Disinfection

is an important step in ensuring that water is safe to drink. Water systems add disinfectants to destroy microorganisms that can cause disease in humans. Primary methods of disinfection are chlorination, chloramines, ozone, and ultraviolet light. Other disinfection methods include chlorine dioxide, potassium permanganate, and nanofiltration. Since certain forms of chlorine react with organic material naturally present in many water sources to form harmful chemical by-products, the U.S. Environmental Protection Agency has proposed maximum levels for these contaminants.

CHLORINE

Chlorine is primarily used as a disinfectant. It can also remove color, ammonia compounds, eliminate hydrogen sulfide, oxidize iron and manganese to insoluble forms and reduce undesirable taste and odors. It is also used to protect receiving waters in waste water treatment plants by treating effluents prior to discharge. It could also control filamentous biomass, oxidation of organics and control of filter flies.

LIQUID CHLORINE

Sodium hypochlorite is the liquid form of chlorine which is available in concentrations of 5 to 15 % chlorine. It is a clear, yellowish solution which is commonly use in many industries and is a good disinfectant or microbial agent. It is commonly used for disinfection for swimming pools, drinking water and treated water from sewage treatment plants.

GAS CHLORINE

Gas chlorine is an effective chemical for removing microbial pathogens in water. It is a yellow-green gas and is liquid at high pressures. It is a dangerous and corrosive gas that needs extra care in handling. It is commonly used in water and waste water treatment plants which needs monitoring and control of pH.

CHLORINE DIOXIDE

Chlorine dioxide is a faster acting disinfectant compared to chlorine. It is superior in the destruction of spores, bacteria, viruses and other pathogens. It has a better solubility in water and requires lower contact time. It is usually supplied as an aqueous solution to prevent gas handling problems.

CALCIUM HYPOCHLORITE

Calcium hypochlorite is a white solid available in granular, tablet or powdered form that easily dissolves in water. It is also a commonly used disinfectant wherein it will be dissolved in a mixing tank before injecting the same as sodium hypochlorite. It is also commonly used for water and waste water treatment plants.

ULTRAVIOLET LIGHT

Disinfection by radiation uses a special lamp which produces UV light wherein the water will be subjected to it. It is a pure physical and chemical free process wherein it penetrates the cell wall of the organism directly. It disrupts the genetic material of the organism cell making it unable to reproduce.

OZONATION

Ozone is a strong oxidizing and disinfecting agent which is also used to control odor and taste. It is formed by passing dry air through a system of high voltage electrodes. It is a widely used primary disinfectant which only requires short contact time compared to chlorine.