Yu Yang, PhD 屋面雨水收集利用可行性研究. Feasibility of roof runoff collection and utilization

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1 The China-UK joint Workshop on Urban Flooding and Sponge Cities & 217 Annual Conference of the IIIRR 屋面雨水收集利用可行性研究 Feasibility of roof runoff collection and utilization Yu Yang, PhD Lanzhou University of Technology, Lanzhou, China

2 Outline Background Aims Methodology Results Conclusion

3 Problems With the climate change in the world, the frequency of extreme rainfall is increasing Urbanization process results in more and more impervious pavement Flood happened in 62% cities of China Pollutants from nonpoint sources of CSO (combined sewer overflow) and SSO(separate sewer overflow) aggravate receiving water pollution Flood CSO 216,4,22

4 Problems More than 1 cities face severe problems of water scarcity, even no water for drinking

5 Guidance and Standard Premier Li Keqiang proposed that improve sponge city construction, making city has face as well as lining in the Report on the Work of the Government, in March, 217 In green building evaluation, 3% and 5% water utilization are required to be non-traditional water source for house and for commercial buildings Roof areas reach 4%-5% of whole impervious area in cities

6 Challenge in roof runoff harvest In different rainfall events, water quality of roof runoff varies significantly, therefore the subsequent treatment process does not work well or is too expensive First flush is expected, so that we can dispose the initial most polluted water. While, if first flush occur or not and how about the flush severity are not clear First flush curve cumulative pollutant load vs. cumulative flow

7 Aims Comparison of water quality between roof runoff and ground runoff, roof runoff in different rains, in different countries Impacts of rain on first flush Design of roof runoff collection system on basis of water quality

8 Methodology Manually collected roof runoff and ground runoff every 5, 1 or 3 minutes In Japan case, automatic sampling system was used Water quality indexes were analyzed by standard methods

9 Manually sample collection points School in Lanzhou city School in Ganzhou city Ground collection point 2 Rain pipe Roof collection point Ground collection point 1

10 Automatic sampling system Rainwater enters from left side The balls in each tank will be lift up by water When the No.1 tank is full, the ball will block the entrance, then No.2 filled Rainwater in different stages can be separated Volume of each tank is 1 L Each tank can collect.7mm rainwater 1

11 Water quality comparison of harvested rain and rainwater standard Comparison of rainwater use standards and roof harvested water quality in China Index Water quality of harvested rainwater # COD(mg/L) SS(mg/L) Rainwater use standard Index Comparison of rainwater use standards and roof harvested water quality in Japan Water quality of harvested rainwater Rainwater use standard [ Turbidity (Degree).1-.5 <2 ph ~8.6 Odor Be acceptable should not be displeased #Roof rainwater was harvested from May23 rd to June the 9 th 217 number of samples =3 Appearance (Color[Degree]) E.coli -1.5 Not Detected should not be displeased should not be detected Water quality of housed hold harvested rainwater from Sep.8th to Oct. 28th, number of samples =9

12 ph COD concentration (mg/l) SS(mg/L) Time Ground runoff vs. roof runoff- same rain in LZ city 8 ground runoff at point 1 ground runoff at point 2 roof runoff Time 4 Time Water quality of roof runoff has similar tendency with ground runoff at point 2 Water quality of ground runoff at point 1 is the worst due to being affected strongly by traffic Only COD has first flush phenomenon

13 ph SS concerntration(mg/l) COD concerntration(mg/l) Roof runoff in different rain and cities roof runoff in 21ml rain roof runoff in 1.8ml rain GZ roof runoff in 16.3ml rain Time from rain start (min) Time from rain start (min) Time from rain start (min) In different rain or different cities, ph and COD of roof runoff have small variation While SS has large change range First flush of COD depends on rain and SS has no obvious first flush

14 Sampled rain in Japan Raining Date Rain data Rainfall(mm) Antecedent dry periods(hour) 21/9/ /9/ /9/ /9/ /1/ /1/ /1/ /1/

15 DOC(mgC/l) Total coliform (cuf/ml) EC(µS/cm) NH 4 -N(mgN/l) Roof runoff in Japan focusing first flush EC 9/8 9/16 9/25 9/3 1/4 1/ Rainfall (mm) 9/8 9/16 DOC 9/25 9/3 1/13 1/ NH 4 + 9/8 9/16 9/25 9/3 1/4 1/ Rainfall (mm) Total coliform 9/8 9/3 1/13 1/24 1/ Rainfall (mm) Rainfall(mm) EC- High conductivity appeared in initial part of first flush on Sep.8 th and decreased rapidly. Ammonia Highest concentration appeared on Sep. 8 th among all the samples. DOC- Concentration increased at initial part of first flush and decreased fast. Total coliform Total coliform was in a low and stable level in each rain events except one sample of Sep. 8 th. 15

16 EC µs/cm ( ) Impacts of rainfall on first flush DOC(mgC/L) T.Coli (cfu/ml) Antecedent dry weather(h) Antecedent dry weather(h) Sep.8 th Sep.8 th EC DOC NH4-N (mg/l) Antecedent dry weather(h) Antecedent dry weather(h) No clear relationship was observed between antecedent dry weather periods and water quality of first flush. Sep.8 th Sep.8 th NH 4 + T.coli

17 Roof runoff collection system 1.Roof drainage 2.Test room 3.Overflow bypass 4.Solenoid valve (three position) 5.Collection bypass 6.Discarding bypass 8 7. Collection box 8.split-flow intelligent control system 9. MCU system 1.Power mode 11.probe 12.USB line 13. Indicator mode

18 Conclusions In China, SS of roof runoff exceeds the rainwater use standard. In Japan, the water quality can reach the Japanese standard In same rain, water quality of ground runoff is similar level or worse than roof runoff, depending on the sampling points ph and COD of roof runoff change slightly in different rains or cities. While SS has large change range In China, COD in roof runoff may have first flush, while other water quality index rarely has first flush. In Japan, only EC has slight first flush and there is no relationship between rain antecedent dry period and first flush

19 Thank you for your attention!