fundamental concepts: mass balance - onsite …...2005. fundamental concepts: mass balance - power...

Fundamental Concepts: Fundamental Concepts: Mass BalanceMass Balance

Ann KenimerAnn KenimerTexas A & M UniversityTexas A & M University

University Curriculum Development for University Curriculum Development for Decentralized Wastewater Decentralized Wastewater

ManagementManagement

NDWRCDP DisclaimerNDWRCDP DisclaimerThis work was supported by the National Decentralized Water This work was supported by the National Decentralized Water Resources Capacity Development Project (NDWRCDP) with Resources Capacity Development Project (NDWRCDP) with

funding provided by the U.S. Environmental Protection Agency funding provided by the U.S. Environmental Protection Agency through a Cooperative Agreement (EPA No. CR827881through a Cooperative Agreement (EPA No. CR827881--0101--0) 0) with Washington University in St. Louis. These materials have with Washington University in St. Louis. These materials have

not been reviewed by the U.S. Environmental Protection not been reviewed by the U.S. Environmental Protection Agency. These materials have been reviewed by Agency. These materials have been reviewed by representatives of the NDWRCDP. The contents representatives of the NDWRCDP. The contents

of these materials do not necessarily reflect the views and of these materials do not necessarily reflect the views and policies of the NDWRCDP, Washington University, or the U.S. policies of the NDWRCDP, Washington University, or the U.S.

Environmental Protection Agency, nor does the mention of trade Environmental Protection Agency, nor does the mention of trade names or commercial products constitute their endorsement or names or commercial products constitute their endorsement or

recommendation for use.recommendation for use.

CIDWT/University DisclaimerCIDWT/University DisclaimerThese materials are the collective effort of individuals from These materials are the collective effort of individuals from

academic, regulatory, and private sectors of the academic, regulatory, and private sectors of the onsite/decentralized wastewater industry. These materials have onsite/decentralized wastewater industry. These materials have

been peerbeen peer--reviewed and represent the current state of reviewed and represent the current state of knowledge/science in this field. They were developed through a knowledge/science in this field. They were developed through a series of writing and review meetings with the goal of formulatiseries of writing and review meetings with the goal of formulating ng a consensus on the materials presented. These materials do not a consensus on the materials presented. These materials do not

necessarily reflect the views and policies of University of necessarily reflect the views and policies of University of Arkansas, and/or the Consortium of Institutes for Decentralized Arkansas, and/or the Consortium of Institutes for Decentralized

Wastewater Treatment (CIDWT). The mention of trade names or Wastewater Treatment (CIDWT). The mention of trade names or commercial products does not constitute an endorsement or commercial products does not constitute an endorsement or

recommendation for use from these individuals or entities, nor recommendation for use from these individuals or entities, nor does it constitute criticism for similar ones not mentioned.does it constitute criticism for similar ones not mentioned.

CitationCitationKenimer, Ann L., J. Kenimer, Ann L., J. VilleneuveVilleneuve and S. and S. SheldenShelden. .

2005. Fundamental Concepts: Mass Balance 2005. Fundamental Concepts: Mass Balance --Power Point Presentation. Power Point Presentation. inin (M.A. Gross and (M.A. Gross and N.E. Deal, eds.) University Curriculum N.E. Deal, eds.) University Curriculum Development for Decentralized Wastewater Development for Decentralized Wastewater Management. National Decentralized Water Management. National Decentralized Water Resources Capacity Development Project. Resources Capacity Development Project. University of Arkansas, Fayetteville, AR.University of Arkansas, Fayetteville, AR.

Conservation of MassConservation of Mass

Mass is neither created nor destroyedMass is neither created nor destroyed

Therefore, mass that enters a system will Therefore, mass that enters a system will either collect in the system or leave the either collect in the system or leave the

systemsystem


Input = Output + AccumulationInput = Output + Accumulation


Often there will be Often there will be multiple inputs and multiple inputs and outputsoutputs

We still assume that We still assume that everything that goes everything that goes in must be equal to in must be equal to the amount that the amount that leaves or leaves or accumulates inside accumulates inside the systemthe system


What is the rate of accumulation of this system?What is the rate of accumulation of this system?


Rate of Accumulation = Input Rate of Accumulation = Input -- OutputOutputInput = 2 kg/s + 2 kg/s = 4 kg/sInput = 2 kg/s + 2 kg/s = 4 kg/sOutput = 4 kg/sOutput = 4 kg/s

Rate of Accumulation = 4 kg/s Rate of Accumulation = 4 kg/s –– 4 kg/s = 0 kg/s4 kg/s = 0 kg/s


Conservation principals are still used when Conservation principals are still used when input materials are mixedinput materials are mixed

1/2 cup of milk is poured into a bowl, along 1/2 cup of milk is poured into a bowl, along with 2 cups of flour, and one egg. The with 2 cups of flour, and one egg. The material is thoroughly mixed. All of the material is thoroughly mixed. All of the material is poured out. How much milk material is poured out. How much milk was poured out of the bowl?was poured out of the bowl?

Types of ProcessesTypes of Processes

Batch ProcessBatch Process

Continuous ProcessContinuous Process


All input materials added into systemAll input materials added into systemInput materials processedInput materials processedAll material released from systemAll material released from system


The follow equation can be applied:The follow equation can be applied:

Accumulation = Input Accumulation = Input -- OutputOutput


Inputs are continuously Inputs are continuously addedaddedMaterial continuously Material continuously processedprocessedOutput material Output material released continuouslyreleased continuously


The following equation may be applied:The following equation may be applied:

Rate of Accumulation = Rate of Accumulation = Rate of Input Rate of Input –– Rate of OutputRate of Output

ConcentrationConcentration

We will often need to know the amount of We will often need to know the amount of matter that passes through a system matter that passes through a system

For example, we might want to know how For example, we might want to know how much particulate matter is going through a much particulate matter is going through a systemsystem


We must know the following:We must know the following:•• How much material is in every unit volumeHow much material is in every unit volume•• What volume of material is passing What volume of material is passing

through the systemthrough the system

Mass flow rate = Conc. * Vol. flow rateMass flow rate = Conc. * Vol. flow rateOrOr

Mass = Concentration * Flow VolumeMass = Concentration * Flow Volume


Mass = Concentration * VolumeMass = Concentration * VolumeMass = 5 particles/ box * 4 boxes = 20 particlesMass = 5 particles/ box * 4 boxes = 20 particles

Percent CompositionPercent Composition

•• Materials may have a percent composition Materials may have a percent composition by mass by mass

•• A slurry might have 30% solids. This A slurry might have 30% solids. This means that for every 100kg of slurry there means that for every 100kg of slurry there are 30kg of solidsare 30kg of solids


Constituent Mass = Constituent Mass = Total Mass * Fraction CompositionTotal Mass * Fraction Composition


The mass of water present can be found by The mass of water present can be found by subtracting the mass of the solid material subtracting the mass of the solid material from the total mass.from the total mass.

Water mass = Water mass = Total mass Total mass –– Constituent massConstituent mass

Cookbook ProcedureCookbook ProcedureIdentify the system and define the system Identify the system and define the system boundariesboundaries——you choose based on your needsyou choose based on your needsDetermine whether the process is batch or Determine whether the process is batch or continuous. Determine whether the materials continuous. Determine whether the materials involved change form or compositioninvolved change form or compositionIdentify all inputs and outputsIdentify all inputs and outputs——diagram as diagram as neededneededIdentify known quantities of mass or flow ratesIdentify known quantities of mass or flow ratesIdentify unknown quantities and assign a Identify unknown quantities and assign a variable to eachvariable to eachUse mass balance equations to determine Use mass balance equations to determine unknowns and solveunknowns and solve

fundamental concepts: mass balance - onsite …...2005. fundamental concepts: mass balance - power...

Documents