Ozonation as a clean technology for fresh produce industry and environment: sanitizer efficiency and wastewater quality

Aims: Inactivating microbial contaminants in fresh produce commonly uses chlorine washing. The effectiveness of ozone was explored as an alternative to chlorine in produce washing for ensuring microbial safety while maximizing water reusability.

Methods and results: An ozone washing system was designed to permit continuous addition of contaminated produce and the reuse of washing water. The effectiveness of ozonation (<2 mg l(-1) ) was determined using Bacillus subtilis spores as a stricter measure of efficiency with processing time of 10 min. As a comparison, chlorine (c. 100 mg l(-1) ) was tested in parallel. Water quality characteristics, including chemical oxygen demand, total suspended solids, disinfectants concentration and microbial reduction were measured. Ozonation showed an average of 1·56 log reduction of B. subtilis spores on lettuce, while chlorination achieved a 1·30 log reduction. The effluents after ozonation demonstrated improved water quality, both in physicochemical quality and microbial quality compared to chlorination.

Conclusion: Aqueous ozone treatment is effective against microbial contaminants on fresh produce and enables extended use of washing water.

Significance and impact of the study: The results provide significant data about ozone disinfection efficacy and its impact on the water reusability, which can facilitate the ozone utilization in the fresh produce production as an environmental friendly alternative.