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Title: The use of zero-valent iron and biosand filtration to inactivate Escherichia coli O157:H7 in irrigation water

item East, Cheryl - Roberts
item Callahan, Mary Theresa
item Ferguson, Sean
item Ingram, David
item Shelton, Daniel
item Patel, Jitu
item WEI, JIE - University Of Delaware
item HOOVER, DALLAS - University Of Delaware
item KNIEL, KALI - University Of Delaware
item Sharma, Manan

Submitted to: International Association for Food Protection Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 3/2/2011
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: Introduction: Foodborne pathogens can be disseminated to produce through contaminated irrigation water. Effective, low cost mitigation strategies, like biosand and zero-valent iron (ZVI) filtration, may be effective in decontaminating irrigation water. Purpose: To determine the effectiveness of biosand and zero-valent iron filters in removing E. coli O157:H7 from water. Methods: Commercial HydraSand biosand filters were built as recommended containing gravel and coarse sand. Columns were then modified to contain either fine sand only(S), a combination of ZVI and fine sand at a 1:1 ratio (SI), or ZVI only (I). Columns were fed daily for two weeks with 20 L of uninoculated groundwater to allow filters to ripen. E. coli O157:H7, cultured in a manure slurry, was added to the columns at 8.5 log CFU/100ml in a 20 L volume. At specific time points, appropriate volumes of E. coli O157:H7 were recovered from filtered water, collected on filters, and enumerated on MacConkey agar. Uninoculated groundwater was fed into each column for up to 30 days, after which filtered water was analyzed for E. coli O157:H7 populations. Results: E. coli O157:H7 counts recovered from S columns from day 0 through 7 were TNTC; however, E. coli O157:H7 counts from SI columns on day 2, 7 and 14 declined to 3.97, 1.79 and 0.34 log CFU/100ml, respectively. Counts in I columns on days 2, 7, and 14 declined to 3.44, 0.46, and -1 log CFU/100ml, respectively. By days 8, 14, 21 and 28, counts recovered from S columns were 4.00, 5.98, 3.20, and 2.22 log CFU/100ml, respectively. No E. coli O157:H7 was recovered from I by day 14 or from SI by day 17. E. coli O157:H7 was recovered from S columns through day 31. Significance: This preliminary works shows that ZVI columns were more efficient than biosand columns in removing E. coli O157:H7 from contaminated water.