NPTEL Water and waste water treatment Week 2 Assignment Answers 2024

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NPTEL Water and waste water treatment Week 2 Assignment Answers 2024

1. In a CSTR, which assumption is made about the concentration in the reactor?

  • It varies with distance in the reactor.
  • It is constant and equal to the influent concentration.
  • It is constant and equal to the effluent concentration.
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2. Compared to CSTRs, plug flow reactors are typically __ in their removal efficiency for a given compound.

  • Less efficient
  • More efficient
  • Equally efficient
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3. The fundamental mass balance equation relates the rate of accumulation of a compound to its __.

  • Rate of formation
  • Rate of removal
  • Both (a) and (b)
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4. Nutrient enrichment (eutrophication) in water bodies can lead to:

  • Increased biodiversity and fish populations
  • Harmful algal blooms and oxygen depletion
  • Improved water clarity and recreational value
  • None of the above
Answer :- 

5. What is the primary concern associated with high nitrate levels in drinking water?

  • Algal blooms and taste/odor issues
  • Increased corrosion of water pipes
  • Blue baby syndrome in infants
  • All of the above
Answer :- 

6.

NPTEL Water and waste water treatment Week 2 Assignment Answers 2024

What can you infer from the figure above?

  • At constant k, higher rates of removal of contaminant are observed in plug flow reactor.
  • At constant k, higher rates of removal of contaminant are observed in CSTR.
  • At constant k, higher rates of removal of contaminant are observed in batch reactor.
  • None of the above
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7. Sewer carrying wastewater containing a compound ‘X’ enters a nearby stream as shown in the figure below.

NPTEL Water and waste water treatment Week 2 Assignment Answers 2024

Concentration of X in WW (wastewater) is 250 mg/L. The stream has a naturally occurring X concentration of 50 mg/L. If the sewer flow rate is 0.5 m3/sec and the stream flowrate is 2 m3/sec, what is the concentration of X (mg/L) in the stream after the discharge point? Assume it to be a ‘steady state conservative’ system.

Answer :- 

8. The flow rate through a reactor is Q m3/h. The concentration (in mg/L) of a compound in the inlet and outlet are Cin and Cout, respectively. The compound degradation follows first order kinetics. The mixing condition of the reactor can be varied such that the reactor becomes either a completely mixed flow reactor (CMFR) or a plug-flow reactor (PFR). The length of the reactor can be adjusted as per the mixing conditions to L(CMFR)  or L(PFR) while keeping the cross-section of the reactor constant. Assuming steady state, for Cout/Cin = 0.8, the value of L(CMFR)/L(PFR) (round off to 2 decimal places) is

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