Post Harvest Water Sanitaton

Post Harvest Water Sanitaton Videos

There are a number of options for sanitizing water used to clean and cool horticultural crops after harvest. Typically, the option chosen depends on the product and the handling system in place. Click on the options shown for a basic, general description of the advantages and best practices for each method.

Water that contacts horticultural crops last must be potable.

Growers who pack on-farm typically need to sanitize their dump or flume tank water to meet this requirement under the Canada Agricultural Products Act.

Testing and Verification

Bleach (food grade)

Chlorine Dioxide

Hydrogen Peroxide

Peroxyacetic Acid

Ultra Violet

Ozone


Post Harvest Water Sanitaton Videos

Testing and Verification



Bleach (food grade)


Chlorine Dioxide

Top

Hydrogen Peroxide

Top



Peroxyacetic Acid

Top

Ultra Violet

Top


Ozone

Top


Post Harvest Water Sanitation Study

Water is a well-known vector for disease. In on-farm food production, a number of trace-back investigations have suggested that contaminated dump tank water contributed to outbreaks in fresh fruit and vegetables.

  • Farmers, have typically relied on bleach-type products to treat their dumptank water. However, more and more farmers would like to find alternatives which are effective, reduce the potential effects on the environment and wear and tear of their equipment.

What was the goal of this study?

The goal of this study was to evaluate seven sanitizing water treatments, including:
Two bleach products (calcium hypochlorite and, sodium hypochlorite), chlorine dioxide, ultra violet radiation (UV), ozone, and two peroxyacetic acid treatments. Each treatment was tested for:

  • efficacy against generic E. coli
  • ease of use and disposal
  • worker safety
  • cost
  • changes in produce quality as a result of their use.

How did we conduct the study?

The sanitizing water treatments followed the manufacturer's specifications.

What were our findings?

All treatments were effective when organic matter and E. coli levels were low. All chemical based sanitizing treatments require training to ensure worker safety. For ozone, it is recommended to have an ozone destruct device installed in the system to ensure worker safety. The following are some of the findings from each of the seven sanitizing treatments:

  • Both bleach type products (calcium and sodium hypochlorite) , were very effective, and inexpensive. However, organic matter reduces their effectiveness dramatically.
  • Chlorine dioxide, was very effective, and less effected by organic matter. However, it is currently 15X more expensive than the bleach-type products. However, this cost may be off-set as it is more stable and active when exposed to organic matter.
  • Peroxyacetic acid was also effective, and approximately 5X the cost of bleach-type products. However, this product is also less affected by organic matter, which may offset the additional cost. Of note, this product acidifies the water, which has worker safety issues, and may affect product quality. In addition, prior to disposal the waste water pH must be increased to 5 (dependent on jurisdiction requirements).
  • UV is also very effective. However, a filtration system is required which removes 100% of particulate matter, as UV is ineffective in the presence of any particles.
  • Ozone is also very effective, and less effected by particulate matter in the water. However, a filtration system is still a requirement. Ozone is more costly than UV, but prices have decreased with improvements in technology.

Water Sanitation Options: Considerations

 

Availiability of Test Strips
Monitoring Device: Oxidation Reduction Potential (ORP) Meters
Monitoring Device: Other
Requires Micro Verification
pH Range of Water During Treatment
Concentration Recommended
Effectiveness in the Presence of Organic Matter
Worker Safety (Risk)
Environmental Impact
Treatment Speed of Large Volumes of Water
Cost*
Unique Attributes

Chlorine (Food Grade)

Yes
Works well
Yes
Yes
6.5 - 7.5
50 - 300 ppm
Limited
Medium: irritant to skin, eyes and throat
Medium
Fast
1 X
Odour. There continues to be some disposal concerns.

Chlorine Dioxide

Yes
Works well
Yes
Yes
6 - 10
5 ppm
Effective
High: irritant to skin, eyes and throat
Medium/High
Fast
15 X
Most demanding form of Chlorine - must produce on-site. Odour.

Hydrogen Peroxide

Yes
Challenging
Yes
Yes
6 - 8
3%
Effective
Medium: irritant to skin, eyes and throat
Low
Medium
90 X
Need to acidify to pH 6

Peroxyacetic Acid

Yes
Challenging
Yes
Yes
< 4
50 - 80 ppm
Effective
High: severe irritant to skin, eyes and throat. Requires ventilated area
Medium
Medium/Fast
5 X
Not ideal for sensitive produce. pH may need to be increased prior to disposal. Very strong ordour.

Ultra Violet (UV)

No
Not suitable
Yes**
Yes
NA
NA
Not Effective (must filter)
Low
Low
Slow
Varies based on facility
Ensure bulb is functional and clear of mineral deposits. Challenges with hard water.

Ozone

No
Challenging
Yes
Yes
6 - 8
3 ppm
Limited (must filter)
Medium: Must have off-destruct device and detector(s)
Low
Slow
Varies based on facility
Fast oxidizer, however, delivery system reduces speed of large water volume sanitation.

* All cost is relative to Chlorine (food grade)
** this is a detector to make sure the bulb is working.


For more information:
Toll Free: 1-877-424-1300
E-mail: FoodSafety@ontario.ca


Author: OMAFRA Staff
Creation Date: 26 March 2010
Last Reviewed: 28 September 2016