Water disinfection methods
Water cleansing is the system of removing undesirable chemicals, materials, and biological contaminants from impure water. The goal is to get water appropriate for a specific purpose.
Most water is cleaned for human consumption (drinking water) but water purification may also be planned for a variety of other purposes, including meeting the requirements of medical, pharmacology, chemical and industrial applications.
In general the systems used contain physical techniques such as filtration and sedimentation, biological processes such as sand filters, chemical processes such as chlorination and the use of radiation such as ultraviolet sterilizers.
The purifying technique of water may cut down the concentration of particulate matter including suspended particles, parasites, bacteria, algae, viruses, fungi; and a range of dissolved and particulate material derived from the substances that water may have come into contact with.
The standards for water quality are generally decided by governments or by international standards. These standards will usually set minimum and maximum concentrations of contaminants for the use that is to be made of the water.
It is not possible to tell whether water is of an acceptable standard by visual analysis. Easy procedures such as heating or the use of activated carbon filters are not adequate for treating all the possible contaminants that may be present in water from an unknown source.
Natural spring water – believed to be safe for all practical purposes in the 1800s – has to now be tested before determining what manner of treatment, may be required. A chemical examination, is the only reliable way to acquire the information required for deciding the appropriate technique of purification.
Filtration
Filtration is a physical operation which is used for the separation of solids from fluids (liquids or gases) by interposing a medium through which only the fluid can pass. Oversize solids in the fluid are held back, but the separation is not complete; solids will be contaminated with some fluid and filtrate will contain fine particles (depending on the pore size and filter thickness).
There are various differentmethods of filtration, all aim to attain the separation of substances. Separation is achieved by some form of interaction between the substance or objects to be removed and the filter. The substance that is to pass through the filter must be a fluid, i.e. a liquid or gas. Methods of filtration change depending on the location of the targeted material, i.e. whether it is dissolved in the fluid phase or suspended as a solid.
Chlorine Dioxide
Chlorine dioxide is used for the disinfection of corporate drinking water and sterilized water systems.
Chlorine dioxide has the advantage that it produces less damaging by-products than chlorine.
Chlorine dioxide gas is used to sterilize medical and laboratory utensils, surfaces, rooms and tools.
Chlorine dioxide can be used as oxidizer or disinfectant. It is a very strong oxidizer and it effectively kills pathogenic micro organisms such as fungi, bacteria and viruses. It also prevents and removes bio film.
As a disinfectant it is mainly used in liquid form. Chlorine dioxide is very effective against spore-forming bacteria.
Chlorine dioxide is used in many industrial water treatment applications as a biocide including cooling towers, process water and food processing. Chlorine dioxide is less corrosive than chlorine and superior for the control of legionella bacteria. Chlorine dioxide is very much superior to copper-silver ionization for Legionella control because unlike copper-silver ionization, chlorine dioxide is not negatively impacted by pH and does not lose efficacy over time because the bacteria grow resistant to the biocide.
It is more effective as a disinfectant than chlorine in most circumstances against water borne pathogenic microbes such as viruses, bacteria and protozoa – including the cysts of Giardia and the oocysts of Cryptosporidium.
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