Most water supplies, whether previously filtered or not, and even if they appear perfectly clear, are most often contaminated by bacteria and pathogenic microbes dangerous to human life. Therefore, they must be destroyed before allowing them for human consumption. There are several processes for disinfecting water, but by far the most widespread is the treatment with chlorine because it has enormous power to kill bacteria instantaneously and effectively even when used in minute doses. Moreover, its reliability and simplicity in handling, lower cost, both initially and in operation, make chlorine a popular and common reagent for the sterilization of water. Its germicidal action even in small doses results in the destruction of enzymes required for the existence of microbic germs. It also possesses very considerable oxidizing powers which would cause the destruction of organic matter easy. Free chlorine reacts with water to hypochlorous acid which sets free the oxygen necessary to destroy these harmful organizations and thereby sterilize water in the most effective manner as shown in the following equation :-
H2O + CL2 = HCL + HOCL + O
It has a high degree of efficiency as a sterilizing agent and is adaptable for domestic water supplies, for sewage effluent, for swimming pool water, for condenser cooling water and everywhere, where bacterially free water is required. Usually, chlorine is given in doses higher than the water requirement to ensure complete and uniform sterilization of water.
Design An open design has been adopted, as it makes it easier to detect possible leaks in time. Also, formation of condensate, which is unavoidable in a closed cabin under certain temperature conditions and which may cause serious external corrosion is restricted to the minimum on account of free access of air. The design allows a more spacious arrangement for parts with advantages of easy accessibility for control, adjustment and replacement or repair. Moreover, disturbances in the chlorine and water feed have no effect on its functioning. The plant is designed for wall panel mounting and requires no floor place.
Detail of Component Parts
They are mounted on Backelite panel board. It consists of primary filter containing glass wool and a diaphragm type pressure gauge on its top to show pressures of chlorine gas in the cylinder and a chlorine adjustment needle valve and a flexible copper pipe heavily electroplated with couplings at both ends. Besides, there are PVC parts such as secondary filter with non return valve on top one chlorine water mixing chamber and one chlorine water solutioniser. In addition, there will be two plastic type double bends joining three PVC chambers and one PVC ‘U’ tube connecting chlorine needle valve with plastic secondary filter Liquified chlorine drawn from a steel cylinder gets vaporized at normal room temperature and is led through copper connecting tube to the primary filter on the panel board.
It contains glass wool which would arrest all possible cylinder impurities in gas so that they would not obstruct the flow of gas through small apertures in the needle valve. Pressure gauge on the filter will show the pressure prevailing in the chlorine cylinder from time to time. Gas will then pass on to the PVC needle valve which is used for adjustment of flow of chlorine gas. The other flexible copper tube or PVC tube will convey gas from this needle valve to the secondary plastic filter containing glass wool where the gas will be further screened to eliminate all impurities so that they do not choke up small orifice in the chlorine measuring tube provided in the water chlorine mixing chamber, with gauge on the outside to indicate flow of gas. There will be a non-return valve on the top of the filter , he nce only chlorine gas will pass onwards and will prevent water to flow back in the filter. Water introduced at the bottom of the central mixing chamber absorb chlorine gas coming from top and the resulting solution will flow by a double bend at top into the adjoining solutioniser. Selected gravels filled in it solutionizer mixes water and chlorine throughly during its passage in this chamber and the solution will be fed in an open chamber by gravity. If it is to be supplied in any pressure pipe, a special plastic injector assembly along with a suitable booster pump is provided. Usually, one litre of water is required for every five grams of gas for making solution in the mixing chamber. Capacities of chlorinators ranging from 300 grams to 5 kgs per hour can easily be changed by providing suitable sizes of chlorine and water measuring tubes in the central chamber. Gas should not be drawn from cylinders at pressures higher than 50 lbs per sq. inch.
Chlorine gas is heavy, yellow, highly irritating and harmful to human beings and attacks the mucous membranes. So operators must be careful in handling the chlorine cylinders and chlorinators. The safest method is to use gas mask in such circumstances. All protection and first aid equipments must be kept outside the room in which chlorine cylinders and the plant are kept. Gas is supplied in the cylinders in the liquid form and evaporates into gas at pressure approximately 5 kg. per sq.cm. under normal working conditions. It is not possible to withdraw more than 2 kg. of gas per hour from one cylinder of 100kg. capacity without frosting up. Therefore, where the capacity of the chlorinators exceeds 2 kg, it is necessary to couple two cylinders to the fitter and having two inlet connections. Chlorinator should be housed in a room which is not exposed to draughts or direct ray of the sun, but which is well ventilated. Its top should be kept 5 feet above the floor so that the reading of the scale will be at the eye level.
Following are the components of the gravity feed type improved chlorinator.
1. Pressure Gauge
2. Primary Filter
3. Chlorine Valve
4. PVC 'U' Tube
5. Secondary Filter
6. Gas Bend
7. Mixing Chamber
8. Water Bend
10. Copper connecting pipe
11. Copper Chamber ( To be supplied by the user)