Page 388 - Fair, Geyer, and Okun's Water and wastewater engineering : water supply and wastewater removal

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348 Chapter 10 Introduction to Wastewater Systems

Figure 10.10 Trickling Filter Bed Using Plastic Media (Courtesy Wikepedia)
http://en.wikipedia.org/wiki/Image:Trickling_filter_bed_2_w.JPG

EXAMPLE 10.3 CAPACITY OF TRICKLING FILTER
Estimate the capacity of the components of a small trickling-filter plant treating 0.8 MGD (3 MLD)
of domestic wastewater from 8,000 people, assuming the following:
a. Sewage flow production 100 gpcd (378 Lpcd)
b. Two primary settling tanks with a depth of 10 ft (3.1 m)
3
3
c. Two sludge digestion tanks with a storage requirement of 2 ft (0.057 m ) per capita
2
2
d. Four sludge drying beds with an area requirement of 1 ft (0.093 m ) per capita
2
e. One trickling filter with a loading of 3 MG/acre/d (28 ML/ha/d 0.0028 ML/m /d)
Solution 1 (U.S. Customary System):
1. Primary settling in two tanks, averaging 10 ft in depth.
a. Assumed detention period 2 h.
3
b. Effective volume/tank flow time 8,000 100 (2>24)>2 33,300 gal 4,460 ft .
2
c. Surface area 4,460>10 446 ft .
d. Dimensions such as 10 ft 45 ft.
2
e. Surface hydraulic loading (800,000>2)>450 890 gpd/ft .
2. Sludge digestion in two tanks:
3
a. Assumed storage requirement 2 ft /capita.
3
b. Effective volume 2 8,000>2 8,000 ft .
c. Assuming an area equal to settling tanks, depth below settling compartment
8,000>450 18 ft (plus 2 ft to keep sludge clear of slots).
3. Sludge-drying beds, four in number:
2
a. Assumed area requirement 1 ft /capita.