Hypothetical SWMM Application in San Juan River Watershed
Transcript of Hypothetical SWMM Application in San Juan River Watershed
Manila Third Sewerage Project
Hypothetical SWMM Application in San Juan River Watershed
Henry Manguerra
GEF-MTSP Consultant
August 3-4, 2011
EW-2
EW-2 Subcatchment as defined in the MWSS 2005 Master Plan
Source:MWSS 2005Master Plan
Source:MTSP BoundaryDelineation Team
EW-2 was arbitrarilydelineated
Source: MWSS 2005 Master Plan, MWSS 2009 Preparatory Survey ReportNote: Estimates were calculated followingprocedures described in the reports.
STPUpperSF River(3,150m)
Hypothetical Future Management Scenario◦ STP design capacity =
0.25 m3/s or 5.7 million GPD (approx. 25% of the total domestic/ commercial wastewater flow
◦ Remaining 75% stays on septic systems but are well maintained/ managed (e.g., SpTP)
◦ STP Permit BOD Limit = 50 mg/lSevilla Bridge
WQ Station
Largest in the world
Rated average day capacity = 370 millions GPD
Wet weather capacity = 1.076 billion GPD
Discharges to Potomac River (Part of Chesapeake Bay Watershed)
Stringent NPDES Permit Limit Requirements (See Table Below)
STPUpperSF River(3,150m)
A SWMM input file was already created for this exercise.
To start the hands-on exercise, open project file c:\SWMMTraining\SWMMData\Example_EW2.inp.
Sevilla BridgeWQ Station
Specify point source discharges and other external inflows
Perform model calibration
Estimate load reduction and resulting in-stream BOD concentration impacts of STP and improved septic maintenance/management
Evaluation of simulated in-stream concentrations against water quality standards both during dry and rainfall event
The input file represents “current” conditions prior to the hypothetical future management scenario◦ Questions: How is “current” domestic/commercial wastewater flow and
BOD loads represented in the model? Q = _____; C = ______ What does the dry weather inflow represent? ____________
Upper SF River was divided into 4 segments/conduits: C1, C2, C3, C4◦ Questions: What is the channel shape? ___________ What are the cross-sectional dimensions? _________ What is the longitudinal slope? _________ (Tip: slope is not
directly an input value but is calculated from the invert elevations of the nodes)
Run the model and quickly view results by clicking Report >> Status from main menu.◦ Confirm that no rainfall event occurred during the
simulation (TIP: Rainfall Gage1 is associated with PPTNO time series which is a dummy time series of zero precipitation)
◦ Question: What is the total BOD loading at the outfall? Answer: 351,011 kg.
◦ Question: What are the inflow – outflow BOD amounts?
Dry Weather Inflow? ____ (baseflow contribution)
External Inflow? ________ (domestic/commercial)
Mass Reacted? _________ (BOD removed due to decay)
Sevilla Bridge Water Quality Monitoring Station◦ 2009 PRUMS report: BOD conc. = 43.4 mg/l (average dry
weather condition) with 1st quarter = 70.2 mg/l
◦ No flow monitoring data available. 2009 PRUMS report showed flow velocity information ranging between 0.1 –0.3 m/s.
◦ PRRC wq of selected esteros showed 125 mg/l for Ermitano, 123 mg/l for Diliman, and 133 mg/l for Mariabolo
For the purposes of illustrating model calibration, use the following:◦ BOD = 70 mg/l
◦ Velocity = 0.1 m/s
Calibration Parameter = channel roughness coefficient (N)◦ Question: What is currently the N value? ________◦ Question: What are the current flow velocities in
the following channels (Tip: Click Report >> Table >> By Variable from main menu): C1: _______ C3: _______
C2: _______ C4 :_______
Adjust the current N value to reduce flow velocities to about 0.1 m/s.◦ Question: What is the new value of N? _______◦ Question: What is the new total BOD loading at the
outfall? _________ What did it change?
Calibration Parameter = BOD decay coefficient (k)◦ Question: What is currently the BOD k value? ________
◦ Question: What are the current in-stream concentration (Tip: Click Report >> Table >> By Variable from main menu):
C1: _______ C3: _______
C2: _______ C4 :_______
Adjust the current BOD k value to obtain in-stream BOD concentrations of about 70 mg/l ◦ Question: What is the new value of k? _______
◦ Question: What is the new total BOD loading at the outfall? _________
Calibrated k = 4.5
Corresponding total BOD loading at the outfall = 121,368 kg about 1/3 of the original estimate value of 351,011 kg.
Analysis: ◦ The resulting BOD removal due to decay is highly
unrealistic.
◦ Typical literature values of k range from 0.05 – 0.5
◦ Therefore, the calibrated k = 4.5 incorporates an additional adjustment factor that significantly removes BOD at the source before it reaches the main streams. What would that be?
HANDS-ON EXERCISE STOPPING POINT
EW-2 Catchment
Q
Direct inflowC = 269 mg/l
Observed C= 70 mg/l
Wet-weatherDriven InflowC << 269 mg/l
Ponds, depressions,stagnant esteros, storage, etc.
Options to model this scenario in SWMM:• Reduce direct inflow Q• Model additional BOD removal due to ponds,
depressions, etc. using a treatment function• Provide network details to include ponds,
esteros, etc.
Section 3.3.10 User‟s Manual – Assign a node a treatment function
Use a first-order decay expression◦ C = BOD * exp (-0.05 * HRT) where
HRT = hydraulic resistance time (hrs) assumed equal to 20 hours for this hands-on exercise.
Assign k = 0.25 (consistent with literature values)
Enter treatment function at node J1 (Tip: see figure next slide)◦ Question: What are the current in-stream
concentration (Tip: Click Report >> Table >> By Variable from main menu): C1: _______ C3: _______
C2: _______ C4 :_______
◦ Question: What is the new total BOD loading at the outfall? Answer: 123,769 kg. Note that this value corresponds to the calibrated „current‟ total BOD loading during dry days prior to the hypothetical future management scenario.
Steps:1. Click Node J12. Click Treatment Field3. Enter Expression
1
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• Results correspond to average steady state conditions
A fully calibrated model is “almost” essential Model should be calibrated for seasonality
(low flow, high flow) at several stream locations◦ Time series of flow and in-stream concentrations
are required
Other measurements can be used for calibration (Section 5.7, p81, User‟s Manual)◦ Runoff◦ Pollutant Washoff◦ Groundwater inflow/baseflow◦ Water Surface Depth
Scenario
◦ STP design capacity = 0.25 m3/s or 5.7 million GPD (approx. 25% of the total domestic/ commercial wastewater flow
◦ Remaining 75% stays septicsystems but are well maintained/ managed (e.g., SpTP)
◦ STP Permit BOD Limit = 50 mg/l
Steps: 1. Save current project file2. Create new project file for new
scenario by Saving As the current project file to Example_EW2_Future.inp
3. Remove treatment function in node J1 (from the previous scenario)
4. Change direct inflowQ = 0.25 m3/sBOD conc. = 50 mg/l
5. Run model
Tip: Run model 2-3 times to stabilize the run since the model is setup to assign initial conditions with model results (Chapter 11.7, User‟s Manual.
Confirm that resulting in-stream BOD concentrations are in the 20-25 mg/l (see Figure below) higher than the BOD standard of 7 mg/l for class C waters.
What is the maximum BOD concentration can the STP discharge so the BOD standard is not exceeded? Answer: 13 mg/l
Graph below shows resulting in-stream concentration (prepared in MS Excel)
Distance Downstream From STP (m)
Conc.,
mg/l)
Question: What is the total BOD loading at the outfall? Answer: 4,404 kg.
This corresponds to a 96.4 percent reduction of the “current” BOD loading = 123,769 kg.
Note that the previous exercises involved running the model in Steady State (i.e., constant inflows)
Question: What are resulting in-stream concentration if effluent discharges are intermittent (e.g., discharging only during Mondays, Wednesdays, and Fridays) at a flow rate equal to twice the previous constant flow (new Q = 0.50 m3/s, BOD = 13 mg/l)
Options: External Inflow TS Use of Baseline Pattern
Step 1. Create Time Series PatternsStep 2. Specify Inflow to Follow a
Pattern
Exceedance ofBOD Standard
Objective: Determine impact of a rainfall event to in-stream BOD concentration
Step 1: Change effluent discharge back to constant Q = 0.25 m3/s and BOD = 13 mg/l
Step 2: Specify Gage1 to be associated with rainfall time series IDF (see Figure)◦ Note that this time series contains a 1-
hr duration rainfall event with a return period of 1 year for NAIA, Philippines (Source: Daniell and Tabios, 2008)
Step 3: Examine catchment attributes including landuse◦ Question: What pollutant buildup and
washoff functions were used?
Step 4: Run the model (see continuity errors in the Figure -numbers might be slightly different)
Step 5: Rerun the model as Dynamic Wave (see continuity errors in the Figure – numbers might be slightly different)
Save project: Click File >> Save from the main menu
Exceedance ofBOD Standard
Tip: The SWMM5 input filefor this Wet Weather Modelinghands-on exercise can be foundat c:\SWMMTraining\SWMMData\Example_EW2_WetWeather.inp
Tip: The SWMM5 input filefor the Wet Weather Modelinghands-On exercise can be foundat c:\SWMMTraining\SWMMData\Example_EW2_WetWeather.inp
Station: Science Garden, Quezon City, 6 hour rainfall interval, 1/1/2003 – 12/31- 2003
Filename: science_swmm.dat
Steps (See Figure):
◦ Change Data Source field = File
◦ Specify FilePath\FileName(C:\SWMMTraining\SWMMData\science_Swmm.data)
◦ Enter Station ID = Science
◦ Enter Rain Units = MM
◦ Enter Time Interval = 6
◦ Specify Simulation Period from 1/1/2003 – 12/31/2003
◦ Run the Simulation
◦ Save project: Click File >> Savefrom the main menu
Click Report >> Statistics from Main Menu
Days
BODmg/l
RunoffCMS
Note: SWMM output exported to and graph produced in MS Excel.
Tip: The SWMM5 input filefor the Rainfall Time Series hands-on exercise can be foundat c:\SWMMTraining\SWMMData\Example_EW2_Continuous.inp
END OF HANDS-ON EXERCISES
Manila Third Sewerage Project
Henry Manguerra
GEF-MTSP Consultant
August 3-4, 2011
EPA SWMM5 has a lot more to offer◦ Groundwater module◦ Other drainage control structures (regulators, storage units,
flow dividers, pumps) in more detailed and complex drainage network
◦ Best management practices (ponds, and low impact development)
◦ Integration with other models
EPA SWMM5 is (relatively) easy to learn, versatile and has wide-ranging applications to many agencies◦ Pollution load allocation/TMDL ◦ Flood modeling◦ Stormwater/Sanitary sewer/Combine Sewer Capacity
Modeling and Design
Don‟t lose what you learned here◦ Continuously find opportunities to apply the model◦ Designate/mentor/empower others◦ Keep building internal capacity for modeling – Model, Data,
Computer Infrastructure, People, Budget
Modeling Workgroup will meet to discuss EPA SWMM5 application in San Juan River Watershed and eventually in Manila Bay watershed