Component |
Level
of Concern |
Comments |
| E.coli |
Maximum
Allowable Value for micro-organisms of Health Significance |
Less
than 1 in 100ml of sample |
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. |
| Guideline
Value for Aesthetic Determinands |
No
Standard |
| Alkalinity |
Maximum
Allowable Value for Inorganic of Health Significance |
No
Standard |
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. |
| Guideline
Value for Aesthetic Determinands |
No
Standard |
| Chloride |
Maximum
Allowable Value for Inorganic of Health Significance |
No
Standard |
A
high level of chloride gives the water a salty taste, and
may make the water corrosive. |
| Guideline
Value for Aesthetic Determinands |
250
mg/L |
| Colour |
Maximum
Allowable Value for Inorganic of Health Significance |
No
Standard |
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 |
| Guideline
Value for Aesthetic Determinands |
10
TCU |
| Copper |
Maximum
Allowable Value for Inorganic of Health Significance |
2
mg/L |
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. |
| Guideline
Value for Aesthetic Determinands |
1
mg/L |
| Conductivity |
Maximum
Allowable Value for Inorganic of Health Significance |
No
Standard |
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). |
| Guideline
Value for Aesthetic Determinands |
No
Standard |
| Fluoride |
Maximum
Allowable Value for Inorganic of Health Significance |
1.5
mg/L |
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. |
| Guideline
Value for Aesthetic Determinands |
No
Standard |
| Hardness |
Maximum
Allowable Value for Inorganic of Health Significance |
No
Standard |
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. |
| Guideline
Value for Aesthetic Determinands |
200 mg/L |
| Iron |
Maximum
Allowable Value for Inorganic of Health Significance |
No
Standard |
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. |
| Guideline
Value for Aesthetic Determinands |
0.2
mg/L |
| Manganese |
Maximum
Allowable Value for Inorganic of Health Significance |
0.6
mg/L |
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. |
| Guideline
Value for Aesthetic Determinands |
0.05
mg/L |
| Lead |
Maximum
Allowable Value for Inorganic of Health Significance |
0.01
mg/L |
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. |
| Guideline
Value for Aesthetic Determinands |
No Standard |
| Nitrate |
Maximum
Allowable Value for Inorganic of Health Significance |
11.2
mg/L measured as Nitrogen |
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. |
| Guideline
Value for Aesthetic Determinands |
No
Standard |
| pH |
Maximum
Allowable Value for Inorganic of Health Significance |
No
Standard |
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. |
| Guideline
Value for Aesthetic Determinands |
7.0
- 8.5 |
| Sulphate |
Maximum
Allowable Value for Inorganic of Health Significance |
No
Standard |
High
levels of sulphate may cause objectionable tastes in drinking
water; it may also help to form a hard scale in water heaters. |
| Guideline
Value for Aesthetic Determinands |
250
mg/L |
| Sulphide |
Maximum
Allowable Value for Inorganic of Health Significance |
No
Standard |
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. |
| Guideline
Value for Aesthetic Determinands |
0.05
mg/L |
| Turbidity |
Maximum
Allowable Value for Inorganic of Health Significance |
No
Standard |
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. |
| Guideline
Value for Aesthetic Determinands |
2.5
NTU |
| Zinc |
Maximum
Allowable Value for Inorganic of Health Significance |
No
Standard |
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. |
| Guideline
Value for Aesthetic Determinands |
3
mg/L |
