Advertisements
Advertisements
Question
How is water purified on a large scale at water works ? Explain with the help of a labelled diagram. Name the substance which is added to kill germs in the drinking water supply ?
Advertisements
Solution
Various processes are used to purify water on large scale at water works. The source of water for cities is nearby a river or a lake. This water generally contains suspended particles, dissolved impurities and germs. In order to supply this water to homes, it has to be purified. Following steps are involved to purify water at water works:
- In water works, 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 lake (reservoir). From there, it is pumped to a 'sedimentation tank'.
- It is kept here for some time to allow the insoluble substances present in water to settle down at the bottom of the tank.
- It is then sent to a 'loading tank', where some alum is added to water.
- Suspended clay particles in water get loaded here with alum particles. After becoming heavy, they settle down at the bottom of the tank. Thus, the process of loading removes the suspended clay particles from water.
- It is then passed through a 'filtration tank' having three layers, i.e., fine sand layer on the top, coarse sand layer in the middle and gravel layer at the bottom .
- These layers act as filters and remove small suspended particles of the water.
- Water is then passed into a chlorination tank. Here, chlorine is added to water to kill the germs present in it.
- Now the clean and disinfected water is pumped to high storage tanks by pumping stations. From these high storage tanks, water is supplied to homes and factories through a network of big and small pipes.
Figure 65. Supply of drinking water in a city.
Chlorine is added to water to kill germs in the drinking water supply.
APPEARS IN
RELATED QUESTIONS
Fill in the blank :
The state of matter with definite volume and definite shape is called______
Name the scientist who studied the movement of pollen grains suspended in water through a microscope. What is this phenomenon known as?
Explain why, osmosis can be considered to be a special kind of diffusion. Classify the following into
(i) osmosis, and (ii) diffusion :
- swelling up of a raisin on keeping in water
- spreading of virus on sneezing
- earthworm dying on coming in contact with common salt
- shrinking of grapes kept in thick sugar syrup
- preserving of pickles in salt
- spreading of smell of cake being baked in the kitchen
- aquatic animals using oxygen dissolved in water during respiration
Which type of elements, metals or non-metals, show the property of brittleness ?
Give reason why copper metal is used for making electric wires.
The property/properties which enable copper metal to be used for making electric wires is/are :
Iron powder and sulphur powder were mixed together and divided into two parts A and B. When part A was heated strongly over a burner, then a substance C was formed. The part B was, however, not heated at all. When dilute hydrochloric acid was added to substance C, then gas D was evolved and when dilute hydrochloric acid was added to part B then gas E was evolved.
- What type of substance is B ?
- What type of substance is C ?
- Name the gas (i) D, and (ii) E ?
- State one characteristic property of gas D.
- Write one test to identify gas E.
There are three substances X, Y and Z. The substance X does not have a fixed melting point or boiling point and it still shows the individual properties of its constituents. The substance Y is a pure substance which occurs in nature as such. The substance Y has a fixed melting point and boiling point but it cannot be broken down into simpler substances by any chemical means. The substance Z is also a pure substance whose properties are entirely different from those of its constituents. The substance Z can, however, be divided by electrolysis into two substances which belong to the same class of substances as Y.
- What type of substance could X be ? Name one substance like X.
- What type of substance could Y be ? Name one substance like Y.
- What type of substance could Z be ? Name one substance like Z.
- Which process involves absorption or release of an appreciable amount of energy : formation of substance X or formation of substance Z ?
- Name the three groups into which all the substances like Y are divided on the basis of their properties.
State whether the following statement is true or false :
Bread is an example of solid foam.
How will you test whether a given solution is a colloidal solution ?
Define solubility of a substance. How does it vary with temperature ?
One of the following liquids will leave behind a residue on heating. This one is :
Name the process by which common salt is obtained from sea-water.
Fill in the following blanks with suitable words :
A heterogeneous mixture of liquid and solid is conveniently separated by...............
Fill in the following blanks with suitable words :
If a mixture contains iron filings as one of the constituents, it can be separated by using a .......................
The best way to recover sugar from an aqueous sugar solution is :
One of the following does not undergo sublimation. This one is :
What's the solution?
We need to rub salt on a corncob, but only salt crystals are available.
Liquids cannot be compressed and they have fixed volume.
