Post Harvest Water Sanitation Technologies

• 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.