Wastewater Treatment And Reuse I Question Paper

Wastewater Treatment And Reuse I

Course:Bachelor Of Science In Water And Environmental Engineering

Institution: Kenyatta University question papers

Exam Year:2009

KENYATTA UNIVERSITY
UNIVERSITY EXAMINATIONS 2009/2010
FIRST SEMESTER EXAMINATION FOR THE DEGREE OF BACHELOR OF
SCIENCE (WATER ENGINEERING)

SET 426:
WASTEWATER TREATMENT AND REUSE I

DATE: Monday, 28th December, 2009

TIME: 11.00 a.m. – 1.00 p.m.
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INSTRUCTIONS:
This paper contains FIVE questions. Attempt THREE questions only.
Question 1
a) Describe
the
principle
involved in the design and construction of the following:
i)
Grit chamber
ii)
Percolating filter
iii)
Skimming tank
(10 marks)
b)
Design an oxidation pond for treating sewage from a group of 10,000 persons at
sewage flow rate of 200 litres per capita per day. The BOD of applied sewage
may be taken as 300 mg/l and the hydraulic loading as 300 kg per hectrare per
day.
Assume operational depth of 1.2m.

(10 marks)

Question 2
a)
Compare and contrast septic tank and Imhoff tank in scope, function and
performance.
(10
marks)
Page 1 of 2

b)
A high rate activated sludge plant with an aeration tank of volume 175m3 has an
applied load of 1.5 Mld with an average BOD of 250 mg/l and suspended solids
of 160 mg/l. the mixed liquor in the aeration tank is held at a concentration of
4,000 mg/ll of suspended solids. Based on this information, calculate:
i)
BOD loading (kg/ha.m)
ii)
BOD loading as F/M ratio
iii)
Aeration period (hrs)
iv)
Sludge age (days)
(10 marks)

Question 3
a)
Distinguish between low rate trickling filters and high rate filters (10 marks)
b)
Differentiate between aerobic and anaerobic treatment of sewage, giving major
end products. Name one treatment method in each category.
(10 marks)

Question 4
With the help of a neat flow diagram of the activated sludge process, describe the
working of the activated sludge
plant. (20
marks)

Question 5
a)
Discuss the mechanism of working of a stabilization pond.
(10 marks)
b)
A rectangular sedimentation basin is to be designed for a flow of 4.5 million litres
a day using a 2 : 1 length to width ratio, an overflow rate of 0.00023m3s-1 and a
detention time of 3 hours. What are the dimensions of the basin? (10 marks

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