About the Chlorine Chemicals for Water Treatment

Chlorine is most effective at the optimum pH range of 6-7.5. At a higher pH, more chlorine is needed for the same result. For example, if there was 1 part per million of free chlorine (HOCl + OCl-) at pH 7, how much free chlorine would be required to have the same effectiveness (HOCl concentration) at pH 8. Adding either sodium hypochlorite or calcium hypochlorite to water produces the hypochlorite ion (OCl-) and hypochlorous acid (HOCl). The balance between these two chemicals is determined by the pH of the water. Hypochlorous acid (which predominates at a solution pH below 7.5) is 20 to 30 times as effective a sanitizer as hypochlorite (favored by a pH above 7.5).

Common Used Chlorine Disinfectants

Calcium and sodium hypochlorite are widely used to control waterborne pathogens and algae in irrigation water. You are probably most familiar with these materials as liquid bleach (sodium hypochlorite) and solid swimming pool "shock" (calcium hypochlorite).

Forms of chlorine commonly used in commercial pools. Pools are treated with chlorine gas, sodium hypochlorite (liquid bleach), calcium hypochlorite granular/tablet, lithium hypochlorite or chlorinated isocyanurates. When any of these compounds contact water, they release hypochlorous acid (HOCl), the active sanitizing agent. Chlorinated isocyanurates, a family of chemical compounds such as sodium dichloroisocyanurate and trichloroisocyanurate, also add cyanuric acid or stabilizer. A stabilizer, which can also be added separately, helps reduce excess loss of chlorine in water due to the ultraviolet rays of the sun.

Applications

Chlorine is an important chemical in water purification, in disinfectants, in bleach and in mustard gas.

Chlorine is also used widely in the manufacture of many products and items directly or indirectly, i.e. in paper product production, antiseptic, dyestuffs, food, insecticides, paints, petroleum products, plastics, medicines, textiles, solvents, and many other consumer products.

It is used to kill bacteria and other microbes from drinking water supplies.

Chlorine is involved in beaching wood pulp for paper making, bleach is also used industrially to remove ink from recycle paper.

Chlorine often imparts many desired properties in an organic compound when it is substituted for hydrogen (synthetic rubber), so it is widely use in organic chemistry, in the production of chlorates, chloroform, carbon tetrachloride, and in the bromine extraction.

Is chlorine harmful to the human body

Breathing high levels of chlorine causes fluid build-up in the lungs, a condition known as pulmonary edema. The development of pulmonary edema may be delayed for several hours after exposure to chlorine. Contact with compressed liquid chlorine may cause frostbite of the skin and eyes. So a general recommendation is to maintain chlorine levels in water at no more than 2 ppm to avoid phytotoxicity of ornamentals, but testing on your crop mix is advised.

Excess chlorine in the pool can sometimes also cause small amounts of vapor to come out of the water. But as overeager swimmers may recall, pools are typically closed right after pool keepers chlorinate the water so that some of those vapors can diffuse, she said. (In high concentrations, chlorine gas is known to be very poisonous. So it is necessary to control the amount.