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Set 426: Wastewater Treatment And Reuse I Question Paper

Set 426: Wastewater Treatment And Reuse I

Course:Water Engineering

Institution: Kenyatta University question papers

Exam Year:2008

KENYATTA UNIVERSITY
UNIVERSITY EXAMINATIONS 2007/2008
INSTITUTE OF OPEN LEARNING
SECOND SEMESTER EXAMINATION FOR THE DEGREE OF BACHELOR
OF SCIENCE (WATER ENGINEERING)
SET 426: WASTEWATER TREATMENT AND REUSE I

DATE: Monday 7th July, 2008 TIME: 3.30 p.m. – 5.30 p.m.
________________________________________________________________________
INSTRUCTIONS
This paper contains FIVE questions. Answer THREE questions only.

Question 1
Describe the principles involved in the design and construction of the following:
(a)
Imhoff tank
(b)
Septic tank
(c)
Percolating filter

[20 marks]

Question 2
A town having a population of 30,000 persons is producing the following sewages:
(i)
Domestic sewage at 120 litres per caput per day having 200mg/l of BOD.
(ii)
Industrial sewage at 300,000 litres per day having 800 mg/l of BOD.
Design high rate single stage trickling filters for treating the above sewage.
Assume that the primary sedimentation removes 35% of BOD. Allow an organic loading
of 10,000 kg/ha-m/day (excluding recirculated sewage).
The recirculation ratio is 1.0, and the surface loading should not exceed 170 ML/ha/day
(excluding recirculated sewage).
Finally, determine the efficiency of the filter and the BOD of the effluent.

[20 marks]

2
Q
Question 3

What is meant by activated sludge? Describe with sketcher the treatment of sewage by
activated sludge process. Mention the advantages and disadvantages of this system.

[20 marks]
Question 4
(a)
Distinguish between low rate (standard) trickling filters and high rate filters.

[10 marks]
(b)
Design a suitable rectangular sedimentation tank for treating the sewage from a
city, provided with an assured public water supply system, with a maximum daily
demand of 12 million litres per day.
Assume the following:
(i)
80% of water supplied to the city becomes sewage
(ii)
Detention period in the tank is 2 hours
(iii)
The flow velocity through the tank is 0.3m/minute
(iv)
The effective depth of the tank is 3m.

[10 marks]
Question 5
Differentiate between aerobic and anaerobic treatment of sewage, giving major end
products. Name one treatment method in each category.

[20 marks]

………………

Set 426: Wastewater Treatment And Reuse I Question Paper

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