Development of Primary Sedimentation Tank Ontology for the Use of Civil and Environmental Engineers Sofija Radulovic (ID: 0508132)

An ontology was created in Protégé to be used for: (1) structural and environmental engineers to have a basic understanding of the other’s design parameters, (2) a knowledge base of minimum/maximum/typical design values, (3) a knowledge base for clients without an engineering background (government officials), and (4) engineering students learning about wastewater treatment. Class hierarchies were determined based on what knowledge is needed to understand the physical (structural) and functional (environmental) sides of a primary sedimentation tank in order for these uses to be achieved.

There are two main types of primary sedimentation tanks: circular and rectangular, which have slightly different components.

 

Fig 1. Circular and Rectangular Primary Sedimentation Tanks

The class hierarchy was determined by what intended users need to know to achieve the ontology’s 4 intended uses and to cover the scope of the ontology. The following questions were answered:

What is the purpose? This ontology serves to streamline conceptual design of a primary sedimentation tank for civil and environmental engineers and provide a knowledge base of design parameters.

What is the scope? This ontology includes both basic structural (materials, components, design) and basic functional (wastewater treatment) components of a primary sedimentation tank. 

Who are the intended users? The intended users are engineers designing the primary sedimentation tank, clients, and students. 

What is the intended use? (1) structural and environmental engineers should have a basic understanding of the other’s design parameters, (2) knowledge base of minimum/maximum/typical design values, (3) use by clients without an engineering background (eg. government officials) to understand basic concepts of a primary sedimentation tank, (4) study tool for learning about primary sedimentation tanks.

2. Protégé Ontology

2.1 Classes and Subclasses 

2.1.1 FunctionalityPrimarySedTank and StructurePrimarySedTank

This division of structural and functionality is for the ontology’s first use: allowing structural and environmental engineers to have easy access to the other’s basic design parameters. The classes FunctionalityPrimarySedTank and StructurePrimarySedTank were disjointed because one relates to the structural engineer, and the other to environmental. Thus, instances were not allowed to be included in both.

Fig 2. FunctionalityPrimarySedTank and StructurePrimarySedTank

2.1.2 FunctionalityPrimarySedTank Subclasses

The first subclass is BioChemMeasurementsPrimarySedTank, which tells the users the most important biochemical parameters that will decrease during treatment. Without this subclass, the system would have no function. 

The second subclass ChemicalsPrimarySedTank represents chemicals added to improve treatment efficiency (Ghosh, 2011). This was added because it is important knowledge to be aware of regarding improving efficiency and corrosion. These subclasses were made disjoint as only one of the chemicals would be added.

Fig 3. Structure of FunctionalityPrimarySedTank

2.1.3 StructurePrimarySedTank Subclasses 

2.1.3.1 StructurePrimarySedTank → SectionsPrimarySedimentationTank

The structural engineer must know what a primary sedimentation tank is—what sections make up a primary sedimentation tank? A primary sedimentation tank’s sections depend if the tank is circular or rectangular, thus creating the need for two subclasses under SectionsPrimarySedimentationTank, as seen in Fig X. SectionsCircularPrimarySedTank and SectionsRectangularSedTank include subclasses of the components which make up each. SectionsRectangularPrimarySedTank includes ControlSystem, Pipes, Tank and Weir. SectionsCircularPrimarySedTank includes all of these and a mixing blade

Fig. 4. SectionsPrimarySedimentationTank split into Circular and Rectangular

2.1.3.2 StructurePrimarySedTank → MaterialPrimarySedTank 

The civil engineer’s knowledge should include which materials make up the respective components (Schnaars, 2018), thus MaterialPrimarySedTank was included. The materials include reinforced concrete (pipes, tank, and weir), stainless steel (mixing blades and scraper blade) and electrical (control system) (Mahdi, 2023) (Schnaars, 2018) (Nixon, 2015). 

Fig 5. MaterialPrimarySedTank and Subclasses of MaterialPrimarySedTank

2.1.3.3 StructurePrimarySedTank → StructuralDesignPrimarySedTank

The design parameters the civil engineer are included here. Subclasses under circular and rectangular design classes were created for the second purpose of the ontology: easy access to maximum/minimum/typical design parameter values. Option 1 represented the minimum (eg. minimum diameter of a primary sedimentation), Option 2 represented the maximum, and Option 3 represented typical (Moore and EPA, 2023). 

2.2 Instances and Property Assertions

Instances had minimum/maximum/typical values as data property assertions. Fig 7 shows minimum parameters for a rectangular tank (Option 1). These data properties were chosen because they were determined by the US Environmental Protection Agency as essential (Moore and EPA, 2023). 

Fig 7. Data Property Assertions (RectangularPrimarySedTankOption1)

Instances of essential treatment parameters were included under the class names of these biochemical measurements, so data property assertions could be added. In Figure 8, instance {BODRemoval} was added under class BODPercentage to add minimum BOD removal percentage acceptable (20%) and maximum BOD removal percentage possible (35%) as data property assertions (Moore and EPA, 2023).

Fig 8. Example of Minimum and Maximum Biochemical Removal Parameters

2.3 Object Properties/Inverse/Domain and Range

2.3.1 Object Properties

The role of each class to structure and functionality was determined and object properties were created for these relationships. For example, MaterialPrimarySedTank are the materials of StructuralPrimarySedTank, thus this role is defined by the object property isMaterialOf.

2.3.2 Inverses The ontology needed to show this role goes both ways: StructuralPrimarySedTank has its materials listed in MaterialPrimarySedTank. Thus, object property hasMaterial was created and made an inverse of isMaterialOf, as seen in Fig 9.

Fig 9. Inverse Object Property Roles

2.3.3 Domain and Range

Each object property’s domain was defined as where the relationship “starts” (top concept) and the range was defined as where the relationship “ends” (bottom concept). Fig 10 shows an example of domain and range.

Fig 10. Domain and Range

2.4 Logic Axioms/SROIQ Constructors The logical axioms used in the ontology were: classes/subclasses, object properties, inverses, domain/range, instances, restrictions, data properties, disjoint classes. An example of each logic axiom is shown in Table 1 (Krötzsch et al., 2013).

Table 1. Examples of Logic Axioms

3. Ontology Procedures According to Noy and McGuinness

3.1 Transitivity: Each subclass must be related to the classes before (Noy and McGuinness). For example, all subclasses under StructuralPrimarySedimentationTank were related to structural aspects of the primary sedimentation tank. 

3.2 Number of Classes: Noy and McGuinness’ suggestion that the number of direct subclasses should be between 2 and 12 was followed

3.3 Generality: The siblings of the same class always had the same level of generality

3.4 Multiple Inheritance Multiple inheritance—a subclass that is a subclass of two classes—was used with SectionsRectangularPrimarySedTank and SectionsCircularPrimarySedTank since both had many of the same components.

3.5 Naming: Spacing was not used to allow the possibility of interacting with other systems. The suggestion to not use abbreviations was not followed. “PrimarySedTank” was used instead of “PrimarySedimentationTank” to avoid hard-to-read classes. Since this is an ontology for primary sedimentation tanks, it is assumed all users would understand.

3.6 Disjointing: StructurePrimarySedTank and FunctionalityPrimarySedTank were disjointed because an instance which belonged to one would not belong to the other.

3.7 Ontology Websites: As mentioned by Noy and McGuinness, ontologies can be uploaded to ontology-sharing sites, where other users can use this ontology as a base to create a more specific or broader ontology. This was taken into account by providing clear annotations and not using spaces in order for the ontology to be clear to new users and possibly work with other systems.

4. Engineering Uses 

1. Improvement of Wastewater Treatment 

Scenario: The primary sedimentation tank at a wastewater treatment plant has an BOD removal efficiency of 25% and environmental engineers and the governmental clients know this value is acceptable, but want to know where it lies on the acceptable range. 

Ontology Use: The environmental engineers and client can easily access the maximum and minimum BOD removal percentages and see that while 25% BOD removal is acceptable, it is on the low end of the range. To improve this, they can see which chemicals can be added to the primary sedimentation tank within the ontology.

2. A new primary sedimentation tank is needed as soon as possible

Scenario: A wastewater treatment plant in a neighboring municipality which had a primary sedimentation tank classified as “Small” is taken out of use. The wastewater of this municipality will be rerouted to our municipality. Engineers in our municipality need to design a new small primary sedimentation tank to treat the increased inflow as soon as possible. 

Ontology Use: Civil engineers in our municipality can use the ontology to have easy access to the minimum design parameters which will suffice for a small primary sedimentation tank to treat the increased flow. By having this information readily available, environmental and civil engineers can work quickly on a design in CAD and structural modelling programs. They can also add values to the ontology as they design, so that there is clearer and faster communication between the two teams.

3. Updating materials of an old primary sedimentation tank 

Scenario: The US has a lot of outdated wastewater infrastructure technologies. The government of a local municipality needs to update various parts of the primary sedimentation tank as it was made of outdated materials and has succumbed to corrosion. 

Ontology Use: The civil engineers of this municipality can access this ontology to have access to the best materials for each section that will not as easily succumb to corrosion. For example, choosing stainless steel for the scraper blade is a great choice against corrosion. The ontology will inform them of what other parts of the primary sedimentation tank this material is connected to. The new design with improved materials can be modelled using other software, namely CAD.

5. Improvements to Ontology

An ontology can always be improved to include more specifics or a larger scope (Hartmann, 2024). More specificity can be added with information used in design calculations, such as material properties (Young’s Modulus). This ontology could be broader by including all basic steps of a wastewater treatment plant.

 

 

Parametric Model for Flexible Design of US Primary Sedimentation Tanks for Use in Neighborhood Wastewater Recycling 

Abstract: A Dynamo parametric model was created for flexible design use of a neighborhood primary sedimentation tank in the US. Fourteen input parameters were adjusted based on wastewater flow and analyzed based on building basement physical constraint. High-performance criteria—detention time and surface overflow rate—were added to assess the design. The parametric model was based on US EPA standards, but the model could be easily transformed for use in other nations. 

The design challenge is threefold:

1. Create a parametric model of a primary sedimentation tank within the physical constraint of a building’s basement. 
2. Dynamo is advantageous over Revit due to flexible design regarding wastewater flow changes (increased population/building use change) or increasing tank elevation (climate-change flooding). 
3. Dynamo allows inclusion of high-performance criteria, allowing civil engineers to verify if chosen structural parameters (tank height/width/length) functionally work before sending it to other engineering teams, thus increasing efficiency in the engineering firm. 

Domain: Rectangular primary sedimentation tank for use in residential buildings for treatment of neighborhood wastewater. 

Intended Users/Uses: (1) Civil engineers can use this model to check if their design functionally works before sending it to other engineering teams to increase efficiency in engineering firms. (2) Combining model with building model using Speckle to reduce design conflicts.

Input Parameters: If personal experience is used, it is cited as (Radulovic, 2025).

Parameter	Range	Purpose
Tank Length	15 to 45 meter (Moore and EPA, 2023) (Radulovic, 2025) Upper limit: building basement constraint	Flexible Design: Increased flow. Required for high performance criteria
Tank Width	3 to 24.3 meter (Moore and EPA, 2023)
Tank Height	3 to 4.5 meter (Moore and EPA, 2023)
Number of Inlet Pipes	1 – 4
Neighborhood Residents	~10,000-100,000 (NYC Planning, 2024).
Wastewater Flow	200 – 300 L/Person/Day (Toprak, 2006)
Industry Wastewater	10,000 to 1,000,000 (Action Manufacturing)
Tank Elevation	0 to 2 meters (Radulovic, 2025)	Flexible Design: Elevating tank if flooding occurs.
Angle of Tank Bottom	0º to 7º (Schnaars, 2018)	Flexible Design: Faster sludge removal if wastewater quality worsens (building use change).
Sludge Scrapers Frequency	1 Scraper Per 1 to 4 Meters (Radulovic, 2025)
Sludge Blanket Height	0.3 to 0.76 meters  (Water Environment Federation, 2017) (Radulovic, 2024) Upper limit decreased for neighborhood application
Sludge Trough Length:Tank Length Ratio	0.05 to 0.2
Sludge Pipe Radius	0.2 to 0.4 meters
Start Point of Inlet Pipes	20% to 40% tank width	Visual Flexible Design Parameter

 

High Performance Criteria: Not all combinations of input parameters will be good choices. A high ratio of tank height to surface area leads to circulation zones, decreasing tank efficiency (Shahrokhi et al., 2012). To avoid circulation zones, surface overflow rate is a high-performance criteria. Surface overflow rate, equal to flow/surface area, should be 32,000 L/day/sq meter to 122,000 L/day/sq meter (Schnaars, 2018). Increasing surface area and decreasing flow will decrease surface overflow rate. 

Detention time is the time solids use to settle and can range 1.5 to 3 hours (Moore and EPA, 2023). Cold environmental temperatures require a higher detention rate (Schnaars, 2018). Flexible design allows engineers to increase detention time in winter. 

Increasing surface area and flow have opposite effects on surface overflow rate and detention time. By evaluating both in Dynamo, engineers have an easy way to make sure their design passes these two high performance criteria while balancing these opposing design parameters.

Design Alternatives: If of interest, design parameter values are in appendix.

 

Engineering Situation 1: Extremely Small Neighborhood with Low Flow+No Industry: 

A residential neighborhood of 10,000 residents using 200 L/resident/day was considered. Detention time was 1.61 hours and surface overflow rate was 44,444 L/day/sq meter. This is a good design because low surface overflow rate means less circulation zones, thus high treatment efficiency. All parameters related to flow (tank height/length/width, pipe radii, number of inflow pipes) were at/close to the extreme low, meaning the model performs well at its extreme low. The tank dimensions would be able to fit into the building physical constraint. Parameters related to wastewater-quality (sludge scraper frequency, sludge blanket height, tank length/trough length ratio) were low since there is no industrial wastewater. 

Engineering Situation 2: Average Residential Population/Resident Flow+Light Industry: 

A neighborhood with 50,000 residents using 250L/resident/day and light industry (restaurants, laundromats) was considered. Industry was 10,000 L/day. Flow-related parameters were increased. Wastewater-quality related parameters were slightly increased due to industry presence. Detention time was 1.78 hours and the surface overflow rate was 55,848 L/day/square meter, considering this to be a well-embodied solution with low presence of circulation zones. The tank size likely requires basement renovation to fit. Since BIM is extremely efficient at finding design conflicts (Hartmann, 2024), I recommend combining this model with a BIM basement model using Speckle during basement renovation.

Engineering Situation 3: High Population+Industry and Possible Flooding: 

A densely populated high-rise neighborhood with 100,000 residents using 300 L/resident/day by a river is considered. Detention time is 1.62 hours and surface overflow rate is 65,811 L/day/square meter. Since surface overflow rate is low, treatment efficiency will be high. Functionally, it is a well-embodied model. Flexible design allowed the model to elevate the tank 1 meter for flooding concerns. Parameters related to wastewater quality stayed the same since wastewater quality stayed the same. This tank is significantly larger and would be hard to fit into the average building’s basement even with construction, approaching the design constraint’s extreme limit. Thus, only the biggest buildings in the neighborhood are recommended for this. Buildings in the US are much bigger than Europe, so this scenario is not feasible if the model wants to be used in Europe. I recommend combining this model with a BIM basement model using Speckle to test if this large design works within a specific building.

Situation 4: Highest Population and Factory 

A factory is part of a high population neighborhood. The factory contributes 200,000 L/day (Action Manufacturing), decreasing the wastewater quality. Population is 100,000 with 300L/resident/day, representing extreme high flow. The model has detention time 1.73 hours and surface overflow rate 61,1143 L/day/square meter. All wastewater-quality related parameters (such as tank angle) were set to deal with worst quality wastewater. This is a tank that would be too big for a residential building, so it is recommended to be within the neighborhood factory. This represents a well-embedded solution because circulation zones are minimized and the tank would be able to fit into a factory physical constraint. Tank/factory design conflicts recommended to be checked with Speckle.

 

Conclusion/Reflection on Improvements/Model Use: This model could be expanded by combining other Dynamo wastewater treatment models using Speckle. Combining models requires advanced modelling of pipes and computing power would increase. High-performance criteria could also be expanded to include structural criteria or material quantity calculation for LCA assessment or cost analysis. 

 

Overall, this model fulfills its use of visual modelling and checking functionality of flexible designs to improve engineering firm efficiency in design of a primary sedimentation tank. Geometry embodiment was kept as simple as possible. The model’s use successfully allows engineers to check if current design still works given new flow/wastewater quality or to find a new design. The model can be combined with a building model in Speckle to find design conflicts.

Bibliography: 

1. Action Manufacturing. (n.d.). Water usage rough estimates. Action Manufacturing. Retrieved January 4, 2025, from https://actionmfg.com/water-usage-rough-estimates/
2. Hartmann, T. (2024) Multi-Physics Lecture.
3. Moore, L. W. (2023, August). EPA Primary Clarifiers. Webinar Series.
4. NYC Department of City Planning. (n.d.). NYC Population FactFinder. Retrieved December 19, 2024, from https://popfactfinder.planning.nyc.gov/
5. Schnaars, K. (2018). What every operator should know about primary treatment. WEF Magazine. Retrieved December 14, 2025.
6. Shahrokhi M, Rostami F., Said A., Sabbagh Y., Saeid R., Syafalni S., and Rozi A. 2012. The effect of baffle angle on primary sedimentation tank efficiency. Canadian Journal of Civil Engineering. 39(3): 293-303. https://doi.org/10.1139/l2012-002
7. Water Environment Federation. (2017). Liquid stream fundamentals: Clarification & sedimentation (WSEC-2017-FS-022). Water Environment Federation. Retrieved January 5, 2025, from https://www.wef.org/globalassets/assets-wef/direct-download-library/public/03—resources/wsec-2017-fs-022-liquid-stream-fundamentals–clarification-sedimentation_final.pdf
8. Toprak, M. (2006). Dokuz Eylül University. Retrieved December 14, 2024, from https://web.deu.edu.tr/atiksu/ana58/coke.html