1. [Flow equalisation, effect of equalisation on BOD mass loading rate]. Consider the volumetric flowrates and BOD concentrations given in the following table: Time period midnight-1am 1am-2am 2am-3am 3am-4am 4am-5am 5am-6am 6am-7am 7am-8am 8am-9am 9am-10am 10am-11am 11am-12 12-1pm 1pm-2pm 2pm-3pm 3pm-4pm 4pm-5pm 5pm-6pm 6pm-7pm 7pm-8pm 8pm-9pm 9pm-10pm 10pm-11pm 11pm-midnight Average flowrate during time period (m³/s) 0.275 0.220 0.165 0.130 0.105 0.100 0.120 0.205 0.355 0.410 0.425 0.430 0.425 0.405 0.385 0.350 0.325 0.325 0.330 0.365 0.400 0.400 0.380 0.345 Average BOD concentration during time period (mg/L) 150 115 75 50 45 60 90 130 175 200 215 220 220 210 200 190 180 170 175 210 280 305 245 180 a) Calculate the equalised average flowrate for the day (flowrate fed to downstream processes). [Ans: 0.307 m³/s = 1105.2 m³/hr] b) Using the graphical method, (use spreadsheet and/or graph paper), calculate the inline storage volume required to equalise the flow rate (flowrate equalisation volume) [Ans: 4110 m³] c) Determine the dampening effect of flow equalisation on BOD mass loading.
1. [Flow equalisation, effect of equalisation on BOD mass loading rate]. Consider the volumetric flowrates and BOD concentrations given in the following table: Time period midnight-1am 1am-2am 2am-3am 3am-4am 4am-5am 5am-6am 6am-7am 7am-8am 8am-9am 9am-10am 10am-11am 11am-12 12-1pm 1pm-2pm 2pm-3pm 3pm-4pm 4pm-5pm 5pm-6pm 6pm-7pm 7pm-8pm 8pm-9pm 9pm-10pm 10pm-11pm 11pm-midnight Average flowrate during time period (m³/s) 0.275 0.220 0.165 0.130 0.105 0.100 0.120 0.205 0.355 0.410 0.425 0.430 0.425 0.405 0.385 0.350 0.325 0.325 0.330 0.365 0.400 0.400 0.380 0.345 Average BOD concentration during time period (mg/L) 150 115 75 50 45 60 90 130 175 200 215 220 220 210 200 190 180 170 175 210 280 305 245 180 a) Calculate the equalised average flowrate for the day (flowrate fed to downstream processes). [Ans: 0.307 m³/s = 1105.2 m³/hr] b) Using the graphical method, (use spreadsheet and/or graph paper), calculate the inline storage volume required to equalise the flow rate (flowrate equalisation volume) [Ans: 4110 m³] c) Determine the dampening effect of flow equalisation on BOD mass loading.
Introduction to Chemical Engineering Thermodynamics
8th Edition
ISBN:9781259696527
Author:J.M. Smith Termodinamica en ingenieria quimica, Hendrick C Van Ness, Michael Abbott, Mark Swihart
Publisher:J.M. Smith Termodinamica en ingenieria quimica, Hendrick C Van Ness, Michael Abbott, Mark Swihart
Chapter1: Introduction
Section: Chapter Questions
Problem 1.1P
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![1. [Flow equalisation, effect of equalisation on BOD mass loading rate]. Consider the volumetric
flowrates and BOD concentrations given in the following table:
Time period
midnight-1am
1am-2am
2am-3am
3am-4am
4am-5am
5am-6am
6am-7am
7am-8am
8am-9am
9am-10am
10am-11am
11am-12
12-1pm
1pm-2pm
2pm-3pm
3pm-4pm
4pm-5pm
5pm-6pm
6pm-7pm
7pm-8pm
8pm-9pm
9pm-10pm
10pm-11pm
11pm-midnight
Average flowrate during Average BOD concentration
time period (m³/s)
during time period (mg/L)
0.275
0.220
0.165
0.130
0.105
0.100
0.120
0.205
0.355
0.410
0.425
0.430
0.425
0.405
0.385
0.350
0.325
0.325
0.330
0.365
0.400
0.400
0.380
0.345
150
115
75
50
45
60
90
130
175
200
215
220
220
210
200
190
180
170
175
210
280
305
245
180
a) Calculate the equalised average flowrate for the day (flowrate fed to downstream processes).
[Ans: 0.307 m³/s = 1105.2 m³/hr]
b) Using the graphical method, (use spreadsheet and/or graph paper), calculate the inline
storage volume required to equalise the flow rate (flowrate equalisation volume)
[Ans: 4110 m³]
c) Determine the dampening effect of flow equalisation on BOD mass loading.
Assume perfect mixing in the equalisation basin/tank
For step-by-step guidance for part (b) and (c): (see back sheet)
Problem text, table, and step-by step guidance adapted/taken from "Example 3-10, pages 245-250,
Metcalf and Eddy, Wastewater Engineering, Treatment and Resource Recovery, 5th ed, vol 1, 2014"](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2Fe25ad2c4-6e03-4d3e-b445-5962fa3ab3d6%2Fca2bd2fb-29d6-406e-a518-60be7404ff21%2Fcgjk1ti_processed.png&w=3840&q=75)
Transcribed Image Text:1. [Flow equalisation, effect of equalisation on BOD mass loading rate]. Consider the volumetric
flowrates and BOD concentrations given in the following table:
Time period
midnight-1am
1am-2am
2am-3am
3am-4am
4am-5am
5am-6am
6am-7am
7am-8am
8am-9am
9am-10am
10am-11am
11am-12
12-1pm
1pm-2pm
2pm-3pm
3pm-4pm
4pm-5pm
5pm-6pm
6pm-7pm
7pm-8pm
8pm-9pm
9pm-10pm
10pm-11pm
11pm-midnight
Average flowrate during Average BOD concentration
time period (m³/s)
during time period (mg/L)
0.275
0.220
0.165
0.130
0.105
0.100
0.120
0.205
0.355
0.410
0.425
0.430
0.425
0.405
0.385
0.350
0.325
0.325
0.330
0.365
0.400
0.400
0.380
0.345
150
115
75
50
45
60
90
130
175
200
215
220
220
210
200
190
180
170
175
210
280
305
245
180
a) Calculate the equalised average flowrate for the day (flowrate fed to downstream processes).
[Ans: 0.307 m³/s = 1105.2 m³/hr]
b) Using the graphical method, (use spreadsheet and/or graph paper), calculate the inline
storage volume required to equalise the flow rate (flowrate equalisation volume)
[Ans: 4110 m³]
c) Determine the dampening effect of flow equalisation on BOD mass loading.
Assume perfect mixing in the equalisation basin/tank
For step-by-step guidance for part (b) and (c): (see back sheet)
Problem text, table, and step-by step guidance adapted/taken from "Example 3-10, pages 245-250,
Metcalf and Eddy, Wastewater Engineering, Treatment and Resource Recovery, 5th ed, vol 1, 2014"
Transcribed Image Text:1.b)
• Step 1
The first step is to develop a cumulative volume curve of the wastewater flowrate expressed in
cubic meters. The cumulative curve is obtained by summing the hourly values to obtain a
cumulative volume curve.
Tutorial 4-Step-by-Step guidance
Step 2
The second step is to prepare a plot of the cumulative volume. Examples of cumulative
volume curves (also called inflow mass curves) are shown in the diagram below taken from
Metcalf and Eddy. The slope of the line drawn from the origin till the end point of the
cumulative volume curve represents the average flow rate (equalised flowrate) for the entire
day!
M
Average
daily
flowrate
Inflow
mass
diagram
N
Required
equalization
volume
Inflow
mass
diagram
M
Time of day
Average
daily
flowrate
N
Сос
Required
equalization
volume
(a) Flowrate pattern A
(b) Flowrate pattern B
Figure 1 - Schematic examples of cumulative volume plots
. Step 3
The required storage volume is determined by drawing a line (or lines) that is (are) tangent to
cumulative volume curve and parallel to the average flow rate line (see examples in figure 1).
The required storage volume is given by the vertical distance from the tangency point to the
average flow rate line (pattern A in Figure 1) or to the other tangent line (pattern B in Figure 1).
1.c) There are different calculation methods to do this, but the simplest way to perform the
necessary calculations is to start with the time period when the equalisation basin/tank is empty.
In this particular problem the equalisation basin is empty at 8am (tangency point) hence the
calculations should start at 8am.
Vsc = Vsp + Vic-Voc
With: Vsc = volume in basin at the end of current period;
Vsp = volume in basin at the end of previous period;
Vie Inflow volume during current period;
Voc = Outflow volume during current period (= equalized flow rate x time)
• Step 1
The first step is to compute the volume in the equalisation basin at the end of each time period
by using the following formula:
Vic. Cic+Vsp Csp
= Vic+Vsp
M
. Step 2
The second step is to compute the average concentration leaving the storage basin during
each time period by using the following formula:
With: Coc = average BOD concentration in the outflow from storage basin during current time
period;
Cic= average BOD concentration in the inflow wastewater volume;
Csp = average BOD concentration in the storage basin at the end of the previous time
period;
. Step 3
The third step is to compute the hourly mass loading using the following:
jkg. (Coc. 9/m³). Equalised flowrate (
Mass loading rate (=
1000
2
• Step 4
The dampening effect of flow equalisation on BOD mass loading can be seen by plotting the
unequalised and equalised hourly mass loadings.
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VIEWStep 4: (c)Determine the dampening effect of flow equalization on BOD mass loading
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