CHAPTER 5
Introduction
For every influent model that is used in a wastewater plant layout, it is important to properly specify the influent characteristics and the influent stoichiometry.
Influent Advisor
To help users better understand influent characterization, a special utility program, called Influent Advisor, was developed by Hydromantis/Hatch. The tool helps users to visualize and debug influent characterization data. It is recommended that users make use of this utility tool so that influent characterization errors can be avoided.
The mathematical description of the influent wastewater that is fed to the plant model is the single most important aspect of a simulated system. Without significant consideration of the influent characterization, the plant model will be limited in its ability to predict the dynamic behavior of the plant.
To access the Influent Advisor tool, right-click on any wastewater influent object, and select the Composition > Influent Characterization menu item.
Figure 5‑1 - Opening the Influent Advisor Tool
The Influent Advisor screen shows three columns of data: User Inputs, State Variables, and Composite Variables, as shown in Figure 5‑2.
Figure 5‑2 - Influent Advisor Menu
The fields in the left-hand column show the inputs available to the user, such as influent concentrations and stoichiometric ratios. The centre and right hand columns show the state variable and composite variable concentrations calculated from the user inputs.
As the user changes values in the left-hand column, the variables in the centre and right-hand columns are automatically updated. This allows for easy debugging of confusing or conflicting influent characterization data.
Clicking on any variable in the centre and right-hand column illustrates how that value is calculated. The formula will be displayed in the formula box (located in the lower middle of the screen – you may need to scroll down to see it). The values used in the formula will be highlighted in the tables so that the applicable cells can be identified. If a negative value is calculated in either table, the cell will turn red. Correcting problematic data is only a matter of adjusting the input cells to achieve non-negative values.
Figure 5‑3 - Influent Advisor Screen Showing Highlighted Cells and Negative Values (Highlighted in Red)
The influent models used in GPS-X make certain assumptions about what data may or may not be available. For instance, no influent model uses both COD and BOD data, even though this data may be available and may provide important information about how that organic material is partitioned into the available state variables. Influent Advisor helps overcome this shortcoming.
Take an example in which BOD and COD data is available and the BODbased model is chosen for the influent object. The applicable data can be entered into Influent Advisor, including the available BOD data. The user can then scroll to the right table and check the COD value calculated based on the input data. If the COD data is in agreement with the measured COD data (assuming no negative values in any cells), then the user can be assured that the input data is consistent with the available data. If the COD data is different from the measured COD, then the unknown (or estimated) input data should be adjusted until acceptable agreement is achieved.
NOTE: Correctly setting up the influent is critically important to the simulation; therefore, a set of warning messages has been developed, and will appear in the Command window, when necessary. For instance, if the user inadvertently enters a value for xsto, but has chosen ASM1 as the local biological model, then a warning message (`time = <timestamp> xsto<streamlabel> is non-zero, xsto is not a state variable in ASM1') will appear in the Log window. This is a signal to go back to the influent data forms and correct a problem with the influent. It is recommended that Influent Advisor be used to debug your influent characterization. Hydromantis recommends that users make full use of the Influent Advisor as a tool to help identify problems, and understand the interconnectivity between state and composite variables.
During a simulation, error messages related to the influent may appear in the simulation Log window. These messages will most likely be the result of improper influent stoichiometry. If an error message does appear, then the influent stoichiometry should be examined for possible errors.
Influent Objects in MANTIS2LIB, MANTIS2SLIB, MANTIS3LIB
There are eight influent objects in each of MANTIS2LIB, MANTIS2SLIB, MANTIS3LIB of GPS-X:
Table 5‑1 - Influent Objects in MANTIS2LIB, MANTIS2SLIB, MANTIS3LIB
|
Name |
Object |
Use |
Models Available |
|
Wastewater Influent |
|
Continuous wastewater flows (steady or dynamic) |
bodbased
states |
|
Batch Influent |
|
Batch deliveries of septage or other discontinuous wastewater flows |
bodbased codbased codstates sludge states tssfrac |
|
Water Influent |
|
Clean water input (steady or dynamic) |
water |
|
Stormwater Runoff |
|
Clean water input from storm events |
runoff |
|
COD Chemical Dosage |
|
Dosage of COD into streams or objects |
codfeed |
|
Acid Dosage |
|
Acid addition for pH control |
acidfeed |
|
Alkali Dosage |
|
Alkali addition for pH control |
alkalifeed |
|
Nutrient Dosage |
|
Nutrient addition |
nutrifeed |
The eight influent objects contain models, options and features that are relevant to the type of influent being used. For example, the continuous wastewater model has options for specifying a diurnal pattern for influent flow, a feature not found in the other influent objects.
Wastewater Influent Object
The flow rate setup in wastewater influent
object is similar to the flow rate setup in other libraries. The
built-in influent advisor also works in a similar way as for the
other libraries. However, a few key differences are with respect to
how the stoichiometric parameters for composite variable
calculations are organized and calculated in this library. In
MANTIS2LIB, the stoichiometric parameters are accessed through
the
System > Input Parameters > Biochemical Model
Settings menu (Figure
5‑4). The stoichiometric
parameters available in the COD to VSS ratio and
Fractions Used in Composite Variable Calculations are shown
in Figure 5‑5
and Figure
5‑6. The stoichiometric
parameters available in the COD to VSS ratio group are the
parameters which are influent specific and representative of a
composite component of unknown composition. On the other hand, the
stoichiometry parameters available in the Fractions Used in
Composite Variable Calculations are parameters which can be
calculated based on the chemical composition (acetic acid, methanol
etc.) of the component or some underlying fundamental estimation
procedure. The default values of inorganic fractions (N, P, etc.)
in different type of biomass may be accessed by pressing the
More… button on the Fractions Used in Composite Variable
Calculations group(Figure
5‑7).
Figure 5‑4 - Accessing the Stoichiometry Parameters in MANTIS2LIB
Figure 5‑5 - Influent Specific Stoichiometric Parameters
Figure 5‑6 - Fixed Stoichiometric Parameters in MANTIS2LIB
Figure 5‑7 - More... Fixed Stoichiometric Parameters in MANTIS2LIB
Batch Influent Object
The difference between the batch influent (truck) object and the continuous influent objects (arrows) concerns the flow and load types. The available flow and load types for the batch influent object are averageand individual.
In the batch influent, if the average flow and load types are selected, the model will behave exactly like the continuous influent.
If the individual flow type is selected, there will be an intermittent (or batch) influent. Under the Flow sub-menu item individual, the user can specify the starting and ending time of the batch influent, and the volume of each truck (1 truck per day by default - the number of trucks per day is specified in the Influent Composition sub-menu). The total volume specified will be fed at an average rate over the total dumping time specified, that is there will be one influent flow spike.
If the individual load type is selected, the loading is determined by the amount specified in the Individual Loadssub-menu. The stoichiometry is specified in the Influent Characterizationmenu and the number of trucks per day is specified in the Compositionsub-menu (see Figure 5‑8).
Figure 5‑8 - Batch Input Menu - Flow Data Model Inputs
Water Influent Object
The water influent object uses the water model (Figure 5‑9). The water influent object allows user to feed water to the system, for water influent, the influent characterization of water can be changed within the influent characterization menu (Figure 5‑10) and influent characterization is shown as Figure 5‑11.
Figure 5‑9 - Water Influent Object Model
Figure 5‑10 - Water Influent Composition Menu
Figure 5‑11 - Water Influent Characterization Menu
Stormwater Runoff
Runoff Model
The runoff flow model uses a parallel linear reservoir model to simulate wet weather flow in sanitary and combined sewer systems. This model is not a mechanistic hydrological model, but a simple mathematical transformation.
The equations are:
Equation 5‑1
and
Equation 5‑2
where:
Pd = rainfall that enters the sewer system directly
Pi = rainfall that enters the sewer system indirectly
Ptotal = total rainfall over the catchment area
Cd = fraction of total rainfall that enters the sewer system directly
Ci = fraction of total rainfall that enters the sewer system indirectly
Total runoff (Qtotal) is calculated with the following equation:
Equation 5‑3
which is based in the following equations:
Equation 5‑4
Equation 5‑5
Equation 5‑6
Equation 5‑7
where:
Kd = decay rate of linear reservoir representing direct runoff
Ki = decay rate of linear reservoir representing indirect runoff
A =total catchment area
Chemical Dosage Object
The COD chemical dosage object uses the codfeed model (Figure 5‑12). The COD chemical dosage object allows user to select the type of COD used in the feed. Six COD sources acetic acid, propionic acid, methanol, molasses, glycerol and generic mixed substrate are available for selection from the Composition > Feed Chemical Details menu (Figure 5‑13). The Feed Chemical Details menu is as shown in Figure 5‑14.
For pure organic chemical acetic acid, propionic acid, methanol and glycerol, two input parameters of % purity and density of chemical solution at the selected %-purity are required as input. Depending on the chemical selection, the concentration of the corresponding state variable is set. For example, if acetic acid is selected, the concentration of acetate (sac) is set to the value determined by the set % purity and density of the chemical solution. For molasses and mixed substrate, in addition to the density and % purity of the compound, N/COD and P/COD ratios in the substrate may be specified by the user. The nitrogen compound in the substrate is assigned to the soluble organic nitrogen state variable (snd) while the phosphorus in chemical is assigned to the soluble ortho-P state variable (sp).
Figure 5‑12 - Models in COD Chemical Dosage Influent Object
Figure 5‑13 - Accessing Feed Chemical Details Menu
Figure 5‑14 - Selection of Feed Chemical and Set-up of Chemical Properties
The COD chemical dosage object has a built-in flow rate controller. The controller is useful for controlling the feed rate of COD based on a user defined controlled variable.
Acid Dosage Object
The acid dosage object is only available in the MANTIS2LIB. The acid dosage object uses the acidfeed model (Figure 5‑15). The acid dosage object allows user to select the type of acid used in the feed. Three acids HCl, H2SO4 and HNO3 are available for selection from the Composition > Feed Chemical Details menu (Figure 5‑16). The Feed Chemical Details menu is as shown in Figure 5‑17. For the selected chemical, two input parameters of % purity and density of chemical solution at the selected %-purity are required. If HCl or H2SO4 is selected, the state variable of other anion (sana) is set to the equivalent dosed amount. If HNO3 is the selected acid then, the state variable of Nitrate-N (snoa) is set to an equivalent concentration.
Figure 5‑15 - Models in Acid Dosage Influent Object
Figure 5‑16 - Accessing Feed Chemical Details Menu
Figure 5‑17 - Selection of Feed Chemical Set-up of Chemical Properties
The acid dosage object has a built-in flow rate controller. The controller is useful for controlling the feed rate of acid based on a control variable (i.e. pH) in a reactor of interest.
Alkali Dosage Object
The alkali dosage object is only available in the MANTIS2LIB. The alkali dosage object uses the alkalifeed model (Figure 5‑18). The alkali dosage object allows user to select the type of alkali (base) used in the feed. Six alkalis NaOH, Ca(OH)2, Mg(OH)2, NaHCO3, CaCO3 and Na2CO3 are available for selection from the Composition > Feed Chemical Details menu (Figure 5‑19). The Feed Chemical Details menu is as shown in Figure 5‑20. For the selected chemical, two input parameters of % purity and density of chemical solution at the selected %-purity are required. The chemical and corresponding state variables which are set in the feed are shown in Table 5‑2.
Figure 5‑18 - Models in Alkali Dosage Influent Object
Figure 5‑19 - Accessing Feed Chemical Details Menu
Figure 5‑20 - Selection of Feed Chemical and Setup of Chemical Properties
Table 5‑2 - Alkali Chemicals and Affected States in the Feed
|
Chemical |
Affected States in Feed |
|
NaOH, |
sana |
|
Ca(OH)2, |
sca |
|
Mg(OH)2, |
smg |
|
NaHCO3 |
sana, stic |
|
CaCO3 |
sca, stic |
|
Na2CO3 |
sana, stic |
The alkali dosage object has a built-in flow rate controller. The controller is useful for controlling the feed rate of alkali based on a control variable (e.g. pH) in a reactor of interest.
Nutrient Dosage Object
The nutrient dosage object is only available in the MANTIS2LIB. The nutrient dosage object uses the nutrifeed model (Figure 5‑21). The nutrient dosage object allows user to select the type of nutrient used in the feed. Four nutrients NH4Cl, Urea, (NH4)3PO4 and H3PO4 are available for selection from the Composition > Feed Chemical Detailsmenu (Figure 5‑22). The Feed Chemical Details menu is as shown in Figure 5‑23. For the selected chemical, two input parameters of % purity and density of chemical solution at the selected %-purity are required. The chemical and corresponding state variables which are set in the feed are shown in
Figure 5‑21 - Models in Nutrient Dosage Influent Object
Figure 5‑22 - Accessing Feed Chemical Details Menu
Figure 5‑23 - Selection of Feed Chemical and Setup of Chemical Properties
Table 5‑3 - Nutrient Chemicals and Affected States in the Feed
|
Chemical |
Affected States in Feed |
|
NH4Cl |
snh, sana |
|
Urea |
snd |
|
(NH4)3PO4 |
snh, sp |
|
H3PO4 |
sp |
|
MgCl2 |
smg, sana |
The nutrient dosage object has a built in flow rate controller. The controller is useful for controlling the feed rate of nutrient for a user-defined control variable.
Influent Objects in PROCWATERLIB
There are seven raw water influent objects in PROCWATERLIB of GPS-X:
Table 5‑4 – Raw Water Influent Objects in PROCWATERLIB
|
Name |
Object |
Use |
Models Available |
|
Wastewater Influent |
|
Continuous wastewater flows (steady or dynamic) |
states |
|
River Water Influent |
|
River water input (steady or dynamic) |
states |
|
Lake Water Influent |
|
Lake water input (steady or dynamic) |
states |
|
Ground Water Influent |
|
Ground water input (steady or dynamic) |
states |
|
Municipal Water Influent |
|
Municipal water input (steady or dynamic) |
states |
|
Brackish Water Influent |
|
Brackish water input (steady or dynamic) |
states |
|
Sea Water Influent |
|
Sea water input (steady or dynamic) |
states |
Wastewater Influent Object
The wastewater influent object in PROCWATERLIB is similar to the wastewater influent object in other libraries.
Water Influent Objects
The water influent object in PROCWATERLIB is similar to the wastewater influent object in other libraries, but with different influent characterization with respect to each water influent category.
The influent object allows user to set water flow rates, water characteristics with respect to concentration of inorganic/organic compounds and pH settings. The main difference between the six influent objects is with respect to the default concentration of inorganic/organic constituents.
User can select an influent object corresponding to the actual water source and then adjust the default concentration of constituents to match the measured concentration.
To adjust turbidity in water and without much understanding about the properties of suspended solids, user may set the value of inorganic inert particulate (xii) in the model. As noted earlier, the colloidal substrate (scol) also affects the turbidity, so if information is available on concentration of colloidal matter, this variable can be set in model.
The estimated color depends on the soluble inert material (Si), which is used as surrogate for Humic and Fulvic acids from organic biomass decay.
Chemical Feed Objects
There are five chemical feed objects in PROCWATERLIB of GPS-X:
Table 5‑5 - Chemical Feed Objects in PROCWATERLIB
|
Name |
Object |
Use |
Models Available |
|
COD Chemical Dosage |
|
Dosage of COD into streams or objects |
codfeed |
|
Acid Dosage |
|
Acid addition for pH control |
acidfeed |
|
Alkali Dosage |
|
Alkali addition for pH control |
alkalifeed |
|
Nutrient Dosage |
|
Nutrient addition |
nutrifeed |
|
Water Chemical Influent |
|
Water chemical addition |
watchem |
COD Chemical/Acid/Alkali/Nutrient Dosage
The COD Chemical Dosage, Acid Dosage, Alkali Dosage, Nutrient Dosage objects in PROCWATERLIB are similar to the respective object in other libraries.
Water Chemical Influent Object
The water chemical influent object is only available in the PROCWATERLIB. The water chemical influent object uses the watchem model (Figure 5‑24). The water chemical influent object allows user to select the type of water chemicals used in the feed. Seven water chemicals gypsum, sodium hydrogen sulfite, sodium hypochlorite, liquid chlorine, liquefied carbon dioxide, ammonia solution, inhibitor is available for selection from the Composition > Feed Chemical Details menu (
Figure 5‑25). The Feed Chemical Details menu is as shown in Figure 5‑26. For the selected chemical, two input parameters of %-purity and density of chemical solution at the selected %-purity are required.
Figure 5‑24 - Models in Water Chemical Influent Object
Figure 5‑25 - Accessing Feed Chemical Details Menu
Figure 5‑26 - Selection of Feed Chemical and Setup of Chemical Properties
Influent Objects in MANTISIWLIB
There are six influent objects in MANTISIWLIB of GPS-X:
Table 5‑6 - Influent Objects in MANTISIWLIB
|
Name |
Object |
Use |
Models Available |
|
Wastewater Influent |
|
Continuous wastewater flows (steady or dynamic) |
states |
|
Batch Influent |
|
Batch deliveries of septage or other discontinuous wastewater flows |
codstates states |
|
Water Influent |
|
Clean water input (steady or dynamic) |
water |
|
Acid Dosage |
|
Acid addition for pH control |
acidfeed |
|
Alkali Dosage |
|
Alkali addition for pH control |
alkalifeed |
|
Nutrient Dosage |
|
Nutrient addition |
nutrifeed |
Wastewater Influent Object
The wastewater influent object in MANTISIWLIB is similar to the wastewater influent object in other libraries.
Batch Influent Object
The batch influent object in MANTISIWLIB is similar to the batch influent object in other libraries.
Water Influent Objects
The water influent object in MANTISIWLIB is similar to the wastewater influent object in other libraries.
Acid/Alkali/Nutrient Dosage
The Acid Dosage, Alkali Dosage, Nutrient Dosage objects in MANTISIWLIB are similar to the respective object in other libraries.