Health parameters

E. coli

Escherichia coli (E. coli) is a type of bacteria used as an indicator of microbiological water quality. The health guideline value for E. coli is that none should be detected in a minimum 100 mL sample.

What does a sample failure mean?
The presence of E. coli in a sample does not itself indicate that the drinking water is unsafe, but may indicate that the source water or the treatment, transmission, or reticulation components of the SEQ interconnected water supply network may be compromised.

E. coli are occasionally detected in treatment, transmission or reticulation systems that are operating effectively.

In the absence of the Australian Drinking Water Guidelines 2011 prescribing a long-term performance measure for microbial water quality, for the purposes of the Customer Confidence Report (Bulk Water), 12 monthly microbial performance is benchmarked against the Public Health Regulation 2018 annual value.

The Australian Drinking Water Guidelines acknowledge that it is unrealistic, both from a statistical viewpoint and practically, to expect a water supply system to have zero indicator bacteria at all times. However, all positive results for E. coli are taken seriously and are reported to the Office of the Water Supply Regulator and will be investigated to ensure the system’s integrity.

 

Copper

Copper is a mineral widely distributed in rocks and soil and is used in domestic plumbing because it is relatively resistant to corrosion.

Copper is present in uncontaminated surface waters at very low concentrations.

Copper has both an aesthetic and a health guideline value. The aesthetic guideline value is 1 mg/L. The health guideline value is 2 mg/L.

What does a sample failure mean?
Aesthetically, copper can cause a metallic taste, blue-green discolouration of the water and staining issues. Concentrations above the aesthetic level may cause blue or green stains on bathroom fixtures.  

Copper is not normally present in the water supplied from a water treatment plant, but may dissolve into the water supply from plumbing and pipes. When a sample exceeds the guideline for copper, this is usually limited to a particular property or small geographical location as it is generally caused by the local plumbing. It is unlikely that a copper exceedence would affect the bulk supply network.  

 

Fluoride

Low levels of fluoride occur naturally in many water sources. Fluoride is also added to drinking water in many parts of the world, including South East Queensland, to help reduce tooth decay. 

The concentration of fluoride at any given point will vary if a fluoridated source is blended with a non-fluoridated source.

The Water Fluoridation Regulation 2020 sets the prescribed concentration for South East Queensland at 0.8 mg/L. This has been determined as being the level at which the optimum oral health benefit is achieved.

The Public Health Regulation 2018 standard is based on health considerations and states the maximum concentration of fluoride.

The Customer Confidence Report (Bulk Water) only covers compliance with the health standards set in the Australian Drinking Water Guidelines and the Public Health Regulation 2018. The health guideline value for fluoride is 1.5 mg/L.

What does a sample failure mean?
The guideline value is set in order to maximise fluoride's beneficial effects. It is unlikely that a fluoride failure would affect the bulk supply network.

 

Lead

Lead can be present in drinking water as a result of dissolution from natural sources or from household plumbing systems containing lead.

Lead is not normally present in the water supplied from a water treatment plant, but may dissolve into the water supply if lead piping or joins are present in plumbing.

The health guideline value for lead is 0.01 mg/L.

What does a sample failure mean?
When a sample shows lead present above the guideline value, this is usually limited to a particular property or small geographical location as it is caused by the local plumbing. It is unlikely that a lead exceedence would affect the bulk supply network.

 

Manganese

Manganese is a mineral present in the environment which can enter the water supply in its soluble form.

Manganese has both an aesthetic and a health guideline value. The aesthetic guideline value is 0.1 mg/L. The health guideline value is 0.5 mg/L.

What does a sample failure mean?
At concentrations exceeding the aesthetic guideline value of 0.1 mg/L, manganese imparts an undesirable taste to water and stains plumbing fixtures and laundry.

Health implications for manganese are unlikely because water will become unacceptable to consumers long before the concentration reaches the health guideline value.

 

Total trihalomethanes

Trihalomethanes are a by-product of the chlorination and chloramination disinfection processes. Disinfection is essential to destroy microorganisms that could otherwise be harmful.

The health guide value for total trihalomethanes is 0.25 mg/L.

What does a sample failure mean?
The health guideline value for total trihalomethanes is set with a wide safety margin and is based on long-term exposure; individual failures of the guidelines are very unlikely to represent a significant health risk.

The Australian Drinking Water Guidelines encourage action to reduce total trihalomethanes, but not at the expense of compromising disinfection. Non-disinfected water poses significantly greater risk to health than total trihalomethanes.

 

Total and Free Chlorine

Chlorine is the most common chemical used for the disinfection of drinking water. It is highly effective at killing bacteria and viruses, at oxidising soluble iron, manganese and sulfides, and removing tastes and odours and some algae toxins.

Chlorine dissociates in water to form free chlorine, which consists of aqueous molecular chlorine, hypochlorous acid and hypochlorite ion. Free chlorine reacts with ammonia and certain nitrogen compounds to form combined chlorine. Combined chlorine can consist of chloramines which are often used as a secondary disinfectant in the supply system. Total chlorine is the sum of free and combined chlorine in a sample.

What does a sample failure mean?
While the odour threshold for chlorine is 0.6 mg/L, there are no ADWG aesthetic guidelines for total and free chlorine. In some supplies, it may be necessary to exceed the odour threshold in order to maintain an effective disinfectant residual throughout the system. Based on health considerations, the ADWG guideline for Total Chlorine in drinking water is 5 mg/L.

 

Arsenic

Arsenic is naturally occurring in the environment but can also be added through human sources, such as mining, industry and agriculture.

What does a sample failure mean?
Inorganic arsenic is highly toxic to humans and has an ADWG derived health guideline of 0.01 mg/L as set in the ADWG.

 

Selenium

Selenium and selenium salts are widespread in the environment and is naturally found in soil; however, concentrations can vary considerably between areas with higher levels found in places with recent volcanic activity. Selenium is released during the burning of coal which is the greatest anthroprogenic source. Selenium can also be leached from the soil into water systems after rainfall but it typically occurs in low levels. It is also considered an essential nutrient and it is recommended for daily intake. 

What does a sample failure mean?
Although selenium is recommended as part of your daily intake, excessive amounts can have adverse health effects such as brittle hair and nails and discolouration of skin and teeth. Based on ADWG health considerations, Selenium levels in water should not exceed 0.01 mg/L.  

 

Cadmium

Cadmium is a metal that is resistant to corrosion, which is why it was often used in steel plating. It is also a common component in zinc ores and a byproduct of zinc production. Zinc or cadmium plated pipes and fittings along with fertilizer may contribute to cadmium contamination in water. Food is the main source of cadmium intake for people, with the average adult taking in 0.03 mg a day.

What does a sample failure mean?
Chronic exposure to cadmium can lead to kidney damage as it is released from the body slowly. Based on ADWG health guidelines, cadmium levels in water should not exceed 0.002 mg/L.

 

Chromium

Chromium is present in the environment in the trivalent (CR(III)) and hexavalent (CR(VI)) states. 

Trivalent is the most common naturally occurring state with small amounts occurring in most soils and rocks, it is also commonly used in industry and agriculture. It is considered an essential element for humans.

Hexavalent chromium occurs infrequently in nature and its presence in water is generally the result of industrial and agricultural waste discharges. It is not considered an essential nutrient and can have harmful effects on humans. 

What does a sample failure mean?
Seqwater tests for total chromium and if total chromium exceeds the ADWG health guideline of 0.05 mg/L then additional analysis for hexavalent and trivalent chromium shall be performed. 

 

Boron

Boron is a metal that can occur in water through the natural leaching of boron-containing minerals or contamination. It is used in manufacturing and in agriculture as fertilisers, herbicides and insecticides. It is also found in many foods such as fruits and vegetables, and intake through food is estimated to be 10 times higher than that from water. 

What does a sample failure mean?
Based on health considerations, boron has an ADWG health derived guideline of 4 mg/L, however, limited information indicates that concentrations in water is less than 0.1 mg/L. 

 

Nickel

Nickel is a metal used largely in the electroplating industry and for making alloys. Its main releases to the environment are from burning fossil fuels and industrial waste discharges. Drinking water typically contains very low concentrations of nickel.

What does a sample failure mean?
Based on ADWG health considerations, nickel concentrations in drinking water should not exceed 0.02 mg/L.

 

Nitrate

Nitrate is a naturally occurring oxide of nitrogen that makes up part of the nitrogen cycle. It is formed from the oxidation of organic waste such as manure, by the action of nitrogen-fixing bacteria in soils or from lightning strikes. It is also manufactured for the use in explosives and inorganic fertilisers. Increased farming practices and sewage effluent disposal to streams has led to an increase of nitrate in the environment. Food, particularly vegetables and cured meat is the major source of nitrate intake for humans. 

What does a sample failure mean?
Based on ADWG health guidelines, the concentration of Nitrate in drinking water should not exceed 50 mg/L to protect bottle fed babies under 3 months of age. Up to 100 mg/L can be safely consumed by people over 3 months of age. If Nitrate exceeds the health limit, those caring for infants under 3 months should seek an alternative water source. The toxicity of nitrate to humans is thought to be solely due to its reduction to nitrite. 

 

Nitrite

Nitrite is a naturally occurring oxide of nitrogen that makes up part of the nitrogen cycle. It is relatively unstable and can be formed by the reduction of nitrate in poorly oxygenated waters. It is rapidly oxidized to nitrate and is seldom present in well oxygenated or chlorinated supplies. The major biological effect of nitrite in humans is its involvement in the oxidation of normal haemoglobin to methaemoglobin which is unable to transport oxygen to the tissues.

What does a sample failure mean?
Based on ADWG health guidelines, Nitrite has a health derived guideline of 3 mg/L.

 

Mercury

Natural levels of mercury in water is low, with most sources coming from industrial spills and emissions. Even so, total mercury levels remain very low in drinking water with most human exposure coming from food. Mercury falls into two categories: inorganic and organic, with organic being the most toxic in the form of methyl mercury. Organic mercury is unlikely to be found in uncontaminated drinking water and likely makes up less than 10% of total mercury. Less than 15% of inorganic mercury in drinking water is absorbed by the gastrointestinal tract, but compounds can accumulate in the kidneys and it has a long half-life.

What does a sample failure mean?
Based on ADWG health guidelines, the concentration of total mercury should not exceed 0.001 mg/L, which is based off the toxicity of methyl mercury. 

 

Chloroacetic acid

Chloroacetic acids are produced in drinking water as a by-product of the reaction between chlorine and naturally occurring humic and fulvic acids. They are commercially used as reagents or intermediates in the preparation for a wide range of chemicals.  

What does a sample failure mean?
Based on ADWG health guidelines, the concentration of Chloroacetic acid in drinking water should not exceed 0.15 mg/L. 

 

Dichloroacetic acid

Dichloroacetic acids are produced in drinking water as a by-product of the reaction between chlorine and naturally occurring humic and fulvic acids. They are commercially used as reagents or intermediates in the preparation for a wide range of chemicals.  Dichloroacetic acid is also an ingredient in some pharmaceutical products. 

What does a sample failure mean?
Based on ADWG health guidelines, the concentration of Dichloroacetic acid in drinking water should not exceed 0.1 mg/L.

 

Trichloroacetic acid

Trichloroacetic acids are produced in drinking water as a by-product of the reaction between chlorine and naturally occurring humic and fulvic acids. They are commercially used as reagents or intermediates in the preparation for a wide range of chemicals.  Trichloroacetic acid is also used as an herbicide, soil sterilant and antiseptic. 

What does a sample failure mean?
Based on ADWG health guidelines, the concentration of Trichloroacetic acid in drinking water should not exceed 0.1 mg/L.

 

Bromate

Bromate is not a normal component of water, but it may be formed from bromide during ozonation within the water treatment process. It is a strong oxidant and will probably react with organic material in water forming bromide as a by-product. There are no published methods to remove bromate from drinking water. 

What does a sample failure mean?
Bromate has an ADWG health guideline of 0.02 mg/L. 

 

NDMA

NDMA or N-Nitrosodimethylamine, is used as an industrial solvent, an anti-oxidant, rubber accelerator and in the preparation of polymers. It is also produced as a by-product of chloramination of drinking water and to a lesser extent by chlorination. It can exist in a liquid or vapour state and may be associated with airborne particulates. It has also been detected in preserved foods such as smoked and salted fish and meats and sausages cured with nitrates. It can also be generated in the stomach through nitrosation of secondary amines of ingested food, such as fish and meat. Drinking water makes up only a small component of exposure concentrations in humans as compared to food or smoking. 

What does a sample failure mean?
Based on ADWG health guidelines, NDMA should not exceed 0.0001 mg/L.

Aesthetic parameters

Aluminium

Aluminium may be naturally present in water or from the water treatment process.

Aluminium sulphate is also used extensively as a coagulant in order to treat water. The aesthetic guideline value for aluminium is 0.2 mg/L.

What does a sample failure mean?
High aluminium may result in ‘milky’ coloured water, though the occurrence of this also depends on factors such as pH and the water treatment chemicals used.

Aluminium can be present in silt, which can accumulate as sediment in the distribution pipes. High aluminium may be caused by the re-suspension of these materials. There is no health affect.

 

Hardness/Soluble Hardness

‘Hard’ water is caused by dissolved calcium and magnesium salts, particularly carbonates and bicarbonates. Total hardness is a calculation of total magnesium and calcium, whereas soluble hardness is a calculation of soluble magnesium and calcium.

The aesthetic guideline value for total hardness, reported as calcium carbonate, is 200 mg/L.

What does a sample failure mean?
There is no health risk with hard water, however, it can be difficult to lather and can cause scaling problems in hot water systems.

 

Iron

Iron can occur naturally in water sources and may also enter the water supply from the corrosion of iron water pipes. The aesthetic guideline value for iron is 0.3 mg/L.  

What does a sample failure mean?
High iron concentrations may affect the taste of water or give water an undesirable rust-brown appearance.  It can cause staining of laundry and plumbing fittings and blockages in irrigation systems.  There is no health affect.

 

pH

pH is a measure of how acidic or alkaline the water is in the system. pH is affected by the source water and also the water treatment process. The aesthetic guideline value for drinking water is between pH 6.5 to pH 8.5.

Water that is naturally pH low may need to be conditioned in order to ensure it complies with the guidelines. This is most commonly achieved by adding lime or passing the water through a bed of limestone chippings.

What does a sample failure mean?
Water with low pH may be corrosive to pipe work and household fittings.  Water with a high pH can cause scaling issues and affect the taste of water. There is no health affect.

 

Total dissolved solids

Total dissolved solids are inorganic salts and small amounts of organic matter that are dissolved in water. The aesthetic guideline value for total dissolved solids in drinking water is 600 mg/L.

What does a sample failure mean?
A high level of total dissolved solids can affect the taste of drinking water. Extremely high levels can cause scaling in pipes and fittings. There is no health affect.

Editions of the Customer Confidence Report (Bulk Water) published prior to the effective date of the Australian Drinking Water Guidelines 2011 had assessed results for total dissolved solids against a now superseded guideline value. The method to assess results published after this effective date has since been amended to reflect the in-effect 2011 guideline value.

 

True colour

‘True colour’ is the colour of the water after particles have been removed by filtration. It is a measure of whether the water appears coloured or tinted due to parameters dissolved in the water.

The aesthetic guideline value for colour is 15 Hazen Units (HU).

What does a sample failure mean?
Colour is an aesthetic parameter and of no health significance, although highly coloured water will be unacceptable to consumers.

The guideline value is based on the colour that is just noticeable in a glass of water.

 

Turbidity

Turbidity is caused by the presence of fine suspended matter such as silt, clay, plankton, and other organisms in the water. It is a measure of the extent to which water appears cloudy or hazy.

The aesthetic guideline value for turbidity is 5 Nephelometric Turbidity Units (NTU). At this level turbidity is just noticeable to the average person.

What does a sample failure mean?
High turbidity can give water a cloudy or muddy appearance making it unacceptable to consumers; however, there is no health affect.

 

Chloride

Chloride is widely distributed in nature as salt through the leaching of rocks into soil and water and also through human sources such as fertilizers, effluent and landfills. Chloride levels can also be increased through the water treatment process with the addition of chlorine and chloride.

What does a sample failure mean?
Chloride does not have an ADWG health guideline, however based on ADWG aesthetic considerations chloride concentrations exceeding 250 mg/L may be detectable to taste. 

 

Sulphate

Sulphate occurs naturally in many minerals and it is used to manufacture many products such as chemicals, paper, soaps and insecticides. It is also used in the mining, pulping and metal industries. In water treatment aluminium sulfate (alum) is used as a flocculant. 

What does a sample failure mean?
Sulphate has an ADWG aesthetic guideline of 250 mg/L due to having a taste threshold between 250-500 mg/L. There is no ADWG health limits, however, levels greater than 500 mg/L may have a laxative effect. 

 

Methylisoborneol (MIB)

Certain bacteria and algae species can produce taste and odour compounds which can give water a strong musty or earthy taste or smell.

What does a sample failure mean?
MIB has no ADWG health or aesthetic guidelines as most individuals do not find these compounds to be offensive in drinking water.

 

Geosmin

Certain bacteria and algae species can produce taste and odour compounds which can give water a strong musty or earthy taste or smell.

What does a sample failure mean?
Geosmin has no ADWG health or aesthetic guidelines as most individuals do not find these compounds to be offensive in drinking water.

 

Zinc

Zinc is a widely distributed metal and occurs in small amounts in most rocks. It is used as a coating for iron and steel products and to manufacture brass. Zinc oxide is also an important component in paint and rubber products. Concentrations of zinc in ground water is low, typically <0.01 mg/L, but drinking water can contain higher concentrations due to corrosion of zinc coated pipes and fittings.  It is also an essential element for humans with a daily recommended intake of 12 mg. 

What does a sample failure mean?
Zinc has an ADWG aesthetic guideline of 3 mg/L as levels above this may cause taste issues. There are no ADWG health guidelines for zinc.

 

Sodium

Sodium is an essential element for all animals and many plants. It is naturally occurring in water systems, but can be added through runoff or during the water treatment process.

What does a sample failure mean?
Based on aesthetic considerations, the ADWG has specified that concentrations of sodium above 180 mg/L may affect the taste of drinking water. Concentrations at or above this level are still safe to consume as it is below the daily recommended intake for salt. There are no ADWG health guidelines for sodium. 

Other parameters

Alkalinity

Alkalinity is a total measure of the parameters (carbonate, bicarbonate and hydroxide content) in water that have acid-neutralising ability.

Alkalinity is different to pH, which measures the strength of an acid or base. Alkalinity indicates a solution’s power to react with acid and ‘buffer’ its pH — that is, the ability to keep its pH from changing.

Alkalinity can be naturally occurring, or altered due to water treatment chemicals. There is no guideline value set for alkalinity.

What does a sample failure mean?
There is no guideline value for alkalinity so there will be no failure of this sample result. However, some industries have to alter processes or machinery settings based on the alkalinity of the water.

 

Temperature

Temperature is mainly an aesthetic criterion for drinking water, with most consumers preferring cool water. Accurate measurement of water temperature is important in the calculation of pH, conductivity and dissolved oxygen.  Low water temperatures can decrease the efficiency of water treatment processes, whereas higher temperatures increase chemical reactions and may lead to greater pipe corrosion and scale formation with hard water. 

What does a sample failure mean?
There are no ADWG guidelines for temperature as it is impractical to try controlling the temperature of water. 

 

Conductivity

Conductivity is the measurement of the water’s ability to conduct electricity. Water is able to conduct electricity when ions are present through the dissolving of salts and other inorganic chemicals. A high conductivity reading would indicate that there are total dissolved solids and minerals present in the drinking water, such as sodium, calcium, magnesium and chloride. Conductivity levels can be influenced by geology, the size of the watershed, pollutant runoff and evaporation. 

What does a sample failure mean?
There are no ADWG guidelines for conductivity.

 

Potassium

Potassium is an essential element for humans. It occurs naturally in water and can also be added during the water treatment process with the addition of potassium permanganate. It seldom, if ever occurs at levels in drinking water at levels that would be of concern to humans.

What does a sample failure mean?
There are no ADWG guidelines for potassium.

 

Calcium

Calcium is an essential element for humans and it occurs naturally in water through leaching of sedimentary rocks and soil runoff. Excessive levels of calcium and magnesium can increase water hardness, leading to difficulty in soap lathering and the deposition of scale. Please refer to hardness for more information. 

What does a sample failure mean?
There are no ADWG guidelines for calcium.

 

Magnesium

Magnesium is an essential element for humans and it occurs naturally in water through leaching of sedimentary rocks and soil runoff. Excessive levels of magnesium and calcium can increase water hardness, leading to difficulty in soap lathering and the deposition of scale. Please refer to hardness for more information. 

What does a sample failure mean?
There are no ADWG guidelines for magnesium.

 

Chlorate

Chlorates are used as herbicides and in manufacturing dyes, matches and explosives. It is also a by-product in the water treatment process. 

What does a sample failure mean?
The ADWG currently doesn’t have a guideline value set for chlorate due to insufficient data.
 

Limits of detection and reporting

Water samples sometimes contain concentrations of chemicals below the limit at which a laboratory can adequately detect. The limit of detection is the lowest quantity of a substance that can be identified before it cannot be found. Limits of detection vary between different laboratories due to differing test methods, and also change over time as the methods improve. Sometimes this is referred to as the limit of reporting.

In the reporting a result that is less than the limit of detection may be reported as "<" (less than).

There are also instances where laboratories provide results for test samples that are at a number of significant figures that do not reflect the limit of detection or the number of decimal places reported upon. Within the Customer Confidence Report (Bulk Water) where this occurs a trailing zero may be added to the result for standardisation of reporting.  

An example of this is as follows:

'A sample result for Aluminium at Capalaba Water Treatment Plant with a limit of detection of 0.005 mg/L may receive a sample result of 0.11 mg/L,  where the laboratory has not provided the sample value to three decimal places. In this instance in the reporting tool will update the 0.11 mg/L value to three decimal places attaching a trailing zero and will now be presented as 0.110 mg/L.