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CORK INSTITUTE OF TECHNOLOGY
INSTITIÚID TEICNEOLAÍOCHTA CHORCAÍ
Autumn Examinations 2008/
Module Title: Water Engineering
Module Code: CIVL 6027
School: Civil, Structural and Environmental Engineering
Programme Title: Bachelor of Engineering in Civil Engineering – Stage 2
Programme Code: CCIVL_7_Y
External Examiner(s): Mr. J. Lapthorne, Mr. J. Kindregan Internal Examiner(s): Mr TL O’Driscoll, Mr P Kennedy
Instructions: Answer four questions
Duration: 2 Hours
Sitting: Autumn 2009
Requirements for this examination:
Note to Candidates: Please check the Programme Title and the Module Title to ensure that you have received the correct examination paper. If in doubt please contact an Invigilator.
Q1. (a) Explain the mechanism of biological treatment of wastewater in a municipal wastewater treatment plant using trickling filters. (8 marks) (b) A wastewater treatment plant is required for a town with a population of 20,000PE. Primary treatment is included, and removes 30% of the BOD. Assume a hydraulic load of 220 L/PE/day and BOD load of 60gBOD/PE/day. (i) Calculate the total plan area required for the primary settlement tanks. Assume an upward flow velocity of 1.5 m^3 /m^2 /hr. (4 marks) (ii) Calculate the plan area required for a conventional activated sludge system (0.56 kg BOD/m^3 /day). Design the activated sludge system with a depth of 4m. (4 marks) (iii) Calculate the F/M ratio of the activated sludge tank if the MLSS is 3000 mg/l. (4 marks) (iv) The wastewater treatment plant discharges to a local river. The BOD 5 level in the river, upstream of the discharge point is 1.0 mg/L. The minimum flow rate in the river during summer is 2 m^3 /s. If the wastewater is treated to the EU 25/35 standard, what is the BOD 5 concentration in the river, downstream of the discharge point? (5 marks)
Q2. (a) A 15,000 PE town receives it’s water supply from a water supply reservoir 15km away. The reservoir has a top water level of 73 mOD, while the outlet level at the town is 28mOD. The 300 mm diameter rising main has a friction factor of 0.002. Peak water demand is calculated based upon a peak flow factor of 3. The minimum water pressure required for domestic supply is 2 bar. Calculate the following: (i) Maximum discharge in the pipeline (Litres/sec) (5 marks) (ii) Total pressure in the pipeline at times of peak flow (bar) (7 marks) (iii) If a new industry is proposed for the town, which requires an average water supply of 1000 m^3 /day, will the existing 300mm pipeline be adequate. If not, what size pipeline will be required. (7 marks) (b) Determine the static water pressure (bar) and maximum moment (in KNm/meter length of wall) at the base of an open 6m deep reinforced concrete tank, which is filled to the top with water. (6 marks)
Q5. (a) The following table shows the monthly river inflow to a storage reservoir over a one year period. The demand on the system is 39 x 10 5 m^3 /month.
Month Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec River Inflow (x10 5 m^3 /month)
(i) Calculate the minimum volume of water that must be stored in the reservoir, prior to month 1, to ensure an adequate water supply at all times during the year. (5 marks)
(ii) Calculate the minimum storage capacity of the reservoir. (5 marks)
(b) Calculate the magnitude and direction of the force on a 90 degree bend in a 150mm diameter pipeline, where the flow through the pipeline is 50 litres per second, and pipeline pressure is 4 bar. (10 marks) (c) Describe at least two common joints used for connection of pressure pipes. Use sketches to support your answer. List the advantages and disadvantages of each system. (5 marks)
Figure A
