ES 203: Water and Wastewater Engineering
Prof. Anurag Garg
Environmental Science & Engineering Department, IIT Bombay
2024-25
Water Quality Parameters
Water Quality Parameters
Physical Suspended solids, turbidity, color, temperature, taste
and odor
Chemical Total dissolved solids, alkalinity, hardness, fluoride,
metals, dissolved gases, BOD, COD and nutrients
Biological Pathogens
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Classification of Total Solids
Suspended (1 - 100 µm)
or non-filterable
Colloidal (0.001 - 1 µm) Total solids
Dissolved (< 0.001µm)
or filterable
Settleable (> 100 µm)
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Problem
• The following test results were obtained for a wastewater sample. All the tests were
performed using a sample size of 50 ml. Determine the concentration of total solids,
total volatile solids, suspended solids, volatile suspended solids, total dissolved
solids, total volatile dissolved solids and total fixed solids. The samples used in the
solid analysis were all either dried or ignited to the constant weight.
i. Mass of evaporating dish = 53.5433 g
ii. Mass of evaporating dish + residue after evaporation at 105°C = 53.5794 g
iii. Mass of evaporating dish + residue after ignition at 550°C = 53.5625 g
iv. Mass of whatman filter after drying at 105°C = 1.5433 g
v. Mass of whatman filter + residue after evaporation at 105°C = 1.5554 g
vi. Mass of whatman filter + residue after ignition at 550°C = 1.5476 g
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Turbidity
✓ It is a measure of the extent to which light is either absorbed or scattered
by suspended or colloidal organic or inorganic materials in water.
✓ The original standard unit is that which is produced by 1 mg of finely
divided silica in 1 liter of distilled water.
✓ Disinfection of turbid waters is difficult.
✓ It is measured using Nephelometer and Formazine is used as reference
compound
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Turbidity standards of 5, 50, and 500 NTU
Color
• True color: Due to dissolved solids
• Apparent color: Due to suspended matter
• Major sources of color in natural water sources can be decaying leaves or microscopic
plants.
• The standard unit of color is produced by dissolving 1 mg of platinum cobalt in 1 liter
of distilled water.
• For public supplies, color number on cobalt scale should not exceed 20 and should be
preferably less than 10.
Temperature
• Temperature of the surface waters governs to a large extent the biological species
present and their rates of activity.
• Cooler waters usually have a wider diversity of biological species.
• At lower temperatures, the rate of biological activity is slower.
• The desired temperature of potable water is around 10°C and a temp. above 25°C is
considered objectionable. 7
Taste and Odor
• Taste and odor are caused by the presence of organic and inorganic
compounds.
✓ Odor is measured and expressed in terms of threshold odor number
(TON).
✓ TON is the ratio by which the sample has to be diluted for the odor to
become virtually unnoticeable.
✓ TON = (A + B)/ A
A = Vol. of odorous water (ml), B = Vol. of odor free water required to make the odor
barely detectable in A.
✓ For public supplies, TON should be 1 and should never exceed 3.
