Drinking water qualities

Drinking water quality- What should it be?

 

S.Vishwanath

www.rainwaterclub.org

www.arghyam.org

 

The greatest bulk of the human body is water. If we are what we eat we are also what we drink and perhaps to a greater extant. Pure water as pure H2O does not exist in nature and therefore what we consume has some mineral or salt or the other. Question is what is right and what is wrong in the presence of things in the waters we drink. Simultaneously with increasing impacts of human activity water is being polluted everywhere in the environment. So what should be the quality of the water we drink?

The Bureau of Indian Standards prescribes the quality of drinking water in its BIS 10500-1991 standards. It lists three major quality parameters- Physical, Chemical and Biological.

 

INDIAN STANDARDS FOR DRINKING WATER  –  SPECIFICATION 

 ( BIS  10500 : 1991 )

Sl.No	Substance or Characteristic	Requirement  (Desirable Limit)	Permissible Limit in the absence of Alternate source
Essential characteristics
1.	Colour, ( Hazen units, Max )	5		25
2.	Odour	Unobjectionable		Unobjectionable
3.	Taste	Agreeable		Agreeable
4.	Turbidity  ( NTU, Max)	5		10
5.	pH  Value	6.5 to 8.5		No Relaxation
6.	Total Hardness (as CaCo3) mg/lit.,Max	300		600
7.	Iron           (as Fe) mg/lit,Max	0.3		1.0
8.	Chlorides  (as Cl) mg/lit,Max.	250		1000
9.	Residual,free chlorine,mg/lit,Min	0.2		—
Desirable Characteristics
10.	Dissolved solids  mg/lit,Max	500		2000
11.	Calcium  (as Ca) mg/lit,Max	75		200
12.	Copper    (as Cu) mg/lit,Max	0.05		1.5
13	Manganese (as Mn)mg/lit,Max	0.10		0.3
14	Sulfate  (as SO4) mg/lit,Max	200		400
15	Nitrate  (as NO3) mg/lit,Max	45		100
16	Fluoride (as F) mg/lit,Max	1.0		1.5
17	Phenolic Compounds (as C 6 H5OH) mg/lit, Max.	0.001		0.002
18	Mercury (as Hg)mg/lit,Max	0.001		No relaxation
19	Cadmium (as Cd)mg/lit,Max	0.01		No relaxation
20	Selenium (as Se)mg/lit,Max	0.01		No relaxation
21	Arsenic (as As) mg/lit,Max	0.05		No relaxation
22	Cyanide (as CN) mg/lit,Max	0.05		No relaxation
23	Lead  (as Pb) mg/lit,Max	0.05		No relaxation
24	Zinc   (as Zn) mg/lit,Max	5		15
25	Anionic detergents (as MBAS) mg/lit,Max	0.2		1.0
26	Chromium (as Cr6+) mg/lit,Max	0.05		No relaxation
27	Polynuclear aromatic hydro carbons  (as PAH) g/lit,Max	—		—
28	Mineral Oil  mg/lit,Max	0.01		0.03
29	Pesticides  mg/l, Max	Absent		0.001
30	Radioactive Materials
	i. Alpha emitters Bq/l,Max	—		0.1
	ii. Beta emitters  pci/l,Max	—		1.0
31	Alkalinity mg/lit.Max	200		600
32	Aluminium  (as Al) mg/l,Max	0.03		0.2
33	Boron  mg/lit,Max	1		5

         Bacteriological standards

         Coliform count             0 in 100 ml of sample

         E.Coli count                  0 in 100 ml of sample

 

Where to get the water tested? Many private laboratories exist in cities to carry out water testing. In addition the State Pollution Control Boards, the Department of Mines and Geology in Bangalore, Karnataka and many engineering and agricultural colleges help in water testing.  Water utilities like the Chennai Metro Water Board list on their website that they provide water testing service too. Charges vary depending on the laboratories but expect to pay anywhere from Rs 200 /- to Rs 900 /- for a complete water test.

Most laboratories will need a sample of at least 2 litres collected in a clean sterilized bottle. There are specific requirements of collection if the water is to be tested for indicator bacteria such as e-coli and the laboratory usually prescribes the method.

 

What to look out for: If your water source is a bore well while you must check for all the parameters listed above, of specific concern will be the Total Dissolved Solids, Nitrates and Fluoride. In many cities leaking sewage pipes have caused ground water to be polluted and the typical pollutant is Nitrate.

Fluoride contamination is reported more through natural sources and is endemic in many villages of India. Fluoride testing kits are available for Rs 1000/- to Rs 1500/- which can give a broad range result. Further testing for more accurate results can then be done in laboratories.

If your water source is from the pipeline then it is the responsibility of the city authorities to ensure that the water you receive confirms to BIS 10500. To avoid bacterial contamination authorities ensure residual chlorine in the water. This can be tested using a chlorine testing kit which is available for Rs 200/- to Rs 500/-. A residual chlorine of 0.20 mg/litre is commonly ensured by water supply providers.

In rural areas where the contamination is most likely to be biological a simple H2S strip test is a very good indicator of the presence of e-coli, the indicator for harmful bacteria. This is a small bottle with a strip of paper coated with an appropriate material. The water to be tested is put into the bottle and the cap closed. In 24 to 36 hours if the water turns black then it indicates bacterial contamination requiring the water to be boiled or sterilized before consumption.

 

Protocol: It is good to develop a protocol for testing waters from other than mainline sources. Bore well waters should be tested at least once in 3 months  for potability and more frequently if any contamination is detected.

It is also important to note that not all water quality improving devices work on all contaminants.             Many which are UV based can take care of bacteria only. Thos that are R.O. based can remove nitrates and fluorides. It is important to see whether the treated water will conform to BIS 10500 requirements before one buys a product. It is also better to check the treated water to see whether a contaminant has been removed

 

Further improvements: China has moved from identifying 35 items to 101 items considering the increase in chemical contaminants in the environment. India needs to move into this mode also and look at more harmful chemical contaminants coming into water.

Water testing laboratories also need to be available in more places and at more affordable price.

Ultimately a risk management strategy needs to be put into place to ensure non-pollution at source rather than a strategy of removal of pollutants.

Awareness and action are critical to change the impacts on drinking water and for the health of us and our children.

Water wisdom lies in understanding the pollutants in our water, ensuring prevention and removal and only then consuming it.