Question

Choose the correct statement about water pollution?
A. Dissolved oxygen is inversely proportional to BOD in waste water.
B. Dissolved ion increases turbidity of water.
C. Turbidity is a measure of transparency of water.
D. Alkalinity is caused by carbonate, bicarbonate and hydroxides.
E. Alkalinity is base neutralising capacity of water.
Choose the correct answer from the options given below:

• A. A, B, C and D Only
• B. A, B, C and E Only
• C. A, C and D Only
• D. A, C, D and E Only

Hint:

Key definitions for water chemistry:
- Alkalinity = Acid-neutralizing capacity (buffering power against acids).
- Acidity = Base-neutralizing capacity.
- Turbidity = Caused by suspended particles, NOT dissolved ions.
- High BOD $\implies$ Low Dissolved Oxygen (DO).

Answer 1

The Correct Option is C

Concept:
Water quality assessment requires monitoring physical, chemical, and biological parameters.
Key indicators include Biochemical Oxygen Demand (BOD), Dissolved Oxygen (DO), Turbidity, and Alkalinity.

Step 1: Statement-by-Statement Scientific Verification:
- Statement A: Biochemical Oxygen Demand (BOD) measures the amount of dissolved oxygen consumed by aerobic bacteria to break down biodegradable organic matter. As organic waste increases, microbial consumption of DO rises, driving ambient DO down. Hence, DO is inversely related to BOD in wastewater. (Correct)
- Statement B: Turbidity is caused by suspended and colloidal solids (such as clay, silt, and finely divided organic matter) that scatter light. Dissolved ions (e.g., $\text{Na}^+$, $\text{Cl}^-$, $\text{Ca}^{2+}$) do not scatter light; they contribute to Total Dissolved Solids (TDS) and electrical conductivity. (Incorrect)
- Statement C: Turbidity quantifies the cloudiness or haze of a liquid, providing an optical measure of its light penetration and loss of transparency. (Correct)
- Statement D: Alkalinity in natural waters is predominantly produced by three chemical bases: bicarbonate ions ($\text{HCO}_3^-$), carbonate ions ($\text{CO}_3^{2-}$), and hydroxide ions ($\text{OH}^-$). (Correct)
- Statement E: Alkalinity is defined as the capacity of water to neutralize acids (acid-neutralizing capacity). Conversely, acidity is the base-neutralizing capacity of water. (Incorrect)

Step 2: Aggregation of Valid Statements:
The valid statements are A, C, and D. Statements B and E are scientifically incorrect.
Final Answer:
The correct option is A, C and D Only, corresponding to option (C).