Page 395 - Fair, Geyer, and Okun's Water and wastewater engineering : water supply and wastewater removal

JWCL344_ch10_333-356.qxd 8/2/10 9:02 PM Page 355

Problems/Questions 355

Sewage
1
Grade 4 ˝ in 1 ft
Septic tank
removable slab cover

1
Grade 8 ˝ in 1 ft
Scum
Sewage Tile sewer to
disposal field
4 to 6 ft
Sludge
Water table

At least 15 ft from
property line

Not over 100´ long

Septic tank Open joints
18˝

Grade
1
2˝ Distribution
Inlet box 16 ˝ in 1 ft
baffle

Laterals of 4˝ unglazed
agricultural tile
Figure 10.12 Typical Individual Wastewater Disposal System:
Septic Tank and Subsurface Absorption Field. Conversion
factors: 1 1 in. 25.4 mm; 1 1 ft 12 in. 0.3048 m

PROBLEMS/QUESTIONS
10.1 A 12-in. sewer is to flow full at a velocity of 3 ft/s. The 30 min, the time needed for the entire drainage area to become
maximum per capita flow is 350 gpcd. Determine using the US tributary to the sewer? The required velocity of flow is to be 3 ft/s
Customary Units (a) the maximum capacity of wastewater (0.90 m/s), and the ratio of the peak rate of runoff to the rate of
3
flow in ft /s and MGD; and (b) the number of people the sewer rainfall on the area is assumed to be 0.65.
can serve. 10.4 Estimate the capacity of the components of a small trick-
10.2 A 300-mm sewer is to flow full at a velocity of 0.90 m/s. ling-filter plant treating 1.6 MGD (6 MLD) of domestic waste-
The maximum per capita flow is 1,300 Lpcd (liter per capita water contributed by 16,000 people.
per day). Determine using the SI Units (a) the maximum capacity 10.5 Estimate the capacity of the components of a small acti-
3
of wastewater flow in m /s and L/day; and (b) the number of vated sludge plant treating 1.6 MGD (6 MLD) of domestic
people the sewer can serve. wastewater contributed by16,000 people.
10.3 A storm sewer is to drain an area of 40 acres or 16.2 ha (the 10.6 Estimate the following for a community of 12,000 per-
area drained by a 12-in. or 300-mm sanitary sewer in Examples sons. Assume that the annual depth of water employed in the ir-
10.1 and 10.2). What is the diameter of this storm sewer if it is rigation of crops is 12 in. (300 mm) and that the wastewater
to carry away rain falling at a rate of 2 in./h (50 mm/h) during flow is 90 gpcd (340 Lpcd).