Here you will find informational articles on topics related to the Excel spreadsheets for civil and mechanical engineering calculations available from the DOWNLOADS page. This includes articles in the clickable categories below: pipe flow calculations, open channel flow, heat transfer/heat exchangers, storm water/hydrology, continuous beam analysis and design, open channel flow measurement, and pipe flow measurement topics. Scroll down on each category page to see all of the articles.
Similar blog articles are available at our companion site, www.EngineeringExcelSpreadsheets.com.
To obtain wastewater treatment Excel 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 Excel bundles.
The wastewater treatment spreadsheet bundles available from the EngineeringExcelTemplates.com DOWNLOADS page are "Biological-Secondary Wastewater Treatment Bundle", "Nitrification and Denitrification Bundle", and "Wastewater Treatment Complete 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 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.
Figure 1. MBBR Wastewater Treatment Flow Diagram for Pre-Anoxic Deniitrification
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.
Figure 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.
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, "Wastewater Treatment Spreadsheet Bundles," an online blog article
3. Bengtson, Harlan H., "Biological Wastewater Treatment Process Design Calculations," available as an Amazon Kindle ebook or as a paperback.
To obtain anSequencing Batch Reactor Denitrification Calculations Spreadsheet, click here to visit our spreadsheet store. This Excel spreadsheet is intended for making design calculations for either pre-anoxic or post-anoxic denitrification in a sequencing batch reactor. You can buy a convenient SBR denitrification calculations spreadsheet for a very reasonable price. It is available in either U.S. units or S.I. units. Read on for background information about sequencing batch reactor denitrification process design calculations.
The sequencing batch reactor is a batch type, fill and draw alternative to the continuous flow activated sludge process for biological wastewater treatment, including BOD removal, nitrification and denitrification. The typical components of a sequencing batch reactor operating cycle for BOD removal and nitrification are shown in the diagram below.
At least two tanks are typically used. In that case, the length of the fill period would be equal to the sum of the times for the react, settle and decant periods. Thus one tank would be filling while the other tank was going through the react, settle and decant periods and then the roles would be reversed.
In order to achieve denitrification, an anoxic period must be added. A typical sequencing batch reactor cycle for a post-anoxic denitrification process is shown in the figure below. A mixed anoxic react period is included after the aerobic react period.
For a pre-anoxic denitrification SBR process, some or all of the fill period would be anoxic and there would be no anoxic react period after the aerobic react period.
An example Sequencing Batch Reactor denitrification calculations spreadsheet is partially shown in the image below. This Excel spreadsheet can be used to set the times for the different parts of the SBR operating cycle, calculate the required tank size and check on the adequacy for nitrification and for denitrification. This Excel spreadsheet, as well as others for wastewater treatment process design calculations, is available in either U.S. or S.I. units for a very reasonable price in our spreadsheet store.
1. Metcalf & Eddy, Inc, (Revised by Tchobanoglous, G, Burton, F.L, Stensel, H.D.), Wastewater Engineering, Treatment and Reuse, 4th Ed., New York, NY, 2003.
2. Metcalf & Eddy, Inc, (Revised by Tchobanoglous, G, Burton, F.L, Stensel, H.D.), Wastewater Engineering, Treatment and Resource Recovery, 5th Ed., New York, NY, 2014.
3. Bengtson, Harlan H., "SBR Denitrification Calculations," an online blog article.
To obtain an Upflow Anaerobic Sludge Blanket Wastewater Treatment Spreadsheet, click here to visit our spreadsheet store. This Excel spreadsheet is intended for making UASB design calculations for the upflow anaerobic sludge blanket wastewater treatment process. You can buy a convenient spreadsheet for making USAB design calculations for a very reasonable price. It is available in either U.S. units or S.I. units. Read on for background information about upflow anaerobic sludge blanket wastewater treatment calculations.
The upflow anaerobic sludge blanket wastewater treatment process is typically used for treatment or pretreatment of wastewaters with a high BOD concentration. The process has a sludge blanket in the reactor zone, through which the influent wastewater flows. Also, the top part of the reactor includes a means for collecting the methane biogas generated by the anaerobic process. A schematic flow diagram of the process is shown here:
An example upflow anaerobic sludge blanket reactor design calculations spreadsheet is partially shown in the image below. This Excel spreadsheet can be used to calculate the required UASB reactor volume and dimensions, sludge production rate, methane production rate, and required alkalinity addition based on user input information on wastewater flow and characteristics, biokinetic parameters, methane stoichiometry parameters, and reactor configuration and design parameters. This Excel spreadsheet, as well as others for wastewater treatment process design calculations, is available in either U.S. or S.I. units for a very reasonable price in our spreadsheet store.
References:
3. Bengtson, Harlan, "UASB Design Calculations Spreadsheet," an online blog article
To obtain a DAF Design Calculations Spreadsheet, click here to visit our spreadsheet store. This Excel spreadsheet is intended for making dissolved air flotation design calculations. You can buy a convenient spreadsheet for making Dissolved Air Flotation design calculations for a very reasonable price. It is available in either U.S. units or S.I. units. Read on for background information about dissolved air flotation design calculations.
Dissolved air flotation is an alternative to clarification for removal of fine suspended mater from a water or wastewater stream. It is especially good for fine suspended matter that doesn't settle out well with regular clarification. The air-solids ratio, A/S, is typically calculated with the following equation:
Where: sa is the air solubility, f is an efficiency factor, P is the recycle pressure, R is the recycle flow rate, Sa is the influent suspended solids concentration, and Q is the influent flow rate. The required DAF area can be calculated based on a design value for DAF hydraulic loading rate or based on a design value for DAF solids loading rate.
An example DAF design calculations spreadsheet is partially shown in the image below. This Excel spreadsheet can be used to calculate A/S, the needed air to solids ratio, and the required DAF area based on user input information on influent design flow and characteristics. This Excel spreadsheet, as well as others for wastewater treatment process design calculations, is available in either U.S. or S.I. units for a very reasonable price in our spreadsheet store.
2. Bengtson, Harlan, "Dissolved Air Flotation Design Calculations Spreadsheet," an online blog article
To obtain a MBR Wastewater Treatment Process Design spreadsheet, click here to visit our spreadsheet store. This Excel spreadsheet is intended for making membrane bioreactor process design calculations. You can buy a convenient MBR wastewater treatment process design spreadsheet for a very reasonable price. This spreadsheet . It is available in either U.S. units or S.I. units. Read on for information about a membrane bioreactor wastewater treatment calculations spreadsheet.
Figure 1. MBR Wastewater Treatment Flow Diagram for BOD Removal and Nitrification
An example MBR wastewater treatment process design spreadsheet is partially shown in the image below. This Excel spreadsheet can be used to calculate the required volume and dimensions for the MBR aeration tank, membrane module, and preanoxic tank, based on user input membrane module information and wastewater design flow and characteristics. This Excel spreadsheet, as well as others for wastewater treatment process design calculations, is available in either U.S. or S.I. units for a very reasonable price in our spreadsheet store.
Figure 2. Screenshot of Membrane Bioreactor Wastewater Treatment Calculations Spreadsheet
2. Zaerpour, Masoud, "Design, Cost & Benefit Analysis of a Membrane Bioreactor," M.S. Thesis, Department of Environmental and Geomatic Engineering, Politecnico di Milan, Academic Year, 2013-2014.
3. Bengtson, Harlan, "Membrane Bioreactor Wastewater Treatment Calculations Spreadsheet," an online blog article
4. Bengtson, Harlan H., "Spreadsheets for MBR Wastewater Treatment Process Design Calculations," an Amazon Kindle ebook.
5. Bengtson, Harlan H., "Biological Wastewater Treatment Process Design Calculations," available at Amazon as a Kindle ebook or as a paperback.
To obtain an MBBR Denitrification Wastewater Treatment spreadsheet, click here to visit our spreadsheet store. This Excel spreadsheet is intended for MBBR nitrification denitrification process design calculations. You can buy a convenient MBBR Denitrification Wastewater Treatment spreadsheet for a very reasonable price. This spreadsheet makes MBBR process design calculations for BOD removal, nitrification, and denitrification. including both pre-anoxic and post-anoxic denitrification processes. It is available in either U.S. units or S.I. units. Read on for information about using an MBBR process design calculations spreadsheet for nitrification and denitrification.
The moving bed biofilm reactor (MBBR) appeared relatively recently on the wastewater treatment scene. It was developed in the 1990's, and is now used in many countries around the world.
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.
An example MBBR denitrification wastewater treatment spreadsheet is partially shown in the two images below. This Excel spreadsheet can be used to calculate the required MBBR tank volume and dimensions, based on user input media information and wastewater design flow and characteristics. This Excel spreadsheet, as well as others for wastewater treatment process design calculations, is available in either U.S. or S.I. units for a very reasonable price in our spreadsheet store.
2. Bengtson, Harlan, "MBBR Nitrification Denitrification Spreadsheet," an online blog article
4. Bengtson, Harlan H., "Spreadsheets for MBBR Denitrification Design Calculations," an Amazon Kindle ebook.
5. Bengtson, Harlan H., "Spreadsheets for MBBR Process Design Calculations," available as an Amazon Kindle ebook or as a paperback.
To obtain a Dissolved Oxygen Solubility in Water Calculator Excel spreadsheet, click here to visit our spreadsheet store. Look in the Dissolved Oxygen category on the Download page. This Excel spreadsheet is intended to calculate the dissolved oxygen solubility at a specified water temperature and atmospheric pressure for water temperature of 35 to 80 degrees F and atmospheric pressure of 600 to 760 mm Hg. You can buy a convenient dissolved oxygen solubility in water calculator Excel spreadsheet for a very reasonable price. This spreadsheet calculates dissolved oxygen saturation concentration based on user specified water temperature and atmospheric pressure. Calculations may be made in either U.S. or S.I. units. Read on for information about using a dissolved oxygen solubility in water calculator spreadsheet.
There are many tables available with values for the dissolved oxygen solubility in water over a range of water temperatures and atmospheric pressures. With an Excel spreadsheet, formulas can be derived using Excels graph plotting capability, for saturation dissolved oxygen concentration as a function of water temperature for a range of different values for atmospheric pressure. The spreadsheet can then conveniently calculate the dissolved oxygen solubility (saturation concentration) at user specified values for water temperature and atmospheric pressure. That is done in the spreadsheet being discussed here. The
Example Dissolved Oxygen Solubility in Water Calculator Excel Spreadsheet
An example dissolved oxygen saturation in water calculator Excel spreadsheet is partially shown in the image below. This Excel spreadsheet can be used to calculate the dissolved oxygen solubility in water at a specified water temperature and atmospheric pressure. This Excel spreadsheet, as well as others for wastewater treatment calculations, is available for both U.S. or S.I. units for a very reasonable price in our spreadsheet store.
References
To obtain a nitrification denitrification wastewater treatment process Excel spreadsheet, click here to visit our spreadsheet store. Look in the wastewater treatment category on the Download page. This Excel spreadsheet is intended for completely mixed activated sludge nitrification/denitrification calculations. You can buy a convenient nitrification denitrification wastewater treatment process Excel spreadsheet for a very reasonable price. This spreadsheet calculates the completely mixed aeration tank volume for BOD removal and nitrification as well as the volume for a pre-anoxic tank to achieve denitrification.. It is available in either U.S. or S.I. units. Read on for information about using a nitrification denitrification activated sludge process Excel spreadsheet.
The activated sludge wastewater treatment process can be designed for removal of BOD (organic matter that exerts an oxygen demand in the water), or for BOD removal and nitrification, or for BOD removal, nitrification and denitrification. Nitrification is oxidation of ammonia nitrogen in the wastewater to nitrate and denitrification is removal of nitrate from the wastewater.
A flow diagram for a nitrification denitrification activated sludge process is shown below. It includes a completely mixed activated sludge aeration tank for BOD removal and nitrification as well as an anoxic basin for denitrification.
An example nitrification denitrification activated sludge process Excel spreadsheet is partially shown in the image below. This Excel spreadsheet can be used to make design calculations for a nitrification denitrification activated sludge process. This Excel spreadsheet, as well as others for wastewater treatment calculations, is available in either U.S. or S.I. units for a very reasonable price in our spreadsheet store.
1. Metcalf and Eddy, Inc, (Revised by Tchobanoglous, G, Burton, F.L., Stensel, H.D.), Wastewater Engineering, Treatment and Reuse, 4th Ed., McGraw Hill, New York, NM, 2003.
1. Bengtson, Harlan H., Nitrification Denitrification Activated Sludge Process Spreadsheets, an informational online blog article.
To obtain an MBBR process design calculations spreadsheet, click here to visit our spreadsheet store. This Excel spreadsheet is intended for MBBR wastewater treatment design calculations. You can buy a convenient MBBR process design calculations spreadsheet for a very reasonable price. This spreadsheet makes MBBR wastewater treatment design calculations for several configurations for BOD removal and for nitrification. It is available in either U.S. or S.I. units. Read on for information about using an MBBR Process Design Calculations spreadsheet.
The moving bed biofilm reactor (MBBR) is a relatively recently developed wastewater treatment process. It was developed in the 1990's, but is now in use in many countries around the world.
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. It is used as a single stage process or as a two-stage or three-stage process.
An example MBBR process design calculations spreadsheet is partially shown in the image below. This Excel spreadsheet can be used to calculate the required MBBR tank volume and dimensions, based in user input media information and wastewater design flow and characteristics. This Excel spreadsheet, as well as others for wastewater treatment process design calculations, is available in either U.S. or S.I. units for a very reasonable price in our spreadsheet store.
1. McQuarrie, J.P. and Boltz, J.P., Moving Bed Biofilm Reactor Technology: Process Design and Performance, Water Environment Research, Vol 83, No 6, June 2011.
2. Bengtson, Harlan, "MBBR Wastewater Treatment Design Spreadsheet," an online blog article
3. Bengtson, Harlan, "Spreadsheets for MBBR Process Design Calculations", Available as an Amazon Kindle e-book and as a paperback.
4. Bengtson, Harlan H., "Biological Wastewater Treatment Process Design Calculations," available as an Amazon Kindle e-book or as a paperback.
To obtain a spreadsheet for trickling filter NRC formula in Excel design calculations, click here to visit our download page. For use in making trickling filter design calculations with the NRC equation, you can buy a convenient spreadsheet for the trickling filter NRC formula in Excel for a very reasonable price. This spreadsheet will use the NRC equations to calculate the trickling filter diameter needed for either a single stage or a two stage system and will calculate the estimated treatment efficiency for a specified trickling filter system, in either U.S. or S.I. units. Read on for information about a trickling filter NRC equation spreadsheet that makes trickling filter design calculations.
The trickling filter process is widely used for biological wastewater treatment all over the world. It is an attached growth biological wastewater treatment process. The aerobic microorganisms grow on a solid medium and the wastewater to be treated flows through the bed. A flow diagram for a typical single stage trickling filter wastewater treatment plant is shown in the diagram below. The diagram shows the typical flow pattern through the primary clarifier, trickling filter and secondary clarifier.
A spreadsheet for the trickling filter NRC equation in Excel is partially shown in the image below. It can be used to calculate the trickling filter diameter needed for either a single stage or a two stage trickling filter system using the NRC formula. The spreadsheet will also calculate an estimated treatment efficiency for a specified single stage or two stage trickling filter system. This Excel spreadsheet, as well as others for wastewater treatment calculations, is available in either U.S. or S.I. units for a very reasonable price in our spreadsheet store.
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. Bengtson, H. H., "Trickling Filter Design Calculations Spreadsheet," a blog article at www.EngineeringExcelSpreadsheets.com
Where to Find a Spreadsheet to Calculate Activated Sludge Oxygen Requirement
To obtain a spreadsheet to calculate activated sludge oxygen requirement, click here to visit our spreadsheet store. For use in calculating oxygen requirements and blower specifications, you can buy a convenient spreadsheet to calculate the activated sludge oxygen requirement for a very reasonable price. This spreadsheet will calculate the oxygen requirement and blower specifications for BOD removal or for BOD removal and nitrification for specified wastewater flow and characteristics and diffuser characteristics, in either U.S. or S.I. units. Read on for information about Excel spreadsheets that can be used to calculate the activated sludge oxygen requirement and blower parameters.
Activated Sludge Oxygen Requirement Calculation Background
The theoretical oxygen requirement for BOD removal can be approximated as ranging from 0.90 lb O2/lb BOD removed at an SRT of 5 days to 1.3 lb O2/lb BOD removed at an SRT of 20 days. This leads to the equation:
O_{2} requirement in lb/day = 0.90 + [(SRT - 5)/(20 - 5)](1.3 - 0.9)(lb/day BOD removed)
A design increase factor (safety factor) is typically multiplied times the calculated oxygen requirement to get the design oxygen transfer rate. The design oxygen transfer efficiency and the air density at design conditions can then be used to calculate the design air flow rate. The blower horsepower can then be calculated from the following equation:
Blower hp = (Q_{air})(ΔP)/(229*η)
Where:
If oxygen is to be provided for nitrification as well as BOD removal, then additional calculations are needed to estimate the oxygen requirement for nitrification.
Example Spreadsheet to Calculate the Activated Sludge Oxygen Requirement
A spreadsheet to calculate the activated sludge oxygen requirement is partially shown in the image below. It can be used to calculate the oxygen requirement and blower specifications for an activated sludge wastewater treatment system. This Excel spreadsheet, as well as others for wastewater treatment calculations, is available in either U.S. or S.I. units for a very reasonable price in our spreadsheet store.
Reference:
1. Bengtson, Harlan H., "A Spreadsheet to Calculate Oxygen Requirement Activated Sludge Process," an online blog article.
2. Bengtson, Harlan H., "Activated Sludge Calculations Spreadsheet: Aeration Tank Calculations," an Amazon Kindle ebook.
3. Bengtson, Harlan H., "Biological Wastewater Treatment Process Design Calculations," available as a paperback book or Amazon Kindle ebook.
Where to Find a SBR Wastewater Treatment Plant Design Spreadsheet
To obtain a SBR Wastewater Treatment Plant Design excel spreadsheet, click here to visit our spreadsheet store. For use in SBR wastewater treatment plant design calculations, you can buy a convenient sequencing batch reactor design calculation excel spreadsheet for a very reasonable price? This spreadsheet will make calculations for BOD removal, nitrification, denitrification, and biological phosphorus removal for given information about wastewater flow rate and characteristics, in either U.S. or S.I. units. Read on for information about Excel spreadsheets that can be used for SBR wastewater treatment plant design calculations.
SBR Wastewater Treatment Plant Design Background
A typical activated sludge wastewater treatment process operates as a continuous flow process, with incoming wastewater flow coming into a primary clarifier and treated effluent continuously coming off from the secondary clarifier. A sequencing batch reactor wastewater treatment system, on the other hand, operates as a batch system. Two or more tanks are required. While one tank is receiving influent wastewater (the "fill" part of the cycle), another tank is undergoing aeration (the "react" part of the cycle), settling (the "settle" part of the cycle) and decanting of treated effluent (the "decant" part of the cycle). This is illustrated in the diagram below.
SBR Wastewater Treatment Plant Design Applications
A sequencing batch reactor wastewater treatment system has a great deal of flexibility. It can be used for traditional BOD removal and nitrification using the four cycle components shown above. In that case there may be aeration for at least part of the fill cycle. If denitrification is to be accomplished also, then there should be no aeration during the fill cycle. If the SBR wastewater treatment system is to be designed for biological phosphorus removal as well, then an anaerobic react period is needed after the fill portion of the cycle, and an anoxic react is needed after the aerobic react part of the cycle, as shown in the diagram below.
Example SBR Wastewater Treatment Plant Design Excel Spreadsheet
The SBR Wastewater Treatment Plant Design excel spreadsheet partially shown in the image below can be used to make a variety of design calculations for a Sequencing Batch Reactor wastewater treatment system. Based on input information about the wastewater flow rate and characteristics, as well as the treatment objectives, the spreadsheet leads the user through calculations for deciding on times for each part of the SBR cycle, tank number and size, and checks on the adequacy of the design. This Excel spreadsheet, as well as others for wastewater treatment calculations, is available in either U.S. or S.I. units for a very reasonable price in our spreadsheet store.
REFERENCE: Bengtson, Harlan H., "Sequencing Batch Reactor Design Calculation Spreadsheet," an online blog article.
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For an activated sludge solids mass balance spreadsheet, click here for our download page. Obtain a convenient, easy to use spreadsheet for solids mass balance 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 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.
Influent and Effluent Input Information for the 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.
Solids Mass Balance 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.
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. 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) at our downloads page. These spreadsheets are set up to make the solids mass balance calculations for four iterations.
2. Bengtson, Harlan H., "Activated Sludge Calculations in a Solids Mass Balance Spreadsheet," an online blog article
Introduction
To obtain an Excel spreadsheet for activated sludge/secondary clarifier design calculations, click here to go to our download page. Obtain a convenient, easy to use primary and secondary clarifier design spreadsheet for only $10.95. Read on for information about the use of an Excel spreadsheet for secondary clarifier design calculations.
Secondary Clarifier Design Parameters
The parameters typically used for activated sludge/secondary clarifier design are the surface overflow rate (SOR), solids loading rate (SLR), and weir overflow rate (WOR). Activated sludge parameters are shown in the flow diagram at the right. The equations defining these three parameters are:
SOR = Q_{o}/A, SLR = (Q_{o} + Q_{r})X/A, and WOR = Q_{o}/L, where:
Typical values of surface overflow rate and solids overflow rate for activated sludge secondary clarifier design are shown in the tables below:
Calculation of Required Secondary Clarifier Surface Area
The equation for calculating the needed secondary clarifier surface area from a design SOR value with units as shown above is: A = Q_{o}*10^{6}/SOR
The formula for calculating secondary clarifier surface area from a design value of SLR with parameter units as shown above is: A = (Q_{o} + Qr)*8.34*X/SLR
An Excel Spreadsheet as a Secondary Clarifier Design Calculator
The Excel spreadsheet template shown below can be used to carry out the secondary clarifier design calculations described above. Why bother to make these calculations by hand? This Excel spreadsheet can handle the secondary clarifier surface area calculations and determine diameter for circular clarifier(s) or length and width for rectangular clarifier(s) and is available in either U.S. or S.I. units at a very low cost (only $10.95) at our download page. These spreadsheets also make weir overflow calculations to aid in effluent weir design.
Reference
Activated Sludge Introduction
The most widely used biological wastewater treatment process in the world is the activated sludge process. The process has only been around for about 100 years, since it was invented in England in the early 1900s. The main function of a properly operating activated sludge plant is removal of biodegradable organic matter (biochemical oxygen demand or BOD) and suspended solids from the incoming wastewater. The diagram below shows a typical activated sludge process flow diagram. Preliminary treatment usually includes screening, flow measurement and grit removal. The primary clarifier removes settleable solids before the flow goes to the aeration tank. The aeration tank and secondary clarifier function as a unit for removal of BOD and maintaining an adequate concentration of microorganisms in the aeration tank.
This article will provide details of the parameters, equations and calculations for design and operation of the aeration tank and secondary clarifier.
Parameters for Activated Sludge Calculations
The aeration tank/secondary clarifier flow diagram at the left shows some of the parameters used for activated sludge design and operational calculations. The parameters shown in the diagram, plus some more, are described with U.S. and S.I. units in the following list.
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Activated Sludge Design Calculations with Excel Templates
The table at the left shows typical values for three commonly used activated sludge aeration tank design parameters: volumetric loading, hydraulic retention time, and food to microorganism ratio. The table includes information for three activated sludge variations: conventional plug flow, complete mix, and extended aeration activated sludge plants.
The spreadsheet image below uses Excel formulas to calculate the required aeration tank volume based on entered values for the input parameters shown: primary effluent flow rate, Q_{o}; primary effluent biochemical oxygen demand (BOD), S_{o}; Aeration tank MLSS, X; design volumetric loading, VL; and % volatile solids in the aeration tank, %Vol. Using input values for these parameters, the Excel formulas in the spreadsheet calculate the design value of aeration tank volume, V, and values for two other design parameters 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.
To download an Excel spreadsheet for making activated sludge design or operational calculations go to our DOWNLOADS PAGE. These spreadsheets are available in U.S units or S.I. units.