# Efficacy of peracetic acid and chlorine in managing Salmonella biofilms in irrigation loop systems

## TL;DR

This study shows that peracetic acid and chlorine reduce Salmonella in irrigation water but cannot fully eliminate biofilms formed by organic fertilizers.

## Contribution

The study reveals that organic fertilizers promote Salmonella biofilm formation, which persists even after sanitization.

## Key findings

- Salmonella biofilms formed in irrigation lines with organic fertilizer but not with synthetic fertilizer.
- Peracetic acid and chlorine reduced Salmonella in water but not in established biofilms.
- Unsanitized lines with organic fertilizer led to cross-contamination of subsequent irrigation events.

## Abstract

Biofouling presents significant challenges to the crop production industry, notably reducing irrigation efficiency and potentially dispersing pathogens to irrigated crops. This study evaluated the efficacy of peracetic acid (PAA) and chlorine (Cl) against Salmonella biofilms in irrigation lines with or without fertilizers. Pond water (PW) with 2-4-1 fish emulsion (O), PW with 4-0-8 synthetic liquid fertilizer (S), or PW with no fertilizer (NoFert) was inoculated with 2 log CFU/mL of a rifampicin-resistant Salmonella cocktail. Inoculated water was then circulated through polyethylene loop irrigation system for a month. Salmonella populations both in the water and attached to the tubing were determined. Data showed that a single point of contamination from the water resulted in a biofilm formation with O and NoFert, but not the S treatments, after 3 days. Both PAA and Cl effectively reduced Salmonella populations for all fertilizer treatments in water samples. However, when no sanitizer was introduced to the line, bacterial dispersion resulted in the contamination of a subsequent irrigation event for the O treatments but not the S and NoFert treatments, which presented no microbial proliferation. Our findings suggest that O treatments resulted in persistent biofilm formation that could lead to contamination of irrigation water when no sanitizers are introduced. These studies provide insight into the behavior of foodborne pathogens in irrigation distribution systems.

The accumulation of bacteria in water distribution systems due to biofouling can lead to contamination, making it crucial to evaluate and implement effective mitigation measures to prevent these issues and ensure safe and efficient irrigation practices. The use of the 2-4-1 fish emulsion in-line may support the establishment of Salmonella biofilms and subsequent cross-contamination of irrigation water if not fully flushed from the system. This study demonstrates that PAA and Cl effectively reduce Salmonella contamination in water but will not eliminate populations in-line once biofilms are established.