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Critical Time refers to the minimum dissolved oxygen concentration occurs, found by differentiating the dissolved oxygen equation with respect to time. Check FAQs
tc=(1KR-KD)log10((KDLt-KRDo+KDDoKDLt)(KRKD))
tc - Critical Time?KR - Reoxygenation Coefficient?KD - Deoxygenation Constant?Lt - Oxygen Equivalent?Do - Initial Oxygen Deficit?

Critical Time Example

With values
With units
Only example

Here is how the Critical Time equation looks like with Values.

Here is how the Critical Time equation looks like with Units.

Here is how the Critical Time equation looks like.

697.8548Edit=(10.22Edit-0.23Edit)log10((0.23Edit0.21Edit-0.22Edit7.2Edit+0.23Edit7.2Edit0.23Edit0.21Edit)(0.22Edit0.23Edit))
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Critical Time Solution

Follow our step by step solution on how to calculate Critical Time?

FIRST Step Consider the formula
tc=(1KR-KD)log10((KDLt-KRDo+KDDoKDLt)(KRKD))
Next Step Substitute values of Variables
tc=(10.22d⁻¹-0.23d⁻¹)log10((0.23d⁻¹0.21mg/L-0.22d⁻¹7.2mg/L+0.23d⁻¹7.2mg/L0.23d⁻¹0.21mg/L)(0.22d⁻¹0.23d⁻¹))
Next Step Convert Units
tc=(12.5E-6s⁻¹-2.7E-6s⁻¹)log10((2.7E-6s⁻¹0.0002kg/m³-2.5E-6s⁻¹0.0072kg/m³+2.7E-6s⁻¹0.0072kg/m³2.7E-6s⁻¹0.0002kg/m³)(2.5E-6s⁻¹2.7E-6s⁻¹))
Next Step Prepare to Evaluate
tc=(12.5E-6-2.7E-6)log10((2.7E-60.0002-2.5E-60.0072+2.7E-60.00722.7E-60.0002)(2.5E-62.7E-6))
Next Step Evaluate
tc=60294655.3173632s
Next Step Convert to Output's Unit
tc=697.854806913926d
LAST Step Rounding Answer
tc=697.8548d

Critical Time Formula Elements

Variables
Functions
Critical Time
Critical Time refers to the minimum dissolved oxygen concentration occurs, found by differentiating the dissolved oxygen equation with respect to time.
Symbol: tc
Measurement: TimeUnit: d
Note: Value should be greater than 0.
Reoxygenation Coefficient
Reoxygenation Coefficient is referred as the parameter used in water quality modeling to describe the rate at which oxygen is transferred from the atmosphere to the water body.
Symbol: KR
Measurement: First Order Reaction Rate ConstantUnit: d⁻¹
Note: Value should be greater than 0.
Deoxygenation Constant
Deoxygenation Constant is referred as the value obtained after decomposing of oxygen in sewage.
Symbol: KD
Measurement: First Order Reaction Rate ConstantUnit: d⁻¹
Note: Value should be greater than 0.
Oxygen Equivalent
The Oxygen Equivalent is referred as the oxidizable organic matter present in sewage.
Symbol: Lt
Measurement: DensityUnit: mg/L
Note: Value should be greater than 0.
Initial Oxygen Deficit
Initial Oxygen Deficit is referred as the amount of oxygen required at initial levels.
Symbol: Do
Measurement: DensityUnit: mg/L
Note: Value should be greater than 0.
log10
The common logarithm, also known as the base-10 logarithm or the decimal logarithm, is a mathematical function that is the inverse of the exponential function.
Syntax: log10(Number)

Other Formulas to find Critical Time

​Go Critical Time when we have Critical Oxygen Deficit
tc=log10DcKRKDLtKD
​Go Critical Time given Self Purification Constant with Critical Oxygen Deficit
tc=log10DcfLtKD
​Go Critical Time given Self Purification Factor
tc=-(log101-(f-1)(DcLt)fKD(f-1))

How to Evaluate Critical Time?

Critical Time evaluator uses Critical Time = (1/(Reoxygenation Coefficient-Deoxygenation Constant))*log10(((Deoxygenation Constant*Oxygen Equivalent-Reoxygenation Coefficient*Initial Oxygen Deficit+Deoxygenation Constant*Initial Oxygen Deficit)/Deoxygenation Constant*Oxygen Equivalent)*(Reoxygenation Coefficient/Deoxygenation Constant)) to evaluate the Critical Time, The Critical Time formula is defined as the crucial time period in which certain tasks must be completed to avoid project delays. It often relates to the critical path method (CPM) where the longest stretch of dependent activities determines the shortest possible duration to complete a project. Critical Time is denoted by tc symbol.

How to evaluate Critical Time using this online evaluator? To use this online evaluator for Critical Time, enter Reoxygenation Coefficient (KR), Deoxygenation Constant (KD), Oxygen Equivalent (Lt) & Initial Oxygen Deficit (Do) and hit the calculate button.

FAQs on Critical Time

What is the formula to find Critical Time?
The formula of Critical Time is expressed as Critical Time = (1/(Reoxygenation Coefficient-Deoxygenation Constant))*log10(((Deoxygenation Constant*Oxygen Equivalent-Reoxygenation Coefficient*Initial Oxygen Deficit+Deoxygenation Constant*Initial Oxygen Deficit)/Deoxygenation Constant*Oxygen Equivalent)*(Reoxygenation Coefficient/Deoxygenation Constant)). Here is an example- 0.002576 = (1/(2.5462962962963E-06-2.66203703703704E-06))*log10(((2.66203703703704E-06*0.00021-2.5462962962963E-06*0.0072+2.66203703703704E-06*0.0072)/2.66203703703704E-06*0.00021)*(2.5462962962963E-06/2.66203703703704E-06)).
How to calculate Critical Time?
With Reoxygenation Coefficient (KR), Deoxygenation Constant (KD), Oxygen Equivalent (Lt) & Initial Oxygen Deficit (Do) we can find Critical Time using the formula - Critical Time = (1/(Reoxygenation Coefficient-Deoxygenation Constant))*log10(((Deoxygenation Constant*Oxygen Equivalent-Reoxygenation Coefficient*Initial Oxygen Deficit+Deoxygenation Constant*Initial Oxygen Deficit)/Deoxygenation Constant*Oxygen Equivalent)*(Reoxygenation Coefficient/Deoxygenation Constant)). This formula also uses Common Logarithm (log10) function(s).
What are the other ways to Calculate Critical Time?
Here are the different ways to Calculate Critical Time-
  • Critical Time=log10((Critical Oxygen Deficit*Reoxygenation Coefficient)/(Deoxygenation Constant*Oxygen Equivalent))/Deoxygenation ConstantOpenImg
  • Critical Time=log10(Critical Oxygen Deficit*Self-Purification Constant/Oxygen Equivalent)/Deoxygenation ConstantOpenImg
  • Critical Time=-(log10(1-(Self-Purification Constant-1)*(Critical Oxygen Deficit/Oxygen Equivalent)*Self-Purification Constant)/(Deoxygenation Constant*(Self-Purification Constant-1)))OpenImg
Can the Critical Time be negative?
No, the Critical Time, measured in Time cannot be negative.
Which unit is used to measure Critical Time?
Critical Time is usually measured using the Day[d] for Time. Second[d], Millisecond[d], Microsecond[d] are the few other units in which Critical Time can be measured.
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