How to Determine the Wastewater Design Flows in Sanitary Sewer Networks with CLOACAS (SEWERS)

We present in this video, the third in a series of five, the multiple options available for determining the wastewater design flows to be used in the design of urban sanitary networks created with CLOACAS (SEWERS).

In the current version (2.0) of our sanitary sewer design software, the tools for potable water demand allocation that we have already added to our other software, The Water Demands Allocator, have been incorporated. As you will see in this video, this incorporation increases the software’s versatility.


Related Tutorials:

Go to the SETTINGS tab and from the Calculation Parameters panel, click on the button Inflows

The Wastewater Design Flow Calculation Methods dialog will be shown. Here you will see four options for calculating the wastewater flows in your sanitary sewer project:

  • The first one allows you to specify, for each pipe section of the sanitary network, the respective wastewater design flow.

Here it is assumed that you’ve previously carried out the corresponding calculation for each sewer pipe in the system.

When this is the chosen option you will see, when editing any sewer pipe section’s properties, that in the upper right of the Pipes Editor dialog, a text box is shown so you can enter the respective wastewater design flow. You have to do so with each of the pipe sections that at least receive inflows from the Parcels or Plots in the urban sector under study.

  • It is also possible to define, through the next option, a unitary wastewater design flow rate for the entire sanitary sewer network, in which case you must enter here the total flow and total contributing area in order to determine the wastewater unitary design flow to be used in the calculation of each sewer pipe section’s design flow.

Note that if you select this option, the sewer pipes editor now prompts you to enter the respective contributing area value for each section in the network.

In the text box below, the pipe’s wastewater design flow will be shown for your information. This is the product of unitary design flow and the area value you enter here.

K y C values.

Note that when you choose any of the above two options, the fields for the use and application of normative coefficients remain disabled. This is because it is assumed that the information you supply in these two methods already includes their effect.

  • But if you now select the third option, in which you must enter for each sewer pipe section the affluent average potable water flow, you will see that these fields become active, so that they will be applied to this water flow in order to obtain the corresponding wastewater design flow.

Thus, you have the option to specify the C and K values or let the software calculate them, either by specifying the design population or through the concept of equivalent population where you have to enter a per capita water demand in this text box.

In the transcript below this video, you will find a link to the tutorial that explains this in more detail.

Here again, at the properties of each sewer pipe section, you will see that the field for you to enter the respective affluent average potable flow is available. Then, when performing the calculation or design, this value will be affected by the relevant normative factors previously mentioned.

Water Demand Parcels and Polygons

  • A new option, or rather, a variation of an option which was already incorporated in the first version of our sanitary sewer design software, is the ability to include in your project the water demand allocation tools from another of our products, the Water Demands Allocator software.

With this last option, it is possible to create Water Demand Parcels and Polygons in the drawing area, with specific properties in terms of potable water demand. Those Demand Parcels will automatically assigned to the sewer pipe sections without having to worry about specifying, section by section, the affluent flow or area as in the above options.

In fact, note that by enabling this option, the sewer pipe editor now shows a button that lets you view parcels or polygons assigned to the current pipe section, instead of the aforementioned text boxes. At this moment it is not enabled because we have not done any calculations with this method.

Let’s perform the wastewater design flow calculation in this sewer network with this method.

When this is the chosen option, you will see the PARCELS tab enabled.

Here you will find the necessary tools to create and assign Demand Parcels and Polygons to each pipe section in the sanitary sewer system and, as I have mentioned, you will find detailed information on the tutorials created for the Water Demands Allocator Software in our blog.

Also, in the video transcript on this page, you will find the links for you to review them carefully.

Creating Water Demand Parcels

Now, following our sanitary sewer network example project, we must include Demand Parcels and Demand Polygons that allow us to determine the average potable water demand and, from it, the respective wastewater design flow.

If we review the available information in the drawing file used as background image and, specifically, if we change the visualization of these layers, you’ll see that they indicate the name and type of each Parcel or Lot as part of the Urban Plan.

So you will see that there are two types of single-family and one type of multifamily homes.

The idea is to create in the drawing, in the front of each lot, one Demand Parcel that represents the water potable consumption corresponding with the type of building.

Then go to the Water Demand Parcels Creator by pressing this button, and let’s create the three typical Parcels in question.

The first will be the single-family house with a lot of land extension of 250 square meters. We create a new one, enter its name and description, and then select from the list of Water Demand libraries the one corresponding to single family homes.

Let’s select this water consumption and add it to the assigned consumptions table of our Demand Parcel. We will enter one in the quantity column, because it represents only a Parcel of this type.

Save the changes and click on the new button again to create the next Parcel, the SF-2, with an area of 410 square meters.

As it is another single-family house lot, we search the corresponding water consumption and add it to the Parcels table.

Finally, we create the multifamily Water Demand Parcel.

In each lot of this type, a building with four levels, four apartments per floor and three bedrooms per apartment, will exist.

Let’s select the Water Demands Library for multifamily housing by selecting the row for three bedrooms per apartment and add it to the Parcel’s table.

Here, as the water consumption is for housing or per unit, we must enter the number of apartments that will be in each plot (that is: per building), i.e., four levels, four apartments per level, 16 units in total.

Note that, in each case, the Parcel’s total water demand is calculated.

Let’s close the dialog and we will see that the Parcels selector is enabled, so that, when selecting a Demand Parcel type here and setting it as the current one, it is possible to create it in the drawing area when you press this button and select its location.

Also note that the respective Demand Parcel’s layers in the Project’s list of layers are now created.

From here you can control their visibility and, more importantly, set whether the respective demands will be taken into account or not in the calculations.

That is, if you turn off the layer’s visibility for any of these Water Demand Parcels, at the time of the calculation or design, it will be like that they were not created in the current Project. We will see some of this theme later.

Importing Demand Parcels and Polygons from Drawing Files

Now we should start the Demand Parcels creation on the sanitary sewer network’s area manually, as described previously, creating one to one on the drawing area.

But it is also possible that those texts used in the background’s drawing file to identify the types of lots will be imported into our project. Just like we did with manholes and sewer pipes.

So let’s remove these Demand Parcels and move to the import dialog at the DRAWING tab.

Once you select the drawing file, note that this option is available in the Parcels and Polygons group.

At this time, it is not enabled the Demand Polygon’s layer selection because we have not created any of them yet.

But, the Demand Parcel’s layer selection is enabled because, as you see in this list, the typical parcels we have previously created are shown.

The importing process then goes by selecting the layer containing the text to be converted.

And by selecting from the list of available Demand Parcels in the project, the type that will be assigned by the import process to each parcel is created.

Let’s start with the single-family type one.

When click in the OK button, you will see that corresponding parcels have been drawn.

Let’s change their location so that they are better placed with respect to the sanitary sewer pipes.

We will do the same with the following types of Demand Parcels.

Demand Parcels Assignment, Assignment Length

At the end, you will see that we have created all our Demand Parcels easily and, with them, by clicking the Assign Demands button on the PARCELS tab, the total potable water demand calculation becomes available.

Note that from this dialog you can access to two different demand calculation tables:

  • The one that shows the summary of total and assigned Demand Parcels as well as the respective water demand.
  • And the one that presents the Demand Parcel’s allocation to each sewer pipe section in the Project. For example, you will see here that in this pipe section are connected five Type 2 single family and one multifamily demand parcels.

Regarding the Parcel’s allocation, note that in the PARCELS tab, Settings panel, there exists a field that lets you set the maximum assignment length to be used as reference in the process of allocation of each Parcel.

That is, if the distance between each parcel and the nearest sewer pipe section is higher than the value you specify here, the parcel will remain as unallocated or unassigned.

Let’s change this value to 8 and click the Assign Demands button again to see what happens.

The information message tells us that the calculation was performed without problems but there are a number of parcels that have not been assigned.

And when you check the summary table, you will see that, by deferring the numbers in the second and third columns, there are parcels that have not been taken into account in the calculation of total water demand.

Further note that the respective assignment lines between parcel and pipe in the drawing area are not created.

Demand Polygons Assignment, Manual Assignment, Demands Calculation, Results Tables

In addition, according to the available information in the background drawing file, there are sectors located at the north that are defined as industrial areas but which have no specific characteristics to model their water demand with demand Parcels.

In cases like this it is possible to use demand polygons and, in the specific case of industrial areas, we will choose the option to create demand polygons of unitary flow type.

Let’s go to the Water Demand polygons dialog in the PARCELS tab.

We will create a new polygon and select the Unitary flow type for it.

Here you will need to enter a value. Let’s use 0.45 liters per second per hectare.

In the links within the video’s transcript on this page, you will find tutorials that explain in detail each type of demand polygon available in this tool.

Close this dialog and see that now the new Demand Polygon is available in the list.

When clicking on this button, it is possible to create the corresponding polygons by drawing them in the drawing area.

But, as you saw previously, it is also possible to convert polylines in a drawing file through importing into the sanitary sewer project.

So that’s what we will quickly do.

Once you have the demand polygons created, click the Assign Demands button again in order to see the Allocation results.

The summary table now includes the allocation information for each type of demand polygon you have created in the current sanitary sewer project.

Also, the sewer pipes table relates those demand polygons allocated to each pipe section, if any.

On the other hand, note that each polygon can be modified through the addition, removal, or displacement of its vertices.

Select it, click the right mouse button, and click the option to apply from the floating menu.

It is also possible to override the automatic allocation or assignment to the sewer pipes sections for individual demand polygons.

Note that, if I select one of the polygons and present its properties dialog, in addition to its features, there exists the option to manually assign it to a pipe.

When active, it is possible to select the sewer pipe section to which it will be assigned from the list.

When you close the dialog and click the Assign Demands button again, you will see the change in the assignment line and, of course, in the properties of the corresponding sewer pipe section, that this polygon’s demand has been assigned.

Layers Visualization, its Effect over the Water Demands Calculation

Finally, we will show you the effect of turning off the display of Demand Parcels and Polygons.

With all the water demand objects visible, the total potable water demand is this.

If, for example, we go to the Project’s Layers editor and turn off the visualization of the Type 2 Single Family Demand Parcels Layer.

When we perform the assignment again, you will see that the total allocated water demand decreased by one liter per second, the corresponding water demand of those Demand Parcels turned off.

As you see, using the Demand Parcels and Polygons, it is very simple to find the average total water demand flow calculation in each sewer pipe section in your projects.

Of course, in the calculation of the sanitary sewer network, as we shall see in the next video, these average values will be affected by the relevant design factors in order to obtain the respective wastewater design flow to be used in the design.