Phosphorus Removal Equations
Environmental Engineering · FE Reference Handbook section
Core formulas for this FE topic
Definitions, applicability, units, assumptions and worked examples for each relation.
This section is conceptual; there are no equations to memorise.
Worked exam-style examples
The four ways this section is written on the real exam — thoughts first, then equations, then substitution.
phosphorus removal chemical dose calculation using metal to phosphorus ratio Given metal to phosphorus molar ratio (MeP) = 1.6000; phosphorus mass to remove (M_P) = 44.0000 kg/day, determine the metal salt dose mass (M_Me) in kg/day.
Given
Find
metal salt dose mass (M_Me), in kg/day
Start with the thinking
- The governing relation printed in this handbook section is Phosphorus Removal Equations.
- Everything except M_Me is given, so isolate M_Me 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.
- Phosphorus removal equations determine the metal salt dose needed for chemical precipitation of phosphorus.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for M_Me:
Step 3 — List the givens: metal to phosphorus molar ratio (MeP) = 1.6000, phosphorus mass to remove (M_P) = 44.0000 kg/day.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning M_Me = 70.4000 kg/day to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 140.8 — kept a factor of two that cancels in the correct rearrangement.
- 35.2000 — dropped that same factor in the other direction.
- 77.4400 — rounded an intermediate value before the final step.
Reference: FE Handbook — Phosphorus Removal Equations
phosphorus removal equations for alum dosing at a treatment plant Given metal to phosphorus molar ratio (MeP) = 1.7000; metal salt dose mass (M_Me) = 971.0 kg/day, determine the phosphorus mass to remove (M_P) in kg/day.
Given
Find
phosphorus mass to remove (M_P), in kg/day
Start with the thinking
- The governing relation printed in this handbook section is Phosphorus Removal Equations.
- Everything except M_P is given, so isolate M_P 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.
- Phosphorus removal equations determine the metal salt dose needed for chemical precipitation of phosphorus.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for M_P:
Step 3 — List the givens: metal to phosphorus molar ratio (MeP) = 1.7000, metal salt dose mass (M_Me) = 971.0 kg/day.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning M_P = 571.2 kg/day to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 1,142 — kept a factor of two that cancels in the correct rearrangement.
- 285.6 — dropped that same factor in the other direction.
- 628.3 — rounded an intermediate value before the final step.
Reference: FE Handbook — Phosphorus Removal Equations
phosphorus removal via chemical precipitation dose determination Given phosphorus mass to remove (M_P) = 155.0 kg/day; metal salt dose mass (M_Me) = 605.0 kg/day, determine the metal to phosphorus molar ratio (MeP).
Given
Find
metal to phosphorus molar ratio (MeP)
Start with the thinking
- The governing relation printed in this handbook section is Phosphorus Removal Equations.
- Everything except MeP is given, so isolate MeP 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.
- Phosphorus removal equations determine the metal salt dose needed for chemical precipitation of phosphorus.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for MeP:
Step 3 — List the givens: phosphorus mass to remove (M_P) = 155.0 kg/day, metal salt dose mass (M_Me) = 605.0 kg/day.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning MeP = 3.9032 to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 7.8065 — kept a factor of two that cancels in the correct rearrangement.
- 1.9516 — dropped that same factor in the other direction.
- 4.2935 — rounded an intermediate value before the final step.
Reference: FE Handbook — Phosphorus Removal Equations
phosphorus removal chemical dose calculation using metal to phosphorus ratio Given metal to phosphorus molar ratio (MeP) = 1.5500; phosphorus mass to remove (M_P) = 100.0 kg/day, determine the metal salt dose mass (M_Me) in kg/day.
Given
Find
metal salt dose mass (M_Me), in kg/day
Start with the thinking
- The governing relation printed in this handbook section is Phosphorus Removal Equations.
- Everything except M_Me is given, so isolate M_Me 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.
- Phosphorus removal equations determine the metal salt dose needed for chemical precipitation of phosphorus.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for M_Me:
Step 3 — List the givens: metal to phosphorus molar ratio (MeP) = 1.5500, phosphorus mass to remove (M_P) = 100.0 kg/day.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning M_Me = 155.0 kg/day to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 310.0 — kept a factor of two that cancels in the correct rearrangement.
- 77.5000 — dropped that same factor in the other direction.
- 170.5 — rounded an intermediate value before the final step.
Reference: FE Handbook — Phosphorus Removal Equations
phosphorus removal equations for alum dosing at a treatment plant Given metal to phosphorus molar ratio (MeP) = 2.7000; metal salt dose mass (M_Me) = 448.0 kg/day, determine the phosphorus mass to remove (M_P) in kg/day.
Given
Find
phosphorus mass to remove (M_P), in kg/day
Start with the thinking
- The governing relation printed in this handbook section is Phosphorus Removal Equations.
- Everything except M_P is given, so isolate M_P 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.
- Phosphorus removal equations determine the metal salt dose needed for chemical precipitation of phosphorus.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for M_P:
Step 3 — List the givens: metal to phosphorus molar ratio (MeP) = 2.7000, metal salt dose mass (M_Me) = 448.0 kg/day.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning M_P = 165.9 kg/day to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 331.9 — kept a factor of two that cancels in the correct rearrangement.
- 82.9630 — dropped that same factor in the other direction.
- 182.5 — rounded an intermediate value before the final step.
Reference: FE Handbook — Phosphorus Removal Equations
phosphorus removal via chemical precipitation dose determination Given phosphorus mass to remove (M_P) = 355.0 kg/day; metal salt dose mass (M_Me) = 608.0 kg/day, determine the metal to phosphorus molar ratio (MeP).
Given
Find
metal to phosphorus molar ratio (MeP)
Start with the thinking
- The governing relation printed in this handbook section is Phosphorus Removal Equations.
- Everything except MeP is given, so isolate MeP 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.
- Phosphorus removal equations determine the metal salt dose needed for chemical precipitation of phosphorus.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for MeP:
Step 3 — List the givens: phosphorus mass to remove (M_P) = 355.0 kg/day, metal salt dose mass (M_Me) = 608.0 kg/day.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning MeP = 1.7127 to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 3.4254 — kept a factor of two that cancels in the correct rearrangement.
- 0.8563 — dropped that same factor in the other direction.
- 1.8839 — rounded an intermediate value before the final step.
Reference: FE Handbook — Phosphorus Removal Equations
phosphorus removal chemical dose calculation using metal to phosphorus ratio Given metal to phosphorus molar ratio (MeP) = 1.9500; phosphorus mass to remove (M_P) = 121.0 kg/day, determine the metal salt dose mass (M_Me) in kg/day.
Given
Find
metal salt dose mass (M_Me), in kg/day
Start with the thinking
- The governing relation printed in this handbook section is Phosphorus Removal Equations.
- Everything except M_Me is given, so isolate M_Me 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.
- Phosphorus removal equations determine the metal salt dose needed for chemical precipitation of phosphorus.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for M_Me:
Step 3 — List the givens: metal to phosphorus molar ratio (MeP) = 1.9500, phosphorus mass to remove (M_P) = 121.0 kg/day.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning M_Me = 236.0 kg/day to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 471.9 — kept a factor of two that cancels in the correct rearrangement.
- 118.0 — dropped that same factor in the other direction.
- 259.5 — rounded an intermediate value before the final step.
Reference: FE Handbook — Phosphorus Removal Equations
phosphorus removal equations for alum dosing at a treatment plant Given metal to phosphorus molar ratio (MeP) = 1.9000; metal salt dose mass (M_Me) = 218.0 kg/day, determine the phosphorus mass to remove (M_P) in kg/day.
Given
Find
phosphorus mass to remove (M_P), in kg/day
Start with the thinking
- The governing relation printed in this handbook section is Phosphorus Removal Equations.
- Everything except M_P is given, so isolate M_P 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.
- Phosphorus removal equations determine the metal salt dose needed for chemical precipitation of phosphorus.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for M_P:
Step 3 — List the givens: metal to phosphorus molar ratio (MeP) = 1.9000, metal salt dose mass (M_Me) = 218.0 kg/day.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning M_P = 114.7 kg/day to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 229.5 — kept a factor of two that cancels in the correct rearrangement.
- 57.3684 — dropped that same factor in the other direction.
- 126.2 — rounded an intermediate value before the final step.
Reference: FE Handbook — Phosphorus Removal Equations
phosphorus removal via chemical precipitation dose determination Given phosphorus mass to remove (M_P) = 353.0 kg/day; metal salt dose mass (M_Me) = 120.0 kg/day, determine the metal to phosphorus molar ratio (MeP).
Given
Find
metal to phosphorus molar ratio (MeP)
Start with the thinking
- The governing relation printed in this handbook section is Phosphorus Removal Equations.
- Everything except MeP is given, so isolate MeP 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.
- Phosphorus removal equations determine the metal salt dose needed for chemical precipitation of phosphorus.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for MeP:
Step 3 — List the givens: phosphorus mass to remove (M_P) = 353.0 kg/day, metal salt dose mass (M_Me) = 120.0 kg/day.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning MeP = 0.3399 to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 0.6799 — kept a factor of two that cancels in the correct rearrangement.
- 0.1700 — dropped that same factor in the other direction.
- 0.3739 — rounded an intermediate value before the final step.
Reference: FE Handbook — Phosphorus Removal Equations
phosphorus removal chemical dose calculation using metal to phosphorus ratio Given metal to phosphorus molar ratio (MeP) = 1.4500; phosphorus mass to remove (M_P) = 285.0 kg/day, determine the metal salt dose mass (M_Me) in kg/day.
Given
Find
metal salt dose mass (M_Me), in kg/day
Start with the thinking
- The governing relation printed in this handbook section is Phosphorus Removal Equations.
- Everything except M_Me is given, so isolate M_Me 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.
- Phosphorus removal equations determine the metal salt dose needed for chemical precipitation of phosphorus.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for M_Me:
Step 3 — List the givens: metal to phosphorus molar ratio (MeP) = 1.4500, phosphorus mass to remove (M_P) = 285.0 kg/day.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning M_Me = 413.3 kg/day to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 826.5 — kept a factor of two that cancels in the correct rearrangement.
- 206.6 — dropped that same factor in the other direction.
- 454.6 — rounded an intermediate value before the final step.
Reference: FE Handbook — Phosphorus Removal Equations