Environmental Engineering Reference
Physico-chemical Properties of Water
After collection the water samples were stored in refrigerator to avoid any microbio-
logical decomposition. Parameters like temperature, pH, electrical conductance (EC)
and dissolved oxygen (DO) and carbon-dioxide (CO 2 ) were measured immediately.
AR grade reagents and double distilled water were used for reagent preparation.
Physico-chemical parameters were measured following methods of Welch
( 1952 ), APHA ( 1992 ), Trivedi and Goel (1986) and Munshi and Munshi ( 1995 ).
1. Physical Parameters
Water temperature: Water temperature was recorded with the help of mercury
thermometer by dipping it into water.
2. Chemical Parameters
( a ) pH: pH was measured on the sampling sites by the portable pH meter (Hanna
pocket pH meter-H196-107 Systronic-361 pH meter).
( b ) Free carbon dioxide: Method of Trivedi and Goyal ( 1986 ) was used for CO 2
estimation. Free CO 2 was determined by titrating the sample using a strong alkali
(pH 8.3). The analysis was done on the sampling site. Drops of neutralized phenolphtha-
lein indicator were added to 100 ml of water sample taken in an Erlenmeyer's flask and
titrated with 0.05 N sodium hydroxide (NaOH) until a pink colour appears. The volume
of titrant was noted down and free CO 2 was calculated using following equation:
FreeCO mg L lNof NaOH
1 000 44
( c ) Total alkalinity: Alkalinity is the expression of the total quantity of base (usu-
ally in equilibrium with carbonate or bicarbonate) and was determined by titration
with a strong acid (as per Hutchinson 1957 ).
( d ) Dissolved oxygen (DO): The DO was estimated on the site by the Winkler's
Iodometric method. The estimation of oxygen in water depends on the fact that
sodium hydroxide together with manganese sulphate gives a white precipitate of
2+ → (
NaOH Mn OH
Water sample was taken in a 300 ml BOD bottle. 1.0 ml of both manganese sul-
phate (MnSO 4 ) and alkaline iodide (KOH + KI) were added to the sample and mixed
gently. Addition of 2.0 ml of conc. sulphuric acid (H 2 SO 4 ) liberates iodine equiva-
lent to DO. 200 ml of the aliquot was titrated with the standardized sodium thiosul-
phate Na 2 S 2 O 3 (0.025 N), aqueous starch was used as indicator. The volume of
titrant used was recorded and the result was expressed as milligram per litre (mg/L).
The formula used to calculate DO was:
DO mg L lNof titrant