1. The town of Camp Verde has been directed to upgrade its primary WWTP to a sec

ID: 1827506 • Letter: 1

Question

The town of Camp Verde has been directed to upgrade its primary WWTP to a

secondary plant that can meet an effluent standard of 25 mg/L BOD5 and 30 mg/L of

suspended solids. They have selected a completely mixed activated sludge system for the

upgrade. The existing primary treatment plant has a flowrate of 0.029m3/s. The effluent

from the primary tank has a BOD5 of 240mg/L. Using the following assumptions,

estimate the required volume of the aeration tank:

(a). BOD5 of the effluent suspended solids is 70 percent of the allowable suspended

solids concentration.

(b). Growth constants values are estimated to be: Ks = 100mg/L BOD5; kd= 0.025 d-1;

BOD5 allowed = soluble BOD5 (S) + suspended solid BOD5

25 mg/L = S + 0.70 (30 mg/L SS)

S = 25-0.70*30

S = 4 mg/L

Also

S =Ks*(1 + kd*?c )/(?c (Yk ? k d ) ? 1)

4 = 100*(1+0.025*?c)/?c*(10d^-1 - 0.025d^-1)

?c = d/(0.375)

?c = 2.67

Now,

X = ?c* Y ( So ? S )/? (1 + kd*?c)

= 2.67*0.8*(240-4)/?(1+0.06675)

X = 3000

? = 0.157

d = 3.7 hrs

V = 3.7*3600*0.029

= 387 m^3

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