The Models
Technical Info


Modeling of Wastewater Treatment Plants
EFOR is an advanced software simulation package for modeling the processes in a wastewater treatment plant. It is a valuable tool for the plant operator or the designer in forecasting or explaining the performance of the wastewater treatment plant. Different scenarios for plant configuration, plant operation and influent can easily be constructed and tested.
EFOR allows the operator to identify process bottlenecks and helps him to optimize the operation and to reduce the operating costs of the wastewater treatment plant. In this way the software package will aid the operator in the day-to-day decision-making at the wastewater treatment plant.

EFOR can be used as a stand-alone program or as an add-on to third party software. The latter can be achieved with the kernel that is available as a self-standing Dynamic Link Library for Windowsâ . This greatly enhances the applications of EFOR. One application, for instance, could be integration with a SCADA system as an online model or in the construction of dedicated educational tools within the field of wastewater treatment.

The History of EFOR:

EFOR was developed in the late eighties – early nineties by a group of Danish consultants in collaboration with the Technical University of Denmark and VKI. The development was partly funded by the Danish Agency for Trade and Industry.

Since late 1991, EFOR has been owned, distributed and supported by a company EFOR ApS, owned by Danish consultant Krüger A/S and Emolet Data. VKI - since January 2000 DHI – has participated actively in a steering group, which has supported the further development and marketing of EFOR ApS.

In December 2000, DHI agreed with Krüger A/S and Emolet Data to take over EFOR and continue the product as an integrated part of the DHI Software product family. As part of the agreement, the EFOR product manager, René Dupont, has been employed by DHI where he will continue to be responsible for the development and support of EFOR.

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EFOR 2002 - The Features

Virtually all wastewater treatment plants that are based on the activated sludge principle can be designed and operated in EFOR 2002. The wastewater treatment plants are easily designed by simple drag and drop of units and connection with pipes on the screen. The properties of the units are accessed and edited through the menu or by a simple double click on the relevant units and pipes.

The operation of the treatment plant is easily established and maintained through the construction of control loops. Control loops are logical connections between meters, controllers and controlled elements. The concept of cycles and phases makes it easy to build control loops, which have dynamic set-points or dynamic performance of pumps and aeration equipment.




Inflow data are presented and easily edited in spreadsheets. Each observation has an individual time stamp and length. The inflow data are transparently checked for mass balance errors and missing data are estimated with an advanced algorithm. Real world data can be imported from external data sources through an import function, which makes it easy to transport analytical data from other programs or from sensors.

The simulation results can be presented dynamically during or after the simulation in terms of charts or tables or both.

A wide range of results are calculated including flow in pipes, concentrations and process rates of analytical and model components in all units as well as sludge blanket in settlers, sludge age, etc. This means that the possibility of monitoring the state of the wastewater treatment plant is nearly unlimited.

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EFOR 2002 - The Models

The mathematical models implemented in EFOR are based on well-known and tested models of biological activated sludge processes. Names such as ASM-1, ASM-2 and ASM-3 should be known by most experts. As EFOR comprises all of these models plus several derived models, it should be possible to select the model that suits your purpose in the best way. The principal model named CNDP is based on ASM-1 and ASM-2d, and is able to model removal of organic matter, nitrification, denitrification and biological and chemical phosphorus removal.


If none of these models suits your needs, custom-made models can easily be built into your EFOR software in co-operation with the developer.

The process models are implemented by default in the activated sludge tanks and can be switched on/off for secondary settlers. This means that it is possible to calculate the effects of the biological processes that take place in the settlers.

Three different hydraulic models are available for the settlers. A split-point settler, a simple 2-layer settler and a full flux-model, which makes it possible to simulate biological processes, sludge-blanket movements and short-circuiting.

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EFOR 2002 - Technical Info
EFOR 3.0 is the latest edition of software tools aimed at simulation and modeling of wastewater treatment plants. EFOR 3.0 has been completely rewritten in an object-oriented language. It is a full 32-bit windows-program compatible with Microsoft Windows 95/98® and Windows NT 4.0®.

The program will run on any standard PC with one of the above operating systems, but as EFOR 3.0 is computationally intensive, speed often becomes crucial. It is therefore recommended to use a PC which is equipped with minimum a Pentium® processor and a screen with a resolution of 800× 600 points.

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