1. What type of settling do the blocks A, B, C and D denote in the figure below.
- A – Zonal settling, B – discrete particle settling, C-flocculent settling, D – Compression settling
- A – flocculent settling, B – discrete particle settling, C- zonal settling, D – Compression settling
- A – compression settling, B – discrete particle settling, C-flocculent settling, D – zonal settling
- A – discrete particle settling, B – flocculent settling, C- Zonal settling, D – Compression settling
Answer :- d
2. In sedimentation with coagulation, generally, the detention period is …………… than that in plain sedimentation.
- Less
- More
- Equal
Answer :- a
3. In natural flow conditions, an unpolluted river would likely to have:
- More dissolved oxygen in summer than in winter.
- Less dissolved oxygen in summer than in winter.
- More or less the same amount of dissolved oxygen in winter and summer.
- The least amount of dissolved oxygen during floods.
Answer :- b
4. In addressing the treatment of a daily water flow of 1200 m3 in vertical direction , a municipal corporation has identified specific parameters for a circular settling tank. The tank’s diameter is estimated at 10.78 meters, with a depth of 4 meters. Determine the overflow rate (SOR) for this circular settling tank designed for the removal of discrete suspended particles.
- 20 m/day
- 13 m/day
- 25 m/day
- 18 m/day
Answer :- b
5. Statement A: Microbiological examinations of water samples are usually based on MPN tests for the detection and enumeration of indicator organisms rather than that of pathogens.
Statement B: The identification of pathogens in water is both time consuming and difficult.
- Both A and B are true, and B is the correct explanation of A.
- Both A and B are true, but B is not the correct explanation of A.
- A is true but B is false.
- A is false but B is true.
Answer :- a
6. The figure below provides insight into the variation of the city population based on the ratio of peak hourly flow to average flow:
- AB denotes the smaller community.
- AB denotes the larger communities.
- BC denotes the larger communities.
- BC denotes the smaller communities.
Answer :- a, c
7. In the figure below, identify the type of treatment unit process indicated by the various blocks labeled A, B, C, D, and E.
![](https://i0.wp.com/storage.googleapis.com/swayam-node1-production.appspot.com/assets/img/noc24_ce39/7.png?w=900&ssl=1)
- A – Primary, B – Preliminary, C-Secondary, D – Tertiary, E – Sludge Processing
- A – Primary, B – Preliminary, C-Secondary, D – Sludge Processing, E – Tertiary
- A – Preliminary, B – Primary, C-Secondary, D – Sludge Processing, E – Tertiary
- A – Preliminary, B – Primary, C-Secondary, D – Tertiary, E – Sludge Processing
Answer :- d
8. What does the presence of free ammonia in river water indicate?
- Recent pollution of water with sewage
- Past pollution of water with sewage
- Intermittent pollution of water with sewage
- No pollution of water with sewage
Answer :- a
9. In a water treatment plant, a horizontal sedimentation basin maintaining laminar flow conditions is designed to handle a flow rate of 0.45 m³/s. The basin has a rectangular shape with dimensions: length = 42 m, width = 16 m, and depth = 5.5 m. Assuming the settling velocity of particles follows Type 1 settling, calculate the removal efficiency of particles.
Given:
Diameter of particle (spherical) = 28 μm,
Particle density = 2.5 g/cm³
Density of water = 1 g/cm³,
Dynamic viscosity of water = 0.01 g/(cm.s),
Acceleration due to gravity = 980 cm/s²
- 85%
- 100%
- 97%
- 95%
Answer :- d
11. Which of the following are attached type treatment systems:
- Activated sludge process
- Trickling filter
- Oxidation pond
- Rotating biological filter
Answer :- b, d
12. A certain type of bacteria multiplies by dividing into two cells every 10 minutes. If you start with 2 × 105 bacterial cells in a Petri dish, how many cells will there be after 40 minutes?
- 3.2 × 10^5
- 6.8 × 10^5
- 6.8 × 10^6
- 3.2 × 10^6
Answer :- d
13. A wastewater treatment plant has influent MLSS as 5500 mg/L. After a settling period, the volume of sludge in the settling tank is measured to be 450 mL/L of mixed liquor. Calculate the Sludge Volume Index (SVI) for the given mixed liquor in mL/g.
Answer :- 78.83
14. In biological nutrient removal, what is the purpose of using anoxic zones in biological treatment processes?
- To promote the growth of aerobic bacteria
- To facilitate denitrification
- To enhance phosphorus precipitation
- To optimize ammonia oxidation
Answer :- b
15. Calculate the specific growth rate of microorganisms (per hour) in an activated sludge wastewater treatment system, where
Maximum specific growth rate = 0.4/hr,
Half-saturation constant = 12 mg/L
Substrate concentration = 6 mg/L.
- 0.09/hr
- 0.18/hr
- 0.13/hr
- 0.17/hr
Answer :- c
16. In a wastewater treatment plant utilizing facultative ponds, what is the unexpected challenge that might arise during the winter season in northern regions?
- Enhanced microbial activity
- Reduced treatment efficiency
- Increased pathogen removal
- Improved settling of solids
Answer :- b
17. A completely mixed flow reactor is designed with the following data: Qo = 20000 m3/d, BOD after PST = 180 mg/I, BOD of the effluent of = 10 mg/l, Y = 0.5 kg/kg, Kd = 0.05 per day, MLSS = 4000 mg/l. Underflow concentration (Xu) = 10000 mg/I for secondary sedimentation tank and mean residence time (Ɵc) = 8 days. The reactor volume is __.
Answer :- 2415,2435
18. Statement A: Heterotrophs are organisms that cannot produce organic compounds from inorganic sources and, therefore, rely on obtaining pre-formed organic molecules from external sources.
Statement B: Autotrophs are organisms capable of synthesizing organic molecules from simple inorganic substances like carbon dioxide.
- Statement A is true.
- Statement B is true.
- Statement A and Statement B both are true.
- Statement A is false, and Statement B is true.
Answer :- c
19. Select the correct options regarding θ (HRT) and θc (SRT) in the ASP:
- If there is no sludge recycling in the ASP, then θ = θc
- θc represents how much time the wastewater spends in the system.
- If there is sludge recycling in the ASP, then θ > θc
- θc represents how much time microbes spend in the system.
Answer :- a, d
20. High (>?) F/M ratio is the best favourable condition for flocculation in the ASP.
- True
- False
Answer :- b
21. _____________ acts as electron donor in the denitrification process
- NO3-
- Organic carbon
- Organic nitrogen
- NO2-
Answer :- b
22. Activated sludge is the_________________
- Removable sludge from the aeration tank
- Sludge in the secondary clarifier, rich in microbial mass
- Sludge in the secondary clarifier, rich in nutrients
- All the above
Answer :- b
23. What is the cause of bulking of sludge?
- Absence of microorganisms
- Good settling of microorganisms
- Poor settling of micro-organisms
- Good mixture of floc and some filamentous bacteria
Answer :- c
24. Two different ASP systems are shown in the picture below.
![](https://i0.wp.com/storage.googleapis.com/swayam-node1-production.appspot.com/assets/img/noc24_ce39/Q6.jpg?w=900&ssl=1)
In which system is addition of methanol/acetone needed as carbon source for effective removal of nitrates?
- System 1
- System 2
- In both system 1 and system 2
- Not required in both systems
Answer :- b
25. The following data pertains to the ASP process shown in figure below
![](https://i0.wp.com/storage.googleapis.com/swayam-node1-production.appspot.com/assets/img/noc24_ce39/Q8.jpg?w=900&ssl=1)
F/M=0.25/day, and mean cell resident time (θc)=12 days, then calculate volume of solid wasted in m3/day.
Answer :- 49.51
26. Calculate the volumetric loading rate in terms of kg/day/m3 by using question number 7.
Answer :- 0.7, 0.8
27. Calculate the BOD removal efficiency in percentage by using question number 7.
Answer :- 86.67
28. Select the correct option about phosphorous removal
- PO43- consumed by bacteria in aerobic zone
- Bacteria forms PHBs by fermentation byproducts in anaerobic zone
- Polyphosphates break down and orthophosphates are released in the anaerobic zone
- All the above
Answer :- d
29. Which of the following pair is not correctly matched
- Trickling filter –> Attached growth system.
- Activated sludge process –> Suspended growth system
- MBBR –> More surface area to grow bacteria
- Secondary Disinfection –> Inactivation of pathogens
Answer :- d
30. Which of the following form of chlorine disinfectant requires highest contact time to inactivate 99% bacteria
- NH4Cl
- OCl-
- HOCL
Answer :- a
31. Identify the following wrong statements
- In disc filtration aeration is controlled by rotation of discs
- Na2SO3 removes free chlorine from the treated wastewater
- Disinfection biproducts also form in drinking water
- Presence of high concentration H2S and Fe2+ will increase the residual chlorine in treated wastewater
Answer :- c, d
32. UV disinfection process produces hydroxyl radicals in treated wastewater
- True
- False
Answer :- a
33.
Answer :- 15,20
34. Choose the correct option by using the chlorination graph shown below
![](https://i0.wp.com/storage.googleapis.com/swayam-node1-production.appspot.com/assets/img/noc24_ce39/A6Q8.jpg?w=900&ssl=1)
- Break point chlorine dose =1.5 mg/l
- Free residual chlorine = 1.2 mg/l
- Combined residual chlorine = 0.5 mg/l
- Total residual chlorine = 1.7 mg/l
- All the above
Answer :- d
35. Select the following advantages of ozone treatment
- No harmful disinfection biproducts
- Improves the taste and odor
- Cheaper than Chlorination
- Requires less contact time
- More disinfecting residual power
Answer :- a, b, c