Diminished Wastewater Treatment: Evaluation of Septic System Performance Under a Climate Change Scenario Jennifer Cooper Laboratory or Soil Ecology and Microbiology, University of Rhode Island
Acknowledgements and Funding Funding: RI Agricultural Experiment Station USDA Hatch Multi-state Project NE-1045 URI Sea Grant URI Enhancement of Graduate Research Awards URI Undergraduate Research Awards Research Team: Jose Amador NRS Tom Boving GEO George Loomis NRS & NEOWTC Dave Kalen NRS & NEOWTC Ivan Morales Ph.D. student Undergraduate Helpers: Juliana DeLuca Ethan Sneesby Joshua Sargent Ian Rambo Rachel Naylor Faith Anderson
How We Treat Human Waste Wastewater Treatment Plants Septic Systems 75% U.S. population Monitored 25% U.S. population Not monitored
Distribution of OWTS in the United States U.S. - 25% RI 31% 10-25% 25-40% > 40%
The Problems Microorganisms: Bacteria Viruses Protozoan Worms Nutrients-N&P: Eutrophication Fresh P Coastal N Anoxia BOD: Low O 2 /Anoxia O 2 O O 2 2 O O 2 2
OWTS Drainfield Treatment Microorganisms: Predation Adsorption/ filtration Nutrients: Phosphorus Fe/Al hydroxides Adsorption/ precipitation Nitrogen Nitrification Denitrification BOD: Microbial degradation
Climate Change - Northeast Intergovernmental Panel on Climate Change (2013 report): 100 year predictions (Northeast) Sea levels rise 3-5 ft. Increased precipitation Elevated temperature 2-5 C Source : Consortium for Climate Risk in the Urban Northeast
Chronic Effects of Climate Change <1 OWTS function under elevated sea level / groundwater conditions Source: NEOWTC @ URI
[O 2 ] (mg/l) Physical Effects of Rising Temperature 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 5 10 15 20 25 30 T ( o C)
Biological Effects of Rising Temperature Davidson et al. (1998)
The Experiment: How Will Climate Change Impact OWTS?
Conventional System 1. Primary Treatment 2. Drainfield WATER TABLE 4. Controls - timers 3. Shallow Drainfield Advanced System 2. Secondary treatment 1. Primary treatment
Intact Soil Mesocosms
Present Climate vs. Climate Change Conventional Advanced 77 cm 77 cm 46 cm Water Table Water Table Water Table 25 C 20 C
RESULTS
Oxygen Conventional Advanced Depth (cm) 0-15 -30-45 -60-75 -90 P&S P&S - present climate P&S - climate change -105 Present climate Climate change -120 18.5 19.0 19.5 20.0 20.5 O 2 (%) Depth (cm) 0 SND -15-30 -45-60 -75-90 -105-120 18.5 19.0 19.5 20.0 20.5 O 2 (%) 0-15 -30-45 -60-75 -90-105 GEO -120 18.5 19.0 19.5 20.0 20.5 O 2 (%) Hotter, wetter soil less oxygen, more reducing conditions
Biochemical Oxygen Demand (BOD) Conventional Advanced 3.0 2.5 P&S 3.0 2.5 SND 3.0 2.5 GEO BOD 5 (mg/l) 2.0 1.5 1.0 BOD 5 (mg/l) 2.0 1.5 1.0 BOD 5 (mg/l) 2.0 1.5 1.0 0.5 0.5 0.5 0.0 Present 1 Climate Climate 2 Change 0.0 Present 1Climate Climate 2 Change 0.0 Present Climate Climate Change 1 2 Increased temperature likely speeds microbial C degradation
Fecal Coliform Bacteria Conventional Advanced 6 P&S 6 SND 6 GEO FC (CFU/100mL) 4 2 FC (CFU/100mL) 4 2 FC (CFU/100mL) 4 2 0 1 2 Present Climate Climate Change 0 1 2 Present Climate Climate Change 0 1 2 Present Climate Climate Change Increased moisture likely diminished microbial attachment
MS2 Bacteriophage - Virus Conventional Advanced No virus in output water Present climate and climate change conditions For all drainfield types ph more important than wetter/hotter conditions Virus will have (+) charge at drainfield ph (~3.2) Aids in retention to ( ) charged soil particles
Total Nitrogen Conventional Advanced 60 40 P&S 60 40 SND 60 40 GEO TN removal (%) 20 0-20 TN removal (%) 20 0-20 TN removal (%) 20 0-20 -40-40 -40-60 1 2 Present Climate Climate Change -60 1 2 Present Climate Climate Change -60 1 2 Present Climate Climate Change Conv.: Increased moisture, more anoxia, more hetero. denit. Adv.: Temperature increased C degradation, limited hetero. denit.
Total Phosphorus Conventional Advanced P&S SND GEO 100 100 100 TP removal (%) 80 60 40 TP removal (%) 80 60 40 TP removal (%) 80 60 40 20 1 2 Present Climate Climate Change 20 Present 1 Climate Climate 2 Change 20 Present 1 Climate Climate 2 Change Increased moisture likely caused reduction/dissolution of metals allowed P mobilization
Phosphorus Conventional Advanced Proportion of P in output water 1.2 1.0 0.8 0.6 0.4 0.2 0.0 Non-metal Mn Al Fe P&S PC Al Fe P&S CC P&S 1.2 1.0 0.8 0.6 0.4 0.2 0.0 Non-metal Mn Al Al SND 1.2 1.0 0.8 0.6 0.4 Non-metal Mn Al Al Fe Fe 0.2 0.0 Fe Fe SND PC SND CC GEO PC GEO CC GEO Climate change: P in output water due to metals becomes more important than non-metal mechanisms (e.g. P-accumulating organism)
Mass Balance Units: kg/yr (FC in CFU/yr)
Mass Balance - Conventional Present Climate BOD 5 : 0.180 FC: 0.0 TN: 6.32 TP: 0.241 Climate Change BOD 5 : 0.05 FC: 1.6 x 10 8 TN: 6.50 TP: 0.489 kg/yr (FC in CFU/yr) in output water
Mass Balance - Conventional Present Climate BOD 5 : 0.180 FC: 0.0 TN: 6.32 TP: 0.241 Climate Change BOD 5 : 0.05 FC: 1.6 x 10 8 TN: 6.50 TP: 0.489 kg/yr (FC in CFU/yr) in output water
Mass Balance - Conventional Present Climate BOD 5 : 0.180 FC: 0.0 TN: 6.32 TP: 0.241 Climate Change BOD 5 : 0.05 FC: 1.6 x 10 8 TN: 6.50 TP: 0.489 kg/yr (FC in CFU/yr) in output water
Mass Balance - Conventional Present Climate BOD 5 : 0.180 FC: 0.0 TN: 6.32 TP: 0.241 Climate Change BOD 5 : 0.05 FC: 1.6 x 10 8 TN: 6.50 TP: 0.489 kg/yr (FC in CFU/yr) in output water
Mass Balance - Advanced Present Climate BOD 5 : 0.10-0.13 FC: 0.0 TN: 6.13-6.26 TP: 0.0-0.011 Climate Change BOD 5 : 0.0-0.03 FC: 1.9-2.2 x 10 8 TN: 6.73-7.04 TP: 0.241-0.259 kg/yr (FC in CFU/yr) in output water
Mass Balance - Advanced Present Climate BOD 5 : 0.10-0.13 FC: 0.0 TN: 6.13-6.26 TP: 0.0-0.011 Climate Change BOD 5 : 0.0-0.03 FC: 1.9-2.2 x 10 8 TN: 6.73-7.04 TP: 0.241-0.259 kg/yr (FC in CFU/yr) in output water
Mass Balance - Advanced Present Climate BOD 5 : 0.10-0.13 FC: 0.0 TN: 6.13-6.26 TP: 0.0-0.011 Climate Change BOD 5 : 0.0-0.03 FC: 1.9-2.2 x 10 8 TN: 6.73-7.04 TP: 0.241-0.259 kg/yr (FC in CFU/yr) in output water
Mass Balance - Advanced Present Climate BOD 5 : 0.10-0.13 FC: 0.0 TN: 6.13-6.26 TP: 0.0-0.011 Climate Change BOD 5 : 0.0-0.03 FC: 1.9-2.2 x 10 8 TN: 6.73-7.04 TP: 0.241-0.259 kg/yr (FC in CFU/yr) in output water
Increasing Coastal Population 39% of US population reside in coastal shoreline counties
Summary Effects of Climate Change Positive Effect BOD Total N* Negative Fecal coliform bacteria Total N* Total P