1. Water quality parameters
• Water pollution may be defined as the presence of impurities in water in such
quantity and of such nature as to impede the use of the water for a stated purpose.
• Many parameters have evolved in order to reflect the impact the various impurities
have on selected water uses.
• These parameters are classified as physical, chemical, and biological.
2. Physical- water quality parameters
• They are the characteristics of water related to the senses of sight, touch, taste or smell. This
category includes suspended solids, turbidity, color, taste and odor, and temperature.
1. Suspended solids
Inorganic nature: Clay, mud, and soil constituents.
A. Source Organic nature: Plants fibers and biological solids (bacteria).
From immiscible liquids: Oils and greases.
They provide adsorption sites for chemical agents.
B. Impact They may biologically degrade resulting in harmful by-products.
Active suspended solids may include disease-causing organisms.
3. Physical- water quality parameters
1. Suspended solids
C. Measurements Gravimetric tests (those involve mass of residues) quantify total
solids in water: suspended and dissolved, and organic (volatile) and inorganic (fixed).
▪ Evaporating the sample to dryness to ≈ 105℃.
▪ The residue after drying is the total solids expressed in (mg/L).
▪ Total solids are then filtered; the dissolved solids are the filtrate fraction, while the
suspended solids are the residue (non-filtrate) fraction.
▪ To determine the organic (volatile) content of suspended solids; the measured
dried residue is fired to ≈ 550℃ for 1 h
𝑜𝑟𝑔𝑎𝑛𝑖𝑐𝑠 + 𝑂2 → 𝐶𝑂2 + 𝐻2𝑂
4. Physical- water quality parameters
2. Turbidity
• Turbidity is a measure of the extent to which light is either absorbed or scattered
by suspended materials in water. If a beam of light is passed through a turbid
sample, its intensity is reduced by scattering, and the quantity of light scattered is
dependent upon the concentration and size of the suspended material.
Surface water: Clay, microorganisms, and metal oxides from the soil.
A. Source
Industrial wastewater: Soaps, detergents, and emulsifying agents.
5. Physical- water quality parameters
2. Turbidity
B. Impact
C. Measurements the cloudiness in a solution is measured photochemically (Tyndall
effect), by determining the percentage of light intensity that is either absorbed or
scattered. In nephelometry, the intensity of the scattered light is measured, while, in
turbidimetry, the intensity of light transmitted through the sample is measured.
Suspended matters in water form a colloid suspension, which acts as an
adsorption sites for harmful chemicals and biological organisms.
Turbidity may alter watercolor (cause water cloudiness).
6.
7. Physical- water quality parameters
3. Color
• The true color of water is indicated by dissolved solids, whereas the apparent
watercolor is indicated by suspended solids.
A. Source
B. Impact Highly colored water is unsuitable for laundering, dyeing, food processing,
and dairy production.
C. Measurements Spectrophotometric techniques are used for industrial wastewater.
Organic residues: yellowish-brown water
Iron oxide: reddish-brown water
Manganese oxides: brown or blackish water
8. Physical- water quality parameters
4. Taste and odor
• Substances that produce odor in water will almost always impart a taste as well. The
converse is not true, many minerals produce taste but no odor. This parameter is
associated with potable (drinking) water.
A. Source
B. Impact Some odors produced by organic substances are more dangerous since
some of these substances are carcinogenic.
Inorganics: taste and no odor
Alkaline materials: bitter taste
Metallic salts: salty or bitter taste
9. Physical- water quality parameters
4. Taste and odor
C. Measurements Threshold Odor Number (TON) which represents the degree of
dilution of odorous water with odor-free (distilled) water at which a hardly-
detectable odor is determined.
𝑇𝑂𝑁 =
𝐴 + 𝐵
𝐴
Where A is the volume of odorous water and B is the volume of odor-free water.
• A similar test can be used to quantify taste.
10. Physical- water quality parameters
5. Temperature
Ambient temperature
A. Source
Use of water for dissipation (removing) of waste heat in industry.
B. Impact
▪ A temperature increase of 10℃ is usually sufficient to double the biological activity. Accelerated
growth of algae often occurs in warm water and become a problem, as the decay products of dead
algae can result in taste and odor problems.
▪ Solubility of gases (e.g., dissolved oxygen) decreases at elevated temperatures. This decreases the
rate of biological oxidation of organics and causes thermal pollution of water as fishes die.
11. Chemical- water quality parameters
• They are related to the solvent capabilities of water. This category includes total dissolved
solids (TDS), hardness, alkalinity, metals, nutrients, and organics.
1. Total dissolved solids (TDS)
Inorganic nature: minerals and gases.
A. Source Organic nature: Decay products of vegetation and organic compounds.
They produce unpleasant color, odor, and taste.
B. Impact Some of them are toxic and carcinogenic.
Some dissolved substances combine to form a compound with worse
characteristics than the original materials.
12. Chemical- water quality parameters
1. Total dissolved solids (TDS)
C. Measurement TDS is expressed in mg/L of the dissolved salts concentration, which is determined as
follows:
▪ Organic (volatile) and inorganic (fixed) dissolved solids are obtained by firing a filtered sample of
water at ≈ 550℃.
Or
▪ A practical analysis for TDS is made by determining the electrical conductivity of water using a
conductivity meter. Since the majority of dissolved solids in the water are dissolved ions, so the
higher the dissolved solids content of water, the higher the value of electrical conductivity.
𝑇𝐷𝑆
𝑚𝑔
𝐿
= 𝑘 × 𝐸𝐶 (
𝜇Ω
𝑐𝑚
); where the constant k depends on the resource of water.
