1. A flow of 1.1 MGD is applied to 50 ft diameter trickling filter, which is 4 feet deep. The BOD of the wastewater applied to the filter is 120 mg/L. Calculate the hydraulic loading on the filter.

2. A flow of 1.1 MGD is applied to 50 ft diameter trickling filter, which is 4 feet deep. The BOD of the wastewater applied to the filter is 120 mg/L. Calculate the organic loading on the filter.

3. The influent BOD to a trickling filter plant is 200 mg/L, and the effluent BOD is 20 mg/L. What is the BOD removal efficiency of the plant?

4. A rotating biological contactor treats a flow of 2.4 MGD. The surface area of the media is 720,000 square feet. The influent has a total BOD of 220 mg/L and suspended solids of 240 mg/L. Assume a K value of 0.5 to calculate the soluble BOD. Calculate the hydraulic loading in liters per day per square meter.

5. A rotating biological contactor treats a flow of 2.4 MGD. The surface area of the media is 720,000 square feet. The influent has a total BOD of 220 mg/L and suspended solids of 240 mg/L. Assume a K value of 0.5 to calculate the soluble BOD. Calculate the organic loading in kilograms of soluble BOD per day per 1,000 square feet of media surface.

Answers:

1. Hydraulic Loading, gpd/sqft = (Flow, gpd) / (Surface Area, sqft)

Convert flow from MGD to GPD (shuffle) = 1.1 MGD X 1,000,000 = 1,100,000 gpd

Find surface area, ft2 = 3.14 X R, ft X R, ft, Radius is 1/2 the Diameter so R = 25 ft OR 0.785 X D, ft X D, ft

3.14 X 25 ft X 25 ft = 1,960 sqft

(1,100,000 gpd) / (1,960 sqft) = 561 gpd/sqft

2. Organic Loading, lbs BOD/day/1000 cuft =

(BOD applied, lbs/day) / (Volume of Media, 1,000 cuft)

BOD applied, lbs/day = Flow, MGD X Conc, mg/L X 8.34 lbs/gal =

1.1 MGD X 120 mg/L X 8.34 lb/gal = 1,100 lbs BOD/day

Volume of Media, 1000 cuft = 3.14 X R, ft X R, ft X Depth, ft OR

0.785 X D, ft X D, ft X Depth, ft

3.14 X 25 ft X 25 ft X 4 ft = 7,840 cuft

(7,840 cuft) / (1,000 cuft) = 7.84 (1,000 cuft)

(1,100 lbs BOD/day) / (7.84 (1,000 cuft) = 140 lbs BOD/day/1,000 cuft

3. Efficiency, % = (In – Out) / (In) X 100 %

(200 mg/L – 20 mg/L) / (200 mg/L) X 100 % =

(180 mg/L) / (200 mg/L) X 100 % = 0.09

0.09 X 100 % = 90 %

4. Hydraulic Loading, gpd/sqft = (Flow, gpd) / (Surface area, sqft)

2.4 MGD = 2,400,000 gpd

(2,400,000 gpd) / (720,000 sqft) = 3.3 gpd/sqft

5. Soluble BOD, mg/L = (Total BOD) – (K X Suspended solids, mg/L)

(220 mg/L) – (0.5 X 240 mg/L) =

220 mg/L – 120 mg/L = 100 mg/L

BOD applied, lbs/day = Flow, MGD X BOD, mg/L X 8.34 lbs/gal

2.4 MGD X 100 mg/L X 8.34 lbs/gal = 2,002 lbs/day

Organic Loading, lbs/BOD/day/1,000 sqft =

(Soluble BOD Applied, lbs/day) / (Surface Area of Media, 1000 sqft)

Surface area of media, 1000 sqft = (720,000 sqft) / (1,000 sqft) = 720

(2,002 lbs/day) / (720) = 2.8 lbs BOD/day/1,000 sqft