Environmental Engineering Reference
In-Depth Information
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
,
×
/
ml sample
2
(
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
manganese hydroxide.
2+ →
(
)
+
MnSO
NaOH Mn OH
Na SO
4
2
4
2
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
/
××
81000
,
/
V VVV
−
2
1
1
Search WWH ::
Custom Search