Component
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Level of Concern
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Comments
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E.coli
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Maximum Allowable Value for micro-organisms of Health Significance
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Less than 1 in 100ml of sample
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E.coli is Escherichia coli are bacteria that normally live in the intestines of humans and animals. Because E.coli are always present in human and animal faeces in very high numbers they are used as an indicator of faecal pollution in the microbiological surveillance of drinking water and can indicate whether other potentially harmful bacteria may be present in the water.
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Guideline Value for Aesthetic Determinands
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No Standard
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Alkalinity
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Maximum Allowable Value for Inorganic of Health Significance
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No Standard
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Alkalinity is a measure of waters ability to resist changes in pH, i.e. the measure of how much acid can be added to a liquid without causing a significant change in pH, therefore making the water corrosive.
There are no particular health effects associated with water in any normal range. 10-500 mg/L. Highly alkaline water would be severely corrosive and while this is potentially harmful, it would be rare that anyone would consider drinking water with sufficient alkalinity to be harmful as it would be otherwise aesthetically undrinkable.
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Guideline Value for Aesthetic Determinands
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No Standard
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Chloride
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Maximum Allowable Value for Inorganic of Health Significance
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No Standard
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A high level of chloride gives the water a salty taste, and may make the water corrosive.
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Guideline Value for Aesthetic Determinands
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250 mg/L
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Colour
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Maximum Allowable Value for Inorganic of Health Significance
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No Standard
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Colour may be indicative of dissolved organic material, inadequate treatment, high disinfectant demand and the potential for the production of excess amounts of disinfectant by products inorganic contaminants such as metals are also common causes of colour
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Guideline Value for Aesthetic Determinands
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10 TCU
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Copper
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Maximum Allowable Value for Inorganic of Health Significance
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2 mg/L
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Copper in water rarely occurs naturally, and is usually the result of the reaction between aggressive water and copper plumbing. It may cause blue/green staining in sinks and tubs and may give the water an astringent taste.
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Guideline Value for Aesthetic Determinands
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1 mg/L
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Conductivity
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Maximum Allowable Value for Inorganic of Health Significance
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No Standard
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Conductivity is a measure of waters ability to conduct an electric current and is directly related to the total dissolved salts (ions) in the water. Conductivity in water is affected by the presence of inorganic dissolved solids such as chloride, nitrate, sulphate, and phosphate anions (ions that carry a negative charge) or sodium, magnesium, calcium, iron, and aluminium cations (ions that carry a positive charge).
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Guideline Value for Aesthetic Determinands
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No Standard
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Fluoride
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Maximum Allowable Value for Inorganic of Health Significance
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1.5 mg/L
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Fluoride occurs naturally in some waters. It has been shown to be beneficial in helping to prevent cavities from occurring in teeth. The fluoride content recommended for drinking water by the New Zealand Ministry of Health for oral reasons is 0.7 - 1.0 mg/L. At high concentrations (above 1.5 mg/L), fluoride can cause a brown staining of the teeth.
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Guideline Value for Aesthetic Determinands
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No Standard
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Hardness
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Maximum Allowable Value for Inorganic of Health Significance
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No Standard
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Total hardness is a measure of the soap or detergent consuming power of water. It is considered to be an expression of the Calcium and Magnesium content of water. Excessively high hardness is undesirable because it causes the formation of soap curds, increased use of soap, deposition of scale in hot water heaters and around fixtures, and may sometimes cause objectionable tastes in drinking water. Very low hardness can make water corrosive. Extremely soft to soft 0-45 mg/L, soft to moderately hard 46-90 mg/L, Moderately hard to hard 91-130 mg/L, Very hard to excessively hard 171-250 mg/L, Too hard for ordinary domestic use over 250 mg/L.
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Guideline Value for Aesthetic Determinands
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200 mg/L
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Iron
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Maximum Allowable Value for Inorganic of Health Significance
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No Standard
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Iron in water may cause reddish-brown staining of porcelain, and can cause the build-up of coatings in the pipes, which may harbour bacteria. At levels of 0.05-0.1 mg/L it can affect the taste of water and alter the colour of prepared drinks and food.
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Guideline Value for Aesthetic Determinands
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0.2 mg/L
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Manganese
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Maximum Allowable Value for Inorganic of Health Significance
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0.6 mg/L
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Manganese may cause brownish-black precipitates in laundry items, and can cause the build-up of coatings in the pipes, which may harbour bacteria. At levels of 3mg/L it can affect the taste of water and alter the colour of prepared drinks and food.
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Guideline Value for Aesthetic Determinands
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0.05 mg/L
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Lead
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Maximum Allowable Value for Inorganic of Health Significance
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0.01 mg/L
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Lead occurs in drinking water supplies primarily as a result of corrosion or wearing away of materials containing lead in household plumbing. These Materials include lead-based solder used to join copper pipe, brass and chrome plated faucets and in some cases pipes made of lead that connect your house to the water main. When water stands in lead pipes or plumbing systems containing lead for several hours or more, the lead may dissolve into your drinking water. This means the first water drawn from the tap in the morning, or later in the afternoon after returning from work or school, can contain fairly high levels of lead.
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Guideline Value for Aesthetic Determinands
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No Standard
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Nitrate
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Maximum Allowable Value for Inorganic of Health Significance
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11.2 mg/L measured as Nitrogen
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Nitrate occurs naturally in drinking waters, however where it exceeds the drinking water standard, it is usually due to runoff from fertilizers, animal wastes, or septic systems. High levels of nitrate pose an immediate threat to the health of infants under three months of age. In some infants nitrate combines with intestinal bacteria and enzymes to reduce the oxygen carrying capacity of the blood, causing an anaemic condition known as methemoglobinemia, or blue baby syndrome.
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Guideline Value for Aesthetic Determinands
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No Standard
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pH
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Maximum Allowable Value for Inorganic of Health Significance
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No Standard
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pH is a measure of how acidic or how basic the water is. It is measured on a scale of 1-14, with 7 being neutral. Both excessively high and low pHs may cause increased corrosion which in turn can create taste and staining problems and significant health hazards. In particular, a low pH can cause a bitter metallic taste and corrosion, and a high pH can cause a slippery feel, a soda taste and deposits. For effective disinfection of the water with chlorine the pH should be less than 8.0.
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Guideline Value for Aesthetic Determinands
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7.0 - 8.5
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Sulphate
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Maximum Allowable Value for Inorganic of Health Significance
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No Standard
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High levels of sulphate may cause objectionable tastes in drinking water; it may also help to form a hard scale in water heaters.
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Guideline Value for Aesthetic Determinands
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250 mg/L
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Sulphide
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Maximum Allowable Value for Inorganic of Health Significance
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No Standard
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Sulphide may impact an objectionable rotten egg smell to water. It can occur when there is a build-up of debris in the distribution system. Chlorination of the system often takes care of this problem.
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Guideline Value for Aesthetic Determinands
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0.05 mg/L
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Turbidity
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Maximum Allowable Value for Inorganic of Health Significance
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No Standard
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Turbidity is a measure of the clarity of water. Excessively turbid water may appear cloudy, and therefore be unappetising. For effective disinfection of water the turbidity can protect micro organisms from disinfection and can be a source of nutrients for further growth.
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Guideline Value for Aesthetic Determinands
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2.5 NTU
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Zinc
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Maximum Allowable Value for Inorganic of Health Significance
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No Standard
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Zinc is an essential and beneficial element in human growth. However concentrations above 3 mg/L may impact a bitter taste to water. It can also cause a milky appearance in water at high concentrations. Zinc most commonly enters the drinking water supply from deterioration of galvanised iron and dezincification of brass.
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Guideline Value for Aesthetic Determinands
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3 mg/L
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