Quality Control of Water Supplies | Environmental Engineering - Civil Engineering (CE) PDF Download

Total Solid and Suspended Solid

Acceptable limit of total solid = 500 mg/lit

Threshold odour number

where TON = Threshold odor number

Constituents of Alkalinity

Major sources → CO^2-₃, HCO^-₃, OH^-
Minor sources → HS, O^-₃, H₂BO^-₃, HPO^2-₄, HS
(a)

Equivalent weight of
 
(b)


(c)

where,
CO^2-₃ → x mg / lit of CaCO₃
HCO^-₃ → y mg / lit of CaCO₃
OH^- → z mg / lit of CaCO₃
Value of water

For strong acid.

For strong base

For neutral solution

Hardness of Water

where,
[Ca²⁺] is concentration of Ca²⁺ in mg / lit.
[Mg²⁺] is concentration of Mg^2- in mg / lit
(a)

Where,
atomic weight of Ca = 40
atomic weight of Mg = 24
atomic weight of O = 16
atomic weight C = 12
valency of Ca = 2
Valency of Mg = 2
Equivalent weight of Ca²⁺
= atomic weight/valency
= 40/2 = 20
Equivalent weight of Mg²⁺
= atomic weight/valency
= 24/2 = 12
Equivalent weight of CaCO₃

∴ valency or n - factor = 2.

Note: -ve value is taken as zero.
(d) Hardness

Household supplies limit 74-115 mg/l
(e) The acceptable limit of hardness = 200 mg/lit as and cause of rejection is 600 mg/lit as CaCO₃

Biochemical Oxygen Demand (BOD)

 whereof 5 days
DO_i - DO_f = Loss of oxygen in mg/lit.
DO_i = Initial dissolved oxygen concentration in the diluted sample.
DO_f = Final dissolved oxygen concentration in the diluted sample.
(After 5 day of incubation of 20ºC)

• Turbidity > 5 units–detectable by naked eye.
• In Nephlometer, turbidity is expressed in FTU.

Biological WQP

Testing of Colliforms is done