24-5

Produce washing and wash water reuse using ozone technology

L. XU, Applications R&D, Praxair, Inc., 7000 High Grove Blvd, Burr Ridge, IL 60521

Chlorine compounds, as sanitation agents, are widely used in the produce industry. However, chlorine by-products are not environmentally friendly. Chlorine compounds are also not effective in killing virus and Crytosporidium. Wastewater contained chlorine compounds will adversely affect POTW system. Limited availability of water can put pressures on the produce industry to reduce water use. In addition, the produce industry receives larger water and wastewater bills, increased costs associated with treating wastewater, and EPA penalties if the limits are exceeded.

Fruit and Vegetable Washing One way to maintain or even improve the safety of fresh produce is to wash vegetables and fruits using ozonated water. For the produce industry, two types of washing systems could be used, spraying and flume, to reduce microbial counts on the surface of produce. Our research has indicated that microbial levels on tomatoes, peppers, walnut and lettuce were reduced 1-2, >2 log, and >1log for APC, Y/M (yeast & mold), and coliform respectively, without any adverse effects such as off-flavor and color change.

Wash Water Recycling Our results indicated that ozone is a perfect candidate for processing water recycling since ozone is a powerful oxidizing agent that has been used to disinfect, to remove color, odor, and turbidity, and to reduce the organic loads of wastewater. Our research has shown that the reconditioned water will have much higher quality (over 90% of turbidity and color removal, about 20-90% of COD reduction, and over 3 log reduction (99.9%) in total aerobic counts) and could be reused.