Water Quality and Receiving-water Pollution - Water & Wastewater Treatment and Management - Environmental Science & Engineering Previous Year Questions

The Streeter–Phelp's oxygen sag equation for a river is based on a few assumptions.
The correct assumption(s) is/are

A 200 mL sample of water has an initial pH = 9. In order to determine alkalinity, the sample was titrated using 0.02 N \(H_2SO_4\) acid to an end point of pH = 4.5. In the titration, 25 mL of 0.02 N \(H_2SO_4\) acid was required. What is the total alkalinity of the sample in *mg/L as \(NaHCO_3\)*? [Atomic weight (g/mol): Ca = 40, Na = 23, H = 1, C = 12, S = 32, and O = 16]

In the context of water quality, which of the following is/are correct for the most probable number (MPN) of a water sample?

Specific conductance is used in water analysis to indirectly estimate dissolved solids. The measurements used in the method accounts for

For testing alkalinity for a water sample, first phenolphthalein indicator is added. The water remains colorless. However, when a few drops of methyl orange is added to the sample, the color turns yellow. As per these observations, the correct choice is

You are doing an experiment to find out BOD₅ of a wastewater. You have taken 25 mL wastewater having ultimate BOD of 75 mg/L and placed it in 300 mL BOD bottle and filled it with dilution water. The initial DO of the diluted sample is 6.5 mg/L. On the 5^th day, you were not able to measure the DO due to some unavoidable circumstances. However, the DO at the end of the 7^th day is found to be 1.25 mg/L. Assume all the experiments are done at the same temperature, and no biodegradable organics are present in the dilution water. The BOD₅ of the wastewater sample is __________ (in mg/L, rounded off to two decimal places).

Which of the following options is/are CORRECTLY listing the species included in Total Kjeldahl Nitrogen (TKN) estimation of an aqueous sample?

The analysis of a water sample is shown in the table. The hardness of the water sample is ______ mg/L as CaCO₃.
Atomic weight (g/mol): Ca = 40; Mg = 24; Na = 23; Cl = 35.5; S = 32; O = 16; N = 14

Species	Concentration (mg/L)
Na+	30
Ca2+	10
Mg2+	15
Cl-	30
SO42-	60
NO3-	5