Task brief
There is a requirement to design a new water treatment plant to replace an existing one in the West midlands area. The water treatment plant must provide treated water for drinking and domestic purposes for the community shown in Table 1.
|
Property type
|
Number
|
|
5-bedroom house
|
650
|
|
4-bedroom house
|
825
|
|
3-bedroom house
|
2,000
|
|
2-bedroom house
|
4250
|
|
4-bedroom flat
|
825
|
|
3-bedroom flat
|
2,000
|
|
2-bedroom flat
|
4,250
|
|
1-bedroom flat
|
17,500
|
|
Schools
|
10
|
|
Hospitals
|
2
|
|
Hotels
|
5
|
|
Offices
|
1 complex
|
|
Commercial
|
2 shopping centres
|
Table 1: Total properties to be served
You are required to carry out a basic desk study and provide the following information:
1. Based on the average property occupancy rate in this region, estimate the current population of this community
2. Table 2 shows the growth information of the city where this community is. Use this growth figure and estimate the total population for years 2025, 2035 and 2045. You must use at least three methods to calculate this and discuss your preferred method, explaining your reasons for this choice.
|
Year
|
Population (capita)
|
|
1981
|
110,500
|
|
1991
|
119,500
|
|
2001
|
125,700
|
|
2010
|
130,800
|
|
2015
|
136,500
|
Table 2: Population growth
3. Estimate the current and future water demand for years 2025, 2035 and 2045.
4. Make any necessary assumptions to support your solution and justify them.
5. Show all steps/procedures of your calculations
Task 1
Task brief
1. You are required to design a two-cell intake tower to extract raw water for the treatment plant mentioned in task 1. The tower must have three ports at three different elevations in each cell. Each port must be able to deliver the design flow rate for year 2045 calculated in task 1. It is also required to install a bar rack with a clear opening of 5 cm and a bar 1.5 cm in width. Determine the area of each port opening taking into account the area occupied by the bar rack. Assuming that there is an adequate water depth and using the design criteria for intake towers, draw your design.
2. Determine the diameter of a concrete pipe to transport the raw water from the intake tower (described in 1) to a low-lift pump station on shore. The maximum flow rate is assumed to be 1.5 Q (for year 2045). The length of the pipe is 250m and the total head loss in the system is estimated to be 1.25m. Your design could include one single pipe or multiple pipes.
Task 2
Task brief
1. With the aid of diagrams, explain the practical method used to find the optimum pH level and coagulant dose.
2. For the following sets of data obtained from a jar test, determine the optimum pH level, Alum dose and coagulation type (sweep or adsorption).
|
|
Jar numbers
|
|
|
1
|
2
|
3
|
4
|
5
|
6
|
|
pH
|
6
|
6.5
|
7
|
7.5
|
8
|
8.5
|
|
Alum dose (mg/L
|
12
|
12
|
12
|
12
|
12
|
12
|
|
Turbidity (NTU)
|
11
|
7
|
5.5
|
5.3
|
6
|
7
|
|
|
|
Jar numbers
|
|
|
|
|
1 1
|
2 1 3 1 4 1
|
5 1
|
6
|
|
pH
|
|
Optimum pH from Table 1
|
|
|
|
Alum dose (mg/L
|
8
|
|
12
|
16
|
21
|
|
24
|
|
26
|
|
Turbidity (NTU)
|
6.5
|
|
5.3
|
4
|
3.7
|
|
5.3
|
|
6
|
Table 2: Optimum Alum dose (mg/L)
3. With the aid of diagrams, briefly discuss the available rapid mixing techniques for each coagulation type (as discussed in Lecture 3).
4. For the flow rate calculated in task 1 (10 of year 2045 but not less than 10,000 m3/day} and using the design criteria discussed in Lecture 3, design a cylindrical flash mixing basin by determining the basin volume, tank diameter, dimensions, required input power, impeller diameter from manufacturer's data provided below, and its rotational speed using the following parameters.
Task 3
Task brief
1. For the flow rate calculated in task 1 (1.5 Q of year 2045 but not less than 10,000 m3/day} and using the design criteria discussed in Lecture 4, design a flocculation basin by determining the basin volume, tank dimensions, required input power, impeller diameter, and its rotational speed using the following parameters and the manufacturer's data (40%):
Flocculation t = 30 nun
Three flocoulator compartments with G = 70, 50, 30 s-1
Water temperature =
Place impeller at one-third the water depth
From manufacturer's data the following impellers are available,
|
|
|
|
Power
|
|
Impeller
type
|
|
Impeller diameters (m)
|
number
|
|
|
|
|
(N,,)
|
|
Radial
|
0.3
|
0.4 0.6
|
5.7
|
|
Axial
|
0.8
|
1.4 2.0
|
U.
|
2. A batch-settling test using a 2.0 m column and coagulated water yielded the data shown in the Table below. For this set of data (refer to Lecture 4, Example 4.3) , determine the detention time (minutes) and overflow rate (mid) to remove 65% of the influent suspended solids (20%).
|
Depth
(m)
|
Sampling time (min)
|
|
5
|
10
|
20
|
40
|
60
|
90
|
120
|
|
0.5
|
44
|
53
|
63
|
70
|
75
|
76
|
79
|
|
1
|
22
|
36
|
48
|
62
|
65
|
73
|
77
|
|
2
|
18
|
34
|
41
|
57
|
62
|
66
|
74
|
Removal rate
3. Using the design criteria discussed in Lecture 4, design a settling tank(s) for the flow rate calculated in task 1 (1.5 Q of year 2045 but not less than 10,000 m3/day).