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Constructed Wetlands and Pathogens. By Stephanie Boone. Background. The cleanest oceans have 1.1x10 29 prokaryotic cells and 7.5x10 7 viruses per teaspoon. Riverine wetland estimated plantonic viruses 3.8x10 5 and surface viruses 1.3x10 7 per ml. Background.
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Constructed Wetlands and Pathogens By Stephanie Boone
Background • The cleanest oceans have 1.1x1029 prokaryotic cells and 7.5x107 viruses per teaspoon. • Riverine wetland estimated plantonic viruses 3.8x105 and surface viruses 1.3x107 per ml.
Background • 2001 265 of deaths worldwide were caused by infectious disease. • Water-related diseases are leading cause of morbidity and mortality. • In the US between 1971 and 1994 there were 650 waterborne outbreaks and 569,754 cases of waterborne illness.
Background • Pathogens enter the groundwater supply 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 outbreaks connected with groundwater. *33% associated with surface water.
Background Microorganisms known for disease transmission by water include; Giardia, Cryptosporidium, Legionella, E. Coli 0157 H7, rotavirus, hepatitis E, norovirus, Hepatitis A, poliovirus, adenovirus, astroviruses.
Wetlands remove pathogens through a combination of: Sedimentation Precipitation Absorption to soil particles Assimilation by plant tissue Microbial transformation Studies indicate that pathogen removal can be effected by: Turbidity Temperature The presence of vegetation Wetland type (subsurface or surface) Constructed Wetland Removal of Pathogens
Constructed Wetland Studies • Turbidity • Higher turbidity decreases viral removal and increases parasite removal. • Blocks UV light. • Temperature • Increase temperature increases viral removal. • Varies depending on parasite.
Constructed Wetland Studies • Vegetation • Increase in vegetation density leads to increase in viral removal. • Effect on parasite removal ???. • Dense vegetation facilitates sedimentation, sorption straining and other decay process. • Plants can damage enteric pathogens by excreting toxic antimicrobial substances from roots.
Type of Wetland • Subsurface flow removed 95% of coliphage and 99% of Polio virus as compared with 40% removal in a duckweed pond. • Duckweed pond removed 89% - 98% of Giardia and Cryptosporidium as compared to 58%-73% in a surface wetland.
Conclusions • Generally factors that decrease heat and UV light have a negative effect on pathogenic virus removal. • Parasites are generally removed by sedimentation and removal factors vary depending on parasite. • Combination of filtration or removal sources are best to insure maximum pathogen removal.
