Development of a Dissolved Oxygen - Biochemical Oxygen ... · Biochemical Oxygen Demand - a measure of organic pollutants in the water - amount of dissolved oxygen needed to break

Brisbane, Australia | 20-24 October 2019

Development of a Dissolved Oxygen -Biochemical Oxygen Demand (DO-BOD) System Dynamics Model of Pasig River,

Philippines using STELLA

Engr. Eduardo Bornilla Jr.

Engr. Tolentino Moya, Ph.D.

Merliza Bonga


What’s important with DO and BOD?Dissolved Oxygen

- an essential element supporting the aquatic life

- provides the maximum information about water quality conditions (Ji, 2008)

Biochemical Oxygen Demand

- a measure of organic pollutants in the water

- amount of dissolved oxygen needed to break down organic matter in water

Polluted aquatic systems lead to reduction of dissolved oxygen. Further reductionto 2 – 3 mg/L DO concentration leads to a hypoxic condition or worse to anoxiccondition (0 mg/L DO) that results to altered breathing patterns or fish kills.


The Case of Pasig River System • Coastal estuarine

• Drains the Philippine National Capital Region

• Connects the Laguna Lake and Manila Bay

• Declared biologically dead in early 2000s (Gorme, et al. 2010)

Source: Pasig River Rehabilitation Commission (PRRC)

Laguna Lake

Manila Bay


Water Quality Standard

• BOD ≤ 7 mg/L

• DO ≥ 5 mg/L

Source: Pasig River Rehabilitation Commission (PRRC)

Annual Water Quality Data


Rationale behind the Pasig River ModelSituationer

• This model was an academic research project in partnership with PRRC for purposes of additional environmental management tool.

Main Objective

• develop a system dynamic model to understand the non-linear behavior of surface water dissolved oxygen (DO) and biochemical oxygen demand (BOD) over time as water moves downstream

Potential Applications

• reconstruct pollution transport and identify the hypoxia hot spots along the river channel

• estimate the BOD load contribution of the Pasig River watershed to Manila Bay

• estimate a daily allowable BOD load from Pasig River tributaries to attain Class C water


The River Water Quality ModelStreeter-Phelps Model

• pioneering river water quality model

• dissolved oxygen is consumed to degrade BOD in water

• mathematically describes the decrease in the DOconcentration by degradation of BOD along a stream

Source: nptel.ac.in

Aquatic hypoxia is a result of complex interactions of biogeochemicaland physical processes. The water quality is a set of parameters thatare mutually interrelated (Khalil et al. 2010) and these processes can becoupled (Jolankai 1997) based on interrelations.


• BOD decay

• K1 temperature correction

• Oxygen deficit equation

• Saturation equation of dissolved oxygen

• Reaeration coefficient

• Denitrification(Jolankai, 1997)

The equations can explain the non -linear DO and BOD interaction as water moves at a distance or downstream.

Modeling Equations


Overall STELLA Model Setup


• run and stop buttons

• f value and temp sliders

• background DO and BOD knobs

• graph and table

STELLA User Interface


Results: Sensitivity Analysis• to identify the important parameters

that affect the model results (Chapra, 1997) for DO and BOD

• done by varying each of the parameters by a set of percentage

• STELLA modeling platform has a built-in parameter perturbation technique for sensitivity analysis.


The parameters were set to: • 7 mg/L dissolved oxygen • 15 mg/L BOD• 2.5 f• 28°C water temperature

The model was run 5 times for 10 days at different parameter with fixed increment.

DO sensitivity to Temperature (20 to 32°C)

Sensitive where at higher temperatures can reach hypoxia and anoxia.

DO sensitivity to Depth (1 to 12 m)

Sensitive where at shallower depth, the faster the oxygen regeneration.

DO sensitivity to Velocity (0.1 to 1.5 m/s)

Highly sensitive where a slight increase in velocity delays the oxygen regeneration

BOD sensitivity to Temp (20 to 32°C)

A slight increase in water temperature does not affect much the rate of BOD decay.

Results: Sensitivity Analysis


Results: Preliminary Scenario Building

Dry Season (from Napindan Station)

• 32 °C, 1.2 f, 28 mg/L BOD, 5.1 mg/L DO

Wet Season (from Napindan Station)

• 23 °C, 2.3 f, 14 mg/L BOD, 6.8 mg/L DO

Anoxic condition is most probable during dry season at high temperature and slowriver velocity. Dissolved oxygen can regenerate faster during wet season.


Further Development: Segmentation

The boundary conditions will be based on the distance of each confluence point from Laguna Lake (0 km).

North Bank Tributary Distance (km)Laguna Lake 0Ilugin Creek 3.86729Marikina River 6.69536Pineda Creek 8.39455

Buayang Bato Creek 9.11592San Juan River 16.7557Estero de Valencia 18.77561Estero de Sampaloc 19.24824Esterdo de Uli Uli 19.51631

Estero de San Miguel 21.41272Estero de la Reina 21.89083

Estero de Binondo 22.47864Manila Bay 25.90958

South Bank Tributary Distance (km)Laguna Lake -0.15Daang Paa Creek 5.18223Pateros-Taguig River 6.64688

Guadalupe Nuevo Creek 9.27288

Balisampan Creek 10.02217Estero de Santa Clara 13.01583Estero de Pandacan B 16.61422Estero de Pandacan A 18.63983Estero de Santibanez 20.00717

Estero de Paco 20.21842Estero de Tanque 20.31066Estero de Balete 20.6049Manila Bay 25.10755


Further Development• Initial BOD and DO condition:

0 km at Laguna Lake

• After transport of x1 km (t1), simulated BOD and DO will be the new boundary conditions

• General dilution equations apply at 21 confluence points until the water mass reaches Manila Bay


Future Works: Calibration and Validation• Calibration is required to “tune”

the model to fit a data set.

• Which data set from the water quality data?• 2016 and 2017 monthly water

quality data will be used for calibration

• For validation, the comparison of simulation results to 2018 actual water quality data.

Sample Output


Challenges, Opportunities and ConclusionModeling Challenges

• Pasig River is tidally-influenced (Tamura, et al. 2000)

• Consistency and availability of water quality data

• Limited hydrologic data; latest data is dated September 2009

• Technical skills of modeler and model users

Modeling Opportunities

• Can be a science-based tool for managing the Pasig River

• Replicable to other river systems

Conclusion

• It is possible to develop a simple model to help us understand the dynamics of a river system.


Major References and AcknowledgementChapra, S. C. (1997). Surface water quality modeling. In Surface water quality modeling.WCB/McGraw-Hill.

Ford, F. A. (1999). Modeling the environment: an introduction to system dynamics models ofenvironmental systems. Island Press.

Gorme, J. B., Maniquiz, M. C., Song, P., & Kim, L. H. (2010). The water quality of the PasigRiver in the City of Manila, Philippines: current status, management and futurerecovery. Environmental Engineering Research, 15(3), 173-179.

Jacinto, G. S., Sotto, L. P. A., Senal, M. I. S., San Diego-McGlone, M. L., Escobar, M. T. L.,Amano, A., & Miller, T. W. (2011). Hypoxia in Manila Bay, Philippines during the northeastmonsoon. Marine pollution bulletin, 63(5), 243-248.

Ji, Z. G. (2008). Hydrodynamics and water quality: modeling rivers, lakes, and estuaries. JohnWiley & Sons.

Jolankai, G. (1997). Basic river water quality models: Computer aided Learning (CAL)programme on water quality modelling (WQMCAL versión 1.1). In Technical documents inhydrology (No. 13). Unesco.

Khalil, B., Ouarda, T. B. M. J., St-Hilaire, A., & Chebana, F. (2010). A statistical approach forthe rationalization of water quality indicators in surface water quality monitoringnetworks. Journal of Hydrology, 386(1), 173-185.

Tamura, H., K. Nadaoka, E.C. Paringit, F.P. Siringan, G..Q. Tabios, C.L. Villanoy, A.C. Blanco, J.Kubota and H.Yagi (2003). Field survey on hydrodynamics and water quality in Manila Bayand Laguna Lake. Proc. Sympo. Environmental Issues Related to Infrastructure Development,JSPS Core Univ. Program on Env. Eng., 81-93.

• University of the Philippines• The Marine Science Institute• Institute of Environmental

Science and Meteorology

• Pasig River Rehabilitation Commission

• Philippine Young Water Professionals

• International RiverFoundation


Documents

Development of a Dissolved Oxygen - Biochemical Oxygen ... · Biochemical Oxygen Demand - a measure of organic pollutants in the water - amount of dissolved oxygen needed to break