Practice Questions

TLS Online TPP Program

#Question id: 2111

The membranes of winter wheat are able to remain fluid when it is extremely cold by:

#SCPH28 | Zoology

increasing the proportion of unsaturated phospholipids in the membrane
decreasing the percentage of cholesterol molecules in the membrane
decreasing the number of hydrophobic proteins in the membrane
increasing the proportion of glycolipids in the membrane

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TLS Online TPP Program

#Question id: 14263

#SCPH05 I Biotechnology

The BOD5 value of a waste-water feed stream to an activated-sludge unit is S0 = 300 mg/l, and the effluent is desired to be S = 30 mg/l. The feed flow rate is F = 2× 10^7 l/day. For the recycle ratio of α = 0.5 and a steady-state biomass concentration of X = 5 g/l, Use the following kinetic parameters:

calculate Biomass concentration in recycle (Xr).

TLS Online TPP Program

#Question id: 14264

#SCPH05 I Biotechnology

The BOD5 value of a waste-water feed stream to an activated-sludge unit is S0 = 300 mg/l, and the effluent is desired to be S = 30 mg/l. The feed flow rate is F = 2× 10^7 l/day. For the recycle ratio of α = 0.5 and a steady-state biomass concentration of X = 5 g/l, Use the following kinetic parameters:

calculate Hydraulic residence time

TLS Online TPP Program

#Question id: 14265

#SCPH05 I Biotechnology

For the activated-sludge, the specific growth rate of cells is given by

The following parameter values are known: F = 500 l/h, α = 0.4, ɣ = 0.1, Xe = 0, V = 1500 l, Ks = 10 mg/l, µm = 1 h-1 , kd = 0.05 h-1 , S0 = 1000 mg/l, Y M X/S = 0.5 g dw/g substrate. Calculate the substrate concentration (S) in the reactor at steady state. -------------------------

TLS Online TPP Program

#Question id: 14266

#SCPH05 I Biotechnology

For the activated-sludge, the specific growth rate of cells is given by

The following parameter values are known: F = 500 l/h, α = 0.4, ɣ = 0.1, Xe = 0, V = 1500 l, Ks = 10 mg/l, µm = 1 h-1 , kd = 0.05 h^-1 , S0 = 1000 mg/l, Y M X/S = 0.5 g dw/g substrate.. Calculate the cell concentration in the reactor.

TLS Online TPP Program

#Question id: 14267

#SCPH05 I Biotechnology

In a trickling biological filter, the BOD value of the feed stream is S_0i = 500 mg/l with a feed flow of F = 10³ l/h. The effluent BOD value is desired to be S₀ = 10 mg/l. The following kinetic parameters for the biocatalysts are known: r_m = 20 mg/S/l .h and K_s = 200 mg S/l. The biofilm thickness is L = 0.1 mm. The cross-sectional area of the filter is A = 2 m² , and the biofilm surface area per unit volume of the bed is a = 500 cm² /cm³ . Assume that dissolved oxygen is the rate-limiting substrate and the diffusion coefficient of oxygen is D_O2 = 2 × 10^-5 cm² /s. Determine the required height of the bed. You can assume first-order bioreaction kinetics?

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TLS Online TPP Program

#Question id: 14268

#SCPH05 I Biotechnology

An activated-sludge waste treatment system is required to reduce the amount of BOD₅ from 1000 mg/l to 20 mg/l at the exit. The sedimentation unit concentrates biomass by a factor of 3. Kinetic parameters are µ_m = 0.2 h-1 , K_s = 80 mg/l, k_d= 0.01 h-1 , and Y ^M_X/S= 0.5 g MLVSS/g BOD₅. The flow of waste water is 10000 l/h and the size of the treatment basin is 50,000 l. What is the value of the solids residence time?