How do scientists determine whether water is safe for drinking, agriculture, industry, or aquatic life? Measurement of Water Quality Parameters provides the scientific basis for assessing water quality through physical, chemical, and biological indicators. Parameters such as pH, DO, BOD, COD, turbidity, and microbial contamination help evaluate the health of aquatic systems and the suitability of water for various uses. A strong understanding of these concepts is essential for environmental monitoring, pollution assessment, and success in UGC-NET/JRF, SLET, ARS, GATE, and other competitive examinations.
Use this curated MCQ bank to assess your conceptual understanding, identify knowledge gaps, and strengthen your preparation for competitive examinations.
Syllabus Outline
- Fundamental concepts of water quality and its significance.
- Water quality parameters (e.g. pH, dissolved oxygen, biochemical oxygen demand, chemical oxygen demand, turbidity, conductivity, total dissolved solids, nutrient levels, coliforms, and organic pollutants).
- Principles and methodologies of measurement techniques for each parameter, including instrumentation, sampling protocols, and analytical methods.
- Quality assurance and quality control procedures, data interpretation, water quality standards and guidelines.
Quick Study Guide
Accurate water quality assessment relies on quantitative physical, chemical, and biological analytical methods to measure contaminants and evaluate aquatic ecosystem health.
- Turbidity and Electrical Conductivity (Physical): Turbidity measures water clarity by quantifying light scattering. Analytical instruments (nephelometers) measure scattered light at a 90-degree angle relative to the incident beam, calibrated against standard Formazin units. Electrical Conductivity serves as a rapid proxy for Total Dissolved Solids, as the migration of dissolved ions under an electric field is directly proportional to ionic concentration.
- Dissolved Oxygen and the Winkler Method (Chemical): DO is a critical survival index for aquatic biotas. It is standardly quantified using the wet-chemical Winkler Method (iodometric titration). In this process, divalent manganese reacts with DO under alkaline conditions to form a precipitate. Acidification then releases elemental iodine in direct proportion to the original DO concentration, which is titrated against a sodium thiosulfate standard.
- Water Hardness and Complexometric Titration (Chemical): Hardness measures the concentration of multivalent metallic cations, primarily calcium and magnesium. It is measured via complexometric titration using EDTA (ethylenediaminetetraacetic acid) as a chelating agent. Operating at a buffered alkaline pH of 10, the reaction uses Eriochrome Black T (EBT) as an indicator, transitioning from a wine-red metal-ion complex to a distinct steel-blue colour at the endpoint.
- Organic Loading Metrics: The organic carbon load determines oxygen depletion risks and is cross-examined via three parameters:
- BOD: Measures the dissolved oxygen consumed by aerobic microbes over a 5-day incubation at 20°C.
- COD: Uses strong boiling potassium dichromate to oxidise both biodegradable and non-biodegradable organic fractions.
- Total Organic Carbon: Provides an absolute measurement by injecting samples into a high-temperature combustion furnace to convert all organic carbon directly into measurable carbon dioxide.
- Bacteriological Water Quality Testing (Biological): Pathogen presence is monitored using harmless indicator bacteria, specifically coliforms. The Most Probable Number (MPN) test uses a multiple-tube fermentation setup to provide a statistical estimate of coliform density based on acid and gas production. Alternatively, the Membrane Filtration technique passes a water sample through a sterile filter grid, which is incubated on selective media for direct colony enumeration.
Test Your Knowledge
This quiz contains 25 concept-based MCQs on “Measurement of Water Quality Parameters“. Each question has a single correct/most appropriate answer.
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1. Which one of the following statements is correct?
a) pKa and pH are positively correlated
b) pKa and pH are negatively correlated
c) pKa and pH are not correlated
d) pKb and pH are positively correlated
2. Acidity of water is its quantitative capacity to react with a ___________ to a designated pH.
a) Weak Base
b) Strong Acid
c) Weak Acid
d) Strong Base
3. Which indicator is used to estimate the Ca-Hardness of a water sample?
a) Methyl Orange and Phenolphthalein
b) Murexide
c) Eriochrome Black T
d) Both B and C
4. Which method is commonly used to measure turbidity in water samples?
a) Spectrophotometry
b) Gravimetric analysis
c) Nephelometry
d) Titration
5. Which of the following is NOT a standard parameter to assess the drinking water quality?
a) Total coliforms
b) coli
c) Turbidity
d) Methane concentration
6. Which of the following is a common method for measuring pH in water?
a) Gravimetry
b) Conductivity
c) Potentiometry
d) Turbidity
7. Which of the following methods is used to determine the alkalinity of water?
a) Titration
b) Gravimetry
c) Chromatography
d) Spectrophotometry
8. Which of the following is a common method for measuring fluoride concentration in water?
a) Ion-selective electrode
b) Gravimetry
c) Turbidity measurement
d) Conductivity measurement
9. Which of the following is a common method for measuring total nitrogen in water?
a) Kjeldahl digestion
b) Ion-exchange chromatography
c) Filtration
d) Conductivity measurement
10. Which method is commonly used to measure TDS in water?
a) Colourimetry
b) Conductivity measurement
c) Titration
d) Spectrophotometry
11. Which analytical technique is commonly used to detect and quantify heavy metals in water samples?
a) Chromatography
b) Atomic Absorption Spectrometry
c) Infrared Spectroscopy
d) Electrochemical analysis
12. Which analytical technique is commonly used to detect and quantify sodium and potassium in water samples?
a) Chromatography
b) Infrared Spectroscopy
c) Flame Photometry
d) Electrochemical analysis
13. Which of the following is a primary standard for pH calibration in water analysis?
a) Sodium chloride
b) Potassium hydrogen phthalate
c) Sodium bicarbonate
d) Sodium hydroxide
14. What is the primary purpose of a gas chromatograph in water analysis?
a) Measure pH levels
b) Determine turbidity
c) Analyse volatile organic compounds
d) Assess electrical conductivity
15. To analyse metal ions present in the water sample, the sample is recommended to be collected in separate bottles and ___________ it to minimize precipitation.
a) Neutralise
b) Acidify
c) Alkalify
d) Cooled
16. Which water parameter needs to be analysed in situ only?
a) pH
b) Temperature
c) Turbidity
d) Conductivity
17. Color of water sample is measured in __________unit.
a) mg/l
b) Hazan
c) NTU
d) mho/cm
18. What is the acceptable limit of E. coli or thermotolerant coliform bacteria in all water intended for drinking as per the Indian Standards of Drinking Water (IS: 10500:2012; Second Revision: 2015)?
a) 0 CFU/100ml
b) 100 CFU/100ml
c) 1 CFU/100ml
d) Undetectable/100ml
19. In a water sample, Ca2+, Mg2+ and Na+ ions concentrations are 50, 60 and 100 mg/L, respectively. What will be the total hardness as CaCO3 of the water sample? (Hints: Molecular weight of Ca, Mg, and Na is 40, 24, and 23, respectively)
a) 210 mg/L
b) 375 mg/L
c) 475 mg/L
d) 39 mg/L
20. What would be the pH of a solution with a hydroxide ion [OH–] concentration of 10-8 M?
a) pH 2
b) pH 6
c) pH 8
d) pH 10
21. The chemical oxygen demand measures the
a) Amount of oxygen required for chemical reactions in wastewater
b) Amount of oxygen required for the growth of microorganisms in water
c) Amount of oxygen required to oxidise the calcium present in wastewater
d) Amount of oxygen that would be removed from the water to oxidise pollution
22. The methyl orange acidity is also known as:
a) CO2 acidity
b) HCO3– acidity
c) Hydronium ions
d) Mineral acidity
23. Conductivity of the water sample is measured in __________unit.
a) mg/l
b) Hazan
c) NTU
d) mho/cm
24. Assertion (A): Total coliform counts in water indicate faecal contamination.
Reasoning (R): Coliform bacteria are commonly found in the intestines of warm-blooded animals, and their presence in water indicates possible faecal contamination and the potential presence of pathogens.
a) Both A and R are correct, and R explains A.
b) Both A and R are correct, but R does not explain A.
c) A is correct, but R is incorrect.
d) A is incorrect, but R is correct.
25. Assertion (A): The presence of algal blooms in water bodies can increase the pH of the surrounding water.
Reasoning (R): During photosynthesis, algae absorb carbon dioxide, leading to a decrease in carbonic acid and an increase in pH levels.
a) Both A and R are correct, and R explains A.
b) Both A and R are correct, but R does not explain A.
c) A is correct, but R is incorrect.
d) A is incorrect, but R is correct.
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Next: Drinking Water Treatment
References
- APHA (2022). Standard Methods for the Examination of Water and Wastewater. 24th Edition, American Public Health Association.
- Metcalf & Eddy (2014). Wastewater Engineering: Treatment and Resource Recovery, McGraw-Hill Education, 5th edition.
- De, Anil Kumar and De, Arnab Kumar (2024). Environmental Chemistry, New Age International, 11th Edition.
- Odum, Eugene P., and Barrett, Gary W. (2004). Fundamentals of Ecology, Thomson Brooks/Cole, 5th Edition.
- Singh, J.S., Gupta, S.R., Singh, S.P. & Singh, R. (2026). Ecology, Environmental Science and Conservation, S Chand Publishing, 2nd Edition.
- Erach Bharucha (2017). Environmental Studies, Universities Press, 4th Edition.
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