[PPT] - Diminished Wastewater Treatment: Evaluation of Septic System PowerPoint Presentation

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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

SLIDE 2

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

SLIDE 3

How We Treat Human Waste

Wastewater Treatment Plants Septic Systems

75% U.S. population
Monitored
25% U.S. population
Not monitored

SLIDE 4

Distribution of OWTS in the United States 10-25% 25-40% > 40%

U.S. - 25% RI – 31%

SLIDE 5

The Problems

BOD:

Low O2/Anoxia

O2 O2 O2 O2 O2

Microorganisms:

Bacteria
Viruses
Protozoan
Worms

Nutrients-N&P:

Eutrophication
Fresh – P
Coastal – N
Anoxia

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OWTS Drainfield Treatment

Nutrients:

Phosphorus
Fe/Al

hydroxides

Adsorption/

precipitation

Nitrogen
Nitrification
Denitrification

BOD:

Microbial

degradation

Microorganisms:

Predation
Adsorption/

filtration

SLIDE 7

Source : Consortium for Climate Risk in the Urban Northeast

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

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Chronic Effects of Climate Change

<1’

OWTS function under elevated sea level / groundwater conditions

Source: NEOWTC @ URI

SLIDE 9

Physical Effects of Rising Temperature

1 2 3 4 5 6 7 8 9 10 11 12 13 14 5 10 15 20 25 30 [O2] (mg/L) T (oC)

SLIDE 10

Biological Effects of Rising Temperature

Davidson et al. (1998)

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The Experiment: How Will Climate Change Impact OWTS?

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1. Primary Treatment
2. Drainfield

WATER TABLE

Conventional System

1. Primary treatment
2. Secondary treatment
4. Controls - timers
3. Shallow Drainfield

Advanced System

SLIDE 13

Intact Soil Mesocosms

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Present Climate vs. Climate Change

20°C 25°C

Water Table

46 cm

Water Table Water Table

77 cm 77 cm

Conventional Advanced

SLIDE 15

RESULTS

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Oxygen

Conventional Advanced

P&S

18.5 19.0 19.5 20.0 20.5

120
105
90
75
60
45
30
15

P&S - present climate P&S - climate change Present climate Climate change

Depth (cm)

O2 (%)

SND

18.5 19.0 19.5 20.0 20.5 Depth (cm)

120
105
90
75
60
45
30
15

O2 (%)

GEO

O2 (%)

18.5 19.0 19.5 20.0 20.5

120
105
90
75
60
45
30
15

Hotter, wetter soil – less oxygen, more reducing conditions

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Biochemical Oxygen Demand (BOD)

Conventional Advanced

P&S 1 2

0.0 0.5 1.0 1.5 2.0 2.5 3.0 Present Climate Climate Change BOD5 (mg/L)

SND 1 2

BOD5 (mg/L) 0.0 0.5 1.0 1.5 2.0 2.5 3.0 Present Climate Climate Change

GEO 1 2

0.0 0.5 1.0 1.5 2.0 2.5 3.0 Present Climate Climate Change BOD5 (mg/L)

Increased temperature likely speeds microbial C degradation

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P&S

1 2

2 4 6 Present Climate Climate Change FC (CFU/100mL)

Fecal Coliform Bacteria

Conventional Advanced

SND

1 2

FC (CFU/100mL) 2 4 6 Present Climate Climate Change

GEO

1 2

2 4 6 Present Climate Climate Change FC (CFU/100mL)

Increased moisture likely diminished microbial attachment

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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

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Total Nitrogen

Conventional Advanced

P&S

1 2

60
40
20

20 40 60 Present Climate Climate Change TN removal (%)

Conv.: Increased moisture, more anoxia, more hetero. denit. Adv.: Temperature increased C degradation, limited hetero. denit.

GEO

1 2

60
40
20

20 40 60 Present Climate Climate Change TN removal (%)

SND

1 2

TN removal (%)

60
40
20

20 40 60 Present Climate Climate Change

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Total Phosphorus

Conventional Advanced

P&S

1 2

20 40 60 80 100 Present Climate Climate Change TP removal (%)

SND 1 2

TP removal (%) 20 40 60 80 100 Present Climate Climate Change

GEO 1 2

20 40 60 80 100 Present Climate Climate Change TP removal (%)

Increased moisture likely caused reduction/dissolution of metals allowed P mobilization

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Conventional Advanced

Phosphorus

P&S

P&S PC P&S CC

Proportion of P in output water

0.0 0.2 0.4 0.6 0.8 1.0 1.2

Non-metal Al Fe Mn

SND

SND PC SND CC 0.0 0.2 0.4 0.6 0.8 1.0 1.2

GEO

GEO PC GEO CC

0.0 0.2 0.4 0.6 0.8 1.0 1.2

Non-metal Non-metal Fe Fe Fe Fe Fe Al Al Al Al Al Mn Mn

Climate change: P in output water due to metals becomes more important than non-metal mechanisms (e.g. P-accumulating organism)

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