Environmental Engineering

Step 1: Convert water requirement to liters per hour.

Step 2: Use filtration rate.
Filtration rate = 4000 liters/hr/m .

Step 3: Consider backwash system factor.
Allowing for backwash reserve, effective filter size ≈ 21 m .

Step 4: Conclusion.
Hence, the size of the filter is 21 m . Correct answer is (B).

Step 1: Particulates.
Particulates cause irritation of mucous membranes and respiratory tract. Hence, A → II.

Step 2: Carbon monoxide.
CO reduces oxygen carrying capacity of blood by binding with hemoglobin. Hence, B → I.

Step 3: Sulfur oxides.
SO gases cause respiratory illness (bronchitis, asthma). Hence, C → IV.

Step 4: Photochemical oxidants.
These cause coughing, eye irritation, headaches, and shortness of breath. Hence, D → III.

Step 5: Conclusion.
Thus, the correct matching is A - II, B - I, C - IV, D - III. Correct answer is (A).

Step 1: Trickling filter.
Trickling filters are attached growth processes, where microbes grow on media surfaces. Hence, A → IV.

Step 2: Activated sludge process.
It is a suspended growth process. Hence, B → III.

Step 3: Aerated lagoon.
Involves mechanical aeration for oxidation. Hence, C → II.

Step 4: Oxidation pond.
It relies on symbiotic relationship between algae and bacteria. Hence, D → I.

Step 5: Conclusion.
Thus, the correct matching is A - IV, B - III, C - II, D - I. Correct answer is (D).

Step 1: Screening and Grit removal.
The first step in wastewater treatment is preliminary treatment, which involves screening and grit removal (B).

Step 2: Primary sedimentation.
This removes settleable solids and reduces suspended matter (A).

Step 3: Secondary treatment and secondary sedimentation.
Biological treatment is applied next, followed by secondary sedimentation to remove biomass (D).

Step 4: Disinfection.
Finally, treated wastewater undergoes disinfection before disposal or reuse (C).

Step 5: Conclusion.
Thus, the correct sequence is B → A → D → C. Correct answer is (C).

Step 1: Formula for BOD at time .
The BOD exerted at time is given by: where, - = BOD exerted at time , - = ultimate BOD, - = reaction rate constant (base 10), - = time in days.

Step 2: Substitution of given values.
It is given that after 4 days: So,

Step 3: Solving for .

Step 4: Conclusion.
Hence, the rate constant is 0.171 per day. Correct answer is (C).