Introduction
A sewer main is a principal pipe in the sewer system, which transports wastewater, and in some cases also rainwater, from connecting branches to a wastewater treatment plant (WWTP). The sewage system is an essential part of a cities sanitary infrastructure, and under every developed city there are kilometers of sewage pipelines. In Berlin for example, there are approximately 9,600 km of sewer pipes. These are divided into wastewater sewers, storm water sewers and combined sewers.
Ontological Development
The sewer main ontology was created using a top down approach. The purposed of the ontology was to present the different design components that must be considered when designing a sewer main. Therefore, the ontology includes the main physical components of a sewer main, as well as the materials and shapes that are commonly used. The ontology further represents the common characteristics of the different main materials, as well as which materials and which shapes are suited to which conditions.
The sewer main ontology was broken down into classes representing its components, its main materials and its main shapes. Further, the class ‘SewerMain’ was used to create individual examples of a combined sewer and a separate sewer, including the constraints of each of these types. Figure 4 below presents a visualisation of the ontology of the Main Pipe.
Parametric Model
The main purpose for developing a parametric model of a sewer main is to support in the planning stages. If the model is overlayed with a map for example, the model can support in the decision making of the placement of the pipe. Generally, the most direct route between the start point and the end point of a section of sewer pipe is not an option, as there can be many obstacles in the way, such as buildings, cellars, other tunnels, etc. Therefore, with the help of the parametric model different routing options can be tested and the model can be used to determine which route is most efficient in terms of materials used for example. Furthermore, as for cost and efficiency reasons it is always favorable to use the natural slope of the terrain in order to allow gravity to transport the wastewater to the WWTP, the model shows the inclination angle between each set of coordinates that are entered.
The input parameters of the sewer main model are the following:
- Coordinates of the start point of the sewer main,
- Coordinates of the end point of the sewer main,
- Coordinates of any number of points that the pipe should travel along,
- The DN (nominal diameter) of the pipe to be used,
- The thickness of the pipe walls.
The output parameters of the sewer main model are the following:
- A visual representation of the pipe,
- The area of the cross-section of the pipe,
- The length of the pipe,
- The inclination angle of the pipe between every set of coordinates,
- A test whether the angle of inclination between the coordinates is suitable for the planned pipe.
High-Performance Criteria
The high-performance criteria (HPC) that were used to help in assessing the performance of the design options were the following:
- High-performance criteria: The length of pipe to be placed underground. As there is generally more than one routing option for a new pipe, the length of pipe is an important factor in determining the costs of the project (i.e. materials required and trench length that needs to be dug).
- High-performance criteria: The angle of inclination of the pipe. The slope of the pipe must be large enough so that the wastewater flows at a velocity that is high enough to prevent sedimentation in the pipe. This velocity is based on the volume of water that the pipe was dimensioned for, therefore the model allows the user to enter the required angle of inclination and to check whether the slope is sufficient at all points.
In the following, the 3D model based on the described parameters shows the geometrical characteristics of the main pipe: