Wastewater from a small town is treated in a trickling filter which is preceeded by a screen, sand-removal and primary clarification. The maximum hydraulic capacity, or peak flow, of the treatment plant is 1,500 m3/h. The dry weather flow (Qdwf) amounts 7,500 m3/day, with a BOD concentration of 300 mg/l.
QUESTION 2C-1
After a while the screen gets clogged. The automated cleaning starts at a head loss of 10 cm. Calculate what percentage of the clean free space is clogged at this head loss. For the calculation: take the impact of clogging on the friction factor into account.
Calculate V in m/s.
QUESTION 2C-2
Calculate at which open screen area (m2) this velocity is reached.
Calculate what percentage of the clean free space is clogged at this head loss.
QUESTION 2D-2
Assume 4 channels. Take a W:L ratio of 1:15
Dimension the rectangular sand removal channels.
Length (m):
Width (m):
Maximum water height (m):
Allow a free waterboard of 15 cm and a maximum grit accumulation height of 20 cm. Give the total height in m of the grit channel.
QUESTION 2C-1: Calculate V in m/s is 1.22
QUESTION 2C-2: Calculate at which open screen area (m2) this velocity is reached - 0.34
Calculate what percentage of the clean free space is clogged ... 32
QUESTION 2D-1: Determine how many parallel channels 4
What is a common W:L ratio? 1:10
To prevent settling of organic matter a Vs should be > 0.03 m/s
Calculate Qdwf in m3/s.0.087
Calculate Qrwf in m3/s.0.42
QUESTION 2D-2: L-12, W-0.8, Max Water Height 0.44, grit Channel 0.8 m
Please help to get this answer ,Ham
8.6
To calculate the required information, we need to follow the steps outlined in the question.
QUESTION 2C-1:
1. Determine the velocity (V) in m/s.
To calculate the velocity, we can use the equation:
Q = A * V
Where,
Q = Flowrate (in m^3/h)
A = Cross-sectional area (in m^2)
Rearranging the equation to solve for V:
V = Q / A
Given the peak flow capacity (Q) of the treatment plant is 1500 m^3/h, and the clogged screen creates a head loss of 10 cm. We can assume that this head loss is equivalent to the pressure drop across the screen, which affects the flowrate. So, we need to take into account the impact of clogging on the friction factor.
However, to calculate the exact percentage of the clogged free space, we would need additional information on the clean screen area and the specific impact on the friction factor. Without that information, it is not possible to directly calculate the clogged area percentage.
2. Calculate the velocity (V) in m/s:
To convert the flowrate from m^3/h to m^3/s, we divide by 3600:
Q (m^3/s) = Q (m^3/h) / 3600
Given Q (peak flow capacity) = 1500 m^3/h:
Q (m^3/s) = 1500 / 3600 = 0.4167 m^3/s
To calculate the cross-sectional area (A), we need to know the hydraulic diameter or the shape of the screen opening and the open screen area. Assuming a rectangular screen, we'll need additional information on the dimensions.
QUESTION 2C-2:
To calculate the open screen area (m^2) at which the velocity is reached, we need the cross-sectional area (A) and the velocity (V). However, without the dimensions of the screen opening, it is not possible to make this calculation.
Similarly, we cannot determine the percentage of the clean free space clogged at this head loss without knowing the specific impact of clogging on the friction factor and the dimensions of the screen.
QUESTION 2D-2:
To dimension the rectangular sand removal channels, we'll need to calculate the length, width, maximum water height, and the total height of the grit channel based on the given W:L ratio, free waterboard allowance, and maximum grit accumulation height.
1. Calculate the length of the rectangular sand removal channel:
Given the W:L ratio of 1:15 and assuming the width is 'W', we can calculate the length as:
Length = W * (15W)
Length = 15W^2
2. Determine the width of the rectangular sand removal channel:
Given the aspect ratio of 1:15, the width is 'W'.
3. Calculate the maximum water height:
The maximum water height is the same as the width of the channel, so it is 'W'.
4. Determine the total height of the grit channel:
Total height = Maximum water height (W) + Free waterboard (15 cm) + Maximum grit accumulation height (20 cm)
So, to provide the final values, we need to know the width (W) of the sand removal channel.