The standard for drinking water is zero E. coli while the standard for primary contact recreational use, such as swimming, is not more than 200 average E. coli per 100 milliliters of water with no single sample more than 400 fecal coliforms per 100 milliliters of water for swimming, Achberger says. The standard for fishing and boating is higher.
Drapcho says the Ag Center research has found that roughly two thirds of the time the concentration of coliform is higher than the DEQ standard for primary contact recreational use of waters even without the impact of dairying.
"These results can be attributed to wildlife and to natural soil organisms that appear to adapt and grow in the south Louisiana climate differently from similar organisms in northern areas," she says.
"When we're looking for E. coli we're finding a lot of interference from Klebsiella," Achberger says.
Klebsiella is a bacterium similar to E. coli, but it can be free-living and can give a false positive for fecal contamination, Achberger says.
"We're learning what other tests can be used to determine the concentration of E. coli without measuring the background contamination of Klebsiella," he adds.
Even a river away from farms and municipalities could have a high background from Klebsiella, so this non-fecal bacteria may indicate a problem that doesn't exit.
"Our work will allow people like DEQ to evaluate data and make recommendations based on evidence," Drapcho says.
Achberger is developing a more sophisticated test using microbiological techniques rather than cultures. He's evaluating different techniques-- comparing molecular analysis with classical bacteriology-- to find the best method for south Louisiana studies. One promising procedure uses an additive that can allow testing without incubating samples and can differentiate between fecal coliform and coliforms.