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How filters Work

Filters are composed of a substance that traps, absorbs, or modifies pollutants in the water that flows through them. This substance is called a medium. There are many different types of filter media. Some mechanically trap pollutants with an ultra-fine sieve or strainer, while others use a process called adsorption, in which contaminants are retained within the microscopic pores of the medium. The rating of a water filter or purifier tells you what size practicals it will and won’t remove. Filters are rated in micrometres or microns. A micron is one millionth of a meter. A human hair is 70 microns in diameter, Cryptosporidium oocyst 2-5 microns, and Giardia oocyst 2-6 microns. There is two types of filter ratings: normal and absolute. A normal rating indicates the smallest particle size that the filter should remove or reduce, in accordance with its design criteria. It is an estimated value, not a precise one. A 1 micron nominal filter, for example, should trap 95% of 1 microns or larger. An absolute filter rating, on the other hand, refers to a certified reduction level, usually 99.9%. Therefore a 1-micron absolute filter will remove 99.9% of practicals or more in diameter.

Sediment filters

Sediment filters are fine sieves that trap dirt and other particles. Using one as a pre filter will protect a water purifier from damage and extend its life, because it will take longer to become clogged with muck. Sediment filters range from coarse to fine, and are rated accordingly. They can be made from wound string, rigid foam or pleated film, and are usu. The life of a sediment filter depends on the level of impurities in the water; 6-12 months is average. Activated carbon filters Activated carbon filters are particularly effective at removing pollutants that create unpleasant taste, colour, and odour in water. These fast acting filters will eliminate or reduce the levels of chlorine by-products, pesticides, herbicides, and other chemicals.

Activated carbon

Activated carbon is made from porous material such as coal, coconut, organic material such as coal, coconut, lignite, and wood. When these are activated by exposure to high temperatures in the absence of oxygen, the result is a substance with millions of microscopic pores and a vast surface area; half a kilo of activated carbon provides more than 50 hectors of surface with the capacity to cling to or absorb smaller organic molecules. There are two forms of carbon in general use; granular and block. Carbon granules are the size of coarse sand, while carbon block is finely powdered carbon compressed into a solid mass. Carbon or carbon block filters with a rating of 1 micron absolute ( Pb1) or less, will remove organic contaminates and a high percentage of pollutants (including protozoan cysts); their life span will be extended if a sediment filter is used.   The effectiveness of activated carbon depends on the type of carbon, the amount used, the filter design. how slowly the water flows through it (contact time), and the water quality. A slow flow rate is desirable, as this allows more impurities to be absorbed.

Reverse osmosis purifiers

Reverse osmosis purifiers (RO) are commonly used to provide pure water for the food, pharmaceutical industries, as well as for home consumers. Osmosis is a process that occurs when two solutions of different concentrations are separated by a semi-permeable membrane. Water passes through the membrane in the direction of the more concentrated solution.  RO water purification works by forcing the water under pressure against an ultra –fine, semi-permeable membrane designed to allow single water molecules to permeate through, while at the same time rejecting most contaminates. The membrane acts as a mechanical filter, straining out particulate matter, micro organic compounds. AQUA WISE  RO filter purifier consists of , four or five filters in series depending on the water quality, plus a storage tank. The first is a sediment filter to remove particulates, eg; (dirt, rust, silt) the second housing contains the ultrafine carbon block, to remove any remaining chlorine by-products such as chloroform or THMs. Once the contaminates are separated from the clean water, they are washed away so that they don’t build up in the purifier. Such a system removes a wide spectrum of impurities; the only energy required is that of mains-pressure. RO removes turbidity, sediment, colloidal matter, total dissolved solids, toxic metals, radioactive elements, pesticides, and herbicides. This can have significant health benefits. Trials at the university of Quebec in Canada in 1993 concluded that ‘individuals consuming the un-modified tap water experienced gastrointestinal symptoms 30% more frequently than those who consumed the water after reverse osmosis treatment: The efficiency of RO depends on the pressure and temperature of the water, AQUA WISE RO units operate with a minimum water pressure (normal tap pressure). A typical system produces water at a slow rate – almost drop by drop- so the system must have a pressurised storage tank (11 litres) and a separate dedicated tap installed over the sink. Water drawn from the tap comes from the storage tank. The RO unit slowly refills the tank. The average system produces about 40 litres per day, more than enough for an average family.

Ultra violet disinfection

Ultra violet disinfection or treatment is perfect when bacteria and microorganisms are a problem, e.g.; tank water or where there is no chlorine present in the water supply. The device contains a Ultra violet lamp giving off a level of radiation that kills bacteria. It is also effective against algal toxins. The lamp is enclosed in a protective UV transparent sleave that allows water to flow around it for effective disinfection. The UV light needs cloud free water so as no bacteria can hide from the light.  a series of two or one pre filters is an essential part of its effective operation