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Waste Water Treatment (Open,Distance &Amp;E-Learning) Question Paper
Waste Water Treatment (Open,Distance &Amp;E-Learning)
Course:Bachelor Of Science (Water & Environmental Engineering)
Institution: Kenyatta University question papers
Exam Year:2011
KENYATTA UNIVERSITY
UNIVERSITY EXAMINATIONS 2010/2011
OPEN, DISTANCE AND E-LEARNING
EXAMINATION FOR THE DEGREE OF BACHELOR OF SCIENCE (WATER ENGINEERING)
SET 426:WASTE WATER TREATMENT
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DATE: SATURDAY 9TH JULY 2011 TIME: 8.00 A.M. – 10.00 AM.
INSTRUCTIONS
This paper contains FIVE questions. Attempt THREE questions only.
Question 1
a)Differentiate between aerobic and anaerobic treatment of wastewater, giving major
end products. (10 marks)
b)Waste water is flowing at 4.5 million litres per day from a primary clarifier to a
standard rate trickling filter. The 5-day BOD of the influent is 160mg/l. The organic
loading and surface loading for the wastewater are 160 g/m3 day and 200 l/m2. day.
respectively.
i)Determine the volume of the filter and its depth.
ii)Calculate the efficiency of the filter plant. (10 marks)
Question 2
a)Discuss the mechanism of working of a stabilization pond. (10 marks)
b)A single filter is to treat a flow of 3.79 million litres per day of raw waste water with BOD of 240 mg/l. The design is for a loading of 11086 kg of BOD in the raw
wastewater per hectare metre, and recirculation ratio is 1. What will be the strength
of the effluent? Assume that 30% of BoD is removed in the primary clarifier.(10 marks)
Question 3
A town having a population of 30,000 persons is producing the following sewage:
i)Domestic sewage at 102 litres per caput per day having 200 mg/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 tank removes 35% of BOD. Allow an organic
loading of 10,000 kg / ha- 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)
Question 4
a)Discuss how a standard rate trickling filter differs from a high rate trickling filter.
(10 marks)
b)A grit chamber is designed to remove particles with a diameter of 0.2 mm and
specific gravity 2.65. Settling velocity for these particles is assumed to range from
0.016 to 0.022 ms-1 , depending on their shape factor. A flow through velocity of a
0.3 ms-1 is maintained by a proportioning weir. Determine the channel dimensions
for a maximum wastewater flow of 10,000 m3/day. Assume the depth of flow is 1m.(10 marks)
Question 5
a)Describe the principles involved in the design and construction of:
i)Septic tank
ii)Imhoff tank (10 marks)
b)A rectangular sedimentation basin is to be designed for a flow of 4.5 million litres a
day using 2:1 length to breadth ratio, an overflow rate of 0.000213 m3s-1 and a
detention time of 3 hours. What are the dimensions of the basin? (10 marks)
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