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Wastewater Engineering Exam: Structural Engineering, CIVL8022, Summer 2010, Exams of Business Management and Analysis

The instructions and questions for the wastewater engineering examination held at cork institute of technology in summer 2010 for the bachelor of engineering (honours) in structural engineering programme. The examination covers various topics related to wastewater treatment, including primary settlement, activated sludge systems, anaerobic digestion, stormwater sewers, and sustainable urban drainage systems.

Typology: Exams

2012/2013

Uploaded on 04/02/2013

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CORK INSTITUTE OF TECHNOLOGY
INSTITIÚID TEICNEOLAÍOCHTA CHORCAÍ
Semester 2 Examinations 2009/10
Module Title: Wastewater Engineering
Module Code: CIVL8022
School: Building and Civil Engineering
Programme Title: Bachelor of Engineering (Honours) in Structural Engineering
Programme Code: CSTRU_8_Y3
EENEN_8_Y1
External Examiner(s): Dr. MG Richardson
Mr. J OMahony
Internal Examiner(s): Mr TL O’Driscoll
Instructions: Answer any four questions.
Duration: 2 hours
Sitting: Summer 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.
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CORK INSTITUTE OF TECHNOLOGY

INSTITIÚID TEICNEOLAÍOCHTA CHORCAÍ

Semester 2 Examinations 2009/

Module Title: Wastewater Engineering

Module Code: CIVL

School: Building and Civil Engineering

Programme Title: Bachelor of Engineering (Honours) in Structural Engineering

Programme Code: CSTRU_8_Y

EENEN_8_Y

External Examiner(s): Dr. MG Richardson

Mr. J O’Mahony

Internal Examiner(s): Mr TL O’Driscoll

Instructions: Answer any four questions.

Duration: 2 hours

Sitting: Summer 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 treatment plant is proposed for a town with a population equivalent (PE) of 10,000.

Assume for this plant that 1PE equates to 60g BOD/day and 220L/PE/day. Wastewater is

to be treated to the 25/35 standard. Suspended solids concentration at the inlet to the

works is 200 mg SS/L.

The treatment plant is to be designed to include primary settlement, followed by an

activated sludge system.

(a) Calculate the plan area and depth of the primary sedimentation tanks and the primary

sludge production rate (m

3 /day), given the following design parameters:

  • Average overflow rate = 1.5 m^3 /m^2 /hr
  • Average hydraulic retention time, 2.5 hours
  • BOD removal rate = 25%
  • Suspended solids removal rate 50%
  • Waste primary sludge concentration 2% solids (4 marks)

(b) Draw a sketch of this primary treatment system, including a description of all

elements included. (4 marks)

(c) Calculate the volume of the aeration tanks, given the following design parameters:

  • Kinetic yield coefficient, Y = 0.6kg cells/kg BOD 5
  • Endogenous decay coefficient, kd = 0.05 day -
  • MLSS (X) = 3000mg/L
  • Mean cell residence time = 10 days
  • Settled sludge concentration = 8000mg/L

X = θc.Y(S o -S) / θ (1+kdθc)

(4 marks)

(d) Calculate the mean hydraulic retention time.

(e) Calculate the F/M ratio for the system. (4 marks)

(f) Calculate the average volume of sludge to be wasted each day.

Qw = MLSS(Va +VC) / (sludge age * S w)

(4 marks)

(g) Describe how a sequencing batch reactor system works, including possible mixing

and aeration systems, and any other controls. What are the advantages of the SBR

system over other types of systems? (5 marks)

8. Minimum and maximum velocities are 1m/s and 3 m/s respectively, for pipe

flowing full.

9. For pipeline design, see Attachments 1: Colebrook White Chart with Ks = 0.6 and

pipe design sheet.

(15 marks)

(b) A Sustainable Urban Drainage System (SUDs) is required for the site as per local

authority guidelines. This requires the first 5mm of rainfall to be intercepted and drained

on-site using infiltration systems. Calculate the total capacity of these infiltration

systems. (3 marks)

A stormwater attenuation system must then be installed to retain the 30 year return period

storm. Calculate the volume of the stormwater attenuation pond required, for a 12 hour

storm duration. The maximum permitted runoff from the site shall be limited to QBAR.

Average annual rainfall for the site is 1100mm. Soil index for the site is 0.37. Include

climate change factor of 1.1.

(7 marks)

QBAR = 0.00108AREA0.89^ SAAR 1.17^ SOIL2.

1 year factor = 0,

30 year factor = 2.

MHE

IL 40.731mOD

Pipe 2.

Pipe 1.

Pipe 1. Pipe 1.

MH A

GL 43.126mOD

MH B

GL 42.654mOD

MH D

GL 41.652mOD

MH C

GL 43.698mOD

Figure 1

Page 7 of 10

Table 2PipeNr

Pipelength(m)

Fall(m)

Slope(m/m)

Diameter

(mm)

Pipefull Velocity

(m/s)

Time

of Entry(mins)

Time

of Flow(mins)

Time

of Conc(mins)

TotalArea(ha)

ImpArea(ha)

TotalImpArea(ha)

Rain (mm/hr)

Q

(L/s)

Capacity

(L/s)

UpstreamIL (mOD)

D/stream IL

(mOD)

Q4(a) A series of annual maximum peak flows are available for a river over a 20 year period as

shown in Table 3 as shown. Calculate the 5 and 10 year return period flows from these

figures. Assume linear interpolation between calculated return periods. (10 marks)

Year Flow (cumecs)

Table 3: Annual maximum peak flows in river.

Weibull equation: Quantile (q) = m/(n+1)

Probability = 1/q