How is water purified on a large scale at waterworks? Explain with the help of a labelled diagram. Name the substance which is added to kill germs in the drinking water supply?
How is water purified on a large scale at waterworks? Explain with the help of a labelled diagram. Name the substance which is added to kill germs in the drinking water supply?
In cities, drinking water is supplied from water works. In waterworks, the methods like sedimentation, decantation, loading, filtration and chlorination, etc., are used to remove undesirable materials from water.
The source of water supply in a city is either a nearby river or a lake (called reservoir). The river water and lake water usually contain suspended solid substances and some germs. So, before this water can be supplied to homes, it must be purified to remove suspended impurities as well as germs. This is done at a place called waterworks. The waterworks of a city is usually situated near the bank of a river or a lake.
The purification of river water (or lake water) is done in the following steps :
(i) The water from a river (or lake) is pumped by the pumping station into a large reservoir called sedimentation tank. This water is allowed to stand in the sedimentation tank for some time. During this time, many of the insoluble substances present in water settle down at the bottom of the tank.
(ii) From the sedimentation tank, water is sent to a 'loading tank'. In the loading tank, some alum (phitkari) is added to water. The heavy particles of dissolved alum deposit on the suspended clay particles in water. In this way, the suspended clay particles in water get 'loaded' with alum particles, become heavy and settle down at the bottom of the tank. Thus, the process of loading (by using alum) removes the suspended clay particles from water.
(iii) The water is then passed through a filtration tank. The filtration tank has three layers: the fine sand layer at the top, coarse sand layer in the middle and gravel (tiny stones) as the bottom layer. The layers of sand and gravel act as filters. When water passes through the layers of sand and gravel, even the small suspended particles and other materials in water get removed.
(iv) The clear water is then passed into a chlorination tank. A little chlorine gas is added to water in this tank. Chlorine is added to water to kill the germs present in it. This is called disinfecting the water (or sterilising the water). The water now becomes fit for drinking (or safe for drinking).
(v) The clean and disinfected water is then pumped by a pumping station into high storage tanks. From the high storage tank, water is supplied to homes and factories in the entire city through a network of big and small pipes
In cities, drinking water is supplied from water works. In waterworks, the methods like sedimentation, decantation, loading, filtration and chlorination, etc., are used to remove undesirable materials from water.
The source of water supply in a city is either a nearby river or a lake (called reservoir). The river water and lake water usually contain suspended solid substances and some germs. So, before this water can be supplied to homes, it must be purified to remove suspended impurities as well as germs. This is done at a place called waterworks. The waterworks of a city is usually situated near the bank of a river or a lake.
The purification of river water (or lake water) is done in the following steps :
(i) The water from a river (or lake) is pumped by the pumping station into a large reservoir called sedimentation tank. This water is allowed to stand in the sedimentation tank for some time. During this time, many of the insoluble substances present in water settle down at the bottom of the tank.
(ii) From the sedimentation tank, water is sent to a 'loading tank'. In the loading tank, some alum (phitkari) is added to water. The heavy particles of dissolved alum deposit on the suspended clay particles in water. In this way, the suspended clay particles in water get 'loaded' with alum particles, become heavy and settle down at the bottom of the tank. Thus, the process of loading (by using alum) removes the suspended clay particles from water.
(iii) The water is then passed through a filtration tank. The filtration tank has three layers: the fine sand layer at the top, coarse sand layer in the middle and gravel (tiny stones) as the bottom layer. The layers of sand and gravel act as filters. When water passes through the layers of sand and gravel, even the small suspended particles and other materials in water get removed.
(iv) The clear water is then passed into a chlorination tank. A little chlorine gas is added to water in this tank. Chlorine is added to water to kill the germs present in it. This is called disinfecting the water (or sterilising the water). The water now becomes fit for drinking (or safe for drinking).
(v) The clean and disinfected water is then pumped by a pumping station into high storage tanks. From the high storage tank, water is supplied to homes and factories in the entire city through a network of big and small pipes
