Clean, fresh water for drinking and home use is vital for our health. Generally, we filter our water supply to remove sediment (silt, rust, and other particles), to remove waterborne cysts such as Giardia and Cryptosporidium, to purify the water from any pesticides or organic chemicals, and to improve the tastes and odours often associated with either collected water, or ‘town’ water.
One common source of water supply in New Zealand is the collection and storage of rainwater, usually from a roof, and delivered to the house via a pressure pump. Although collected rainwater is generally very good in regards to mineral and chemical components, it is in MOST CASES contaminated with microorganisms from faecal matter of birds, possums, cats, mice and rats. Another source of water supply is from springs, streams, rivers and dams. This too, is almost always contaminated with suspended solids, surface run off and faecal matter from wildlife and farm animals. Underground water collection via shallow wells and bores is also utilized, and can have the same contamination issues as surface water.
The main purpose of filtering your water is to make it microbiologically safe to drink, cook with, and bathe in.
The Ministry of Health recommends a two-barrier approach to this – namely, filtration followed by disinfection. Although we can provide a number of solutions that suit your requirements, the simplest solution is for cartridge filtration followed by ultraviolet disinfection.
Filtration is based on a micron rating, and is most commonly achieved with coarse pre-filtration, usually with a 20 micron washable, pleated cartridge for the bulk of suspended solids removal, followed by a fine depth filter of one micron. This step is most important for the removal of giardia and cryptosporidium cysts, by trapping them in the filter.
Disinfection is by exposure to ultraviolet light. This inactivates bacterial and viral contaminants. The Steriflo systems are designed to deliver consistency of water pressure based on existing flow rates. Alternative, but less popular methods of disinfection include the use of oxidizing chemicals such as Acquasafe (NB – this will not kill giardia and cryptosporidium cysts.)
An additional option in the water treatment process can be purification – the removal of dissolved substances and gases which affect taste and odour. Activated carbon is a media which can remove chlorine and its byproducts, pesticides and sulphur. These media filters are often chosen for treating the drinking water only. Some are able to remove giardia cysts, some pesticides, tastes and odours. They will NOT, however, remove bacteria and viruses.
Want to know what’s lurking in your water? Click here to find out how Water Testing can help you make the right choices when it comes to treating your water.