Potable Water - Sources and Methods of Purification at Domestic level

by

MANOJ KUMAR

1.    

  POTABLE WATER:

Water which has been filtered cleaned or treated to meet the standards of drinking water and is reasonably clear for contaminants and harmful bacteria are considered as potable water.

            Potable water access is crucial and people in developed countries may not worry where they get potable water from. They may simply turn ON their taps and get potable water. But the people in developing countries have very limited access to potable water.

            Most non-potable water will be raw and untreated, which may contain unknown contaminants. It is possible for non-potable water to taste normal but carry health risks.

2.    

  STANDARDS FOR POTABLE WATER IN INDIA

According to BIS (Bureau of Indian Standards, 2012) potable water is water intended for human consumption for drinking and cooking from any source. The following table shows the parameters, their upper limit as per BIS and possible impacts on health.

TABLE – 1: SHOWING PARAMETERS, THEIR APPROVED UPPER LIMITS AS PER BIS AND POSSIBLE HEALTH HAZARDS (as per BIS water quality standards, 2012)

parameters	upper limits as per BIS standards	possible health risks
total dissolved solid	200 mg/L	GI irritation, Bad taste
pH	6.5 - 8.5	affects mucous membrane, bitter taste
alkalinity	600 mg/L	boiled rice turns yellowish
hardness	600 mg/L	poor lathering with soap, skin irritation, boiled meat/food becomes poor quality
Ca	200 mg/L	deteriorates clothes, pipe incrustation
Mg	100 mg/L	deteriorates clothes, pipe incrustation
Fe	1.0 mg/L	cloth staining, bitter taste
Mn	0.3 mg/L	poor taste, staining of clothes
Al	0.2 mg/L	neurological disorders, Alzheimer disease
Cu	1.5 mg/L	liver damage
Zn	15 mg/L	vomiting, abdominal pain
Ammonia	NIL	indicates pollution
Nitrite	NIL	forms nitrosoamine which is carcinogenic
Nitrate	100 mg/L	blue baby disease
Sulphate	400 mg/L	GI irritation, laxative effect
Chloride	100 mg/L	corrosive to alimentary cannal
Fluoride	1.5 mg/L	dental and skeletal disorders
Hg	0.001 mg/L	minamata disease
Cadmium	0.01 mg/L	itai itai disease
Lead	0.05 mg/L	bioaccumulation, neurological disorders
Chromium	0.05 mg/L	Carcinogenic
Pesticides	0.001 mg/L	affects CNS
detergents	NIL	undesirable foaming

3.      SOURCES OF POTABLE WATER:

As per the Indian Census, 2011 the potable water sources in India and their comparative shares in household potable water consumption is as follows.

TABLE 2: SHOWING VARIOUS SOURCE OF POTABLE WATER AND THEIR PERCENTAGE SHARES IN TOTAL HOUSEHOLD POTABLE WATER CONSUMPTION (as per the Indian Census Report, 2011)

SOURCE	PERCENTAGE SHARE
Tap water	43.5
Well	11.0
Hand pump	33.5
Tube well	8.5
Spring	0.5
River	0.6
Pond/Lake	0.8
Other sources	1.5

4.      METHODS OF PURIFICATION OF POTABLE WATER AT DOMESTIC LEVELS

A.     BOILING:

It is a satisfactory method of purifying water for house hold purposes. While using this method, the water must be brought to a 'rolling' boil. Boiling should be done for 5-10 minutes. Boiling destroys all forms of disease producing organisms usually found in water. When the water is boiled, the container becomes sterilized or the water should be boiled preferably in the same container.

B.     SEDIMENTATION AND DECANTATION:

It is a natural method of water purification. In this method water is collected from the source and stored in a jar or container. The water if allowed to remain for some time in container, the impurities (e.g. stone, sand, chalk, mud, etc.) will settle down at the bottom. We will be able to pour out the water without disturbing the impurities. This process of water filtration is called sedimentation and serves the following purpose:

The solid matter in suspension falls to the bottom by gravity and is called sediment.

C.     SAND FILTERATION:

This is also called the filtration of water by four pitchers system. It is old fashioned filter system. In this method, the four pitchers are placed one above the other on a wooden stand. All the vessels except the last one have small pores at the bottom. The upper most vessel contains thick layer of charcoal which is filled with water and which percolated through a hole made at its bottom, along with a piece of cloth plugged into the hole of the second pitcher.

The second pitcher contains a layer of sand, and the third contains gravel. Water drips into each of these vessels. The last or fourth pitcher contains filtered water.

Nowadays one can buy a manufactured filter from the market. The principle of these filters is that water is made to pass through porous 'candle' and in doing so it is purified.

D.     CHLORINATION:

Water is most essential for the maintenance of life but it is also a vehicle for infection and responsible for severe and wide spread water borne diseases. In such a context, bacteria, helminthic,  protozoal and other pathogenic infection causing cholera, diarrhea, typhoid, worm, dysentery, gardenias can be caused. It is essential to make the water safe for drinking from whatever source it is obtained. In this regard, one of the most widely used disinfectants for treating drinking water is chlorine and when it is added to water in proper proportion, it is effective in killing pathogenic organism.

E.      DISTILLATION:

In the process of distillation water is heated and evaporation takes place, whereby water changes back to water when cooled; this process is called condensation. The condensed water is the purest form of water, free from microbes, and impurities.

But it loses its taste and odor. Through aeration or passing oxygen through it the water becomes consumable.

This method is quite expensive and time - consuming. But in place like laboratories, on sea-ships or places where pure water is not available, this method is found to be very useful.

F.      FILTRATION:

Different varieties of filters are used to purify the water at domestic level. Filter rods (candies) are installed in the upper chamber. These rods are made of china porcelain and it is porous and hollow from the centre. When water is filled in the upper chamber it purifies and drips in the lower chamber. This water is free of any suspended matter but still has microbes in it

G.     CHEMICAL METHODS OF PURIFICATION

(a) Aluminum Sulphate (b) Chlorine

(c) Potassium Permagnate purification by Ultra-Violet Rays

In a school where a large number of students and teachers depend on the water supplied by the local civic bodies, extra measures to ensure good quality of water are needed especially when it is routed through drinking water coolers.

These water collars should be cleaned at regular periodicity and should be pilferage free. Besides, ultra-violet rays may be used for destroying micro- organism from the water without any chemical change. It has the following advantages: -

(a) Ultraviolet rays destroy all kinds of bacteria and virus, which produce diseases.

(b) Besides the boiling method, this method is safe and water can immediately be used. There is no chance of any contamination in storing it for 48 hours. Water stored in ordinary filters and pitchers provide a breeding place for the microbes.

(c) Water is purified in its natural form; there is no chemical change in it.

(d) The quality of water remains intact.

(e) It has an electronic method for water purification, which is more reliable

 *the data and notes have been collected from books and online contents