How Do You Calculate Dimensions for Wastewater Treatment Processes?

[Stacyg]

I'm not sure where to start with these any help would be great. Not sure if this is the right place to put these questions but this site has helped before.
Thanks

1)
A treatment plant consists of a primary sedimentation tank followed by a trickling filter that removes 80% of the influent BOD. The flow is then directed to a constructed marsh system that has an influent target BOD concentration of 30 mg/l before being discharged to a small stream.

Using the following table of % BOD removal to overflow rate and calculate the dimensions of a circular sedimentation tank suitable for the imposed flow with a detention time of 1.5 hours. Assume BOD and flow of wastewater entering the plant to be 214.245 mg/l and 848 kL/day.
BOD Removal % 22.0 31.5 33.5 35.5 36.5 37.5
Overflow rate m3/m2/day 100 50 40 30 25 20


2)
A community of 200 people has its gravity main sewer discharging to a treatment plant located near the town. The water consumption rate is 280 l/h/d, all of which could be assumed to discharge to the main sewer. The domestic sewage flow contains an average BOD loading of 75 g/h/d and a suspended solids loading of 84 g/c/d.
A cheese factory situated nearby, processing milk products, is also connected to the treatment plant inlet and discharges a raw effluent with a BOD loading of 110 g/m3 and an SS loading of 130 g/m3 at an average flow rate of 10 l/s over a period of 8 hours in one day.
Calculate the combined average concentrations of BOD and SS at the treatment plant inlet.
3)
Design an activated sludge plant for the following figures given for a community
Design Population 4500 people producing 320 liters per head per day
Raw Sewage Strength BOD – 206 mg/l, SS – 320 mg/l
Contact Stabilization Time 24 minutes
Extended Aeration Time 0.07 kg BOD/m3 of tank/hr
Sedimentation Overflow 48 meters per day
Depth Of Settling Tank 3.0m
Air Requirement 4.5 m3/hour/m3 of tank volumes

Calculate the volumes of the three process tanks (CS, EA and Sedimentation tanks) and the total air flow.
b) For the same sewage flow, design a fixed growth reactor. Assume the primary sedimentation stage removes 38% of the BOD. Use the following design criteria:
BOD Loading 0.08 kg BOD/m3/day
Hydraulic Loading o.3 m3/m3/day

4)
For a primary domestic sewage (1276 m3/day, BOD 240 mg/l), the treatment process is to be conventional activated sludge. Sketch and find the volumes of the contact tank, the aeration tank and the diameter of the settling tank, given the following design loading :
Contact Stabilization Time 1.5 hours
Aeration Tank BOD loading 0.56 kg BOD/m3/day, detention time: 9 hours
Settling tank overflow rate 1.25m/hour

Homework Equations

The Attempt at a Solution

 

[Valkarie]

1) Detention time = flow rate/tank volume, so tank volume = flow rate/detention time = 848000/(1.5*3600) = 235.556 m3. To calculate the diameter of the circular sedimentation tank, use the equation: d = (4*volume/π)^0.5. This gives d = 10.867 m. 2) For the combined average concentrations of BOD and SS at the treatment plant inlet, first calculate the total flow rate (QT) by adding the domestic sewage flow rate (QD) and the effluent from the cheese factory (QE): QT = QD + QE = (200*280) + (10*3600) = 86800 l/h/d.The combined average BOD concentration (CBOD) can be calculated as follows: CBOD = (QD*BODD + QE*BODE)/QT= (200*280*75 + 10*3600*110)/86800= 98.9 mg/h/dSimilarly, the combined average SS concentration (CSS) can be calculated as follows: CSS = (QD*SSD + QE*SSE)/QT= (200*280*84 + 10*3600*130)/86800= 114.6 mg/h/d3) The required volumes of the contact stabilization (CS), extended aeration (EA) and sedimentation tanks can be calculated as follows: CS tank volume = (Q*tcs)/Vcs = (320*4500*24*60)/0.213 = 16,847,712 litersEA tank volume = (Q*tcs*tea*Vea)/(Vcs*Vea) = (320*4500*24*60*0.07)/(0.213*0.213) = 2,623,717 litersSedimentation tank volume = (Q*tcs*tea*Voverflow)/(Vcs*Vea*Voverflow) = (320*4500*24*60*48)/(0.213*0.213*

 

[Mene]

1) To calculate the dimensions of the circular sedimentation tank, we need to first determine the overflow rate for the given BOD removal percentage of 80%. Using the table provided, we can see that an overflow rate of 30 m3/m2/day corresponds to a BOD removal percentage of 35.5%. This is the closest value to our desired 80% BOD removal.

Next, we need to calculate the total volume of wastewater entering the plant per day. This can be done by multiplying the flow rate (848 kL/day) by the BOD concentration (214.245 mg/l) and converting to cubic meters (1 kL = 1 m3). This gives us a total volume of 181.7 m3 of wastewater per day.

To find the required surface area of the sedimentation tank, we can use the equation:

Surface area = Volume / Detention time

Plugging in the values, we get:

Surface area = 181.7 m3 / 1.5 hours = 121.13 m2

Now, we can use the formula for the area of a circle to calculate the diameter of the tank:

Area = π * (diameter/2)^2

Solving for diameter, we get:

Diameter = 2 * √(Surface area / π) = 2 * √(121.13 / 3.14) = 12.41 meters

Therefore, the dimensions of the circular sedimentation tank suitable for the given flow rate and BOD removal efficiency are 12.41 meters in diameter and 121.13 m2 in surface area.

2) To calculate the combined average concentrations of BOD and SS at the treatment plant inlet, we first need to convert the flow rates from liters per hour to cubic meters per day:

Water consumption rate = 280 l/h/d = 0.28 m3/h/d = 6.72 m3/d
Cheese factory flow rate = 10 l/s * 8 hours = 80 m3/d

Next, we can calculate the total BOD and SS loadings from both sources:

BOD loading = 200 people * 75 g/h/d + 110 g/m3 * 80 m3/d = 15,000 g/d + 8,800 g/d = 23,800 g/d
SS loading = 200 people * 84 g/c/d + 130 g