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Water Quality Analysis Laboratory Methods

Water Quality Analysis Laboratory Methods

Dispersion & Dissolution in Water / Adverse Effects of Impurities for water Problem Constituents Responsible chemicals, and Water Quality Analysis 

  •  Aesthetically not acceptable                           Clay, Silt, Humus, Colour
  •  Health-related problems                              pH
  •  Gastro-intestinal irritation.                             Hardness, TDS, Ca, Mg, SO4 
  •  Dental and skeletal fluorosis                          Fluoride
  •  Methemoglobinemia                                     Nitrate
  •  Encrustation in water supply structure            Hardness, TDS
  • Adverse effects on domestic use                      Ca, Mg, Cl
  • Eutrophication of the water body                        Zoo & Phyto, Phosphate, Nitrate
  •  Taste, discolouration, and corrosion                 Iron, Mn, Cu, Zn, Alkalinit of pipes fittings and utensils
  •  Promotes iron bacteria                                    Fe & Mn
  •  Corrosion in water supply system                   pH, Cl
  •  Carcinogenic effect                                         Cr, As
  •  Toxic effect                                                     Cd, Pb, Hg
  •  Formation of chlorophenols with                   Phenol chlorine
  •  Imparts unpleasant taste and odor Oil & greas after chlorination
  •  Water-borne diseases                                      Bacteria & viruses

Contamination / Pollution in water

  •  During its traverse water picks up impurities in varying amounts
  •  Gases from atmosphere
  •  Inorganic and organic salts from topsoil and geological strata
  •  During its traverse water get contaminated by inorganic and organic salts sometimes beyond desirable limits
  • Pollution
  •  The presence of undesirable substances in quantities that are harmful to man vegetation or property is referred to as pollution
  •  The quality of water depends upon the quality and quantity of inorganic and organic salts present in the water

Water Quality Assessment

  •  To measure the concentration of the constituents in quantity for characterization of water for different uses
  •  Of the various parameters in potable water, few are objectionable even when present in a very small quantity
  •  Others if only present in unusual quantities as to relegate the water from the potable to the unusable class
  •  The analyst familiar with water quality characterization will often select parameters to be measured based on experience and intuition
                                                               
Water Quality Analysis Laboratory Methods
   

Water Quality Consideration 

 1. Irrigation

  •  pH
  •  Conductivity
  •  Sodium & Potassium
  •  Nutrients
  •  Specific compounds
2. Industries
  •  As per specific requirement
  •  Domestic Consumption
  •  As per BIS Standards
 3. Water Bodies
  •  As per CPCB guidelines
  • Water
Dissolved Oxygen

All living organisms depend upon oxygen to maintain the
metabolic processes that produce energy for growth and reproduction.
Dissolved oxygen is important in the precipitation and dissolution of inorganic substances
in water.

Need.

To assess the quality of raw water.
To check on pollution.
Determination of biological changes by aerobic or anaerobic organisms.
D.O. is the basis of the BOD test to evaluate the pollution potential of wastes.
All aerobic biological wastewater treatment processes.
An important factor in corrosion.

Methodology of BOD

The Winkler method with Azide modification Oxygen present in the sample oxidizes the divalent manganous to its higher valency which precipitates as a brown hydrates oxide after the addition of NaOH and KI.

Upon acidification, manganese reverts to a divalent state and liberates Iodine from KI equivalent to D.O. content in the sample.

The liberated iodine is titrated against a standard (N/40) solution of Sodium thiosulphate using starch as an indicator. and Palatability decreases affect the mucous membrane       

Procedure of BOD

Collect sample in BOD bottle 2 ml MnSO4+ 2 ml Alkali iodide-azide+close stopper  Mix well + allow the ppt to settle.

Add 2 ml concentrated H2SO4 + mix well till ppt dissolves.

Take 203 ml (Correspond to 200 ml) sample in a conical flask+titrate against Sodium thiosulphate (0.025 N) till pale yellow colour + starch + titrate till blue to colourless

Calculation:

1 ml of 0.025N Na2S2O3 = 0.2 mg of O2
D.O. in mg/l = (0.2 x 1000) x ml of thiosulphate / 200

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