Suppose a waste water stream is to be treated using bacteria immobilized within

Question

Suppose a waste water stream is to be treated using bacteria immobilized within 2 mm porous beads. The intrinsic kinetics of contaminant conversion by this culture, measured for suspended cells in free form, is given by r (rm S) CKs S), where r 1400 mg/L h and K 800 mg/L. The table below shows the observed dependence of r on contaminant concentration after immobilization in porous beads of various sizes (in every case, the concentration of immobilized cells is equal to the concentration of cells used in the suspended cells experiment). In the table below, S refers to bulk contaminant concentration, and r refers to the rate at which contaminant is consumed per bead volume. The effects of external mass transfer limitations can be safely ignored in all cases. (1 mm beads) 2 mm beads) mm beads) AS (mg/L r (mg/L h r (mngi r (m 100 48 43 250 114 92 14 500 150 36 204 800 300 1000 348 215 60 2000 492 300 104 2500 546 336 120 3000 590 366 160 4000 600 420 200 5000 600 470 245 a. Estimate the kinetic parameter r mg/Lh) for contaminant conversion by cells immobilized in the 2 mm beads. If this cannot be determined, explain why that is so b. Suppose the concentration of cells immobilized in the 2 mm beads is to be increased, but in a manner introducing no changes to immobilized cell physiology or pore diameter, i e., there will simply be more of them adhered to the surface within the pores. Specify whether each of the parameters below would increase, decrease, or remain constant, and provide a brief explanation r your response in each case. (ii) K Sapp (iii) n (when S Ksapp)

Explanation / Answer

(a)

values of I/r and i/s were calculated and a graph was plotted between them. intercept of y axis will give 1/rmax therefore from the above data plotted on excel sheet

1/Rmax = 0.002

Rm = 500 mg/l h

(b) on increasing cell concentration and keeping other factors constant

rm will remain same, km will increase and n will be Rmax/2

as increasing number of the cells does not increase maximum rate of conversion but it will increase the concentration at which it will achieve

1/s 1/v 0.01 0.023 0.004 0.01 0.002 0.0066 0.00125 0.0053 0.001 0.0046 0.0005 0.0033 0.0004 0.00297 0.00033 0.00273 0.00025 0.0023 0.0002 0.00212

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