Urban Runoff Characteristics in Tehran, Iran

Transcription

1 9 th International Conference on Urban Drainage Modeling Belgrade 212 Urban Runoff Characteristics in Tehran, Iran Meisam Kamali, Sharif University of Technology Somayeh Ghazvinizadeh, Sharif University of Technology Massoud Tajrishy, Sharif University of Technology Masoud Kayhanian, University of California, Davis

2 Outline Background Methodology Results Conclusion 2

3 Background Climate 245 mm average annual rainfall 3214 rainy days on average depending on altitude Index of annual precipitation decreased during the last 2 years Stormwater collection system Urban streams/sewers Storm channel Curbs and gutters Streets/ impervious surfaces 3

4 Stormwater Collection in Tehran Various methods of stormwater collection methods Stormwater channel Urban stream Curb and gutter Sewer 4

5 Major urban cities monitoring data Monitoring data limitation in Tehran City Austin Minneapolis Los Angeles Riyadh Tehran Esfahan Calgary Year AAR (mm) Land use Moderate climate Highway Highway Freeway Arid/semiarid climate Parking lot/ Street Highway Residential/ Commercial Residential TSS (mg/l) TP (mg/l) TN (mg/l).371.7** * * * TKN, ** NNO 3 5

6 Previous urban pollution study in Tehran Studies by Khakriz Ab Co. (1997) Groundwater Master plan for urban runoff management Illicit discharge by Mahab Qods and Poiry (21)to urban Monitoring flow and quality of urbanstreams streams Human Decline in of stormwater Monitoring flow and quality health risk during rain events Quality urban Use of new LID/ BMP techniques stormwater runoff Aquatic life 6

7 Methodology: Pollution Sources Runoff and stream sample collection from each source Urban Stream Galvanized roof Storm channel Asphalt street Rusted roof 7

8 Methodology: Sampling and Chemical Analysis Up to 1 samples collected (depending on rain duration) Each 5 ml subsample was analyzed for TSS, TP, PO 4, NH 4 N, NO 3 N, Zn, Cu, Pb. Volume/flow based techniques were used for flow measurement. EMC was computed based on sample concentration and the flow rate. 8

9 Results: Particulate Pollutants EMC particulate pollutants Impervious surface Urban stream (A1) Date 3 Nov 29 Q avg (L/s) 36.7 TSS (mg/l) TP (mg/l) 4.96 Rusted roof (B3) 26 Feb Galvanized roof (C3) 26 Feb Asphalt street (D1) 26 Feb Asphalt street (D2) 8 Apr Mosaic roof (E1) 24 Apr Urban stream (A2) 2 May Storm channel (F1) 13 Dec Urban stream Mean (A3) 27 Oct Urban stream Median (A4) 6 Nov

10 Results: Dissolved Pollutants EMC dissolved pollutants Impervious surface Date PO 4 (mg/l) NO 3 N (mg/l) NH 4 N (mg/l) Zn (µg/l) Cu (µg/l) Pb (µg/l) Urban stream (A1) 3 Nov Rusted roof (B3) 26 Feb Galvanize roof (C3) 26 Feb Asphalt street (D1) 26 Feb Asphalt street (D2) 8 Apr Mosaic roof (E1) 24 Apr Urban stream (A2) 2 May Storm channel (F1) Urban stream Mean (A3) Urban stream Median (A4) 13 Dec Oct Nov

11 Results: Event Mean Concentration Event Mean Concentration (EMC) Average TSS EMC is 15 times of allowable limit (4 mg/l) in Iran. Average TP EMC is very close to allowable limit (5 mg/l) in Iran. The average NO 3 N plus NH 4 N EMCs is almost half of NO 3 N discharge limit to drinking waters (1 mg/l). Heavy metals, especially Pb and Zn, must be considered. 11

12 Results: Concentration First Flush (CFF) Effect Particulate pollutants, rusted roof Particulate pollutants, galvanized roof Concentration (mg/l) First flush Second flush Q (L/s) concentration (mg/l) First flush Q (L/s) Time (min) TP TSS/2 Q Time (min) TP TSS/2 Q

13 CFF Effect (continue) 3 Dissolved pollutants, rusted roof.25 3 Dissolved pollutants, galvanized roof First flush First flush.2 Concentration (mg/l) Q (L/s) Concentration (mg/l) Q (L/s) Time (min) NH4N NO3N Time (min) NH4N NO3N NO2N Zndiss NO2N Zndiss PO4 Q PO4 Q 13

14 CFF Effect (continue) 3.5 Particulate pollutants, urban stream 6 Dissolved pollutants, urban stream Concentration (mg/l) Q (L/s) Concentration (mg/l) Q (L/s) Time (min) TP TSS/2 Q Time (min) NO3N NO2N TDS/2 PO4 Q

15 Results: Mass First Flush (MFF) Effect MFF for TSS MFF for TP %Mass %Runoff Volume B3 C3 D1 D2 A3 A4 XY %Runoff Volume B1 B3 C3 D1 D2 A3 A4 F1 XY 15

16 MFF Effect (Continue) MFF for NH 4 N MFF for NO 3 N %Mass %Runoff Volume B1 B3 C3 D1 D2 A1 XY %Runoff Volume B1 B3 C3 D1 D2 A1 A3 A4 XY 16

17 Conclusion On average the EMC of TSS, TP and most heavy metals exceed standard discharge limit to receiving waters in Iran. Concentration first flush was observed in dissolved and particulate pollutants. Second flush can be observed depending on presence and availability of TSS. Stronger and more frequent mass first flush was observed for dissolved pollutants from small impervious areas. 17

18 Conclusion (continued) In streams, first flush is lagging behind because of higher time of concentration. The findings of our study stressed that source control should be viewed as a viable option of pollutions management discharged into urban runoff and streams. The information gathered as part of this study could be used as a basis for future monitoring and stormwater management program in Tehran. 18

19 Thank for your attention! Presenter: Somayeh Ghazvinizadeh 19