Determination of Chlorine Bulk and Wall Decay Coefficients for Calibration of the GCWW All-Pipes Distribution System Model

Transcription

1 Determination of Chlorine Bulk and Wall Decay Coefficients for Calibration of the GCWW All-Pipes Distribution System Model Haishan Piao Yeongho Lee David Hartman Cheryl Bush OAWWA Annual Conference September 22, 2010 Columbus, Ohio

2 Presentation Overview GCWW System Overview Chlorine Monitoring Field Test Chlorine Bulk/Wall Decay Coefficients Calibration Goals and Results Conclusions

3 Greater Cincinnati Water Works: System Overview 2 Treatment plants: Miller: Surface Bolton: Ground Avg. day pumpage: 140 MGD 3100 miles of Water main 20 Pumping stations 27 Storage tanks 11 Pressure zones Customers Retail Wholesale Population: 1.1 millions

4 Distribution System Model: All Pipes Model Built from System- Wide GIS Data Includes all pipes 2 in diameter Pipes: 200,000 Hydraulic Calibration Chlorine Calibration Master Planning, WQ Analyses, and Operational Modeling

5 Model Calibration Flow Chart All Pipes Model Construction Flow/Pressure/Head Loss Field Testing Chlorine Monitoring Hydraulic Calibration Max Day Calibration Min Day Calibration Hydraulic Verification Chlorine Calibration Bulk/Wall Decay Coefficients Options Chlorine Calibration Model Scenarios

6 Friction Coefficient (C-Value) Model Hydraulic Calibration Detailed Analysis and Assignment of C Factors All Mains Constructed Since 1947 (New Mains) 1947 to Present Before 1947 Mains Constructed before 1947 (Old Mains) as shown > =42" 24" to 36" 12" to 20" <=10 0 Pipe Age (Years) Max/Min Day Hydraulic Calibration

7 Field Testing to Monitor Chlorine Residuals Conducted during summer and fall of monitoring zones 38 temporary monitors per zone Free chlorine ph Total 190 locations Calibration day for each zone

8 Field Testing to Monitor Chlorine Residuals (cont d) Monitoring Equipments Free chlorine and ph: ATi Q45H/62 Data Logger: Hobo H Chlorine/pH Controller Chlorine Probe Pressure Regulator ph Probe

9 Water Surface Elevation (ft) Model Hydraulic Verification /23/07 7/30/07 8/6/07 8/13/07 SCADA Data Model Data

10 Bulk Decay Nature of source water Type of water treatment Wall Decay Pipe material Pipe condition Chlorine Decay

11 Chlorine Bulk Decay Coefficients Bulk decay coefficients were developed based on simulated distribution system (SDS) test conducted during field testing program Four samples collected for SDS tests at 10-day intervals August 9 August 20 August 30 September 10 1 st order curves were developed based on water age and source

12 Miller Plant First Order Bulk Decay Curves Miller Plant

13 Bolton Plant First Order Bulk Decay Curves Bolton Plant

14 Chlorine Wall Decay Coefficients Approaches to develop wall decay coefficients: Standard global coefficients: Software built-in F curves based on C factor Wall Decay Coefficient = F/C Multiple curves based on C factor, pipe diameter, and water source Single customized curves based on C factor

15 Wall Decay Coefficients: Software Built-in F curves

16 Wall Decay Coefficients: Multiple Curves Based on C-Factor and Diameters Wall Option 1 (W1)

17 Wall Decay Coefficients: Multiple Curves Based on C-Factor & Source W4 & W5

18 Wall Decay Coefficients : Single Custom Curve Based on C-Factor W2, W3 & W6

19 Wall Decay Coefficients: Overview W1 Lined W1 Unlined - Small Diam W1 Unlined - Large Diam W2 - Single Curve W3 - Single Curve W4 - Single Curve - Miller W4 - Single Curve - Bolton W5 - Single Curve - Miller W5 - Single Curve - Bolton W6 - Single Curve

20 Model Inputs for Water Quality Runs Bulk and wall decay coefficients Chlorine concentration at clearwells Hydraulic time step 60 min Water quality time step 2 min Simulation time 21 days

21 Chlorine Calibration Goals Age - Chlorine Older water further out in the system 0-12 hrs hrs 0.15 >24 hrs 0.2

22 Miller Plant First Order Bulk Decay Curves Miller Plant

23 Calibration Results: Bulk Decay Options Comparison Summary of B1 and B2 Results with Comparative Wall Decay Options Number of Locations Calibrated Water Age 0-12 hrs hrs > 24 hrs Calibration Goals 0.1 mg/l 0.15 mg/l 0.2 mg/l Total Locations % Calibrated Number of Locations B1W B1F B1F B2W B2F B2W

24 Calibration Results: Wall Decay Options Comparison Software Built-in Wall Decay F Curves Decay coefficients depend only on C factor Wall decay Coefficient = F/C Less accurate results

25 Wall Decay Coeficient, Kw Wall Decay Coefficients: 0.00 Wall Decay Coefficients Hazen Williams C Value W1 Lined W1 Unlined - Small Diam W1 Unlined - Large Diam W2 - Single Curve W3 - Single Curve W4 - Single Curve - Miller W4 - Single Curve - Bolton W5 - Single Curve - Miller W5 - Single Curve - Bolton W6 - Single Curve -0.35

26 Calibration Results: Wall Decay Comparison (cont d) 170 Points of Calibration (After Eliminating Bad and Questionable Data) Number of Locations Calibrated Water Age < 12 hrs hrs > 24 hrs Calibration Goals Number of Locations 0.1 mg/l 0.15 mg/l 0.2 mg/l Total Locations % Calibrated B2W B2W B2W B2W B2W B2W

27 Calibration Results: Wall Decay Comparison (cont d) Test Zone Modeled Concentration vs. Observed Concentration (170 Points of Calibration) Option B2W1 Deviation in Chlorine Concentration (mg/l) Option B2W2 Option B2W3 Option B2W4 Option B2W5 Option B2W6 Zone Zone Zone Zone Zone System

28 Conclusions Field testing data were used for chlorine calibration of GCWW all pipes distribution system model. Chlorine Bulk Decay Coefficients: Bulk decay coefficients can be variable. Especially for Miller water. Higher decay rate for younger water than older water. Multiple 1 st order decay curves had to be developed based on water age for each water source to obtain the best results.

29 Conclusions (cont d) Chlorine Wall Decay Coefficients Aggressive decay for older pipes compared to younger pipes. Software Built-in F curves did not yield desirable results. Highest degree of calibration achieved by using curve based on pipe roughness, pipe diameter, and water source. Wall decay coefficients simplified by a single custom curve based on C-factor without sacrificing calibration accuracy.

30 Acknowledgement Black & Veatch Eva Sinha, P.E. Jeff Stillman, P.E. Marissa Albright, P.E. Kevin Laptos, P.E. Larry Gaddis, P.E. ID Modeling Jerry Edwards, P.E.

31 Questions??? GCWW.Cincinnati-Oh.gov