Tag Archives: activated sludge

Wastewater Treatment Spreadsheet Bundles

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Where to Find Wastewater Treatment Spreadsheet Bundles

To obtain wastewater treatment spreadsheet bundles, click here to visit our spreadsheet store. You can buy your choice of several different convenient wastewater treatment excel spreadsheet bundles  for a very reasonable prices.  These Excel spreadsheet bundles include process design calculations for MBBR wastewater treatment processes, MBR wastewater treatment processed, SBR wastewater treatment processes, activated sludge design calculations, and several other wastewater treatment processes.  These Excel spreadsheets are available in either U.S. units or S.I. units.  Read on for more information about these wastewater treatment spreadsheet bundles.

Available Wastewater Treatment Spreadsheet Bundles

The wastewater treatment spreadsheet bundles available from the EngineeringExcelTemplates.com DOWNLOADS page are “Biological-Secondary Wastewater Treatment Bundle“,  “Nitrification and Denitrification Bundle“, “Wastewater Treatment Complete Spreadsheet Bundle“. and “MBBR-MBR-SBR Spreadsheet Bundle”.

Descriptions of these spreadsheet bundles and descriptions of the spreadsheets included in each of them are available through the links in the previous paragraph.

MBBR processes in Wastewater Treatment Spreadsheet Bundles

MBBR wastewater treatment process design spreadsheets are included in all of the wastewater treatment spreadsheet bundles described above.  The MBBR wastewater treatment process is quite flexible.  It is used for domestic and industrial wastewater treatment and can be designed for BOD removal alone or in combination with nitrification or with nitrification and denitrification.  It is used as a single stage process or as a two-stage or three-stage process.

The diagram below shows the general configuration of a Pre-anoxic nitrification denitrification MBBR wastewater treatment process.  Denitrification can also be carried out in a Post-Anoxic nitrification denitrification process.

MBBR process in wastewater treatment spreadsheet bundles

Figure 1. MBBR Wastewater Treatment Flow Diagram for Pre-Anoxic Deniitrification

MBR Processes in Wastewater Treatment Spreadsheet Bundles

A membrane bioreactor wastewater treatment system (MBR) can provide a compact alternative to the conventional activated sludge process. The MBR process uses filtration through a membrane instead of secondary clarification, so it produces a very high quality effluent.  Primary clarification is not typically used in a membrane bioreactor wastewater treatment system.  Fine screening is needed as a minimum pretreatment, and depending upon wastewater characteristics, coarse screening and grit removal may be needed also. The diagram below shows a general flow diagram for a MBR wastewater treatment system for BOD removal and nitrification.

MBR flow diagram from Wastewater Treatment Spreadsheet BundlesFigure 2. MBR Wastewater Treatment Flow Diagram for BOD Removal and Nitrification

Currently the membrane module is typically immersed in the aeration tank as shown in the flow diagram.  Denitrification can also be carried out by adding a preanoxic tank before the aeration tank.

 References:

1. McQuarrie, J.P. and Boltz, J.P., Moving Bed Bio-film Reactor Technology: Process Design and Performance, Water Environment Research, Vol 83, No 6, June 2011.

2. Bengtson, Harlan, “MBBR Denitrification Design Spreadsheet,” an online blog article

3. Bengtson, Harlan, “MBR Wastewater Treatment Process Design,” an online blog article

3. Bengtson, Harlan H., “Biological Wastewater Treatment Process Design Calculations,” available as an Amazon Kindle ebook or as a paperback.

Activated Sludge Calculations in a Solids Mass Balance Spreadsheet

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Where to Find a Solids Mass Balance Spreadsheet for Activated Sludge Calculations

For Excel solids mass balance spreadsheets to make activated sludge calculations calculations, click here to visit our spreadsheet store.  Obtain a convenient, easy to use spreadsheet for solids mass balance activated sludge calculations for only $22.95. Read on for information about the use of an Excel spreadsheet for estimating the effect of recycle flow, BOD and TSS through solids mass balance activated sludge calculations.

Solids Mass Balance Background for Activated Sludge Calculations

Several streams from sludge treatment processes are typically recycled back into the wastewater treatment plant inflow.  Examples are sludge thickener overflow, anaerobic digester supernatant, aerobic digester supernatant, centrate from centrifuge dewatering, and filtrate from filtration dewatering.  The liquid flow, BOD load, and TSS load in these recycled streams contribute to the wastewater flow to be handled by the mainstream wastewater treatment processes.

An iterative solids mass balance is an organized procedure for estimating the total flow rate, BOD load, and TSS load in the recycled flows from sludge treatment and handling processes.  This type of calculation is illustrated in an eight page example in Metcalf and Eddy (Reference #1).  The flow diagram below shows a typical set of sludge treatment processes and recycle flows for an activated sludge plant.

Solids Flow Diagram for Activated Sludge Calculations


Activated Sludge Calculations Influent and Effluent Inputs for Spreadsheet

General information about the wastewater influent flow and characteristics will need to be input to the spreadsheet along with information about target effluent characteristics.  The screenshot below shows typical influent and effluent inputs needed.

Activated Sludge Calculations Solids Mass Balance Spreadsheet

Solids Mass Balance Activated Sludge Calculations for Each Treatment Process

The next step is solids mass balance calculations for each of the treatment processes, leading to estimates of the recycle flow rate, BOD load and TSS load for each recycle stream.  For a wastewater treatment plant with the flow diagram shown above, there would need to be solids mass balance calculations for the primary clarifier, the aeration tank/secondary clarifier, the sludge thickener, the anaerobic digester, and the sludge dewatering process.  The screenshot below shows typical inputs and outputs for a solids mass balance over a sludge thickener.

Screenshot thickener calculations - Activated Sludge Calculations

Similar calculations would be made for each of the wastewater treatment and sludge treatment/management processes, leading to information about recycle flow rate, BOD load, and TSS load, for each recycle stream as shown in the summary tables in the next section.  After completion of the first iteration, the recycle flowrate, BOD load and TSS load are added to values for those parameters for the incoming wastewater and all of the solids mass balance calculations are repeated in a second iteration.

Summary Tables

The screenshot below shows a set of tables summarizing the results of the calculated recycles flows from the first three iterations of the activated sludge calculations.   Spreadsheets are available to make this type of solids mass balance calculations in either U.S. or S.I. units at a very low cost (only $22.95) in our spreadsheet store.  These spreadsheets are set up to make the solids mass balance calculations for four iterations.

Summary Tables for Activated Sludge Calculations Solids Mass Balance

References

1. Metcalf & Eddy, Inc, (revised by Tchobanoglous, G, Burton, F.L., Stensel, H.D., Wastewater Engineering Treatment and Reuse, 4th Edition, New York, NY, 2003.

2. Bengtson, Harlan H.,  “Activated Sludge Solids Mass Balance Spreadsheet,”  an online blog article.

 

 

Activated Sludge Aeration Tank Design with Excel Spreadsheets

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Where to Find Spreadsheets for Activated  Sludge Aeration Tank Design

For Excel spreadsheets to use for activated sludge aeration tank design or operation calculations, click here to visit our spreadsheet store.  Get an easy to use spreadsheet to make a variety of activated sludge aeration tank design calculations for a very reasonable price. Read on for information about activated sludge aeration tank design and operation calculations.

The activated sludge process is widely used for biological wastewater treatment all over the world.  This method of biological wastewater treatment was invented in England in about 1914.  An activated sludge wastewater treatment system always has an aeration tank and secondary clarifier, which function as a unit to remove biodegradable organic matter (biochemical oxygen demand or BOD) and suspended solids from the wastewater and keep the aerobic microorganisms that carry out the treatment in the system.  Most types of activated sludge processes also have a primary clarifier that removes settleable solids from the incoming wastewater before it goes to the aeration tank.  A flow diagram for a typical activated sludge wastewater treatment plant is shown in the diagram below.  The diagram shows the typical flow pattern through the primary clarifier, aeration tank and secondary clarifier mentioned above, plus initial preliminary treatment (screening, flow measurement and grit removal) and disinfection, which is usually the final step in wastewater treatment.

diagram for activated sludge aeration tank design

This article will emphasize the equations, parameters, and calculations for design and operation of the aeration tank/secondary clarifier of an activated sludge plant.

Parameters for Activated Sludge Aeration Tank Design Calculations

Activated Sludge Aeration Tank Design Flow DiagramThe diagram at the left shows a typical flow pattern for a conventional activated sludge aeration tank and secondary clarifier.  Some of the parameters that are typically used in activated sludge aeration tank design calculations are shown for the primary effluent, secondary effluent, waste activated sludge, and recycle activated sludge. The following list shows those parameters, along with some others that are used for activated sludge calculations, with their U.S. and S.I. units.

  • primary effluent flow rate, Qo,  (MGD – U.S. or m3/day – S.I.)
  • primary effluent biochemical oxygen demand (BOD) concentration, So, (mg/L – U.S. or g/m3 – S.I.)
  • primary effluent suspended solids conc., Xo, (mg/L – U.S. or g/m3 – S.I.)
  • aeration tank volume, V, (ft3 – U.S. or m3 – S.I.)
  • aeration tank MLSS (suspended solids conc.), X, (mg/L – U.S. or g/m3 – S.I.)
  • secondary effluent flow rate, Qe,  (MGD – U.S. or m3/day – S.I.)
  • secondary effluent susp.solids conc., Xe, (mg/L – U.S. or g/m3 – S.I.)
  • secondary effluent biochemical oxygen demand (BOD) concentration, Se, (mg/L – U.S. or g/m3 – S.I.)
  • waste activated sludge flow rate, Qw, (MGD – U.S. or m3/day – S.I.)
  • waste activated sludge biochemical oxygen demand (BOD) conc., Sw, (mg/L – U.S. or g/m3 – S.I.)
  • waste activated sludge susp. solids conc., Xw (mg/L – U.S. or g/m3 – S.I.)
  • recycle activated sludge flow rate, Qr, (MGD – U.S. or m3/day – S.I.)
  • Food to Microorganism ratio, F:M, (lb BOD/day/lb MLVSS – U.S. or kg BOD/day/kg MLVSS – S.I.)
  • Hydraulic retention time, HRT, (hours for U.S or S.I.)
  • Sludge retention time (also called sludge age), SRT, (days for U.S. or S.I.)
  • Volumetric loading, VL, (lb BOD/day/1000 ft3 – U.S. or kg BOD/day/m3 – S.I.)
  • % volatile solids in the aeration tank mixed liquor suspended solids, %Vol.

Activated Sludge Aeration Tank Design Calculations with Excel Spreadsheets

The table below shows the typical range of values for three commonly used activated sludge aeration tank design parameters: volumetric loading, hydraulic retention time, and food to microorganism ratio. The table includes design information for three activated sludge variations: conventional plug flow, complete mix, and extended aeration activated sludge plants.

Activated Sludge Aeration Tank Design Parameters Table

The spreadsheet image below uses Excel formulas to calculate the required aeration tank volume based on values provided for the input parameters shown in the spreadsheet: primary effluent flow rate, Qo; primary effluent biochemical oxygen demand (BOD), So; Aeration tank MLSS, X; design volumetric loading, VL; and % volatile solids in the aeration tank, %Vol.  The Excel spreadsheet uses the input data to calculate the design value of aeration tank volume, V, and values for two other design parameters that are sometimes used to size the aeration tank, hydraulic retention time in the aeration tank, HRT, and food to microorganism ratio, F:M, using the following equations.

  • V = [ (8.34*So*Qo)/VL ] (1000)
  • VMG = V*7.48/1,000,000
  • HRT = 24*VMG/Qo
  • F:M = (8.34*So*Qo)/(8.34*%Vol*X*VMG)  =  (So*Qo)/(%Vol*X*VMG)

For Excel spreadsheets to make a variety of activated sludge aeration tank design and operation calculations in either U.S. or S.I. units for a very reasonable price, click here to visit our spreadsheet store.

Activated Sludge Aeration Tank Design Calculations Spreadsheet

Activated Sludge Aeration Tank Operational Calculations with Excel Spreadsheets

The table below shows typical ranges for several commonly used operational activated sludge waste water treatment process parameters. Note that the values for all of these parameters remain the same for U.S. or S.I. units.  MLSS concentration will have the S.I. unit of g/m3, which is numerically equal to the U.S. units of mg/L. SRT will have units of days for either the U.S. or S.I. system.  F:M will have the S.I. unit of kg BOD/day/kg MLVSS, which is numerically equal to the U.S. unit of lb BOD/day/lb MLVSS. The % unit for Qr/Qo remains the same for U.S. or S.I. units.

Activated Sludge Aeration Tank Design Operational ParametersThe Excel spreadsheet image shown below uses the input values to calculate the activated sludge operational parameters shown.  The input parameters required are: primary effluent information (flow rate, Qo; BOD, So; and TSS, Xo); TSS in the waste and recycle activated sludge streams, Xw; the aeration tank volume, V; aeration tank MLSS, X; % volatile solids in the MLSS, %Vol; and sludge retention time, SRT.

The activated sludge operational parameters calculated by the Excel formulas in the spreadsheet are: recycle activated sludge flow rate, Qr; waste activated sludge flow rate, Qw, and aeration tank food to microorganism ratio, F:M. The equations used are as follows:

  • Qr = (X – Xo)/(Xw – X)
  • VMG = V*7.48/1,000,000
  • Qw = (8.34*VMG*X)/(8.34*SRT*Xw)  =  (VMG*X)/(SRT*Xw)
  • F:M = (8.34*So*Qo)/(8.34*%Vol*X*VMG)  =  (So*Qo)/(%Vol*X*VMG)

For Excel spreadsheets to make a variety of activated sludge aeration tank design and operation calculations in either U.S. or S.I. units at a very reasonable price, click here to visit our spreadsheet store.

Activated sludge aeration tank design and operations spreadsheet

References

References for Further Information:

1. Metcalf & Eddy, Inc, (revised by Tchobanoglous, G, Burton, F.L., Stensel, H.D., Wastewater Engineering Treatment and Reuse, 4th Edition, New York, NY, 2003.

2. Vesilind, P.A. and Morgan, S.M., Introduction to Environmental Engineering, 2nd Edition, Belmont, CA, Brooks/Cole, 2004.

3. Grady, C.P.L., Daigger, G.T., Lim, H.C., Biological Wastewater Treatment, 2nd Edition, New York, NY, Marcel Dekker, Inc., 1999.

4. Bengtson, Harlan H. “Biological Wastewater Treatment Process Design Calculations,” available as an Amazon Kindle e-book and as a paperback.

5. Bengtson, Harlan H., “Activated Sludge Calculations Spreadsheet: Aeration Tank Calculations,” an Amazon Kindle e-book.