Question

\The flow rate to treat is 5.6 MGD and the BOD concentration is 150 mg/L. The design solids concentration (X) at steady-state is 2,000 mg/L. The design MCRT is 7 days. The kinetic coefficients are as follows: k = 2 g BOD/g cells*day; K_s = 25 mg BOD/L; k_d = 0.06 1/day; Y = 0.5 g cells/g BOD. The influent ammonia concentration is 40 mg/L and nitrification is needed. It takes 1400 ft³ of air per pound of BOD. Use rectangular tanks with a depth of 12 feet, a length to width ratio of 6 to 1, and a maximum length of 110 ft. Determine the following:

a) the hydraulic retention time (hr)

b) the steady-state effluent BOD concentration (mg/L)

c) the number of tanks and their lengths (ft) and widths (ft)

d) the air requirement (ft³/min)

Answer 1

eiPIC306 Given data BOD (So) to mgll 7tu ast Oc (MCRT) : 2000 776u kd BOO BO 1L Ks HRT3 cal culat on know We HRT(0) reador valume fex caleulation V=QXORXYS-S) C1t kd 0c 21198.306 X7x05X(150-40) o00 (1+D06K7 &161 347.81 2840 2&73. 71 m3 VE

HRT(O) 9873-71x 911 98.306 1 HRT 3 25h ithin 3 to Sh) (b) the ateadystate ofluent BOO COnc(ag Iuls Rs(1+ Kd Bc) max asume lmax 3d1 25 (1t0 06x 7) t 73-006)-1

ais seguiremest calculationss dotal oxygen segsuireroent OCS0-S) 1 1.42 X Ow X X R acciraulatiog rah (ORIQ) D6 wx XR ng hee Or uixemeut ieshiaateal kneuing the ulbinat ast BOD watey (So-S) D2seguiement is 1198 306XIS0-40 02ld 38 86.3 new censides air centaun 23 OXgen yu & density weth Au bFOC-1 201X0 23 3 886-3 140 8079 mld

ces idasiog oxygen trausex ffeof 87. O.07 2 Id 140 80.79 176009. &75 122. 22 m min. 122. 22 X(328 t31 2. 84Y 131 min