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The Impact of First Flush Removal on Rainwater Quality and Rainwater Harvesting Systems’ Reliability in Rural Rwanda Kelly...
Outline <ul><li>Project context </li></ul><ul><li>Intro to first flush (FF) </li></ul><ul><li>Fieldwork </li></ul><ul><li>...
Project Details <ul><li>Project Location </li></ul><ul><ul><li>Bisate Village, Rwanda </li></ul></ul><ul><li>Project Partn...
Project Context <ul><li>Problem: </li></ul><ul><li>95-99% of the population infected with worms </li></ul><ul><li>Inadequa...
Average Monthly Rainfall Distribution Rainfall Depth (mm)
Rainwater Tanks 2007
<ul><li>The Clinic- 41.35 m 3 </li></ul>Trackers’ House-42.5 m 3 Primary School-40 m 3 <ul><li>People Served: </li></ul><u...
The  first portion  of the total discharged storm volume which contains the  main proportion  of the pollutant load during...
Constant Volume Diverter Storage tank Gutters Diversion pipe Removable cap Tank inlet Courtesy of Matt Stevenson
Research Questions <ul><li>How much first flush to divert? </li></ul><ul><li>How is reliability affected? </li></ul>
The GIZMO <ul><li>Graduated Inflow-collector for Zero Mixing with Overflow </li></ul>
New Clinic Roof (CL) First setup: 0.66 mm rain Second setup: 1.34 mm rain Roof material: new iron sheets Location: close p...
Rusty Roof House (HS) Roof material: old, rusty iron sheets Location: far from vehicle road Captures first 1.45 mm of rain
Potato House (PT) Roof material: old clay tiles Location: moderate distance from vehicle road Captures first 1.61 mm of rain
Water Quality <ul><li>Membrane filtration </li></ul><ul><ul><li>Total Coliform </li></ul></ul><ul><ul><li>E. coli </li></u...
Turbidity Reduction Trends-CL
Turbidity Reduction Trends-HS
Turbidity Reduction Trends-PT
Previous Work <ul><li>Martinson and Thomas 2005 </li></ul><ul><ul><li>Uganda </li></ul></ul><ul><ul><li>k range 0.65 – 2.2...
Recommendation to divert 1st mm of runoff: Turbidity reduction
Storage-Reliability-Yield (SRY) Simulation Model q = time-based reliability d f  = # days demand is not met n = total days...
SRY Simulation Results <ul><li>15% losses, no FF diversion </li></ul>15% losses, 1 mm diversion after 3 consecutive days e...
Effect of FF Diversion on Reliability in Bisate 7 days 4 days 6 days Additional days not meeting demand with first flush d...
Conclusions <ul><li>1 mm diversion of runoff </li></ul><ul><li>Small reduction in reliability (<2%) </li></ul><ul><li>50% ...
Murakoze Cyane! <ul><li>Pete Shanahan </li></ul><ul><li>John Peter Nshimyimana </li></ul><ul><li>Bernard Isaacson </li></u...
Questions?
Storage-Reliability-Yield (SRY) Simulation Model <ul><li>Simulate daily water balance within tank </li></ul><ul><ul><li>YA...
Pseudo-daily Rainfall Generation <ul><li>P m : probability of a day being wet </li></ul><ul><li>R m : actual monthly rainf...
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EWRI: Kelly Doyle's Presentaiton- The Impact of First Flush Removal on Rainwater Quality and Rainwater Harvesting Systems’ Reliability in Rural Rwanda

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EWRI: Kelly Doyle's Presentaiton- The Impact of First Flush Removal on Rainwater Quality and Rainwater Harvesting Systems’ Reliability in Rural Rwanda

  1. 1. The Impact of First Flush Removal on Rainwater Quality and Rainwater Harvesting Systems’ Reliability in Rural Rwanda Kelly C. Doyle – Montgomery Associates: Resource Solutions Dr. Peter Shanahan – Massachusetts Institute of Technology May 17, 2010
  2. 2. Outline <ul><li>Project context </li></ul><ul><li>Intro to first flush (FF) </li></ul><ul><li>Fieldwork </li></ul><ul><li>Storage-Reliability-Yield (SRY) simulation </li></ul><ul><li>Effects of FF on SRY </li></ul>
  3. 3. Project Details <ul><li>Project Location </li></ul><ul><ul><li>Bisate Village, Rwanda </li></ul></ul><ul><li>Project Partner </li></ul><ul><ul><li>Dian Fossey Gorilla Fund International </li></ul></ul>African Conservation Foundation
  4. 4. Project Context <ul><li>Problem: </li></ul><ul><li>95-99% of the population infected with worms </li></ul><ul><li>Inadequate water supply (volume) </li></ul><ul><li>Contaminated water supply </li></ul><ul><li>Approach : </li></ul><ul><li>Rainwater harvesting (water supply) </li></ul><ul><li>First flush diversion (treatment) </li></ul>
  5. 5. Average Monthly Rainfall Distribution Rainfall Depth (mm)
  6. 6. Rainwater Tanks 2007
  7. 7. <ul><li>The Clinic- 41.35 m 3 </li></ul>Trackers’ House-42.5 m 3 Primary School-40 m 3 <ul><li>People Served: </li></ul><ul><li>20,000 people served </li></ul><ul><li>100 patients per day </li></ul><ul><li>15 patient beds </li></ul><ul><li>People Served: </li></ul><ul><li>1,700 students </li></ul><ul><li>People Served: </li></ul><ul><li>50 trackers </li></ul>Rainwater Tanks 2008
  8. 8. The first portion of the total discharged storm volume which contains the main proportion of the pollutant load during a storm event (Bertrand-Krajewski et al. 1998) What is the First Flush?
  9. 9. Constant Volume Diverter Storage tank Gutters Diversion pipe Removable cap Tank inlet Courtesy of Matt Stevenson
  10. 10. Research Questions <ul><li>How much first flush to divert? </li></ul><ul><li>How is reliability affected? </li></ul>
  11. 11. The GIZMO <ul><li>Graduated Inflow-collector for Zero Mixing with Overflow </li></ul>
  12. 12. New Clinic Roof (CL) First setup: 0.66 mm rain Second setup: 1.34 mm rain Roof material: new iron sheets Location: close proximity to road
  13. 13. Rusty Roof House (HS) Roof material: old, rusty iron sheets Location: far from vehicle road Captures first 1.45 mm of rain
  14. 14. Potato House (PT) Roof material: old clay tiles Location: moderate distance from vehicle road Captures first 1.61 mm of rain
  15. 15. Water Quality <ul><li>Membrane filtration </li></ul><ul><ul><li>Total Coliform </li></ul></ul><ul><ul><li>E. coli </li></ul></ul><ul><li>Turbidity </li></ul><ul><li>pH </li></ul><ul><li>Conductivity </li></ul>
  16. 16. Turbidity Reduction Trends-CL
  17. 17. Turbidity Reduction Trends-HS
  18. 18. Turbidity Reduction Trends-PT
  19. 19. Previous Work <ul><li>Martinson and Thomas 2005 </li></ul><ul><ul><li>Uganda </li></ul></ul><ul><ul><li>k range 0.65 – 2.2 </li></ul></ul><ul><li>Doyle 2008 </li></ul><ul><ul><li>Rwanda </li></ul></ul><ul><ul><li>k range 0.63 – 2.0 </li></ul></ul><ul><ul><ul><li>(without outliers) </li></ul></ul></ul>
  20. 20. Recommendation to divert 1st mm of runoff: Turbidity reduction
  21. 21. Storage-Reliability-Yield (SRY) Simulation Model q = time-based reliability d f = # days demand is not met n = total days in study
  22. 22. SRY Simulation Results <ul><li>15% losses, no FF diversion </li></ul>15% losses, 1 mm diversion after 3 consecutive days each with < 1mm rain X X Storage (m) Storage (m) Yield Yield
  23. 23. Effect of FF Diversion on Reliability in Bisate 7 days 4 days 6 days Additional days not meeting demand with first flush diversion 1.7% 1.0% 1.5% Reduction in reliability from diversion scheme 87% 30% 91% 15% losses, 1 mm diversion after three consecutive days each with <1 mm rain 89% 31% 92% 15% losses, no diversion Trackers’ House Primary School Health Clinic Scenario Reliability (%)
  24. 24. Conclusions <ul><li>1 mm diversion of runoff </li></ul><ul><li>Small reduction in reliability (<2%) </li></ul><ul><li>50% reduction in turbidity </li></ul><ul><li>Reduced coliform and E. coli </li></ul>Rainwater from the gutters Diverted first flush Removal cap to empty pipe with chain Soak-away pit Cleaner water to main tank
  25. 25. Murakoze Cyane! <ul><li>Pete Shanahan </li></ul><ul><li>John Peter Nshimyimana </li></ul><ul><li>Bernard Isaacson </li></ul><ul><li>DFGFI </li></ul><ul><li>MIT PSC </li></ul><ul><li>Montgomery Associates </li></ul>
  26. 26. Questions?
  27. 27. Storage-Reliability-Yield (SRY) Simulation Model <ul><li>Simulate daily water balance within tank </li></ul><ul><ul><li>YAS: yield after storage </li></ul></ul><ul><ul><li>Constant demand </li></ul></ul><ul><ul><li>Daily rainfall </li></ul></ul><ul><ul><li>Storage Term Yield Term Reliability </li></ul></ul>α = yield fraction [unitless] y = yield [m 3 /day] μ dp = avg. daily precip [m/day] A c = roof area [1 m 3 ] S r = physical storage ratio [m] s = tank storage capacity [m 3 ] A c = roof area [1 m 3 ] q = time-based reliability d f = # days demand is not met n = total days in study
  28. 28. Pseudo-daily Rainfall Generation <ul><li>P m : probability of a day being wet </li></ul><ul><li>R m : actual monthly rainfall value </li></ul><ul><li>A: 800 mm (empirical) </li></ul><ul><li>n wm : number of wet days in a month </li></ul><ul><li>R wm : mean wet day rainfall </li></ul><ul><li>Z: scaling factor </li></ul><ul><li>Wet day if random number < P m </li></ul>

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