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quality of drinking water

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    quality of drinking water

    PREAMBLE

    The Quality of drinking water in Chennai is maintained and monitored by Chennai Metropolitan Water Supply and Sewerage Board through the Quality Assurance Wing. The Quality of water is monitored through sampling, testing and reporting through the team of trained personnel in the laboratory and field. This division is headed by Executive Engineer and consists of Engineers and Analysts.
    The Engineers of this wing provides the necessary Engineering service for effective functioning of the wing and does investigation, preventive actions, sanitary survey and providing necessary assistance to the field staff in water quality surveillance.
    The Analysts does the work of collecting water samples, analysis and report to the Engineers concerned in regard to the quality of water supplied to the public confirming to water quality standards.


    MONITORING WATER QUALITY
    The scientific personnel in the Analytical section have a periodical sampling programme as per the W.H.O. norms, for monitoring water quality at the sources, treatment plants, Water distribution stations and in the distribution net work.
    Water samples are being collected, treated once in a month from the three lakes, which is major source of water supply to the Chennai City daily . The treated water from the water treatment plants are collected from the test tap and samples were examined for conformity to physical, chemical and Bacteriological standards, besides monitoring the treatment process at various units.
    About 500 samples are collected from the City distribution system every month for physical, chemical and Bacteriological analysis, besides checking of minimum level of Residual chlorine in 100 sample daily in the distribution net work to ensure the water is safe for drinking.
    Apart from the sampling carried out by Quality Assurance wing , 161 depot. Engineers monitor the minimum level of Residual chlorine available in the water distribution net work.
    The water supplied to the public is assured as per norms laid down in BIS: 10500 -1991, the Indian Standard. The Physical, Chemical and Bacteriological quality of water should not exceed the limits shown in the table below:
    INDIAN STANDARD 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 Unobjectonable Unobjectionable
    3. Taste Agreeable Agreeable
    4. Turbidity ( NTU, Max) 5 10
    5. pH Value 6.5 to 8.5 No Relaxsation
    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 1.9 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 Cadmiun (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
    I. Water entering the Distribution system Coliform count in any sample of 100 ml should be Zero. A sample of the water entering the distribution system that does not conform to this standard calls for an immediate investigation in to both the efficacy of the purification process and the method of sampling.
    II.Water in the distribution system
    1. E.coli count in 100ml of any sample should be zero. 2. Coliform organisms not more than 10 per 100 ml in any sample. 3. Coliform organisms should not be present in 100 ml of any two consecutive samples or more than 5% of the samples collected for the year.
    PRIVATE SAMPLES
    Besides monitoring the Quality of water supplied by Metro Water, the C.M.W.S.S.B. facilitates the public to assess the water quality of their own sources (Well / Bore Well water) by testing for Physical and Chemical examination on nominal charges as follows:

    1 Public (Individual houses-Drinking) Rs 75/- Per Sample
    2 Private Institute(Drinking) Rs 200/- Per Sample
    3 Private Institute(Construction) Rs 200/- Per Sample
    The following parameters are tested for Physical and Chemical Examination: Colour and Transparency, Odour, Turbidity (N.T.U.), Dissolved Solids mg/l, Calcium mg/l (as Ca), Magnesium mg/l (as Mg), Total Hardness mg/l (as CaCO3), Chlorides mg/l (as Cl), Ammoniacal Nitrogen mg/l ( as N), Albuminoid Nitrogen mg/l (as N), Nitrous Nitrogen mg/l (as N), Nitric Nitrogen mg/l ( as N), Oxygen absorbed mg/l, (Tidy's 4 hrs test), Hydrogen ion concentration (pH), Alkalinity to Phenolphthalein mg/l (as CaCO3 ), Alkalinity to Methyl orange mg/l (as CaCO 3 ), Sulphates mg/l (as SO4 ), Phosphates mg/l (as PO 4), Iron mg/l (as Fe), Fluorides mg/l (as F) and Specific Conductance (micro siemens/cm) at 25 o C.
    In case of water quality for Construction purpose the following parameters are tested for its suitability

    1.To neutralise 200 ml of sample of water , using Phenolphthalein as an indicator, it should not require more than 2.0 ml of 0.1 (N/10) Normal sodium hydroxide.
    2.To neutralise 200 ml of sample of water, using methyl orange as an indicator, it should not require more than 10 ml of 0.1 (N/10) Normal Hydro chloric acid.
    3. Suspended matter, Soleplate (as SO4), Chlorides as Cl, Inorganic solids, Organic solids
    Quantity of samples required for testing are as follows: •
    Drinking Purpose:- 2 liters.
    Construction Purpose:- 5 liters.
    The Containers used for collecting water samples should be free from any contamination. It is advised to use new plastic container of required capacity as mentioned above.
    Procedure for remittance of Testing Charges :
    On request, Junior Administrative officer, Q.A.Wing issues a challan for making payment at Canara Bank (Kellys Branch) located at Purasawalkam (Near Madharsha) and remitted challan is returned to Q.A.Wing for testing.
    The Analytical Report shall be collected from the laboratory after15 days.from the date of receipt
    of samples.


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