[Week 12] NPTEL Wastewater Treatment And Recycling Assignment Answer 2023

Wastewater Treatment And Recycling Assignment Answer

NPTEL Wastewater Treatment And Recycling Week 12 Assignment Answer 2023

Q1. Identify the incorrect statement regarding wastewater recycling trends:
a. The trend of reclaimed water use has been increasing worldwide
b. Systems for wastewater recycling and reuse are generic, and hence can easily be replicated at other places
c. Agriculture sectors is largest consumer of the reclaimed water
d. Public acceptance of reclaimed water uses in progressively growing

Answer:- b

Q2. The challenges in wastewater recycling include:
a. Technologies available for water recycling are prone to frequent failure
b. There is always high health risk when crops are irrigated with recycled water
c. Higher cost is incurred in wastewater recycling
d. All of the above

Answer:- d

Q3.

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Answer:- c

Q4. The decision making on the selection of an optimum treatment sequence for wastewater recycling is becoming a challenge for the designers, due to:
a. Steadily growing number of alternative processes
b. Inferior performance of the wastewater treatment units
c. Growing level of social unacceptability towards wastewater recycling schemes
d. All of the above

Answer:- a

Q5. Identify the correct statements regarding fit-for-purpose wastewater treatment:
Statement I: Fit-for-purpose wastewater treatment advocates treating wastewater to produce reclaimed water which is fit for all type of potable and non-potable uses.
Statement II: Fit-for-purpose wastewater treatment may require over treatment in order to make water fit for any possible reuse, including potable.
a. Statement I is correct, while statement II is incorrect
b. Statement II is correct, while statement I is incorrect
c. Both, statements I and II are correct
d. Both, statements I and II are incorrect

Answer:- b

Q6. The country which recycles maximum of its wastewater is:
a. Israel
b. Russia
с. France
d. Australia

Answer:- a

Q7. Usually the public acceptance of recycled treated sewage is highest for:
a. Potable uses (drinking and cooking)
b. Bathing and washing cloths
c. Fish farming and food crop irrigation
d. Watering lawns and car washing

Answer:- d

Q8. The focus of research on water-energy nexus is on exploring:
a. More energy-efficient technologies for water and wastewater treatment
b. Energy production and recovery from wastewater and sludge processing
c. Optimization of energy uses in water supply
d. All of the above

Answer:- b

Q9. Globally, some of the most known success stories of wastewater recycling include:
a. Toowoomba (Australia) and Peris (France)
b. Singapore’s NEWater and Orange County in California (United State)
c. Bangalore (India) and San Diego (United States)
d. All of the above

Answer:- b

Q10. Identify the correct statements regarding public acceptance of recycled wastewater:
Statement I: People with higher levels of education often have higher level of acceptance of recycled water.
Statement II: Knowledge about the recycling technology and safety measures being taken up by utility results in greater acceptance of recycled water.
a. Statement I is correct, while statement II is incorrect
b. Statement II is correct, while statement I is incorrect
c. Both, statements I and II are correct
d. Both, statements I and II are incorrect

Answer:- c

Q11. Which of the statements below are correct about public acceptance in wastewater recycling?
a. Younger population are more accepting to recycled water uses.
b. Women are more accepting of recycled water than men
c. Religious people are more willing to use recycled water than non-religious people.
d. All of the above

Answer:- a

Q12. Yuck Factor leading to public protest against wastewater recycling scheme is mainly attributed to:
a. Unfair distribution of recycled wastewater
b. Tariffs charged for using recycled wastewaters
c. Health risk concerns even with adequately treated reclaimed waters
d. Disgust about idea of using wastewater

Answer:- d

Q13. Potable reuse systems for wastewater recycling in Singapore and USA typically use advanced treatment techniques, including:
a. Multi-Grade Filtration (MGF) and Activated Carbon Filtration (ACF), followed by Chlorination
b. Advanced Oxidation Processes (AOP) and Ion-Exchange (IX), followed by UV Disinfection
c. Microfiltration (MF) and Reverse Osmosis (RO), followed by UV Disinfection
d. Ozonisation and Ultrafiltration (UF), followed by Reverse Osmosis (RO)

Answer:- c

Q14. Ensuring treatment and complete recycling of industrial effluents is mandated under:
a. Swachh Bharat Mission (SBM)
b. Zero Liquid Discharge (ZLD)
c. Jal Jeevan Mission (JJM)
d. National Mission for Clean Ganga (NMCG)

Answer:- b

Q15. IUWM Considers:
a. Integrating wastewater, stormwater and rainwater as alternate resources in an urban water cycle
b. Using artificial intelligence and machine learning in urban water management
c. Combining industrial wastewater management targeting complete recycling
d. Arranging investments and loans for projects linked to wastewater treatment and recycling in cites

Answer:- a

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NPTEL Wastewater Treatment And Recycling Week 11 Assignment Answer 2023

Q1. Among the given different types of wastewater, easiest to treat and recycle is:
a. Industrial wastewaters
b. Blackwater
c. Municipal Sewage
d. Greywater

Answer:- d

Q2. The impact of wastewater recycling and reuse on freshwater resources include:
a. Improved water quality of freshwater resources
b. Reduced water withdrawal from freshwater resources
c. Both, a and b
d. Neither a, nor b

Answer:- c

Q3.

Answer:-b

Q4. Which of these driving factors for wastewater reuse and recycling is directly linked to
financial implications?
a. Environmental and social responsibility
b. Regulatory requirements on wastewater treatment and disposal
c. Easy accessibility of wastewater as an alternate water source
d. All of the above

Answer:- b

Q5.

Answer:- c

Q6.

Answer:- b

Q7.

Answer:- c

Q8.

Answer:- a

Q9.

Answer:- d

Q10.

Answer:- b

Q11.

Answer:- d

Q12.

Answer:- b

Q13.

Answer:- d

Q14.

Answer:- c

Q15.

Answer:- d

NPTEL Wastewater Treatment And Recycling Week 10 Assignment Answer 2023

Q1. Identify the correct statements regarding wastewater treatment:
Statement I: The choices of wastewater treatment units depend on several factor such as desired degree of treatment, cost and available funds, and suitability of technology.
Statement II: In general, natural processes based wastewater treatment units always provide most efficient contaminant removal.
a. Statement I is correct, while statement II is incorrect
b. Statement II is correct, while statement I is incortect
c. Both, statements I and II are correct
d. Both, statements I and II are incorrect

Answer:- a

Q2. Which of the followings is a major treatment mechanism in a constructed wetland?
a. Advanced Oxidation
b. Phytoremediation
c. Disinfection
d. All of the above

Answer:- b

Q3.

Answer:- b

Q4.

Answer:- c

Q5.

Answer:- d

Q6.

Answer:- c

Q7.

Answer:- a

Q8.

Answer:- d

Q9.

Answer:- c

Q10.

Answer:- a

Q11. In comparison to external configuration of MBR, submerged MBR:
a. Can operate at higher fluxes
b. Have lower energy consumption
c. Offer better maintenance control
d. All of the above

Answer:- b

Q12. A MBBR reactor is conceptually a:
a. ASP supplied with inert media as biofilm carriers operating in mixed motion
b. MBR operated under batch flow conditions
c. SBR combined with a biofilm growth on the surface of a support material
d. MBR combined with biofilter process

Answer:- a

Q13.

Answer:- b

Q14. Among the followings, best removal of suspended solids and biomass can be obtained by:
a. SBR
b. MBR
c. MBBR
d. SBBR

Answer:- b

Q15.

Answer:- a

NPTEL Wastewater Treatment And Recycling Week 9 Assignment Answer 2023

1. The advanced (tertiary) treatment of wastewater is used to remove:
a. Suspended solids
b. Nutrients, pathogens and emerging contaminants
c. Sediments, oils and grease
d. All of the above

Answer :- b

2. Which of the following are emerging pollutants in wastewater?
a. PPCPs (Pharmaceuticals and Personal Care Products)
b. Nutrients
c. Organic Matter
d. All of the above

Answer :- a

3.

Answer :- d

4. Activated carbon-based adsorption units are regarded as highly effective for the removal of:
a. Microbial contaminants
b. Nutrients
c. Alkalinity and hardness
d. Pesticides

Answer :- d

5. The first step of adsorption mechanism majorly involves the process of:
a. Mass transfer to adsorbent surface
b. Diffusion into adsorbent pores
c. Pore surface adsorption
d. All of the above

Answer :- a

6. The most preferred flow and regeneration pattern for a typical ion-exchange system is:
a. Down-flow in normal service run and co-flow regeneration
b. Up-flow in normal service run and co-flow regeneration
c. Down-flow in normal service run and reverse-flow regeneration
d. Up-flow in normal service run and reverse-flow regeneration

Answer :- c

7.

Answer :- d

8. Which of these is not used for the disinfection of treated wastewaters
a. UV irradiation
b. Microfiltration
c. Cl2 gas
d. NaOCI

Answer :- b

9.

Answer :- d

10. The advanced oxidation processes (AOPs) target oxidation through •OH radicals, which typically produced by:
a. Photochemical degradation processes
b. Photocatalysis processes
c. Chemical oxidation processes
d. All of the above

Answer :- d

11. Electrodialysis uses the principle of:
a. Attraction and repulsion by anode and cathode of opposite charged ions
b. Ion-selective membranes to permeate the ions of specific charges while
rejecting opposite charged ions
c. Both a) and b)
d. Neither a) nor b)

Answer :- c

12. Which pre-treatment process may be used to control fouling of membranes
a. Filtration
b. Chlorination
c. UV irradiation
d. All of the above

Answer :- d

13. The total solids (TS) removal efficiency of UF is approximately (in %):

Answer :- 74, 86

14. No internet connection, or can not reach OCR server

Answer :- 540, 660

15. What is the percentage of treated water (permeate) produced from RO unit (in %):

Answer :- 60, 75

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NPTEL Wastewater Treatment And Recycling Week 8 Assignment Answer 2023

1. Settleable inorganic and organic solids removed from raw wastewater, are components of:
a. Screenings
b. Primary Sludge
c. Secondary Sludge
d. Digested Sludge

Answer :- b

2. The sludge produced from the secondary clarifier of a conventional STP is known as:
a. Screenings and Grit
b. Primary sludge
c. Digested sludge
d. Waste activated sludge

Answer :- d

3.

Answer :- b

4. Increasing the solid content of the sludge through mechanical or gravity thickeners, leads to:
a. No change in the total volume of sludge
b. Increase in the total volume of sludge
c. Decrease in the total volume of sludge
d. Fluctuations in the total volume of the sludge

Answer :- c

5. Which of the followings are examples of mechanical sludge thickening systems?
a. Filter Press. and Belt Press
b. Screw Press, and Rotary Drums
c. Centrifuges
d. All of the above

Answer :- d

6. In the process of anaerobic sludge digestion, organic matter is converted to:
a. COz
b. CHa
c. New bacterial cells
d. All of the above

Answer :- d

7. A sludge digestion process usually leads to:
a. Less water content in the sludge
b. Less total mass of solids in the sludge
c. Higher total mass of solids in the sludge
d. Digestion process does not alter liquid or solid mass in the sludge

Answer :- b

8. Coagulants such as ferric chloride, alum or organic polymers may be added to wastewater sludge for:
a. Sludge stabilization
b. Sludge thickening
c. Sludge conditioning
d. Sludge hygienisation

Answer :- c

9. Identify the correct statements regarding sludge dewatering:
Statement I: Sludge Drying Beds are one of the simplest methods of dewatering they have large land footprint.
Statement II: Dewatered sludge essentially have zero or near zero water content
a. Statement I is correct, while statement II is incorrect
b. Statement II is correct, while statement I is incorrect
c. Both, statements I and II are correct
d. Both, statements I and II are incorrect

Answer :- a

10. Identify the correct statements regarding sludge dewatering:
Statement I: Sludge Drying Beds are one of the simplest methods of dewatering, but they have large land footprint.
Statement II: Dewatered sludge essentially have zero or near zero water content.
a. Statement I is correct, while statement II is incorrect
b. Statement II is correct. while statement I is incorrect
c. Both. statements I and II are correct
d. Both. statements I and II are incorrect

Answer :- d

11. Water content of a 6400 kg/d wet sludge was reduced from 98.5 % to 96 % using a sludge thickening unit. What’s the net change in the total quantity of dry solids present in the sludge through this thickening process:
a. 0 % No change)
b. Increased by 2.5 %
c. Decreased by 2.5 %
d. Increased by 250 %

Answer :- a

12. A thickened sludge is having the ratio of volatile to total solids (VS/IS) as 0.75. The sludge is further digested where 72% of the organic (volatile) fraction is converted to liquid and gaseous products. Neglecting any loss in inorganic (non-volatile) fraction of solids during digestion process, the VS/TS ratio of the digested sludge would be:
a. 0.93
b. 0.68
c. 0.54
d. 0.32

Answer :- b

13. The total amount of dry solids in the thickened sludge is (in kg/d):

Answer :- 600

14. The total volume of sludge produced after sludge thickening is (in m3/d):

Answer :- 10

15. Assuming no reduction in the inorganic fraction of solids during the digestion, the percentage reduction in the organic fraction of solids during the digestion process is (in %):

Answer :- 74

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NPTEL Wastewater Treatment And Recycling Week 7 Assignment Answer 2023

1.

Answer :- a

2. In the biogas produced during an anaerobic wastewater treatment:
a. Fraction of methane is higher than the fraction of carbon dioxide
b. Fraction of methane is lower than the fraction of carbon dioxide
c. Fraction of methane is equal to the fraction of carbon dioxide
d. Any of the two, methane or carbon dioxide, could have higher fraction than
the other

Answer :- a

3.

Answer :- b

4. The reaction CH3COOH – CH + CO2 represents:
a. Acetogenesis
b. Acidogenesis
c. Acetoclastic methanogenesis
d. Hydrogenotrophic methanogenesis

Answer :- c

5. Which of the following is a major concern with anaerobic processes?
a. Longer start-up time
b. Lesser efficiency for nutrient removal
c. Sensitive to toxic compounds
d. All of the above

Answer :- d

6 .

Answer :- b

7. GLSS in a UASB Reactor is used to separate:
a. Solids and effluent from the mix
b. Biogas and effluent from the mix
c. Solids and biogas from the mix
d. Solids, biogas as well as effluent from the mix

Answer :- d

8. During anaerobic treatment, high ammonia concentration in the reactors:
a. Reduces sludge production
b. Enhances sludge production
c. Reduces methanogenic activity
d. Enhances methanogenic activity

Answer :- c

9.

Answer :- a

10. The collection of biogas from municipal wastewater treatment is rare, due to:
a. Getting municipal wastewater for anaerobic treatment is challenging
b. Technologies are not available for collection of biogas
c. Methane recovery and purification process is costly
d. All of the above

Answer :- c

11.

Answer :- a

12. The volumetric organic loading rate of the reactor is (in kg COD/m’-d):

Answer :- 15

13. The COD of the treated effluent is (in mg/L):

Answer :- 180

14. The daily sludge production in the reactor is (in kg /d):

Answer :- 110, 130

15. The total amount of power produced per day in the form of CH4 is (in kWh):

Answer :- 6200,7200

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NPTEL Wastewater Treatment And Recycling Week 6 Assignment Answer 2023

1.

Answer :- d

2. Heterotrophic microorganisms derive energy required for cell synthesis from:
a. Photosynthesis
b. Hydrogen and sulphur
c. Oxidation of organic matter
d. External thermal power sources

Answer :- c

3. In comparison to anaerobic microorganisms, aerobic microorganisms have:
a. Higher nutrient requirement and higher growth rate
b. Higher nutrient requirement but lower growth rate
c. Lower nutrient requirement but higher growth rate
d. Lower nutrient requirement and lower growth rate

Answer :- a

4. Under microbial growth in a batch process, stationary phase occurs when:
a. Rate of growth becomes nearly zero, while rate of decay is positive
b. Rate of growth becomes nearly equal to rate of decay
c. Rate of growth is exponential, but constant
d. Rate of decay exceeds the rate of growth

Answer :- b

5.

Answer :- b

6. Biological treatment of wastewater can reduce Unit:
a. Only BOD
b. Only COD
c. Both. BOD and COD
d. Neither BOD nor COD

Answer :- c

7. Which of the following in NOT a component of typical Activated Sludge Process (ASP) unit:
a. Secondary settling tank
b. Aeration tank
c. Biomass growth media
d. Sludge recycling

Answer :- c

8. Among Activated Sludge Process (ASP), Rotating Biological Contractor (RBC and Trickling Filter (TF), wastewater treatment systems that are based on the attached growth of biomass, include:
a. ASP and RBC
b. TF and RBC
c. ASP and TF
d. ASP, RBC and IF

Answer :- b

9. In an activated sludge process, kg of BOD applied (without including the return sludge flow) per unit of MLVSS per day, is referred as:
a. Sludge Volume Index (SVI)
b. Organic Loading Rate (OLR)
c. Solid Retention Time (SRT)
d. Food to Microorganism (F/M Ratio

Answer :- d

10.

Answer :- a

11. The specific growth rate u of a microbial species was observed as 3.42 d at 240 mg/L BOD. If the half saturation constant Ks for the species is 48 mg/L, the maximum specific growth rate Umax for the species would be:
a. 3.7 d-1
b. 4.1 d‘
c. 6.2 d-1
d. 8.5 d

Answer :- b

12. The 4500 m° size aeration unit of an activated sludge process is maintaining steady state biomass concentration at 4000 mg L, while treating 3.5 MLD sewage. The 3.2 MLD effluent coming out from the secondary settling tank has negligible biomass washout, while the biomass concentration in 0.3 MLD sludge wastage line is 12000 mg/L. For this ASP, the approximate sludge retention time would be:
a. 2 days
b. 3 days
c. 4 days
d. 5 days

Answer :- d

13) The effective volume of the aeration tank should be (in m°):

Answer :- 3700,4500

14. The food to micro-organism ratio is (in kg of BOD/kg of biomass/ d):

Answer :- 0.001024

15) The daily requirement of oxygen is (in kg/d):

Answer :- 3.52128

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NPTEL Wastewater Treatment And Recycling Week 5 Assignment Answer 2023

1.

Answer :-c

2. Which of the given treatment stages is NOT included in the preliminary treatment of wastewater:
a. Oil and greases are removed by skimming tanks
b. Suspended matters are removed by sedimentation tank
c. Floating materials are removed by screening
d. Grit and sand are removed by grit chambers

Answer :- b

3. Which of these units has a detention period of the order of 1 min:
a. Grit Chamber
b. Primary Sedimentation
c. Secondary Sedimentation
d. Aeration Tank

Answer :- a

4. Which of the following could be an appropriate velocity through the screens?
a. 0.08 m/s
b. 0.8 m/s
c. 8 m/s
d. 80 m/s

Answer :- b

5. The equalization tank is used to:
a. Eliminate variation in flow-rate
b. Improve performance of downstream processes
c. Balance fluctuating concentrations in the influent
d. All of the above

Answer :- d

6.

Answer :- c

7. Settling velocity under flocculent settling 15:
a. Same as under discrete settling
b. Lower than the discrete settling
c. Higher than the discrete settling
d. Could be lower or higher than the discrete settling

Answer :- c

8. The zone located at the bottom of a rectangular sedimentation basin 15:
a. Inlet Zone
b. Outlet Zone
c. Settling Zone
d. Sludge Zone

Answer :- d

9. The tube and plate settlers compared with conventional sedimentation tank, generally require
a. Lesser area but higher input energy
b. More area but lower input energy
c. More area and higher input energy
d. Lesser area and lower input energy

Answer :- d

10.

Answer :- c

11. Surface loading rate of a settling basin is 18 m’ hr/m?. Approximately, what percent of the particles that have a settling velocity of 0.006 m/sec will be removed?
a. 40 %
b. 60 %
c. 80 %
d. 100 %

Answer :- d

12. The terminal settling velocity of a 0.01 mm diameter spherical particle with specific gravity 2.65, in water of density 998.2 kg/m and dynamic viscosity 1.002 × 10-3 Ns/m?, would be:
a. 90 cm/s
b. 9 cm/s
c. 0.09 cm/s
d. 0.009 cm/s

Answer :- c

13. A circular primary clarifier is to be designed at an overflow rate of 40 m/day to treat 500C m/day of wastewater flow. The approximate diameter of the tank should be:
a. 12.6 m
b. 20 m
c. 28.2 m
d. 36.5 m

Answer :- a

14. The headloss through a bar rack with an approach velocity of 0.70 m/s and velocity through the screen of 1.05 m/s, will be:
a. 30 mm
b. 45 mm
c. 60 mm
d. 75 mm

Answer :- b

15. A grit chamber, with a detention time of 40 seconds is treating a wastewater flow of 8,000 m3day, with a flow-through velocity of 0.3 m/s. The length of the grit chamber would be:
a. 7.2 m
b. 10 m
c. 12 m
d. 18.6 m

Answer :- c

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NPTEL Wastewater Treatment And Recycling Week 4 Assignment Answer 2023

1. Self-purification processes in rivers, refers to:

a. Installing in-situ sediment filters for contaminant removal in rivers
b. Setting up in-stream natural-processes based treatment systems in rivers
c. Dosing chemicals to the rivers which leads to precipitate and remove
pollutants
d. Naturally-occurring processes in rivers which reduces the pollutant levels in river water

Answer :- d

2. Match the type of processes for contaminant fate and transport given in first column with the specific process given in second column:

Type of process

(i) Mass Transport
(ii) Phase Transfer
(iii Transformation

Contaminant Fate and Transport Processes
A. Biodegradation
B. Dispersion
C. Volatilization

a. (i)-B, (ii)-A.(iii)-C
b. (i)-B. (ii)-C. (iii)-A
c. (i)-C, (in)-A. (ill)-B
d. (1)-A. (in)-C. (il)-B

Answer :- b

3. After the point of discharge of a wastewater stream, the first zone to appear in a river is:

a. Decomposition Zone
b. Septic Zone
c. Recovery Zone
d. Reaeration Zone

Answer :- a

4. For a river receiving wastewater discharge, the most critical stretch is considered, where:

a. DO is minimum
b. DO is maximum
c. BOD is minimum
d. BOD is maximum

Answer :- a

5. The Streeter Phelps Equation is used to describes the variation of DO in a stream receiving wastewater discharge. Which of the following assumptions is correct about the classical Streeter Phelps Equation?

a. The flow pattern in the river follows plug-flow
b. Only re-aeration is taken as the source of DO in the river water
c. Only carbonaceous BOD is considered responsible for DO consumption
d. All of the above

Answer :- d

6. Identify the correct statements regarding conservative pollutants:
Statement I: Conservative pollutants are non-degradable, thus stable and persistent in nature.
Statement II: Since conservative pollutants are not degraded in nature, it poses lesser environmental risk than non-conservative pollutants.

a. Statement I is correct. while statement II is incorrect
b. Statement II is correct. while statement I is incorrect
c. Both. statements I and II are correct
d. Both. statements I and II are incorrect

Answer :- a

7. Consider the following generic mass balance equation (in usual notations):

Answer :- c

8. For mass balance equation in a Continuous Stirred Tank Reactor (CSIR):

a. Inflow and outflow flux is considered as zero
b. Reaction term in the mass balance equation is considered as zero
c. The outflow concentration of contaminant is taken same as the concentration
in the reactor
d. All of the above

Answer :- c

9. If the reaction kinetics in a mass balance equation is expressed as dCIdt = k.C”, the order of the reaction is:

a. First order
b. nt order
c. Ct order
d. It order

Answer :- b

10. Mixing or no-mixing in a reactor guides in identifying:

a. Conservative or reactive nature of pollutant
b. Steady or unsteady state in the reactor
c. Batch or continuous flow process
d. Plug flow conditions in the reactor

Answer :- d

11. A plug-flow reactor of volume 250 m’ is operating under steady state at 16 m°h flow of a wastewater stream having influent BODs as 360 mg/L. If the BOD decay rate constant is 0.141 per hour, the outlet BOD Concentration would be:

a. 20 mg/L
b. 40 mg/L
c. 80 mg L
d. 160 mg/I

Answer :- b

12. A mixed tank reactor is to be designed for treating phenol in an industrial wastewater, form an initial concentration of 70 mg/L to a final outlet concentration of 5 mg/L, where phenol is expected to undergo first order decay at a rate constant of 0.65/d. If the reactor is to be operated at steady state, the design volume of reactor for treating 20 kL/d wastewater would be:

а. 135 m3
b. 294 m3
с. 400 m°
d. 620 m

Answer :- c

Question Statement (13-15): The 5-day BOD of a wastewater sample measured at 20°C incubation temperature was found to be 320 mg/L. The laboratory data revealed that the BOD reaction rate constant (at 20°C) k2o (base e) was 0.26/day, and the temperature coefficient was 1.035. Based on the information. answer the following questions:

13) The ultimate BOD of wastewater, at 20°C incubation temperature, is (in mg/L)

Answer :- 403.2

14. The 3-day BOD of this wastewater, at 20°C incubation temperature, is (in mg/L)

Answer :- 276.16

15. The 3-day BOD of this wastewater. at 27°C incubation temperature. is (in mg L):

Answer :- 292.1

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NPTEL Wastewater Treatment And Recycling Week 3 Assignment Answer 2023

1. Turbidity in water is usually measured based on:

a. Measuring rate constant of chemical reactions
b. Gravimetric measurements (by weighing)
c. Detecting scattering of light passed through water
d. Detecting potential for conducting electric current

Answer:- c

2. Spectrophotometers are typically used to measure:

a. Redox potential
b. Colour
c. Conductivity and TDS
d. All of the above

Answer:- b

3. At 20 °C temperature, and atmospheric pressure, the saturation dissolved oxygen level in water is approximately:

a. 9 mg/L
b. 2 mg/L
c. 0.5 mg/L
d. Zero

Answer:- a. 9 mg/L

At 20°C temperature and atmospheric pressure, the saturation dissolved oxygen level in water is approximately 9 mg/L (milligrams per liter). This value can vary slightly based on factors such as salinity and pressure, but as a general guideline, 9 mg/L is a common approximation for freshwater at this temperature and pressure conditions.

4. Do vary with water temperature and altitude, as:

a. Cold water holds more oxygen than warm water, and water at lower altitudes holds less oxygen than water at higher altitudes
b. Cold water holds less oxygen than warm water, and water at lower altitudes holds less oxygen than water at higher altitudes
c. Cold water holds more oxygen than warm water, and water at lower altitudes holds more oxygen than water at higher altitudes
d. Cold water holds less oxygen than warm water, and water at lower altitudes holds more oxygen than water at higher altitudes

Answer:- c

5. The pH of a water sample was measured as 6.4 unit. The measured total alkalinity and measured total acidity of water would be:

a. Total Alkalinity = 0; Total Acidity = 0
b. Total Alkalinity = 0; Total Acidity > 0
c. Total Alkalinity > 0; Total Acidity = 0
d. Total Alkalinity > 0; Total Acidity > 0

Answer:- d

6. Among the given options, the likeliest value of BOD of a wastewater sample, having 450 mg/L COD, is:

a. Zero
b. 270 mg/L
c. 450 mg/L
d. 700 mg/L

Answer:- b

7. Match the type of effects of improper wastewater management with the related examples:

Class of pollutants in wastewater
(i) Organic pollutants
(ii)Emerging Contaminants
(iii) Nutrients
Examples
A. BOD and COD
B. Orthophosphate and nitrate
C. Antibiotics and pesticides

a. (i)-B. (ii)-A .(ini)-C
b. (i)-C. (ii)-A. (iii)-B
c. (i)-C. (ii)-B. (iii)-A
d. (i)-A. (ii)-C. (iii)-B

Answer:- d

8. The BODs values of two wastewater samples A and B were measured as 80 mg/L and 210 mg L, respectively. This signifies that:

a. Sample A has lesser biodegradable organic matter load than Sample B.
b. Sample A has higher biodegradable organic matter load than Sample B.
c. Sample A has less quantity of biomass present than that in Sample B
d. Sample A has more quantity of biomass present than that in Sample B

Answer:- a

9. Identify the correct statements regarding emerging contaminants, or contaminants of emerging concern: Statement

I: Emerging contaminants are generally bioaccumulative, but are non- persistent, and have very less toxicity. Statement
II: Emerging contaminants have become relatively easily identifiable with the new techniques for chemicals identification and separation.

a. Statement I is correct, while statement II is incorrect
b. Statement II is correct. while statement I is incorrect
c. Both, statements I and II are correct
d. Both, statements I and II are incorrect

Answer:- b

10. A wastewater contains 180 mg L acetic acid (CH;COOH). The contribution of acetic acid to the theoretical COD of this wastewater is [Governing oxidation reaction: CH&COOH + 202 = 2H20 + 2C02]

a. 76 mg/L
b. 180 mg/L
c. 192 mg/L
d. 360 mg/L

Answer:- c

11. 5 mL of a wastewater sample was diluted with aerated distilled water, made up to 300 mL in a BOD bottle. The initial DO was measured as 8.2 mg L, which dropped to 1.8 mg/L in 5 days’ time. BODs of the sample is:

a. 384 mg/L
b. 256 mg/L
c. 180 mg/L
d. 64 mg/L

Answer:- a

12. In a MPN Test, 10 mL, 1 mL, and 0.1 mL of wastewater was inoculated in 5 replicates in nutrient broth, and resulted in 5, 2 and 0 positives tests, respectively, after 48 hrs of incubation. The MPN index / 100 mL of the wastewater would be (use the 5-replicates MPN table):

a. 20
b. 49
c. 70
d. 112

Answer:- b

Question Statement (13-15): A 100 mL wastewater sample was filtered using a GF/C filter paper of weight 1.750 g and the filtrate collected in a silica crucible of weight 24.802 g. Both, crucible and filter paper were dried for 24 hr in an oven at 104 °C. Post drying, the weight of the filter paper and crucible was measured as 1.924 g. and 24.928 g. respectively. Thereafter, both crucible and filter paper were placed in muffle furnace for 20 mins at 550 °C. Post ignition, the weight of the filter paper and crucible was measured as 1.842 g, and 24.866 g. respectively. Bases on the data, answer the followings:

13. The Total Suspended Solids (TSS) concentration in the wastewater is (in mg L)

Answer:- 820

14. The Volatile Suspended Solids (VSS) concentration in the wastewater is (in mg/L)

Answer:- 640

15. The Total Solids (TS) concentration in the wastewater is (in mg/L):

Answer:-230520

NPTEL Wastewater Treatment And Recycling Week 2 Assignment Answer 2023

1. The quantity of municipal wastewater generated from a city depends on:

a. Population of the city
b. Water consumption pattern of the inhabitants
c. Both, population and water consumption pattern
d. Neither population nor the water consumption pattern

Answer :- c

2. Dry Weather Flow is:

a. The actual flow of sanitary sewage
b. The stormwater contribution to sewers in dry season
c. Combined stormwater flow plus sanitary sewage flow
d. Quantity of sanitary sewage flow subtracted from stormwater flow

Answer :- a

3. Identify the correct statements regarding design capacity of sewer systems:
Statement I: Incorrect estimation of the quantity of sewage generated may lead to
inadequate or hydraulically inefficient sewer system design.
Statement II: Under-estimation of the design sewage flow will make the system uneconomical.

a. Statement I is correct, while statement II is incorrect
b. Statement II is correct, while statement I is incorrect
C. Both, statements I and II are correct
d. Both, statements I and II are incorrect

Answer :- a

4. Design period of various sewerage components are usually based on:

a. Availability of funds for design
b. Useful life of the specific components
c. The duration of the sewerage services required
d. Average life of the sewerage facility

Answer :- b

5. Which of these population forecasting method is likely to overestimate the forecasted population for a city of moderate size and age:

a. Arithmetic Increase Method
b. Incremental Increase Method
c. Geometric Increase Method
d. Logistic Growth Method

Answer :- c

6. Using Growth Composition Analysis Method (Demographic Method), population is estimated based on annual birth rate, death rate and migration rates. Which of these is relatively the most difficult to estimate:

a. Birth rate
b. Death rate
c. Migration rate
d. All of the above

Answer :- c

7. The peak factor is used to estimate peak for sewer designs. The correct relation between peak factor for sewage flow estimation with the increase in population, is:

a. Peak factors have large fluctuations for highly populated cities
b. Peak factor is independent of population increase
c. Peak factor typically increased with the increase in population.
d. Peak factor typically decreases with the increase in population.

Answer :- d

8. Population forecast in a logistic growth model is limited by the:

a. Availability of the master plan of the region
b. Exponential growth rate of the population
c. Migration rate of the population
d. Population carrying capacity of region

Answer :- d

9. As per CPHEEO Manual (20212), the conventional sewers shall be designed for a minimum sewage flow of:

a. 30 litres per capita per day
b. 55 litres per capita per day
c. 100 litres per capita per day
d. 250 litres per capita per day

Answer :- c

10. Which of the these may lead to additional inflow to sewer lines?

a. Water used from unaccounted private water supplies
b. Water used for gardening and horticulture
c. Water losses from water supply systems
d. All of the above

Answer :- a

Question Statement (11-13):
The population of a city was recorded as 2.5 lakhs, 3.2 lakhs, 4.1 lakhs, and 5.2 lakhs in
1991, 2001, 2011, and 2021, respectively. Based on the data, answer the following:

11. The forecasted population in 2041 using arithmetic increase method, would be (in Lakhs)

Answer :-  6.6,7.4

12. The forecasted population in 2041 using arithmetic increase method, would be (in Lakhs)

Answer :- 8,9

13. The forecasted population in 2041 using arithmetic increase method, would be (in Lakhs)

Answer :- 7.2,8

14. A city with 12 lakh populations receives 150 lped water supply. Assuming that 80% of the water used is received as municipal sewage, the maximum daily flow of sewage from the city, assuming a daily peak factor of 2, would be:

a. 360 MLD
b. 288 MID
c. 180 MLD
d. 72 MLD

Answer :- b

15. The average daily sewage flow from city is 16 MLD. Assuming daily and hourly peak factor as 2 and 1.5, respectively, the maximum (peak) hourly flow of the sewage would be:

a. 172 m°/h
b. 768 m3д
c. 1240 m’h
d. 2000 m3д

Answer :- d

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NPTEL Wastewater Treatment And Recycling Week 1 Assignment Answer 2023

1. Which of the following component of wastewater is often not considered as a resource?

a. Water
b. Nutrient
c. Organic matters
d. Pathogens

Answer :- d. Pathogens

Pathogens are microorganisms, such as bacteria, viruses, and parasites, that can cause diseases. While other components of wastewater like water, nutrients, and organic matter can be treated and potentially reused or recycled, pathogens are typically not considered a resource due to their potential to pose health risks if not properly treated and removed from wastewater. The focus is on eliminating or reducing pathogens to prevent the spread of diseases rather than utilizing them as resources.

2. Wastewater generated from laundry and showers are typically referred as:

a. Brown water
b. Greywater
c. Black water
d. Stormwater

Answer :- b. Greywater

Wastewater generated from laundry and showers is typically referred to as greywater. Greywater is the relatively clean wastewater that comes from non-toilet fixtures, such as sinks, showers, bathtubs, and laundry machines. It contains fewer contaminants compared to "black water" (toilet wastewater), and it can be treated and reused for purposes like irrigation, flushing toilets, and other non-potable uses.

3. Identify the correct statements regarding non-point sources of pollution:

Statement I: Non-point pollution sources are usually difficult to monitor and control
in comparison to point sources
Statement II: The individual as well as collective contributions of the non-point
sources are always small.

a. Statement I is correct. while statement Il is incorrect
b. Statement II is correct, while statement I is incorrect
c. Both, statements I and II are correct
d. Both, statements I and II are incorrect

Answer :- a

4. Sort the following in Point and Non-Point sources of pollution:

i. Industrial Effluent
ii. Urban runoff
iii. Discharge from sewage treatment plant
iv. Atmospheric deposition

a. Point Sources – i, iv; Non-Point Sources – ii, iii
b. Point Sources – i. iii: Non-Point Sources – ii. iv
c. Point Sources – ii. iii: Non-Point Sources – i. iv
d. Point Sources – ii, iv; Non-Point Sources – i. iii

Answer :- b

5. Adequate wastewater treatment may result in the recovery of:

a. Reclaimed water
b. Nitrogen and Phosphorous
c. Energy
d. All of the above

Answer :- d

6. Which of these is included in greywater:

a. Toilet flush
b. Urine
c. Kitchen drain
d. All of the above

Answer :- c

7. Identify the correct statements regarding contaminants and pollutants:

Statement I: A pollutant always has harmful effects on the surroundings while a contaminant may or may not have the same.
Statement II: A pollutant may be a component of the system while a contaminant is usually introduced from the outside.

a. Statement I is correct. while statement II is incorrect
b. Statement II is correct, while statement I is incorrect
c. Both, statements I and II are correct
d. Both, statements I and II are incorrect

Answer :- c

8. An example of the direct impact of inadequately managed wastewater on the ecosystem is

a. Eutrophication
b. Climate Change
c. Acid Rain
d. All of the above

Answer :- a

9. Which of this is not a technique for the wastewater treatment?

a. Septic Tank
b. Settling and filtration
c. Dilution with freshwater
d. Biological processing for organic contaminants breakdown

Answer :- c

10. Match the type of effects of improper wastewater management with the related examples:

a. (1)-B, (ii)-A (in1)-C
b. (i)-C. (ii)-A. (iii)-B
c. (i)-C. (ii)-B. (iii)-A
d. (i)-A. (ii)-C. (ini)-B

Answer :- b

11. Which of the following wastewater types are relatively easiest to treat for reuse applications?

a. Municipal sewage
b. Black water
c. Greywater
d. Industrial effluent

Answer :- c

12. Which of the following is more adequate as an example of wastewater reuse in environmental sector?

a. Discharge of treated sewage to agricultural fields
b. Discharge of untreated sewage to a river
c. Treated wastewater recycling for toilet flushing
d. Artificial groundwater recharge with treated sewage

Answer :- d

13. Typically, pollution load is considered highest in:

a. Municipal Wastewater
b. Industrial Wastewater
c. Agricultural Wastewater
d. Stormwater

Answer :- b

14. Which of the following is India’s central government programme does include wastewater or greywater management as one of their components?

a. Swachh Bharat Mission
b. National Mission for Clean Ganga
c. Jal Jeevan Mission
d. All of the above

Answer :- d

15. Identify the CORRECT statements regarding decentralized wastewater management:

a. Recycling of wastewater is comparatively easier
b. Disposal or treatment location may be far away from the origin point
c. Large wastewater treatment plant is needed
d. Long-distances transport of sewage is needed

Answer :- a

Course Name	Wastewater Treatment And Recycling
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NPTEL Wastewater Treatment And Recycling Assignment Answer Week 1 2022

1. Wastewater is considered a potential resource because:

a. 99 % of wastewater comprises water
b. The pollution content of wastewater is very high
c. Wastewater processing to remove contaminants is fairly easy
d. Reclaimed wastewater is readily accepted by consumers for reuse

Answer :- a. 99 % of wastewater comprises water

2. Which of the following is NOT a non-point source of wastewater pollution?

a. Sediment overflow from eroding stream banks
b. Large sanitary landfills
c. Nutrients from livestock and pet waste
d. Irrigation runoff from agricultural lands

Answer :- b. Large sanitary landfills

3. Which of the following is correct for domestic wastewater composition?

a. Greywater + blackwater
b. Greywater + brownwater
c. Brownwater + Urine
d. Heavy greywater + blackwater

Answer :- a. Greywater + blackwater

4. Which of the following is a component of blackwater?

a. Urine
b. Feces
c. Flush water
d. All of the above

Answer :- d. All of the above

5. Identify the CORRECT statement concerning pollutants and contaminants.

a. Pollutants may or may not create harmful effects
b. Pollutants are foreign matter, typically introduced from outside
c. Contaminants may or may not create harmful effects
d. Contaminants are either harmful or poisonous in nature

Answer :- c. Contaminants may or may not create harmful effects

6. Non-point sources of pollution are usually difficult to monitor and control because:

a. Many small diffuse sources from different locations comprise such sources
b. Requires several spatially-distributed monitoring stations
c. Difficult to determine the dispersion rates of pollutant flow rates
d. All of the above

Answer :- d. All of the above

7. Which of the following is NOT an ideal practice of wastewater recycling?

a. Use of treated domestic wastewater for horticulture
b. Discharge of treated domestic sewage into agricultural fields
c. Use of treated industrial effluent in cooling towers
d. Discharge of domestic sewage into irrigation channels

Answer :- d. Discharge of domestic sewage into irrigation channels

8. Degradation of natural aquatic ecosystems due to poor water management may lead to:

a. Eutrophication
b. Dead zones
c. Both a. and b.
d. Putrefaction

Answer :- c. Both a. and b.

9. Which of the following central government schemes is aimed at attaining nationwide cleanliness and hygiene?

a. Swachh Bharat Abhiyan
b. Unnat Bharat Abhiyan
c. Namami Gange
d. None of the above

Answer :- a. Swachh Bharat Abhiyan

10. Constructed wetlands can be used for:

a. Water conservation
b. Preservation of flora and fauna
c. Wastewater treatment
d. All of the above

Answer :- d. All of the above

11. A resource management option to recover energy from wastewater is:

a. Protein feed for livestock
b. Wetland technology
c. Biomass production
d. Agricultural irrigation

Answer :- c. Biomass production

12. A prominent disadvantage of decentralized wastewater management systems is:

a. Higher number of sewage treatment plants
b. Considerably longer duration of sewage transport
c. Difficulty of recycling treated effluent
d. Difficulty related to operations and maintenance

Answer :- a. Higher number of sewage treatment plants

13. A common water-borne disease caused by pathogenic microbes spread via poor wastewater treatment is:

a. Diarrhea
b. Typhoid
c. Cholera
d. All of the above

Answer :- d. All of the above

14. Identify the INCORRECT statements concerning the negative impacts of poor wastewater management.

I. Poor wastewater management is likely to increase the cost of drinking water treatment
II. Increased greenhouse gas emissions are a possible positive impact of poor wastewater management
III. Poor wastewater management may supposedly also result in decreased biodiversity in the long run

a. Only statement I is correct
b. Only statement II is incorrect
c. Statement I and II are incorrect
d. All statements are incorrect

Answer :- b. Only statement II is incorrect

15. Which of the following is NOT true for centralized wastewater management systems?

a. Large wastewater treatment plants are needed in centralized systems
b. Fresher sewage is difficult to obtain in centralized systems
c. Recycling sewage is comparatively easy in centralized systems
d. Centralized systems are preferred for communities with fewer options for effluent reuse.

Answer :- c. Recycling sewage is comparatively easy in centralized systems

NPTEL Wastewater Treatment And Recycling Assignment Answer Week 2 2022

1. Which of the following parameters is NOT used to quantify the municipal wastewater generated from a city/town?

a. Total population of the city/town
b. Per capita water demand
c. Percentage of utilized water reaching the sewers
d. Stormwater received in the city

Answer :- d. Stormwater received in the city

2. The population of a planned city needs to be forecasted for a period of 50 years. Which of the following methods will generally result in the highest design population?

a. Arithmetic increase method
b. Geometric increase method
c. Incremental increase method
d. All these methods will result in the same population estimate

Answer :- b. Geometric increase method

3. The master plan method of population estimation is based on:

a. Population density and zone size
b. Annual birth/death rate and migration rates
c. Growth rate characteristics of living beings within limited space and economic constraints
d. Ratio of local to national population in the past few decades

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Answer :- a. Population density and zone size

4. For design of sewers, estimates of per capita sewage generation is usually based on:

a. Design population
b. Design period
c. Recommended water use and wastewater generation pattern
d. Wear and tear of the sewers

Answer :- c. Recommended water use and wastewater generation pattern

5. Under which of the following population forecasting method, the maximum population of the city is limited by saturation population or carrying capacity?

a. Graphical method
b. Demographic method
c. Ratio method
d. Logistic growth method

Answer :- d. Logistic growth method

6. ‘Population growth is progressively increasing or decreasing’ is an assumption under which of the following method for population forecasting?

a. Incremental increase method
b. Arithmetic increase method
c. Geometric increase method
d. Growth Composition Analysis Method

Answer :- a. Incremental increase method

7. Among the following commercial institutions, the expected generation of wastewater (per user) is highest from:

a. Day Schools/Colleges
b. Hospitals with beds
c. Restaurants
d. Cinema Halls

Answer :- b. Hospitals with beds

8. The population recorded in 2001, 2011, and 2021 for a city was 4.2 lakhs, 5.6 lakhs, and 7.2 lakhs, respectively. Using the arithmetic increase method, the estimated population in the year 2051, would be:

a. 9.6 lakhs
b. 11.7 lakhs
c. 12.2 lakhs
d. 13 lakhs

Answer :- b. 11.7 lakhs

9. For a city with an initial population of 8 lakhs having an annual growth rate of 1.7 %, the estimated approx. population after 10 years would be: (Use the Geometric increase method and find the value to the nearest thousands)

a. 886 thousand
b. 925 thousand
c. 814 thousand
d. 1020 thousand

Answer :- c. 814 thousand

10. The inflow in sewers may exceed the design flow due to:

a. Sprinkling over the roads
b. Households using private water supplies
c. Water used in horticulture and landscaping
d. None of the above

Answer :- b. Households using private water supplies

11. The dry weather flow of a community is usually less than the per capita consumption due to:

a. Evaporation loss
b. Ground seepage
c. Sewer leakage
d. Any or all of the above

Answer :- d. Any or all of the above

12. Identify the CORRECT statement concerning flow estimation in sewer design.

a. The peak factor of a community typically decreases with the increase in population.
b. The minimum design flow in a sewer may vary from 1/3 to 1/2 of the average flow.
c. The maximum hourly flow is equal to one-third of the annual average daily flow.
d. Both a. and b.

Answer :- d. Both a. and b.

13. Typically, the peak factor of a community does NOT depend on:

a. Dry weather flow
b. Population density
c. Site topography
d. Supply hours

Answer :- a. Dry weather flow

14. If the average daily consumption of a town is 1,20,000 m³, the peak hourly demand will be:

a. 5,000 m³/ℎ
b. 7,500 m³/ℎ
c. 15,000 m³/ℎ

Answer :-  15,000 m3/ℎ

15. Determine the approximate quantity of wastewater generated from a city with total daily water consumption of 165 lpcd, if the conversion rate of water to wastewater is 85 % and the total population of the city is 165000.

a. 165 MLD
b. 27 MLD
c. 23 MLD
d. 85 MLD

Answer :- c. 23 MLD

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