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Multiple Limiting Substrates

Environmental Engineering · FE Reference Handbook section

Environmental Engineering
2 formulas
10 exam-style examples
~49 min
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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.

Example 1
Multiple Limiting Substrates (Monod) — solve for specific growth rate — Multiple Limiting Substrates

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

  • maximumspecificgrowthrate(mumax)=7.20001/daymaximum specific growth rate (mu_max) = 7.2000 1/day
  • limitingsubstrateconcentration(S)=164.0mg/Llimiting substrate concentration (S) = 164.0 mg/L
  • half−saturationconstant(Ks)=66.0000mg/Lhalf-saturation constant (K_s) = 66.0000 mg/L

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

  1. Step 1 — State the governing relation:

    μ=μmaxSKs+S\mu = \mu_{max} \dfrac{S}{K_s + S}
  2. Step 2 — Rearrange symbolically for mu:

    μ=μmaxSKs+S\mu = \mu_{max}\dfrac{S}{K_s+S}
  3. 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.

  4. Step 4 — Substitute the given values:

    μ=7.2000164.0Ks+164.0\mu = 7.2000\dfrac{164.0}{K_s+164.0}
  5. Step 5 — Evaluate:

    μ=5.1339 1/day\mu = 5.1339\ \text{1/day}
  6. Step 6 — Check: returning mu = 5.1339 1/day to

    μ=μmaxSKs+S\mu = \mu_{max} \dfrac{S}{K_s + S}

    reproduces the given quantities, and both sides carry the same units.

Answer:
μ=5.1339 1/day\mu = 5.1339\ \text{1/day}

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)

Example 2
Multiple Limiting Substrates (Monod) — solve for maximum specific growth rate — Multiple Limiting Substrates (2)

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

  • limitingsubstrateconcentration(S)=126.0mg/Llimiting substrate concentration (S) = 126.0 mg/L
  • half−saturationconstant(Ks)=7.0000mg/Lhalf-saturation constant (K_s) = 7.0000 mg/L
  • specificgrowthrate(mu)=1.16001/dayspecific growth rate (mu) = 1.1600 1/day

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

  1. Step 1 — State the governing relation:

    μ=μmaxSKs+S\mu = \mu_{max} \dfrac{S}{K_s + S}
  2. Step 2 — Rearrange symbolically for mu_max:

    μmax=μ(Ks+S)S\mu_{max} = \dfrac{\mu (K_s+S)}{S}
  3. 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.

  4. Step 4 — Substitute the given values:

    μmax=1.1600(Ks+126.0)126.0\mu_{max} = \dfrac{1.1600 (K_s+126.0)}{126.0}
  5. Step 5 — Evaluate:

    μmax=1.2244 1/day\mu_{max} = 1.2244\ \text{1/day}
  6. Step 6 — Check: returning mu_max = 1.2244 1/day to

    μ=μmaxSKs+S\mu = \mu_{max} \dfrac{S}{K_s + S}

    reproduces the given quantities, and both sides carry the same units.

Answer:
μmax=1.2244 1/day\mu_{max} = 1.2244\ \text{1/day}

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)

Example 3
Multiple Limiting Substrates (Monod) — solve for half-saturation constant — Multiple Limiting Substrates (3)

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

  • maximumspecificgrowthrate(mumax)=9.80001/daymaximum specific growth rate (mu_max) = 9.8000 1/day
  • limitingsubstrateconcentration(S)=89.0000mg/Llimiting substrate concentration (S) = 89.0000 mg/L
  • specificgrowthrate(mu)=8.15001/dayspecific growth rate (mu) = 8.1500 1/day

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

  1. Step 1 — State the governing relation:

    μ=μmaxSKs+S\mu = \mu_{max} \dfrac{S}{K_s + S}
  2. Step 2 — Rearrange symbolically for K_s:

    Ks=S(μmaxμ−1)K_{s} = S\left(\dfrac{\mu_{max}}{\mu}-1\right)
  3. 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.

  4. Step 4 — Substitute the given values:

    Ks=89.0000(9.80008.1500−1)K_{s} = 89.0000\left(\dfrac{9.8000}{8.1500}-1\right)
  5. Step 5 — Evaluate:

    Ks=18.0184 mg/LK_{s} = 18.0184\ \text{mg/L}
  6. Step 6 — Check: returning K_s = 18.0184 mg/L to

    μ=μmaxSKs+S\mu = \mu_{max} \dfrac{S}{K_s + S}

    reproduces the given quantities, and both sides carry the same units.

Answer:
Ks=18.0184 mg/LK_{s} = 18.0184\ \text{mg/L}

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)

Example 4
Multiple Limiting Substrates (Monod) — solve for specific growth rate (case 2) — Multiple Limiting Substrates (4)

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

  • maximumspecificgrowthrate(mumax)=9.30001/daymaximum specific growth rate (mu_max) = 9.3000 1/day
  • limitingsubstrateconcentration(S)=97.0000mg/Llimiting substrate concentration (S) = 97.0000 mg/L
  • half−saturationconstant(Ks)=68.0000mg/Lhalf-saturation constant (K_s) = 68.0000 mg/L

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

  1. Step 1 — State the governing relation:

    μ=μmaxSKs+S\mu = \mu_{max} \dfrac{S}{K_s + S}
  2. Step 2 — Rearrange symbolically for mu:

    μ=μmaxSKs+S\mu = \mu_{max}\dfrac{S}{K_s+S}
  3. 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.

  4. Step 4 — Substitute the given values:

    μ=9.300097.0000Ks+97.0000\mu = 9.3000\dfrac{97.0000}{K_s+97.0000}
  5. Step 5 — Evaluate:

    μ=5.4673 1/day\mu = 5.4673\ \text{1/day}
  6. Step 6 — Check: returning mu = 5.4673 1/day to

    μ=μmaxSKs+S\mu = \mu_{max} \dfrac{S}{K_s + S}

    reproduces the given quantities, and both sides carry the same units.

Answer:
μ=5.4673 1/day\mu = 5.4673\ \text{1/day}

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)

Example 5
Multiple Limiting Substrates (Monod) — solve for maximum specific growth rate (case 2) — Multiple Limiting Substrates (5)

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

  • limitingsubstrateconcentration(S)=182.0mg/Llimiting substrate concentration (S) = 182.0 mg/L
  • half−saturationconstant(Ks)=61.0000mg/Lhalf-saturation constant (K_s) = 61.0000 mg/L
  • specificgrowthrate(mu)=2.55001/dayspecific growth rate (mu) = 2.5500 1/day

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

  1. Step 1 — State the governing relation:

    μ=μmaxSKs+S\mu = \mu_{max} \dfrac{S}{K_s + S}
  2. Step 2 — Rearrange symbolically for mu_max:

    μmax=μ(Ks+S)S\mu_{max} = \dfrac{\mu (K_s+S)}{S}
  3. 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.

  4. Step 4 — Substitute the given values:

    μmax=2.5500(Ks+182.0)182.0\mu_{max} = \dfrac{2.5500 (K_s+182.0)}{182.0}
  5. Step 5 — Evaluate:

    μmax=3.4047 1/day\mu_{max} = 3.4047\ \text{1/day}
  6. Step 6 — Check: returning mu_max = 3.4047 1/day to

    μ=μmaxSKs+S\mu = \mu_{max} \dfrac{S}{K_s + S}

    reproduces the given quantities, and both sides carry the same units.

Answer:
μmax=3.4047 1/day\mu_{max} = 3.4047\ \text{1/day}

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)

Example 6
Multiple Limiting Substrates (Monod) — solve for half-saturation constant (case 2) — Multiple Limiting Substrates (6)

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

  • maximumspecificgrowthrate(mumax)=5.10001/daymaximum specific growth rate (mu_max) = 5.1000 1/day
  • limitingsubstrateconcentration(S)=159.0mg/Llimiting substrate concentration (S) = 159.0 mg/L
  • specificgrowthrate(mu)=2.83001/dayspecific growth rate (mu) = 2.8300 1/day

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

  1. Step 1 — State the governing relation:

    μ=μmaxSKs+S\mu = \mu_{max} \dfrac{S}{K_s + S}
  2. Step 2 — Rearrange symbolically for K_s:

    Ks=S(μmaxμ−1)K_{s} = S\left(\dfrac{\mu_{max}}{\mu}-1\right)
  3. 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.

  4. Step 4 — Substitute the given values:

    Ks=159.0(5.10002.8300−1)K_{s} = 159.0\left(\dfrac{5.1000}{2.8300}-1\right)
  5. Step 5 — Evaluate:

    Ks=127.5 mg/LK_{s} = 127.5\ \text{mg/L}
  6. Step 6 — Check: returning K_s = 127.5 mg/L to

    μ=μmaxSKs+S\mu = \mu_{max} \dfrac{S}{K_s + S}

    reproduces the given quantities, and both sides carry the same units.

Answer:
Ks=127.5 mg/LK_{s} = 127.5\ \text{mg/L}

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)

Example 7
Multiple Limiting Substrates (Monod) — solve for specific growth rate (case 3) — Multiple Limiting Substrates (7)

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

  • maximumspecificgrowthrate(mumax)=4.60001/daymaximum specific growth rate (mu_max) = 4.6000 1/day
  • limitingsubstrateconcentration(S)=184.0mg/Llimiting substrate concentration (S) = 184.0 mg/L
  • half−saturationconstant(Ks)=71.0000mg/Lhalf-saturation constant (K_s) = 71.0000 mg/L

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

  1. Step 1 — State the governing relation:

    μ=μmaxSKs+S\mu = \mu_{max} \dfrac{S}{K_s + S}
  2. Step 2 — Rearrange symbolically for mu:

    μ=μmaxSKs+S\mu = \mu_{max}\dfrac{S}{K_s+S}
  3. 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.

  4. Step 4 — Substitute the given values:

    μ=4.6000184.0Ks+184.0\mu = 4.6000\dfrac{184.0}{K_s+184.0}
  5. Step 5 — Evaluate:

    μ=3.3192 1/day\mu = 3.3192\ \text{1/day}
  6. Step 6 — Check: returning mu = 3.3192 1/day to

    μ=μmaxSKs+S\mu = \mu_{max} \dfrac{S}{K_s + S}

    reproduces the given quantities, and both sides carry the same units.

Answer:
μ=3.3192 1/day\mu = 3.3192\ \text{1/day}

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)

Example 8
Multiple Limiting Substrates (Monod) — solve for maximum specific growth rate (case 3) — Multiple Limiting Substrates (8)

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

  • limitingsubstrateconcentration(S)=147.0mg/Llimiting substrate concentration (S) = 147.0 mg/L
  • half−saturationconstant(Ks)=18.0000mg/Lhalf-saturation constant (K_s) = 18.0000 mg/L
  • specificgrowthrate(mu)=1.53001/dayspecific growth rate (mu) = 1.5300 1/day

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

  1. Step 1 — State the governing relation:

    μ=μmaxSKs+S\mu = \mu_{max} \dfrac{S}{K_s + S}
  2. Step 2 — Rearrange symbolically for mu_max:

    μmax=μ(Ks+S)S\mu_{max} = \dfrac{\mu (K_s+S)}{S}
  3. 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.

  4. Step 4 — Substitute the given values:

    μmax=1.5300(Ks+147.0)147.0\mu_{max} = \dfrac{1.5300 (K_s+147.0)}{147.0}
  5. Step 5 — Evaluate:

    μmax=1.7173 1/day\mu_{max} = 1.7173\ \text{1/day}
  6. Step 6 — Check: returning mu_max = 1.7173 1/day to

    μ=μmaxSKs+S\mu = \mu_{max} \dfrac{S}{K_s + S}

    reproduces the given quantities, and both sides carry the same units.

Answer:
μmax=1.7173 1/day\mu_{max} = 1.7173\ \text{1/day}

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)

Example 9
Multiple Limiting Substrates (Monod) — solve for half-saturation constant (case 3) — Multiple Limiting Substrates (9)

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

  • maximumspecificgrowthrate(mumax)=7.40001/daymaximum specific growth rate (mu_max) = 7.4000 1/day
  • limitingsubstrateconcentration(S)=155.0mg/Llimiting substrate concentration (S) = 155.0 mg/L
  • specificgrowthrate(mu)=4.85001/dayspecific growth rate (mu) = 4.8500 1/day

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

  1. Step 1 — State the governing relation:

    μ=μmaxSKs+S\mu = \mu_{max} \dfrac{S}{K_s + S}
  2. Step 2 — Rearrange symbolically for K_s:

    Ks=S(μmaxμ−1)K_{s} = S\left(\dfrac{\mu_{max}}{\mu}-1\right)
  3. 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.

  4. Step 4 — Substitute the given values:

    Ks=155.0(7.40004.8500−1)K_{s} = 155.0\left(\dfrac{7.4000}{4.8500}-1\right)
  5. Step 5 — Evaluate:

    Ks=81.4948 mg/LK_{s} = 81.4948\ \text{mg/L}
  6. Step 6 — Check: returning K_s = 81.4948 mg/L to

    μ=μmaxSKs+S\mu = \mu_{max} \dfrac{S}{K_s + S}

    reproduces the given quantities, and both sides carry the same units.

Answer:
Ks=81.4948 mg/LK_{s} = 81.4948\ \text{mg/L}

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)

Example 10
Multiple Limiting Substrates (Monod) — solve for specific growth rate (case 4) — Multiple Limiting Substrates (10)

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

  • maximumspecificgrowthrate(mumax)=6.00001/daymaximum specific growth rate (mu_max) = 6.0000 1/day
  • limitingsubstrateconcentration(S)=133.0mg/Llimiting substrate concentration (S) = 133.0 mg/L
  • half−saturationconstant(Ks)=14.0000mg/Lhalf-saturation constant (K_s) = 14.0000 mg/L

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

  1. Step 1 — State the governing relation:

    μ=μmaxSKs+S\mu = \mu_{max} \dfrac{S}{K_s + S}
  2. Step 2 — Rearrange symbolically for mu:

    μ=μmaxSKs+S\mu = \mu_{max}\dfrac{S}{K_s+S}
  3. 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.

  4. Step 4 — Substitute the given values:

    μ=6.0000133.0Ks+133.0\mu = 6.0000\dfrac{133.0}{K_s+133.0}
  5. Step 5 — Evaluate:

    μ=5.4286 1/day\mu = 5.4286\ \text{1/day}
  6. Step 6 — Check: returning mu = 5.4286 1/day to

    μ=μmaxSKs+S\mu = \mu_{max} \dfrac{S}{K_s + S}

    reproduces the given quantities, and both sides carry the same units.

Answer:
μ=5.4286 1/day\mu = 5.4286\ \text{1/day}

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)

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