Table 2: Treatment processes used in New Zealand, the approximate numbers of treatment plants recorded as using the process, and primary contaminants the process is designed to remove
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| Treatment process |
Treatment plants |
Primary contaminants |
|---|---|---|
Pre-treatment |
||
Chlorine |
40 |
Iron, manganese |
Ozone |
1 |
Iron, manganese |
Potassium permanganate |
6 |
Iron, manganese |
Copper sulphate |
3 |
Cyanotoxins (by control of cyanobacterial growth) |
Aeration |
30 |
Gases (eg, hydrogen sulphide, carbon dioxide) and volatile trace organic compounds |
Particle removal |
||
Combined processes |
||
Coagulation/flocculation/rapid sand filtration |
82 |
Particles, protozoa |
Individual filtration processes |
||
Bag filtration |
8 |
Particles, protozoa |
Cartridge filtration |
26 |
Particles, protozoa |
Diatomaceous earth filtration |
5 |
Particles, protozoa |
Membrane filtration |
624 |
Particles, bacteria, protozoa |
Slow sand filtration |
6 |
Particles, bacteria, protozoa |
Greensand filtration |
4 |
Iron, manganese |
Disinfection |
||
Chlorine |
508 |
Bacteria, viruses, cyanotoxins |
Ozone |
22 |
Bacteria, viruses, protozoa, cyanotoxins |
UV irradiation |
621 |
Bacteria, viruses, protozoa |
Chlorine/UV |
13 |
Bacteria, viruses, protozoa, cyanotoxins |
Chlorine/ozone |
3 |
Bacteria, viruses, protozoa, cyanotoxins |
Additional processes |
||
Ion exchange |
5 |
Iron, manganese, hardness |
Activated carbon |
13 |
Pesticides, industrial solvents, taste and odour compounds, cyanotoxins |
