities may order the household well water to be studied if there is reason to suspect that the water quality may pose a risk to health. If household water does not meet the set quality requirements for healthy water, the municipal health protection authority must inform the water user about possible health risks.

The authority may giver orders regarding the monitoring, purifying and use of household well water in order to prevent negative effects on health. Municipal health protection authorities must also ensure that households acquiring water for their own use get enough information about the quality of household water in the area, related health risks and the possibilities to eliminate them.

According to the recommendation, the quality of water must be studied every three years.

A. MICROBIOLOGICAL QUALITY REQUIREMENTS

cfu = colony-forming unit

Escherichia coli, quality requirement: 0 cfu/100 ml

The Escherichia coli bacteria lives in the intestines of humans and warm-blooded animals. It is considered to be the best indicator of faecal-related contamination of water.

Intestinal enterococcus, quality requirement: 0 cfu/100 ml
The enterococcus genus of bacteria includes species living in other environments in addition to the intestines of humans and warm-blooded animals. The specification attempts to identify species that appear mostly in intestines.

Their presence in water may point to faecal-related contamination.

Coliform bacteria, quality requirements: fewer than 100 cfu/100 ml

The amount of coliform bacteria is used in grading the hygienic quality of drinking water. Coliform bacteria, with the exception of Escherichia Coli, may come from the soil, plants or waste water in addition to faeces. The presence of coliform bacteria is not a clear sign of faecal contamination, but indicates a general contamination and often means that soil water has gotten into a well.

B. CHEMICAL QUALITY REQUIREMENTS

µg/l = micrograms per litre; mg/l = milligrams per litre
For example: 10 micrograms per litre = 0.01 milligrams per litre = 0.00001 grams per litre

Arsenic, maximum concentration allowed: 10 µg/l

Arsenic is one of the worst well water contaminants, alongside radon and uranium. Like these two compounds, arsenic cannot be detected without a water analysis. It is an odourless and flavourless carcinogenic material. Arsenic increases the risk of cancer, particularly skin cancer. Certain wood impregnation materials have contained arsenic. Prolonged exposure to arsenic in daily doses of 2–5 mg/l causes symptoms of poisoning, including weakness in the limbs, loss of appetite and nausea. Arsenic can occasionally be found in bedrock, especially black shale areas in the Tampere region, but also the Hattula-Tuusula-Mäntsälä sector.

Fluoride, maximum concentration allowed: 1.5 mg/l

Fluoride is an odourless and flavourless trace element that the human body requires in small amounts. Excessive consumption of fluoride causes white spots in the teeth. When consumed in large amounts, fluoride affects the structure of the cancellous bone and increases the risk of bone fractures. Fluoride is especially harmful to children, but adults should also not use water with a fluoride concentration of over 2 mg/l for long periods of time. Fluoride is most common on gruss rock areas. These can be found along the Finnish coast in South-West and South-East Finland.

Copper, maximum concentration allowed: 2.0 mg/l

A high concentration of copper makes water taste bitter, stains sanitary fittings green and may give blond hair a green tint. The human body does require copper in tiny amounts, but large concentrations are suspected to be poisonous. Large concentrations of copper salts may also cause stomach and intestinal infections.

A combination of a high copper concentration and low selenium concentration in household water may contribute to a proliferation of cardiovascular diseases.

Copper typically gets into water from copper water pipes and appears more commonly in warm water. Acidic well water, i.e. whose pH value is under 7, prevents a protective oxide layer from forming. As such, acidic water increases the corrosion of copper pipes. The copper concentration will lower rapidly by letting the water run, but the corrosion will not stop entirely.

Corrosion often leads to water damages, as water seeps unnoticed into house structures.

Nitrate, maximum concentration allowed: 50 mg/l

Nitrate is odourless and flavourless, and cannot be detected by human senses.

The health risks of nitrate mainly affect infant children. Nitrite, which is formed from nitrate, can disrupt the metabolism of their red blood cells, causing the so-called Blue Baby syndrome. Nitrite has also been suspected to increase the risk of stomach and bladder cancer. Nitrate can also enter well water from fertilisers and as a result of materials containing nitrogen decomposing.

Previously, the maximum allowed concentration of nitrate was 25 mg/l. This figure was fairly commonly exceeded in Finland. Humans may consume a large dose of nitrate from e.g. sausage products as well as intensively farmed vegetables and fruit.

Nitrite, maximum concentration allowed: 0.5 mg/l

Nitrite is formed as a result of nitrogen compounds such as ammonium oxidising imperfectly. Nitrite’s effects on health are described in the section about nitrate.

C. CHEMICAL QUALITY RECOMMENDATIONS, OTHER BASIC ANALYSES

µg/l = micrograms per litre; mg/l = milligrams per litre
°dH = German water hardness degree; Bq = Becquerel

For example: 10 micrograms per litre = 0.01 milligrams per litre = 0.0001 grams per litre

Alkalinity, no quality recommendation

Alkalinity describes water’s buffer capacity, i.e. its ability to withstand changes in pH value. Alkalinity is the sum of compounds with alkaline behaviour: hydroxide, carbonate and bicarbonate. With a high alkalinity, water can resist external changes in pH. Together with lime, this is usually enough for metal pipes to form an adequate protective layer.

Alkalinisation of water (typically the increase of pH) is the easiest way to protect metal pipes from corrosion.

Aluminium, maximum concentration allowed: 0.2 mg/l

Aluminium is the most common metal in the Earth’s crust. There is a suspected connection between aluminium and certain neurological disorders and e.g. Alzheimer’s disease. However, studies have not found concrete evidence for the claim.
In naturally acidic alum clay areas, the aluminium concentration of water may reach several milligrams per litre. Aluminium may also dissolve off of aluminium dishes or fittings.

Ammonium, maximum concentration allowed: 0.5 mg/l

Ammonium salts are not particularly harmful, but very high concentrations of ammonium can make water smell or taste pungent. Ammonium can also corrode pipes, especially those made of copper. The presence of ammonium in water typically points to a contamination related to animals or waste water.

Smell (suggestive recommendation: no strange smells)

Clean water is odourless and nearly flavourless. However, people can have varying sensitivities to odours and flavours. Only hydrogen sulphide can clearly be detected in the smell, which resembles that of a rotten egg. Another distinct odour showed by laboratory tests is the so-called cable odour, which may occur if e.g. a pump’s electric cable is not food-grade. Other odours are less distinct, and may be described as stale, pungent or swampy. Besides hydrogen sulphide, compounds that cause odours are virtually impossible to detect with normal measuring equipment.

Chloride, maximum concentration allowed: 100 mg/l

Chloride is not known to have negative effects on health, but it does worsen the taste of water already in concentrations of 100–200 mg/l. Chloride has a corrosive effect on metals, especially stainless steel, which increases already in concentrations of under 50 mg/l and, as such, its concentration should be kept to a minimum. Chloride occurs in ground water, especially around Finland’s coasts, but inland areas also feature salt pockets left over from old seafloors. Spreading salt on highways may also increase the chloride concentration of water, especially near major highways.

KMnO4 number or potassium permanganate, maximum allowed concentration: 20 mg/l (suggested recommendation: less than 12 mg/l)

The KMnO4 number represents the amount of biodegradable organic materials in water. Such organic compounds include tannin, lignin, humin and fulvic and humus acids, commonly referred to as humus or humus materials. Humus, by itself, is not harmful to human health. As for dug wells, the number is usually used to refer to the condition of the well, as a high kMnO4 number indicates that ground water is getting into the well. With bore wells, the number may be used to describe the effects of surface water, but it may also mean a direct water connection to a nearby swamp, pond or lake. The potassium permanganate number may be under 4 mg/l in high-quality well water. A decent reference value is under 10–12 mg/l. If the value exceeds 12–15, the water may become increasingly coloured.

Water hardness, no recommendation (suggested recommendation:

less than 12°dH or Ca 100 mg/l; Mg 50 mg/l)

Water hardness refers to the calcium and magnesium content in water, both of which have positive effects on heath.

However, water hardness forms boiler stone in heat exchangers and other water supply equipment, which diminishes heat transfer and forms light-toned deposits upon drying. Hard water requires more detergent than soft water. Water is considered soft, when its hardness is under 5°dH. Water is considered hard, when its hardness is over 10°dH.

Flavour (suggestive recommendation: no strange flavours)

Clean water is odourless and nearly flavourless. On the one hand, flavour is often related to water temperature and, on the other hand, people can have varying sensitivities to the odours and flavours of compounds. Other than by odour, most materials that affect the flavour of natural water can be specified and measured. (1) Iron tastes metallic and leaves a long-lasting, bitter or prickly flavour in the mouth. The flavour can be identified almost all over the mouth. (2) Manganese also tastes metallic and zesty. The flavour of manganese can be felt especially in the palate. It is sometimes followed by a dry feeling mouth and a compulsive need to swallow. Water with a high concentration of (3) calcium rarely tastes fresh. If (4) the pH value is momentarily at significantly high levels (pH 9.5–10) due to alkalinisation, the water might taste “rocky and stale”. It may even momentarily damage the mouth’s mucous membrane. If water (5) has a high concentration of copper, it may taste metallic and bitter. A sixth clearly identifiable taste is the so-called (6) taste of salt. A salty taste in Finnish natural water may be due to sodium and its counterions, i.e. chloride, sulfate or bicarbonate. (7) Carbon dioxide, or carbonic acid in water makes water taste fresh. However, free carbonic acid and a low pH are a combination that damages metals. Plentiful (8) oxygen (air) may also make water taste fresh.

Manganese 0.1 mg/l (suggested recommendation: less than 0.05 mg/l)

There is no clear evidence of manganese having negative effects on health. According to some studies, manganese may cause neurological disorders if consumed in large amounts. Manganese can make water taste unpleasant, form into deposits on sanitary fittings and discolour laundry. It’s negative effects in water can be seen as a black, soot-like crud that is slightly oily and smelly. Manganese is usually related to a low oxygen content in water and a stale smell. Manganese in well waters is of natural origin and manganese typically occurs together with iron.

Sodium, see the section on electrical conductivity

pH, recommended pH range: 6.5–9.5

Finnish dug well water is usually acidic (pH under 7) or even considerably acidic (pH under 6.0). Bore well water is usually somewhat basic (pH over 7) or acidic (pH under 7). Acidic water may cause corrosion in especially copper pipes. A high limestone concentration in water (water hardness) and alkalinity decrease the risk of pipe corrosion, but may increase the risk of limescale (also see the section on alkalinity, limestone, water hardness and copper). If water has a high pH value (pH 8–9), the water may taste like limestone. In such cases, it is possible that fluoride has also dissolved into the water due to the composition of bedrock (see section Fluoride). If fluoride has not been analysed, fluoride analysis should be performed, especially in households with children.

Radon, maximum concentration allowed: 1000 Bq/l (suggested recommendation: 300 mg/l)

Radon is an odourless, flavourless and colourless gaseous element that is created in the soil, especially from uranium-rich granites. Radon dissolves in water and is easily spread into the air. Radiation always poses a risk of cancer, and radon carried in water causes the stomach to receive a dose of radiation. Radon absorbs into blood from the intestinal tract and exits through exhaled air. According to latest studies, around 200 cases of cancer in Finland are linked to radon in Finland. Other radioactive materials in water increase the dose of radiation received by other organs.

For example, using water to shower increases the radon concentration of room air. The Finnish Radiation and Nuclear Safety Authority advises to analyse water for other radioactive materials as well if radon concentration exceeds 1000 Bq/l. The measurements can be made by the Radiation and Nuclear Safety Authority, or Helsinki City’s environmental centre.

Iron, maximum concentration allowed: 0.4 mg/l (suggested recommendation: 0.2 mg/l)

Iron is a common and naturally occurring element found in soil. It can stain water brown and thicken it. Iron tastes metallic and leaves a lingering or prickly sensation in the mouth. Sensitivity to the flavour of iron varies by person between 0.5–1mg/l. Iron does not cause health risks in concentrations at which consuming water based on suspicious appearance is possible.

Large quantities of iron cause technical problems as it forms deposits in pipes and water fittings. Iron may stain light-coloured sanitary fittings brown in an undesirable way, even permanently. Oily membranes occasionally appearing in water are typically iron or manganese. If household water pipes are made of iron, corrosive water may cause corrosion, further increasing the iron concentration of household water.

Hydrogen sulphide (suggested recommendation 0.0 mg/l)

Hydrogen sulphide is a gaseous sulphur compound that smells like rotten eggs. It occurs especially in deep bore well water, low-oxygen ground water in clay soil and acidic swamp water. Hydrogen sulphide does not occur in oxygen-rich or properly aerated well water.

Turbidity, goal level 1.0 NTU/FTU

Water turbidity is typically due to clay or iron, and has no negative effects on health. New bore wells may give turbid water for a long time before the dust from boring is drained and the water becomes clearer.

Deposits

Deposits are caused by iron, whose colour ranges from brown to reddish; manganese, coloured dark or black; water hardness, i.e. limestone, light-coloured or brown together with iron; humus, colour ranging from yellow to brown; copper together with other compounds (such as soap), coloured teal. Bore wells may also contain sand and clay. Surface water may contain impurities, moss and small aquatic animals.

Sulfate, maximum concentration allowed: 250 mg/l

High concentrations of sulfate may have laxative effects. Sulfate increases the corrosiveness of water, so it must, therefore, be far much below the maximum allowed concentration.

Conductivity and salts (2500 μS/cm; suggested recommendation <400 µS/cm)

Electric conductivity describes the amount of salt – such as sodium chloride, NaCl – dissolved in water. High conductivity indicates a high concentration of salt, which is harmful for health and corrosive for water supply equipment. Chloride comes from sea water, salt layers, highway salt or industrial waste water. Chloride causes an unwanted flavour in water and corrodes water supply equipment in concentrations exceeding 50–200 mg/l. Sodium concentration should not exceed 150mg/l, due to sodium’s known property of increasing blood pressure.

Uranium (suggested recommendation 0.03–0.1mg/l)

Granite stones in Finnish bedrock contain more uranium than other types of rock. Our soft bedrock waters are also rich in bicarbonates, into which uranium dissolves. Uranium is a chemical poison. In large concentrations it changes the functioning of kidneys and is suspected to cause osteoporosis.

Extensive studies have shown changes especially in the form of increased calcium, phosphate and glucose concentrations in the test group’s urine. Since knowledge of uranium’s health risks is still incomplete, exposure to it must be minimized for safety reasons. Finland has not yet specified a definitive threshold value for uranium, but it can be expected to be within the range 0.03–0.1mg U/l.

Colour of water, target level 5 mg Pt/l

The colour of water is a measure for the yellowish brown colour given to water by humus or iron. The colour of water does not have direct health effects, but is used as a fast and simple indicator to describe the overall quality of water. If tap water is always yellow or yellowish, the cause is typically humus materials. If the colour starts out neutral and clear but the water turns yellowish brown after standing still, the cause is most likely iron. If the colour is dark or black and precipitation-like, the colour most likely comes from manganese. If the colour starts out turbid but the water brightens fairly quickly, the colour may come from dissolved gases such as oxygen or carbon dioxide. If the colour is always turbid (see also the section on turbidity), the cause is most likely clay.

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