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CORK INSTITUTE OF TECHNOLOGY
INSTITIÚID TEICNEOLAÍOCHTA CHORCAÍ
Semester 1 Examinations 2010/
Module Title: Water Engineering
Module Code: CIVL
School: Building & Civil Engineering
Programme Title: BEng (Hons) in Structural Engineering Cert in Environmental & Energy Engineering
Programme Code: CSTRU_8_YR3 / EENEN_8_Y
External Examiner(s): Dr. Mark Richardson, Mr. John O’ Mahony Internal Examiner(s): Dr. J. Harrington
Instructions: Answer Question No. 1 and Two Other Questions
Duration: 2 Hours
Sitting: Winter 2010
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) Discuss water treatment (with the aid of diagrams where appropriate and give one example of a local application in each case ) under the following headings: (i) Raw Water Storage (4 marks) (ii) Screening (6 marks) (iii) Rapid Gravity Filtration (6 marks)
(b) A water treatment plant supplies a community of 20,000 population equivalent (in Ireland) with water. It receives its supply from a nearby river where eutrophication is an issue in the summer months, otherwise the river water quality is generally good. A raw water storage tank is required. Complete the following: (i) Identify the two separate approaches that may be taken to address the eutrophication issue. (2 marks) (ii) Propose a suitable treatment process sequence and present it in flow diagram format clearly showing the individual treatment processes. (4 marks) (iii) Estimate the water demand from the community. (2 marks) (iv) Size the main elements of the treatment plant. (8 marks)
Element Design Parameter Design Parameter Value Radial Flow Tank Retention Time Loading Rate
2 - 4 hours 1 – 1.5 m/hour Upward Flow Sludge Blanket Tank
Retention Time Loading Rate
1 – 2.5 hours 2 – 2.5 m/hour DAF Unit Retention Time
Loading Rate
30 mins. (Floc. Tank) 20 mins. (Flotation Tank) 8 - 14 m/hour Rapid Gravity Filter Filtration Rate 5 – 20 m/hour
Chemical Dosage Conc. (mg/l) Chemical Dosage Conc. (mg/l) Activated Carbon 5 Chlorine 0. Soda Ash 1 Fluoride 0. Alum 25 Lime 5 Polyelectrolyte 0.
(e) If the river in (d) is 250m wide and discharges into a downstream reservoir of capacity 1.5 x 10^7 m^3 , find the design life expectancy of this reservoir assuming the sediment to have a porosity of 0.3. (4 marks)
Q4. (a) Discuss the following: (i) Types of River Water Pollution (4 marks) (ii) EU Water Framework Directive (8 marks) (iii) Wastewater Reuse and Recycling (6 marks)
(b) (i) Determine the minimum capacity of a storage reservoir located in a river valley and which is required to maintain a constant water supply for a population equivalent of 150,000 in Ireland given the following monthly mean inflow values (in m^3 /month):
Month 1 2 3 4 5 6 7 8 9 10 11 12 Inflow (x10^6 )
(7 marks) (ii) Check your answer using an alternative approach. (4 marks) (iii) Comment on the limitations associated with this storage analysis approach. (3 marks) (iv) If the reservoir also provides some water discharge to a downstream river comment on the potential impacts of the reservoir on sediment transport in the river downstream of the reservoir. (2 marks)
EQUATIONS
Open Channel Flow
Chezy Eqn.: v C mS 0
Manning Eqn.: 01 /^2
2 / 3 v mn S 1 / 3 2
2
gB dc Q
Sediment Transport
Vertical Suspended Sediment Profile: ku^ *
v r
r r
s Y y
Y y y
y C
C (^)
Shear Velocity: u (^) * gmS 0
Stoke’s Law: 18 ^
(^2) vs ^ gd p
