Removal of Escherichia coli from stormwater using mycofiltration

Alicia Ann Flatt

Pathogens from nonpoint sources are the leading cause of water quality impairments in US surface waters. Pathogen contamination causes millions of waterborne illnesses and tens of thousands of beach closures each year, and poses a serious threats to coastal shellfish harvesting—a critical economic activity in Washington State. Because of its low cost, ease of operation, and unique biochemical properties, there is growing interest in the use of mycofiltration to sustainably remove pollutants from urban and agricultural runoff. This study assessed the feasibility of mycofiltration to remove E. coli from synthetic stormwater as part of a Phase I EPA Small Business Innovative Research grant. Fungi species including Irpex spp., Stropharia spp. and Pleurotus spp. were grown in mycofilters consisting of 5 gallon buckets with dense but permeable mycelium growth on wood chips and/or straw. Replicate mycofilters were loaded with dechlorinated tap water spiked with ~700 cfu/100 mL of E. coli at low (0.5 L/min) and high (2.2 L/min) hydraulic loading. Mycofilters were also tested in series (3 filters) at a hydraulic loading of 0.3 L/min. Influent and effluent was monitored for fecal coliform and E. coli using the EPA approved Coliscan membrane filter method. Biological monitoring was more of a challenge than anticipated due to the complex microbiology of the mycofiltration media. Results generally confirmed that mycofilters had the capacity to remove E. coli under sedimentfree conditions at a rate of roughly 20% per linear foot, with better removal at low hydraulic loading, increased filter media (series tests), and sediment-containing conditions. However, the mycofiltration media, in some cases, exported bacteria that caused false positives for fecal coliform (Raoultella spp. formally Klebsiella spp.) and E. coli (Enterobactor spp. and Staphylococcus spp.), which were identified via genetic testing. Results highlight the challenges of using traditional microbial indicator methods, such as enzyme-linked chromogenic media, to assess the capacity for ecotechnologies like mycofiltration to remove pathogens from polluted waters.

Removal of Escherichia coli from stormwater using mycofiltration

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