Download UNIVERSITY OF NAIROBI UNIVERSITY EXAMINATIONS 2005

UNIVERSITY OF NAIROBI
UNIVERSITY EXAMINATIONS 2005/2006
FIFTH YEAR EXAMINATIONS FOR THE DEGREE OF BACHELOR
OF SCIENCE IN ENVIRONMENTAL AND BIOSYSTEMS
ENGINEERING
FEB 517: DESIGN OF WASTE MANAGEMENT SYSTEMS
DATE: 22ND FEBRUARY 2006
TIME: 8.30 A.M. - 10.30 A.M.
INSTRUCTIONS
(i)
(ii)
Attempt question one and any other 3 questions.
You are allowed upto 5 minutes before the examination starts to read the question
paper.
(iii)
Use of notes or textbooks is not permitted in the examination room.
(iv)
Provide brief but precise answers.
(v) Credit will be given for explaining your answers, reasoning and calculations.
(vi)
You will require a scientific calculator.
(vii) If any doubt exists as to the interpretation of any question, the candidate is urged to
state on the answer paper a statement of any assumptions made.
(viii) Marks for each correct answer are given.
(ix)
Direct any other questions you may have regarding the regulations for conducting
this examination to the supervisors present.
(x)
Good luck!
QUESTION ONE
The Kyoto Protocol came into effect in the year 2005 as the international treaty on combating
climate change, which is caused by outdoor air pollution.
(a) Briefly explain how the Green House Effect arises (5 marks)
(b) Name the main Green House Gases covered under the Kyoto Protocol, and explain
why water vapour is not among them. (5 marks)
(c) Describe how carbon sequestration can be used to mitigate climate change (5 marks).
(d) Briefly discuss the main limitations of the Kyoto Protocol. (10 marks)
QUESTION TWO
(a) Explain the meaning of the following terms as used to describe noise pollution:
(10 marks)
(i) Noise directionality factor
(ii) Noise power level
(b)
Emissions of odours from industrial activities is one of the most objectionable
environmental pollution. Name 5 main methods used to manage odours. (5 marks)
(c) Indoor air pollution is a major problem in Kenya. Describe how you would set up a
program to manage Indoor Air Pollution at a workplace.
(10 marks)
QUESTION THREE
(a)
Distinguish between the following pairs of terms as used in wastewater engineering:(6 marks)
(i)
Biochemical Oxygen Demand (BOD) and Chemical Oxygen Demand (COD).
(ii)
Total Suspended Solids (TSS) and Volatile Suspended Solids.
(iii)
Solids Retention Time (SRT) and Hydraulic Retention Time (HRT).
(b) Using a sketch of the Monod's curve explain how you would estimate the following
design parameters of a bio-reactor;(i)
The waste conversion efficiency.
(ii)
The bio-reactor size.
(6 marks)
(c) The BOD in a bio-reactor was found to be 300mg/litres 2 days after the
commencement of digestion, and 200mg/l 3 days later. What should be the bioreactor
mean retention time to obtain a waste conversion efficiency of 90%? (6 marks)
(d) How would you estimate the MRT of a continuous flow waste treatment pond? What
are the main factors that would limit the accuracy of your estimated parameters?
(6 marks)
QUESTION FOUR
Wastewater treatment can be approximated using first order chemical process kinetics.
(a) What are the main assumptions made in this approximation?
(2 marks)
(b) How can the rate constant for the process be estimated?
(3 marks)
(c) The rate of reaction in a batch waste water bio-reactor can be described by the
following relationship:
rc
=
KC
P+C
K - Maximum reaction rate, mg/litre
C - Substrate concentration, mg/litre
P - half-saturation castons, mg/litre
Derive an equation that can be used to predict the reduction of substrate concentration
with time.
(5 marks)
(d) Wastewater is to be treated in the reactor. Assuming that the reaction has a reaction
rate equal to 0.15 days, determine the flowrate that can be treated if the reactor has a
volume of 20m3 and 98% treatment efficiency is required?
(15 marks)
QUESTION FIVE
Municipal solid waste management is a major problem in the city of Nairobi.
(a)
In your view, what can be done to reduce solid waste generation in the city?
(6 marks)
(b) What are the main factors limiting solid waste recycling? (6 marks)
(c) What are the main disadvantages of waste incineration? (6 marks)
(d)
Briefly describe the main considerations in the design of a bio-gas plant? (7 marks)