Water Quality Parameters And Measurement

Step 1: Understanding oxygen demand terms.
ThOD represents the total oxygen required for complete oxidation of organic matter theoretically. COD measures chemically oxidizable matter, while BODu measures biologically oxidizable matter over infinite time. BOD measures oxygen demand over only 5 days.
Step 2: Comparing magnitudes.
Since ThOD assumes complete oxidation, it is the highest. COD is lower than ThOD as some matter may not be chemically oxidized. BODu is lower than COD because not all organic matter is biodegradable. BOD is the lowest since it measures oxygen demand for a limited time.
Step 3: Evaluating options.
(A) Incorrect ordering.
(B) Incorrect, ThOD cannot be lower than COD.
(C) Correct, it follows the correct decreasing order.
(D) Incorrect, ThOD should be the highest.
Step 4: Conclusion.
The correct comparison is ThOD > COD > BODu > BOD .

Step 1: Understanding color test of water.
The color test of water measures the presence of dissolved colored substances such as organic matter, metals, or industrial waste. It is an important parameter in water quality analysis.
Step 2: Identifying the correct instrument.
A tintometer is specifically designed to measure the color intensity of water by comparing it with standard color solutions.
Step 3: Analyzing the options.
(A) Colorimeter: Used to measure concentration of colored solutions, but not standard for water color testing.
(B) Turbidimeter: Measures turbidity, not color.
(C) Tintometer: Correct, as it is used for color determination of water.
(D) Nephlometer: Measures turbidity using light scattering.
Step 4: Conclusion.
The correct instrument for color testing of water is (C) Tintometer.