Multiple Limiting Substrates
Environmental Engineering · FE Reference Handbook section
Core formulas for this FE topic
Definitions, applicability, units, assumptions and worked examples for each relation.
Worked exam-style examples
The four ways this section is written on the real exam — thoughts first, then equations, then substitution.
Monod kinetics with multiple limiting substrates for microbial growth in a bioreactor Given maximum specific growth rate (mu_max) = 7.2000 1/day; limiting substrate concentration (S) = 164.0 mg/L; half-saturation constant (K_s) = 66.0000 mg/L, determine the specific growth rate (mu) in 1/day.
Given
Find
specific growth rate (mu), in 1/day
Start with the thinking
- The governing relation printed in this handbook section is Multiple Limiting Substrates (Monod).
- Everything except mu is given, so isolate mu symbolically first — never rearrange after the numbers are in.
- Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
- Multiple limiting substrates growth kinetics use the Monod equation to relate specific growth rate to substrate concentration.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for mu:
Step 3 — List the givens: maximum specific growth rate (mu_max) = 7.2000 1/day, limiting substrate concentration (S) = 164.0 mg/L, half-saturation constant (K_s) = 66.0000 mg/L.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning mu = 5.1339 1/day to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 10.2678 — kept a factor of two that cancels in the correct rearrangement.
- 2.5670 — dropped that same factor in the other direction.
- 5.6473 — rounded an intermediate value before the final step.
Reference: FE Handbook — Multiple Limiting Substrates (Monod Kinetics)
Monod multiple limiting substrate model for activated sludge biomass growth Given limiting substrate concentration (S) = 126.0 mg/L; half-saturation constant (K_s) = 7.0000 mg/L; specific growth rate (mu) = 1.1600 1/day, determine the maximum specific growth rate (mu_max) in 1/day.
Given
Find
maximum specific growth rate (mu_max), in 1/day
Start with the thinking
- The governing relation printed in this handbook section is Multiple Limiting Substrates (Monod).
- Everything except mu_max is given, so isolate mu_max symbolically first — never rearrange after the numbers are in.
- Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
- Multiple limiting substrates growth kinetics use the Monod equation to relate specific growth rate to substrate concentration.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for mu_max:
Step 3 — List the givens: limiting substrate concentration (S) = 126.0 mg/L, half-saturation constant (K_s) = 7.0000 mg/L, specific growth rate (mu) = 1.1600 1/day.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning mu_max = 1.2244 1/day to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 2.4489 — kept a factor of two that cancels in the correct rearrangement.
- 0.6122 — dropped that same factor in the other direction.
- 1.3469 — rounded an intermediate value before the final step.
Reference: FE Handbook — Multiple Limiting Substrates (Monod Kinetics)
multiple limiting substrates Monod equation for nutrient-limited growth Given maximum specific growth rate (mu_max) = 9.8000 1/day; limiting substrate concentration (S) = 89.0000 mg/L; specific growth rate (mu) = 8.1500 1/day, determine the half-saturation constant (K_s) in mg/L.
Given
Find
half-saturation constant (K_s), in mg/L
Start with the thinking
- The governing relation printed in this handbook section is Multiple Limiting Substrates (Monod).
- Everything except K_s is given, so isolate K_s symbolically first — never rearrange after the numbers are in.
- Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
- Multiple limiting substrates growth kinetics use the Monod equation to relate specific growth rate to substrate concentration.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for K_s:
Step 3 — List the givens: maximum specific growth rate (mu_max) = 9.8000 1/day, limiting substrate concentration (S) = 89.0000 mg/L, specific growth rate (mu) = 8.1500 1/day.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning K_s = 18.0184 mg/L to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 36.0368 — kept a factor of two that cancels in the correct rearrangement.
- 9.0092 — dropped that same factor in the other direction.
- 19.8202 — rounded an intermediate value before the final step.
Reference: FE Handbook — Multiple Limiting Substrates (Monod Kinetics)
Monod kinetics with multiple limiting substrates for microbial growth in a bioreactor Given maximum specific growth rate (mu_max) = 9.3000 1/day; limiting substrate concentration (S) = 97.0000 mg/L; half-saturation constant (K_s) = 68.0000 mg/L, determine the specific growth rate (mu) in 1/day.
Given
Find
specific growth rate (mu), in 1/day
Start with the thinking
- The governing relation printed in this handbook section is Multiple Limiting Substrates (Monod).
- Everything except mu is given, so isolate mu symbolically first — never rearrange after the numbers are in.
- Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
- Multiple limiting substrates growth kinetics use the Monod equation to relate specific growth rate to substrate concentration.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for mu:
Step 3 — List the givens: maximum specific growth rate (mu_max) = 9.3000 1/day, limiting substrate concentration (S) = 97.0000 mg/L, half-saturation constant (K_s) = 68.0000 mg/L.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning mu = 5.4673 1/day to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 10.9345 — kept a factor of two that cancels in the correct rearrangement.
- 2.7336 — dropped that same factor in the other direction.
- 6.0140 — rounded an intermediate value before the final step.
Reference: FE Handbook — Multiple Limiting Substrates (Monod Kinetics)
Monod multiple limiting substrate model for activated sludge biomass growth Given limiting substrate concentration (S) = 182.0 mg/L; half-saturation constant (K_s) = 61.0000 mg/L; specific growth rate (mu) = 2.5500 1/day, determine the maximum specific growth rate (mu_max) in 1/day.
Given
Find
maximum specific growth rate (mu_max), in 1/day
Start with the thinking
- The governing relation printed in this handbook section is Multiple Limiting Substrates (Monod).
- Everything except mu_max is given, so isolate mu_max symbolically first — never rearrange after the numbers are in.
- Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
- Multiple limiting substrates growth kinetics use the Monod equation to relate specific growth rate to substrate concentration.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for mu_max:
Step 3 — List the givens: limiting substrate concentration (S) = 182.0 mg/L, half-saturation constant (K_s) = 61.0000 mg/L, specific growth rate (mu) = 2.5500 1/day.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning mu_max = 3.4047 1/day to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 6.8093 — kept a factor of two that cancels in the correct rearrangement.
- 1.7023 — dropped that same factor in the other direction.
- 3.7451 — rounded an intermediate value before the final step.
Reference: FE Handbook — Multiple Limiting Substrates (Monod Kinetics)
multiple limiting substrates Monod equation for nutrient-limited growth Given maximum specific growth rate (mu_max) = 5.1000 1/day; limiting substrate concentration (S) = 159.0 mg/L; specific growth rate (mu) = 2.8300 1/day, determine the half-saturation constant (K_s) in mg/L.
Given
Find
half-saturation constant (K_s), in mg/L
Start with the thinking
- The governing relation printed in this handbook section is Multiple Limiting Substrates (Monod).
- Everything except K_s is given, so isolate K_s symbolically first — never rearrange after the numbers are in.
- Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
- Multiple limiting substrates growth kinetics use the Monod equation to relate specific growth rate to substrate concentration.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for K_s:
Step 3 — List the givens: maximum specific growth rate (mu_max) = 5.1000 1/day, limiting substrate concentration (S) = 159.0 mg/L, specific growth rate (mu) = 2.8300 1/day.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning K_s = 127.5 mg/L to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 255.1 — kept a factor of two that cancels in the correct rearrangement.
- 63.7686 — dropped that same factor in the other direction.
- 140.3 — rounded an intermediate value before the final step.
Reference: FE Handbook — Multiple Limiting Substrates (Monod Kinetics)
Monod kinetics with multiple limiting substrates for microbial growth in a bioreactor Given maximum specific growth rate (mu_max) = 4.6000 1/day; limiting substrate concentration (S) = 184.0 mg/L; half-saturation constant (K_s) = 71.0000 mg/L, determine the specific growth rate (mu) in 1/day.
Given
Find
specific growth rate (mu), in 1/day
Start with the thinking
- The governing relation printed in this handbook section is Multiple Limiting Substrates (Monod).
- Everything except mu is given, so isolate mu symbolically first — never rearrange after the numbers are in.
- Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
- Multiple limiting substrates growth kinetics use the Monod equation to relate specific growth rate to substrate concentration.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for mu:
Step 3 — List the givens: maximum specific growth rate (mu_max) = 4.6000 1/day, limiting substrate concentration (S) = 184.0 mg/L, half-saturation constant (K_s) = 71.0000 mg/L.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning mu = 3.3192 1/day to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 6.6384 — kept a factor of two that cancels in the correct rearrangement.
- 1.6596 — dropped that same factor in the other direction.
- 3.6511 — rounded an intermediate value before the final step.
Reference: FE Handbook — Multiple Limiting Substrates (Monod Kinetics)
Monod multiple limiting substrate model for activated sludge biomass growth Given limiting substrate concentration (S) = 147.0 mg/L; half-saturation constant (K_s) = 18.0000 mg/L; specific growth rate (mu) = 1.5300 1/day, determine the maximum specific growth rate (mu_max) in 1/day.
Given
Find
maximum specific growth rate (mu_max), in 1/day
Start with the thinking
- The governing relation printed in this handbook section is Multiple Limiting Substrates (Monod).
- Everything except mu_max is given, so isolate mu_max symbolically first — never rearrange after the numbers are in.
- Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
- Multiple limiting substrates growth kinetics use the Monod equation to relate specific growth rate to substrate concentration.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for mu_max:
Step 3 — List the givens: limiting substrate concentration (S) = 147.0 mg/L, half-saturation constant (K_s) = 18.0000 mg/L, specific growth rate (mu) = 1.5300 1/day.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning mu_max = 1.7173 1/day to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 3.4347 — kept a factor of two that cancels in the correct rearrangement.
- 0.8587 — dropped that same factor in the other direction.
- 1.8891 — rounded an intermediate value before the final step.
Reference: FE Handbook — Multiple Limiting Substrates (Monod Kinetics)
multiple limiting substrates Monod equation for nutrient-limited growth Given maximum specific growth rate (mu_max) = 7.4000 1/day; limiting substrate concentration (S) = 155.0 mg/L; specific growth rate (mu) = 4.8500 1/day, determine the half-saturation constant (K_s) in mg/L.
Given
Find
half-saturation constant (K_s), in mg/L
Start with the thinking
- The governing relation printed in this handbook section is Multiple Limiting Substrates (Monod).
- Everything except K_s is given, so isolate K_s symbolically first — never rearrange after the numbers are in.
- Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
- Multiple limiting substrates growth kinetics use the Monod equation to relate specific growth rate to substrate concentration.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for K_s:
Step 3 — List the givens: maximum specific growth rate (mu_max) = 7.4000 1/day, limiting substrate concentration (S) = 155.0 mg/L, specific growth rate (mu) = 4.8500 1/day.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning K_s = 81.4948 mg/L to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 163.0 — kept a factor of two that cancels in the correct rearrangement.
- 40.7474 — dropped that same factor in the other direction.
- 89.6443 — rounded an intermediate value before the final step.
Reference: FE Handbook — Multiple Limiting Substrates (Monod Kinetics)
Monod kinetics with multiple limiting substrates for microbial growth in a bioreactor Given maximum specific growth rate (mu_max) = 6.0000 1/day; limiting substrate concentration (S) = 133.0 mg/L; half-saturation constant (K_s) = 14.0000 mg/L, determine the specific growth rate (mu) in 1/day.
Given
Find
specific growth rate (mu), in 1/day
Start with the thinking
- The governing relation printed in this handbook section is Multiple Limiting Substrates (Monod).
- Everything except mu is given, so isolate mu symbolically first — never rearrange after the numbers are in.
- Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
- Multiple limiting substrates growth kinetics use the Monod equation to relate specific growth rate to substrate concentration.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for mu:
Step 3 — List the givens: maximum specific growth rate (mu_max) = 6.0000 1/day, limiting substrate concentration (S) = 133.0 mg/L, half-saturation constant (K_s) = 14.0000 mg/L.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning mu = 5.4286 1/day to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 10.8571 — kept a factor of two that cancels in the correct rearrangement.
- 2.7143 — dropped that same factor in the other direction.
- 5.9714 — rounded an intermediate value before the final step.
Reference: FE Handbook — Multiple Limiting Substrates (Monod Kinetics)