Q-213. Evidence for the Offsite Transport of Pathogen Indicator Bacteria Associated with Land-Application of Biosolids

M. A. Esseili1, V. Sigler1, I. I. Kassem1, K. A. Esseili2;
1Univ. of Toledo, Toledo, OH, 2Lebanese Univ., Hadath, LEBANON.

The pollution of surface water following biosolids application to an artificially drained agricultural field was investigated. Pre- (n = 5) and post-application (n = 2) water samples were collected upstream and downstream of a field drainage tile, while samples of biosolids were collected during subsurface application. All water and biosolids samples were enumerated for E. coli (standard plate counts) and subjected to E. coli community fingerprinting (denaturing gradient gel electrophoresis analysis) to characterize the contribution of biosolids E. coli to surface water. In addition, 1140 E. coli isolates generated from biosolids and water samples were each tested for resistance to several antibiotics. Since no pre-application rainfall events induced tile drainage to allow enumeration of E. coli in drainage water, E. coli was enumerated in field soils (n = 32) as a proxy for pre-application drainage levels. E. coli was not detected in any of the soil samples. E. coli densities were not significantly different in upstream vs. downstream samples or in pre- vs. post-application samples. However, following a heavy rainfall event, the E. coli density in water exiting the drainage tile reached 5200 ± 458 CFU 100 ml-1 after one day and steadily declined to 30 ± 6 CFU 100 ml-1 within eight days. Cluster analysis revealed that E. coli communities in the biosolids, drainage tile and post-application samples (70% similar as a group) were only 47% similar to the pre-application communities, suggesting that E. coli co-applied with biosolids contaminated drainage- and receiving waters. Further analysis revealed a significant increase (vs. pre-application levels) in ampicillin and amoxicillin resistance among the E. coli isolated from the drainage tile and post-application water samples. In conclusion, although land-applied biosolids did not significantly increase the level of E. coli density in receiving waters, tile drainage induced by rainfall resulted in contamination by E. coli communities that originated in biosolids. Efforts are currently underway to type individual E. coli isolates to further quantify the contribution of land-applied biosolids to receiving waters.