The following table shows the mean values of chemical analysis of the water supply from the Wainuiomata Water Treatment Plant, from 1 July 2019 - 30 June 2020, compared with the maximum allowable value (MAV) or guideline value (GV) for each element as set out in the Drinking Water Standards New Zealand (DWSNZ).

Notes: (A) MAV denotes the maximum acceptable value to comply with the Drinking-water Standards. (B) GV denotes the maximum guideline value in the Drinking Water Standards.

 

Parameter

DWSNZ MAV (A) / GV (B)

No of samples

Mean value

Max value

Alkalinity - total g CaCO3/m³

-

13

31.23

38

Aluminium - total g/m³

0.1 (B)

14

0.0325

0.052

Arsenic - total g/m³

0.01 (A)

2

<0.002

<0.002

Boron - total g/m³

1.4 (A)

2

<0.05

<0.05

Cadmium - total  g/m³

0.004 (A)

2

<0.001

<0.001

Calcium hardness g CaCO3/m³

200 (B)

13

29.23

36

Chloride g/m³

250 (B)

1

23.1

23.1

Chromium total g/m³

0.05 (A)

2

<0.001

<0.001

Conductivity at 25°C mS/m

-

1

15.3

15.3

Copper - total g/m³

2 (A)

13

<0.013

<0.013

Cyanide g/m³

0.6 (A)

2

<0.005

<0.005

Fluoride g/m³

1.5 (A)

107

0.07

0.45

Hydrogen sulphide g/m³

0.05 (B)

1

<0.05

<0.05

Iron - total g/m³

0.2 (B)

13

0.034

0.065

Lead - total g/m³

0.01 (A)

2

<0.001

<0.001

Manganese - total g/m³

0.04 (A)

13

0.048

0.048

Mercury - total g/m³

0.007 (A)

2

<0.001

<0.001

Nickel - total g/m³

0.08 (A)

2

<0.001

<0.001

Nitrate - nitrogen g/m³

50 (A)

2

0.035

0.04

pH

7.0-8.5 (B)

14

7.807

8.3

Selenium - total g/m³

0.01 (A)

2

<0.005

<0.005

Silica g/m³

-

2

12.6

13.7

Sulphate g/m³

250 (B)

1

4.43

4.43

Total dissolved solids g/m³

1000 (B)

1

75

75

Zinc - total g/m³

1.5 (B)

13

0.016

0.016