Constructed Wetlands and Pathogens By Stephanie Boone

Background The cleanest oceans have 1.1x10 29 prokaryotic cells and 7.5x10 7 viruses per teaspoon. 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. Riverine wetland estimated plantonic viruses 3.8x10 5 and surface viruses 1.3x10 7 per ml.

Background of deaths worldwide were caused by infectious disease of deaths worldwide were caused by infectious disease. Water-related diseases are leading cause of morbidity and mortality. 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. 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 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.

Constructed Wetland Removal of Pathogens Wetlands remove pathogens through a combination of: Wetlands remove pathogens through a combination of: Sedimentation Sedimentation Precipitation Precipitation Absorption to soil particles Absorption to soil particles Assimilation by plant tissue Assimilation by plant tissue Microbial transformation Microbial transformation Studies indicate that pathogen removal can be effected by: Studies indicate that pathogen removal can be effected by: Turbidity Turbidity Temperature Temperature The presence of vegetation The presence of vegetation Wetland type (subsurface or surface) Wetland type (subsurface or surface)

Constructed Wetland Studies Turbidity Turbidity –Higher turbidity decreases viral removal and increases parasite removal. –Blocks UV light. Temperature Temperature –Increase temperature increases viral removal. –Varies depending on parasite.

Constructed Wetland Studies Vegetation Vegetation Increase in vegetation density leads to increase in viral removal. Increase in vegetation density leads to increase in viral removal. Effect on parasite 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. 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. 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. 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. 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. Combination of filtration or removal sources are best to insure maximum pathogen removal.

References Available upon Request