Ozone Food Rinse South Africa

“Ozone in water is often described as an alternative to hypochlorite as a disinfectant or sanitizer.”

“Some packinghouse processes where ozone in water could be applied include:

Ozonation to santitize packing line process water. The water in tanks where fresh fruit are dumped or floated before cleaning, sorting, and packing operations is an important site for the accumulation of pathogens that infect fruit later in storage, shipping, or marketing. Examples are blue mold of apples and pears, caused by Penicillium expansum, and green mold of citrus, caused by Penicillium digitatum. Therefore, disinfection of this water is important, and usually is accomplished with hypochlorite. Ozone has been employed in flume water in apple and pear packinghouses, and some facilities have ozonated hydrocooler water. Pre-conditioning of the water (to reduce particulates, BOD, turbidity, etc.) before ozonation is needed in systems where water is recycled, and this can be difficult and expensive. A contact time of two minutes in 1.5 μg/ml ozone killed 95-100% of all eight fungi tested, and none survived 3 minutes of contact (Figure 1). Spores of these pathogens die quickly in ozonated water, but fruit, soil, and other debris in the water can reduce the ozone concentration completely or to ineffective low levels.”

Attribute	Hypochlorite	Ozone
Microbial potency	Kills plant pathogens and microbial saprophytes effectively. Some human- pathogenic, spore-forming protozoa resistant. Maximum allowable rates under regulatory control	Kills plant pathogens and microbial saprophytes effectively, including spore-forming protozoa. Maximum rate limited by ozone solubility, difficult to exceed about 10 μg/ml
Cost	Chemical cost low. Repeated delivery required, sometimes pH and concentration controller systems needed, minor maintenance and energy costs, chlorine storage issues	Variable: no chemical cost, but high initial capital cost for generator, usually needs filtration system when water re-used some are complex, modest maintenance and energy costs
Influence of pH	Efficacy diminishes as pH increases, above pH 8, pH adjustment may be needed. Chlorine gas released at very low pH (4 or less)	Potency not influenced very much by pH, but ozone decomposition increases at high pH
Disinfection by- products	Some regulatory concern, tri-halo compounds, particularly chloroform, of some human safety concern	Less regulatory concern, small increase in aldehydes, ketones, alcohols, and carboxylic acids created from organics, BrO3- from OBr-
Worker safety issues	Chloroamines can form and produce an irritating vapor, chlorine gas systems require on-site safety measures, OSHA (TWA) limit for chlorine gas: 1 μg/ml	Off-gas ozone from solutions an irritant and must be managed. MnO2 ozone destruction efficient and long-lived. OSHA (TWA) limit for ozone gas: 0.1 μg/ml
Persistence in water	Persists hours in clean water, reduced persistence to minutes in dirty water	Persists minutes in clean water, reduced persistence to seconds in dirty water
Use rates	Limited by regulation to 25 to 600 μg/ml, depending on application	Not limited by regulation, but Henry’s law limits theoretical maximum ozone in water to about 30 μg/ml at 20°C (68°F). Most ozone systems produce 5 μg/ml or less.
Use in warm water	Increases potency, some increase in vapors	Not practical, rapidly accelerates ozone decomposition, increases off- gassing, decreases ozone solubility
Influence on product quality	Little risk of injury at recommended rates. Some injury possible above 50 μg/ml on tree fruits. Off-flavors on some products at high rates	In brief water applications, risk of product injury low. Stem, calyx, and leaf tissue more sensitive than fruits. Risk of injury needs more evaluation.
Impact on water quality	Minor negative impact: water salt concentration increases somewhat, may interfere with fermentation used to reduce Biological Oxygen Demand, some pesticides inactivated, discharge water dechlorination may be required.	Mostly positive impact: does not increase salt in water, many pesticides decomposed, Biological/Chemical Oxygen Demand may be reduced, flocculation and biodegradability of many organic compounds enhanced, precipitates iron, removes color, odors
Corrosiveness	High, particularly iron and mild steel damaged	Higher, particularly rubber, some plastics, yellow metals, aluminum, iron, zinc, and mild steel corroded

Information from Ozonize

Ozone Food Rinse South Africa – Contact – Wassertec