Monod Kinetics—Substrate Limited Growth
Environmental Engineering · FE Reference Handbook section
Handbook notes for this section
Definitions and conditions exactly as the handbook states them.
- Continuous flow systems where growth is limited by one substrate (chemostat):
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) = 5.5000 1/day; limiting substrate concentration (S) = 86.0000 mg/L; half-saturation constant (K_s) = 57.0000 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) = 5.5000 1/day, limiting substrate concentration (S) = 86.0000 mg/L, half-saturation constant (K_s) = 57.0000 mg/L.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning mu = 3.3077 1/day to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 6.6154 — kept a factor of two that cancels in the correct rearrangement.
- 1.6538 — dropped that same factor in the other direction.
- 3.6385 — 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) = 14.0000 mg/L; half-saturation constant (K_s) = 11.0000 mg/L; specific growth rate (mu) = 6.1000 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) = 14.0000 mg/L, half-saturation constant (K_s) = 11.0000 mg/L, specific growth rate (mu) = 6.1000 1/day.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning mu_max = 10.8929 1/day to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 21.7857 — kept a factor of two that cancels in the correct rearrangement.
- 5.4464 — dropped that same factor in the other direction.
- 11.9821 — 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) = 2.2000 1/day; limiting substrate concentration (S) = 146.0 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) = 2.2000 1/day, limiting substrate concentration (S) = 146.0 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 = -32.5018 mg/L to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- -65.0035 — kept a factor of two that cancels in the correct rearrangement.
- -16.2509 — dropped that same factor in the other direction.
- -35.7519 — 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) = 8.2000 1/day; limiting substrate concentration (S) = 47.0000 mg/L; half-saturation constant (K_s) = 38.0000 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) = 8.2000 1/day, limiting substrate concentration (S) = 47.0000 mg/L, half-saturation constant (K_s) = 38.0000 mg/L.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning mu = 4.5341 1/day to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 9.0682 — kept a factor of two that cancels in the correct rearrangement.
- 2.2671 — dropped that same factor in the other direction.
- 4.9875 — 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) = 129.0 mg/L; half-saturation constant (K_s) = 17.0000 mg/L; specific growth rate (mu) = 1.0800 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) = 129.0 mg/L, half-saturation constant (K_s) = 17.0000 mg/L, specific growth rate (mu) = 1.0800 1/day.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning mu_max = 1.2223 1/day to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 2.4447 — kept a factor of two that cancels in the correct rearrangement.
- 0.6112 — dropped that same factor in the other direction.
- 1.3446 — 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) = 3.2000 1/day; limiting substrate concentration (S) = 114.0 mg/L; specific growth rate (mu) = 4.5900 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) = 3.2000 1/day, limiting substrate concentration (S) = 114.0 mg/L, specific growth rate (mu) = 4.5900 1/day.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning K_s = -34.5229 mg/L to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- -69.0458 — kept a factor of two that cancels in the correct rearrangement.
- -17.2614 — dropped that same factor in the other direction.
- -37.9752 — 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) = 4.7000 1/day; limiting substrate concentration (S) = 9.0000 mg/L; half-saturation constant (K_s) = 90.0000 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) = 4.7000 1/day, limiting substrate concentration (S) = 9.0000 mg/L, half-saturation constant (K_s) = 90.0000 mg/L.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning mu = 0.4273 1/day to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 0.8545 — kept a factor of two that cancels in the correct rearrangement.
- 0.2136 — dropped that same factor in the other direction.
- 0.4700 — 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) = 49.0000 mg/L; half-saturation constant (K_s) = 86.0000 mg/L; specific growth rate (mu) = 5.1600 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) = 49.0000 mg/L, half-saturation constant (K_s) = 86.0000 mg/L, specific growth rate (mu) = 5.1600 1/day.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning mu_max = 14.2163 1/day to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 28.4327 — kept a factor of two that cancels in the correct rearrangement.
- 7.1082 — dropped that same factor in the other direction.
- 15.6380 — 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) = 4.3000 1/day; limiting substrate concentration (S) = 176.0 mg/L; specific growth rate (mu) = 8.2800 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) = 4.3000 1/day, limiting substrate concentration (S) = 176.0 mg/L, specific growth rate (mu) = 8.2800 1/day.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning K_s = -84.5990 mg/L to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- -169.2 — kept a factor of two that cancels in the correct rearrangement.
- -42.2995 — dropped that same factor in the other direction.
- -93.0589 — 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) = 3.1000 1/day; limiting substrate concentration (S) = 110.0 mg/L; half-saturation constant (K_s) = 8.0000 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) = 3.1000 1/day, limiting substrate concentration (S) = 110.0 mg/L, half-saturation constant (K_s) = 8.0000 mg/L.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning mu = 2.8898 1/day to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 5.7797 — kept a factor of two that cancels in the correct rearrangement.
- 1.4449 — dropped that same factor in the other direction.
- 3.1788 — rounded an intermediate value before the final step.
Reference: FE Handbook — Multiple Limiting Substrates (Monod Kinetics)