Stone media TF design

• Example 1 – Calculate the BOD loading, hydraulic loading, BOD removal efficiency, and effluent BOD concentration of a single-stage trickling filter based on the following data: – Design assumptions: • Influent flow =1530 m 3 /d • Recirculation ratio = 0.5

• Primary effluent BOD = 130 mg/L • Diameter of filter = 18 m • Depth of media = 2.1 m • Water temperature =18 o C

Stone media TF design

Solution) (1) BOD loading rate (kg/m 3 /d) – BOD load = BOD Conc. x Influent flow = 130 mg/L x 1530 m 3 /d =198.9 kg/d – Volume of filter = surface area of filter x depth = π (18 m x 18m)/4 X 2.1 m = 533 m 3 – BOD loading rate = BOD load / volume of filter =0.37 kg/m 3 /d

Solution)

Stone media TF design

(2) Hydraulic loading rate (m 3 /m 2 /d) – Total flow to the media = influent + recirculation flow – – = 1530 m 3 /d + (1530 m 3 /d x 0.5) Surface area of filter = π (18 m x 18m)/4 = 254 m 3 Hydraulic loading rate = Total flow to the media / area of filter = 9.04 m 3 /m 2 /d

Stone media TF design

Solution) (3) Effluent BOD (mg/L) – BOD removal efficiency for first-stage filter at 20 o C, %

E

1  1  0 .

100 4432

w

1

VF E

1  100 1  0 .

4432

F

 ( 1  1 

R R

/ 10 ) 2  1  0 .

5 ( 1  0 .

5 / 10 ) 2  1 .

36

w

1

VF

 100 1  0 .

4432 0 .

37 1 .

36  81 .

2 %

E

18 

E

20 ( 1 .

035 ) 18  20  81 .

2 ( 1 .

035 )  2  75 .

7 %

Effluent BOD

(

mg

/

L

)  130

mg

/

L

 ( 100  75 .

7 ) 100

Stone media TF design

• Example 2 – A municipal wastewater having a BOD of 200 mg/L is to be treated by a

two-stage trickling filter

. The desired effluent quality is 25 mg/L of BOD. If both of the filter depths are to be 1.83 m and the recirculation ratio is 2:1,

find the required filter diameters

. Assume the following design assumptions apply.

– Design assumptions: • Influent flow =7570 m 3 /d • Recirculation ratio = 2 • Depth of media = 1.83 m • Water temperature =20 o C • BOD removal in primary sedimentation = 35% • E 1 =E 2 =0.65

Stone media TF design

• Example 2 BOD=200mg/L Primary Clarifier TF 1 TF 2 Secondary Clarifier BOD=25mg/L

E

1  100 1  0 .

4432

w

1

VF E

2  100 1  0 .

4432 1 

E

1

w

2

VF

Stone media TF design

Solution) (1) Compute the recirculation factor

F

 ( 1  1 

R R

/ 10 ) 2 = (1+2)/ (1+0.2) 2 = 2.08

Solution)

Stone media TF design

(2) Compute the BOD load for the first filter – BOD load = BOD Conc. x Influent flow = 200mg/L*(1-0.35) x 7570 m 3 /d =1234kg/d (3) Compute the volume for the first stage

E

1  100 1  0 .

4432

w

1

VF

– V= 388 m3 64 .

6  100 1  0 .

4432 1234

V

( 2 .

08 )

Solution)

Stone media TF design

(4) Compute the diameter of the first filter A= V/depth = 388 m 3 /1.83m = 212 m 2 Diameter = 16.4 m (5) Compute the BOD load for the second filter – BOD load to the second filter = (1-E1) x BOD load to the first filter = (1-0.646) x 1234 kg BOD/d = 437 kg BOD/d

Solution)

Stone media TF design

(6) Compute the volume for the first stage

E

2  100 1  0 .

4432 1 

E

1

w

2

VF

64 .

6  100 1  0 .

4432 1  0 .

646 437

V

( 2 .

08 ) – V= 1096 m 3 (7) Compute the diameter of the first filter A= V/depth = 1096 m 3 /1.83m 599 m 2 Diameter = 27.6 m

Solution)

Stone media TF design

(8) Compute the BOD loading to each filter (9) Compute the hydraulic loading to each filter

Plastic media

Plastic media

Schulze formula

•

The liquid contact time (t) of applied wastewater

t



CD q n

Where: t = liquid contact time, min D= depth of media (m) q = hydraulic loading, (m 3 /m 2 /h) C, n = constants related to specific surface & configuration of media

Plastic media

•

hydraulic loading (q)

q



Q A

Where: Q= influent flow rate L/min A=filter cross section area m 2

Plastic media

TF design

Schulze formula

S e S o



e

( 

kD

/

q n

) Where: S e = BOD concentration of settled filter effluent, mg/L S o = influent BOD concentration to the filter, mg/L k=wastewater treatability and packing coefficient, (L/s) 0.5

/m 2 D=packing depth, m q= hydraulic application rate of primary effluent, excluding recirculation, L/m 2 *s n=constant characteristic of packing used (assumed to be 0.5).

Plastic media TF design

• Example 3 – Given the following design flow rates and primary effluent wastewater characteristics, determine the following design parameters for a trickling filter design assuming 2 reactors at 6.1 m depth, cross-flow plastic packing with a specific surface area of 90 m 2 /m 3 , a packing coefficient n value of 0.5, & a 2-arm distributor system. The required minimum wetting rate=0.5L/m 2 *s. Assume a secondary clarifier depth of 4.2m and k value of 0.23.

– Design conditions Item Flow BOD TSS Temp unit m 3 /d mg/L mg/L o C Primary effluent 15,140 125 65 14 Target effluent 20 20

Plastic media TF design

• Example 3 –Calculate the followings

• Diameter of TF, m • Volume of packing require, m 3

Plastic media TF design

• Solution – (1) Diameter of tower trickling filter, m a. Correct k for temperature effect

k T



k

20 ( 1 .

035 )

T

 20  0 .

23 ( 1 .

035 ) 14  20  0 .

187

Plastic media TF design

Solution – (1) Diameter of tower trickling filter, m b. Determine the hydraulic loading rate

S e S o



e

( 

kD

/

q n

)  25 125 

e

(  0 .

187  6 .

1 /

q

0 .

5 )

solve for

"

q

".



q

 0 .

3875

L

/

m

2 

s

c. Determine the tower area

q



Q A

, 

A



Q q

 0 .

15 , 140 3875

L m

/ 3

m

/

d

2 

s

 175 .

2

L

/

s

0 .

3875

L

/

m

2 

s

 452 .

2

m

2 d. Determine the tower diameter

Area

/

No

.

of Diameter tower

  17

m each

452 .

2

m

2

for two

/ 2 

filter

226 .

1

m

2