MCQOPTIONS
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MCQOPTIONS
This section includes 118 Mcqs, each offering curated multiple-choice questions to sharpen your Waste Water Engineering knowledge and support exam preparation. Choose a topic below to get started.
| 1. |
Physical adsorption ________ with increase in temperature. |
| A. | Decreases |
| B. | Increases |
| C. | Remains same |
| D. | Fluctuates |
| Answer» B. Increases | |
| 2. |
What is the highest enthalpy of adsorption for chemical adsorption? |
| A. | 100 KJ mol-1 |
| B. | 200 KJ mol-1 |
| C. | 300 KJ mol-1 |
| D. | 400 KJ mol-1 |
| Answer» E. | |
| 3. |
Chlorine is used as the disinfectant in a municipal water treatment plant. It achieves 50 percent of disinfection efficiency measured in terms of killing the indicator microorganisms (E-Coli) in 3 minutes. The minimum time required to achieve 99 percent disinfection efficiency would be |
| A. | 9.93 minutes |
| B. | 11.93 minutes |
| C. | 21.93 minutes |
| D. | 19.93 minutes |
| Answer» E. | |
| 4. |
24,00,000 litres of water passes through a sedimentation tank which has 300 cubic meter volume per day. The detention time for the tank is: |
| A. | 1.25 hours |
| B. | 8 days |
| C. | 3 hours |
| D. | 0.875 hours |
| Answer» C. 3 hours | |
| 5. |
Assertion A: Alum is the most commonly used coagulant in water treatment.Reason R: Alum is very effective in killing pathogens present in the water.Which of the following is correct? |
| A. | Both A and R are true, but R is not a correct explanation of A. |
| B. | A is true but R is false. |
| C. | Both A and R are true, and R is the correct explanation of A |
| D. | A is false but R is true. |
| Answer» B. A is true but R is false. | |
| 6. |
Aeration of water is done to remove: |
| A. | Suspended impurities |
| B. | Colour |
| C. | Dissolved Salts |
| D. | Dissolved gases |
| Answer» E. | |
| 7. |
If the length dimension of a square filter bed increases to two times (while the rate of filtration remains unchanged), the amount of water filtered would become |
| A. | 4 times |
| B. | 2 times |
| C. | 1 time |
| D. | 16 times |
| Answer» B. 2 times | |
| 8. |
A rural water supply scheme serves a population of 10,000 at the rate of 50 litres per capita per day. For the chlorine dose of 2 ppm, what will be the required amount of bleaching with 20% available chlorine? |
| A. | 15 kg |
| B. | 5 kg |
| C. | 10 kg |
| D. | 0.5 kg |
| Answer» C. 10 kg | |
| 9. |
A suspension of sand like particles in water with particles of diameter 0.10 mm and below is flowing into a settling tank at 0.10 m3/s. Assume g = 9.81 m/s2 , specific gravity of particles = 2.65, and kinematic vescosity of water = 1.0105 x 10-2 cm2/s. The minimum surface area (in m2) required for this settling tank to remove particles of size 0.06 mm and above with 100% efficiency is_________ |
| A. | 30.21 |
| B. | 31.21 |
| C. | 32.21 |
| D. | 33.21 |
| Answer» C. 32.21 | |
| 10. |
Consider the following statements regarding removal of impurities from water:1. Settleable solids are removed by filtration.2. Volatile solids are removed through sedimentation.3. Dissolved solids are removed through reverse osmosis.4. Colloidal solids are removed by coagulation.Which of the above statements are correct? |
| A. | 1 and 2 only |
| B. | 3 and 4 only |
| C. | 2 and 3 only |
| D. | 1 and 4 only |
| Answer» C. 2 and 3 only | |
| 11. |
A surface water treatment plant operates round the clock with a flow rate of 35 m3/min. The water temperature is 15°C and jar testing indicated an alum dosage of 25 mg/l with flocculation at a Gt value of 4×104 producing optimal results. The alum quantity required for 30 days (in kg) of operation of the plant is ____________ |
| A. | 378 |
| B. | 3780 |
| C. | 37800 |
| D. | 378000 |
| Answer» D. 378000 | |
| 12. |
A city has a population of 100000 with an average rate of demand of 160 liters per head per day. What is the actual number of filters required if the size of each filter is 9 m×5 m? Assume the average filtration rate as 4500 liters per hour per m2. |
| A. | 1 |
| B. | 2 |
| C. | 4 |
| D. | 5 |
| Answer» E. | |
| 13. |
In water treatment process, Aeration of water is carried out to |
| A. | Remove hardness and chlorides from water |
| B. | Add calcium and magnesium to water |
| C. | Removes gases like carbon dioxide, hydrogen sulfide and to add oxygen to water |
| D. | Remove oxygen from water and to add carbon dioxide to impact test and odour to water |
| Answer» D. Remove oxygen from water and to add carbon dioxide to impact test and odour to water | |
| 14. |
A 50 mL sample of industrial wastewater is taken into a silica crucible. The empty weight of the crucible is 54.352 g. The crucible with the sample is dried in a hot air oven at 104 °C till a constant weight of 55.129 g. Thereafter, the crucible with the dried sample is fired at 600 °C for 1 h in a muffle furnace, and the weight of the crucible along with residue is determined as 54.783 g. The concentration of total volatile solids is _______. |
| A. | 8620 mg/L |
| B. | 1700 mg/L |
| C. | 6920 mg/L |
| D. | 15540 mg/L |
| Answer» D. 15540 mg/L | |
| 15. |
A sewage treatment plant mainly consists of1. Screening 2. Grit removal 3. Secondary sedimentation 4. Aeration 5. primary sedimentation The correct sequence of operations is |
| A. | 1 - 2 - 3 - 4 - 5 |
| B. | 1 - 2 - 5 - 4 - 3 |
| C. | 2 - 1 - 4 - 5 - 3 |
| D. | 2 - 1 - 4 - 3 - 5 |
| Answer» C. 2 - 1 - 4 - 5 - 3 | |
| 16. |
As compared to high rate filter, standard rate filter requires _________ land area. |
| A. | more |
| B. | less |
| C. | equal |
| D. | no |
| Answer» B. less | |
| 17. |
Electrical conductivity (EC) of water and total dissolved solids (TDS) are interrelated. The value of EC will |
| A. | Decrease with increase in TDS |
| B. | Increase with increase in TDS |
| C. | Decreases initially and then increase with increase in TDS |
| D. | Increase initially and then decrease with increase in TDS |
| Answer» C. Decreases initially and then increase with increase in TDS | |
| 18. |
Determine maximum adsorption capacity of alumina (Langmuir isotherm: Q = [22Ct]/[1+35Ct] where Q is mol Anthracene/kg alumina; Ct = mol Anthracene/L liquid)? |
| A. | 0.02 mol/kg |
| B. | 0.629 mol/kg |
| C. | 375 L/mol |
| D. | 22 mol/kg |
| Answer» C. 375 L/mol | |
| 19. |
Order 4 disinfectants in increasing order of their disinfection power? |
| A. | Ozone < HOCl < monochloramine < NCl3 |
| B. | Ozone < NCl3 < Monochloramine < HOCl |
| C. | NCl3 < HOCl < Monochloramine < Ozone |
| D. | NCl3 < Monochloramine < HOCl < Ozone |
| Answer» E. | |
| 20. |
If the total hardness and alkalinity of a sample of water are 300 mg/L and 100 mg/L (CaCO3 scale) respectively, then its carbonate and non – carbonate hardness (in units of mg/L) will be respectively. |
| A. | 100 and 200 |
| B. | 400 and 300 |
| C. | 100 and 400 |
| D. | 400 and zero |
| Answer» B. 400 and 300 | |
| 21. |
Calculate contribution of removal of phosphorous in primary settling tank to overall removal in wastewater treatment plant? Plant schematic is: Influent water→ Primary settling tank→ Biological aeration tank→ Secondary settling tank→ Effluent water.ParameterInfluent waterAfter settling (i.e. influent to aeration)Effluent waterPhosphorous7 mg/L6 mg/L5 mg/L |
| A. | 40% |
| B. | 45% |
| C. | 50% |
| D. | 52% |
| Answer» D. 52% | |
| 22. |
Methemoglobinemia, the ‘blue baby’ syndrome is caused by consuming water containing excess of |
| A. | Fluoride |
| B. | Phosphate |
| C. | Nitrate |
| D. | Nitrite |
| Answer» D. Nitrite | |
| 23. |
For a given discharge, efficiency of sedimentation tank can be increased by |
| A. | Increasing depth of the tank |
| B. | Increasing surface area of the tank |
| C. | Decreasing the depth of the tank |
| D. | Decreasing the surface area of the tank |
| E. | Both decreasing the depth and surface area of the tank combined |
| Answer» C. Decreasing the depth of the tank | |
| 24. |
During the chlorination process, aqueous chlorine reacts rapidly with water to form Cl-, HOCl, and H+ as shown belowCI2 (aq) + H2O ⇋ HOCI + CI- + H+The most active disinfectant in the chlorination process from amongst the following is |
| A. | H+ |
| B. | HOCI |
| C. | CI |
| D. | H2O |
| Answer» C. CI | |
| 25. |
In comparing slow sand filters (SSF) and rapid sand filters (RSF), which of the following is an incorrect statement |
| A. | SSF require larger area for its installation |
| B. | Cost of operation of RSF is lower |
| C. | Depreciation of SSF is lower |
| D. | SSF cannot meet variations in the demand |
| E. | SSF requires cleaning at a frequency of one month |
| Answer» C. Depreciation of SSF is lower | |
| 26. |
Chlorine usage in the treatment of 25,000 m3/day of water has been 9 kg/day.The residual chlorine after 10 minutes of contact is 0.2 mg/l. The chlorine demand of water would be nearly |
| A. | 0.28 mg/l |
| B. | 0.22 mg/l |
| C. | 0.16 mg/l |
| D. | 0.12 mg/l |
| Answer» D. 0.12 mg/l | |
| 27. |
Look at the following relationship between concentration of free residual chlorine and contact time required for 99% kill (Watson's Law: C0.86 tp = λ (constant) for different pathogens).Pathogen typeAdenovirusE.coliCoxsackievirus A2AAλ (Constant) 0.0980.246.30.110Which pathogen has maximum resistance for chlorination? |
| A. | E.coli |
| B. | Adenovirus |
| C. | Coxsackievirus A2 |
| D. | AA |
| Answer» D. AA | |
| 28. |
A water treatment plant of capacity, 1 m3/s has filter boxes of dimensions 6 m × 10 m. The loading rate to the filters is 120 m3/day/m2. When two of the filters are out of service for back washing, the loading rate (in m3/day/m2) is |
| A. | 144 |
| B. | 122 |
| C. | 133 |
| D. | 124 |
| Answer» B. 122 | |
| 29. |
Flocculation is the process of |
| A. | Gently mixing the water and coagulant allowing the formation of large particles of floc |
| B. | Removing relatively large floating and suspended debris |
| C. | Flow, which is slowed enough so that gravity will cause the floc to settle |
| D. | Mixture of solids and liquids collected from the settling tank are dewatered and disposed of |
| Answer» B. Removing relatively large floating and suspended debris | |
| 30. |
Look at the following table:Non-carbonate hardness92 mg/L as CaCO3Total magnesium15 mg/LAlkalinity68 mg/L as CaCO3Desired Total hardness in water80 mg/L as CaCO3Residual carbonate hardness (can not be removed)35 mg/L as CaCO3 Calculate the amount of magnesium hardness (in mg/L as CaCO3)? |
| A. | 31.25 mg/L as CaCO3 |
| B. | 3.12 mg/L as CaCO3 |
| C. | 10 mg/L as CaCO3 |
| D. | 100 mg/L as CaCO3 |
| Answer» B. 3.12 mg/L as CaCO3 | |
| 31. |
Consider the following statements in respect of slow sand filter and rapid sand filter:1. The two filters differ in respect of the standards regarding non-uniformity of the sans used in their filtering media.2. The two filters do not differ in respect of the effective size of the sand used in them.3. The tow filters differ in respect of their respective under-drainage system.4. The two filters differ in respect of their respective rate of filtration.Which of the above statements are correct? |
| A. | 1, 2 and 3 |
| B. | 1, 2 and 4 |
| C. | 2, 3 and 4 |
| D. | 1, 3 and 4 |
| Answer» E. | |
| 32. |
A settling tank in a water treatment plant is designed for a surface overflow rate of 30 m3/day.m2 . Assume specific gravity of sediment particles = 2.65, the density of water (ρ) = 1000 kg/m3, dynamic viscosity of water (μ) = 0.001 N.s/m2, and Stroke’ law is valid. The approximate minimum size of particles that would be completely removed is: |
| A. | 0.01 mm |
| B. | 0.02 mm |
| C. | 0.03 mm |
| D. | 0.04 mm |
| Answer» C. 0.03 mm | |
| 33. |
If the total hardness of a water sample from complete analysis is found to be 120 mg/l and the non-carbonate hardness is 50 mg/I. The carbonate hardness (in mg/l) shall then be |
| A. | 170 |
| B. | 70 |
| C. | 20 |
| D. | 2.4 |
| E. | 0.42 |
| Answer» C. 20 | |
| 34. |
Air binding in rapid sand filters is encountered when |
| A. | the water is subjected to prolonged aeration |
| B. | the water contains high dissolved gases |
| C. | the filter bed comprises largely of coarse sand |
| D. | there is excessive negative head |
| Answer» E. | |
| 35. |
Consider the following statements in respect of injecting chlorine between rapid sand filter and storage tank:1. More contact time is available.2. Chlorine demand is reduced.3. NHCl2 is formed which is more effective than residual chlorine.4. Break point chlorination takes place.Which of the above statements are correct? |
| A. | 1, 2, 3 and 4 |
| B. | 1, 2 and 3 only |
| C. | 1 and 2 only |
| D. | 3 and 4 only |
| Answer» D. 3 and 4 only | |
| 36. |
A rapid sand filter for a town with water requirement of 1 MLD is to be provided with rate of filtration at 4000 l / hr / m2, with backwash system. What would be the size of the filter and its under-drainage system to the nearest approximation? |
| A. | 10 and 0.032 sq. m |
| B. | 11 and 0.022 sq. m |
| C. | 12 and 0.045 sq. m |
| D. | 15 and 0.062 sq. m |
| Answer» C. 12 and 0.045 sq. m | |
| 37. |
lf the chlorine dose required for disinfection is 0.25 mg/l and a plant disinfects 10000000 l water per day, then the per day requirement of bleaching powder containing 25% useful chlorine |
| A. | 10 kg |
| B. | 0.625 kg |
| C. | 2.5 kg |
| D. | 25 kg |
| E. | 32.5 kg |
| Answer» B. 0.625 kg | |
| 38. |
A certain water needs alum treatment to the extent of 10 p.p.m. How much alum, in quintals per day, would be needed to treat 10 MLD of water? |
| A. | 10 |
| B. | 1 |
| C. | 100 |
| D. | 1000 |
| Answer» C. 100 | |
| 39. |
Consider the following statements regarding coagulant aids:1. They are employed when temperature is low as they then accelerate the process of coagulation.2. They are employed when flocs are small and water is coloured.3. With their use, water purification capacity of the plant is increased.4. Most widely used materials are oxidants absorbents, weighing agents, activated carbon and polyelectrolytes.Which of the above statements are correct? |
| A. | 1, 2, 3 and 4 |
| B. | 1, 2 and 3 only |
| C. | 1 and 4 only |
| D. | 2, 3 and 4 only |
| Answer» B. 1, 2 and 3 only | |
| 40. |
For rapid sand filter, sand should have the following specifications: |
| A. | Effective size 0.1 – 0.5 mm, Uniformity co-efficient = 2 to 4 |
| B. | Effective size 0.2 – 0.5 mm, Uniformity co-efficient = 2 to 3 |
| C. | Effective size 0.45 – 0.7 mm, Uniformity co-efficient = 1.3 to 1.7 |
| D. | Effective size 0.7 – 0.9 mm, Uniformity co-efficient = 1 to 5 |
| Answer» D. Effective size 0.7 – 0.9 mm, Uniformity co-efficient = 1 to 5 | |
| 41. |
A sample of water has been analyzed for common ions and results are presented in the form of abar diagram as shown.The non-carbonate hardness (expressed in mg/L as CaCO3) of the sample is: |
| A. | 40 |
| B. | 165 |
| C. | 195 |
| D. | 205 |
| Answer» B. 165 | |
| 42. |
10 MLD water is to be chlorinated in a clear water reservoir (CWR) with 0.8 mg/l chlorine dose with providing contact time of 40 minutes. The required CWR capacity is nearly |
| A. | 220 m3 |
| B. | 280 m3 |
| C. | 28 m3 |
| D. | 22 m3 |
| Answer» C. 28 m3 | |
| 43. |
A rapid sand filter comprising a number of filter beds is required to produce 99 MLD of potable water. Consider water loss during backwashing as 5%, rate of filtration as 6.0 m/h and length to width ratio of filter bed is 1.35. The width of each filter bed is to be kept equal to 5.2m. One additional filter bed is to be provided to take care of break-down, repair and maintenance. The total number of filter beds required will be |
| A. | 19 |
| B. | 20 |
| C. | 21 |
| D. | 22 |
| Answer» D. 22 | |
| 44. |
How many kg of bleaching powder is needed per day to chlorinate 4 MLD of water so than, after 40 minutes of contact, there remains residual chlorine of 0.25 mg/l. The input water has a chlorine demand of 1.25 mg/l. And that the bleaching powder has only 25% available chlorine. |
| A. | 8 kg |
| B. | 20 kg |
| C. | 24 kg |
| D. | 6.6 kg |
| Answer» D. 6.6 kg | |
| 45. |
One of the techniques used for desalination of seawater isA. FiltrationB. DistillationC. evaporationD. Condensation |
| A. | C |
| B. | B |
| C. | A |
| D. | D |
| Answer» C. A | |
| 46. |
In a sedimentation tank design, surface overflow rate (S. O. R) is calculated as |
| A. | Surface area / velocity of water (Q / V / V) |
| B. | Discharge / Plan area (Q /B × L) |
| C. | Volume of tank / discharge (V / Q) |
| D. | Surface area / setting velocity of the particle (A / Vs) |
| Answer» C. Volume of tank / discharge (V / Q) | |
| 47. |
Permanent hardness of water can be removed by: |
| A. | Adding alum |
| B. | Adding lime |
| C. | Adding chlorine |
| D. | Zeolite process |
| Answer» E. | |
| 48. |
In a water treatment, the optimum time of flocculation is usually given as 30 minutes. In case the time of flocculation is increased beyond this value, the flocs will |
| A. | become heavy and settle down in the flocculation tank itself |
| B. | Entrap air and will float in the sedimentation tank |
| C. | Break up and defeat the purpose of flocculation |
| D. | Stick to the paddles |
| Answer» C. Break up and defeat the purpose of flocculation | |
| 49. |
A water filtration unit is made of uniform-size sand particles of 0.4 mm diameter with shape factor of 0.84 and specific gravity of 2.55. The depth of the filter bed is 0.70 m and the porosity is 0.35. The filter bed is to be expanded to a porosity of 0.65 by hydraulic backwash. If the terminal settling velocity of sand particles during during backwash is 4.5 cm/s, the required backwash velocity is |
| A. | 0.69 cm/s |
| B. | 6.35 × 10-3 m/s |
| C. | 5.79 × 10-3 m/s |
| D. | 0.75 cm/s |
| Answer» C. 5.79 × 10-3 m/s | |
| 50. |
For a given discharge, the efficiency of sedimentation tank can be increased by: |
| A. | Increasing the depth of the tank |
| B. | Increasing the surface area of the tank |
| C. | Decreasing the depth of the tank |
| D. | Decreasing the surface area of the tank |
| Answer» C. Decreasing the depth of the tank | |