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

23

• 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