Constructed Wetlands Constructed Wetlands and Pathogensand Pathogens

By Stephanie BooneBy Stephanie Boone

Background

• The cleanest oceans The cleanest oceans have 1.1x10have 1.1x102929 prokaryotic cells prokaryotic cells and 7.5x10and 7.5x1077 viruses viruses per teaspoon.per teaspoon.

• Riverine wetland Riverine wetland estimated plantonic estimated plantonic viruses 3.8x10viruses 3.8x1055 and and surface viruses surface viruses 1.3x101.3x1077 per ml. per ml.

Background

• 2001 265 of deaths 2001 265 of deaths worldwide were caused worldwide were caused by infectious disease.by infectious disease.

• Water-related diseases Water-related diseases are leading cause of are leading cause of morbidity and mortality.morbidity and mortality.

• In the US between 1971 In the US between 1971 and 1994 there were and 1994 there were 650 waterborne 650 waterborne outbreaks and 569,754 outbreaks and 569,754 cases of waterborne cases of waterborne illness.illness.

Background

– Pathogens enter the Pathogens enter the groundwater supply groundwater supply through:through:

• Sewage treatment effluents *Excretion of 1011 viral particles per gram of feces.

• Onsite septic waste treatment discharges *traced viruses travel 328 ft. through groundwater

• Leachates from sanitary landfills

• Land runoff from urban, agricultural and natural areas..

**58% waterborne 58% waterborne outbreaks connected outbreaks connected with groundwater.with groundwater.

*33% associated with *33% associated with surface water.surface water.

Background

Microorganisms known for disease transmission by water include; Microorganisms known for disease transmission by water include; Giardia, Cryptosporidium, Legionella, E. Coli 0157 H7, rotavirus, Giardia, Cryptosporidium, Legionella, E. Coli 0157 H7, rotavirus, hepatitis E, norovirus, Hepatitis A, poliovirus, adenovirus, hepatitis E, norovirus, Hepatitis A, poliovirus, adenovirus, astroviruses.astroviruses.

Constructed Wetland Constructed Wetland Removal of PathogensRemoval of Pathogens

• Wetlands remove Wetlands remove pathogens through a pathogens through a combination of:combination of:

• SedimentationSedimentation

• PrecipitationPrecipitation

• Absorption to soil Absorption to soil particlesparticles

• Assimilation by plant Assimilation by plant tissuetissue

• Microbial transformation Microbial transformation

• Studies indicate that Studies indicate that pathogen removal can pathogen removal can be effected by:be effected by:

• TurbidityTurbidity

• TemperatureTemperature

• The presence of The presence of vegetationvegetation

• Wetland type Wetland type (subsurface or (subsurface or surface) surface)

Constructed Wetland Constructed Wetland StudiesStudies• TurbidityTurbidity

– Higher turbidity Higher turbidity decreases viral removal decreases viral removal and increases parasite and increases parasite removal.removal.

– Blocks UV light.Blocks UV light.

• TemperatureTemperature– Increase temperature Increase temperature

increases viral removal.increases viral removal.– Varies depending on Varies depending on

parasite. parasite.

Constructed Wetland Constructed Wetland StudiesStudies

• Vegetation Vegetation • Increase in vegetation Increase in vegetation

density leads to density leads to increase in viral increase in viral removal.removal.

• Effect on parasite Effect on parasite removal ???.removal ???.– Dense vegetation Dense vegetation

facilitates sedimentation, facilitates sedimentation, sorption straining and sorption straining and other decay process.other decay process.

– Plants can damage enteric Plants can damage enteric pathogens by excreting pathogens by excreting toxic antimicrobial toxic antimicrobial substances from roots. substances from roots.

Type of WetlandType of Wetland

• Subsurface flow removed 95% of Subsurface flow removed 95% of coliphage and 99% of Polio virus as coliphage and 99% of Polio virus as compared with 40% removal in a compared with 40% removal in a duckweed pond.duckweed pond.

• Duckweed pond removed 89% - 98% Duckweed pond removed 89% - 98% of Giardia and Cryptosporidium as of Giardia and Cryptosporidium as compared to 58%-73% in a surface compared to 58%-73% in a surface wetland. wetland.

ConclusionsConclusions

• Generally factors that decrease heat and Generally factors that decrease heat and UV light have a negative effect on UV light have a negative effect on pathogenic virus removal.pathogenic virus removal.

• Parasites are generally removed by Parasites are generally removed by sedimentation and removal factors vary sedimentation and removal factors vary depending on parasite.depending on parasite.

• Combination of filtration or removal Combination of filtration or removal sources are best to insure maximum sources are best to insure maximum pathogen removal. pathogen removal.

References Available upon References Available upon RequestRequest