Title: Pilot study of the effect of biofilms in irrigation pipes on the microbial water quality of irrigation water Authors
Submitted to: BARC Poster Day
Publication Type: Abstract Only
Publication Acceptance Date: March 15, 2011
Publication Date: April 27, 2011
Citation: Davies, G.E., Downey, A., Guber, A.K., Morrow, J., Pachepsky, Y.A., Rowland, R.A., Shelton, D.R. 2011. Pilot study of the effect of biofilms in irrigation pipes on the microbial water quality of irrigation water. BARC Poster Day. #10. Technical Abstract: Irrigation is an essential element in the production of many food crops. Irrigation water is often delivered to fields from surface or subsurface sources via pipe-based systems. Surface waters are known to contain pathogenic microorganisms. Disease outbreaks in crops that are eaten raw (i.e. leafy greens) could be linked to microorganisms in irrigation water. The purpose of this study was to examine the formation of biofilms in sprinkler irrigation systems and the effect of biofilms on bacteria concentrations in water passing through. E. coli was selected as the common indicator microorganism used to characterize microbial quality of irrigation waters. An irrigation system was constructed from aluminum pipes and fed with water from the perennial Paint Branch creek in Beltsville, MD. A two-hour irrigation event was performed every week for four weeks. Water samples were taken from the creek and the sprinkler heads at hourly intervals during irrigation events and analyzed for E. coli concentration. Additionally, pipe sections were removed before each irrigation event, scraped, and analyzed for E. coli concentration. Substantial differences were found between E. coli concentration in creek water at the pump’s uptake and the water from the sprinklers, leading us to believe E. coli was released from the pipe’s inner surfaces to flowing water, or otherwise was captured from the flowing water. Sprinkler water on average contained more E. coli than the creek water after the second and the third week, and less E. coli after the first week. E. coli release declined as the irrigation events progressed. High E. coli concentrations were found in the stagnant water residing in pipes between irrigation events, indicating the potential opportunity for E. coli growth in irrigation systems between cycles. Flushing the irrigation system may be a useful management practice to decrease the risk of microbial contamination of produce. Because biofilms in irrigation systems can modify the microbial water quality, it is imperative to monitor the quality of water coming from sprinklers rather than at the pump intake. Currently, there is no literature on microbial populations in biofilms in irrigation systems, and further research is needed.