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Post-Harvest Water Sanitation
Post-Harvest Water Sanitation 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
VideosTesting and Verification Bleach (food grade)
Chlorine
DioxideTop Hydrogen
PeroxideTop Peroxyacetic
AcidTop Ultra
VioletTop OzoneTop
Post Harvest
Water Sanitation StudyWater 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 | 19 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
buld 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: advantage@ontario.ca
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