Water ‘metrics’
Updated treatment rules have growers learning how to use new chemicals as safeguarding tools
As planting for this winter’s first produce crop gets underway, the Arizona Leafy Greens Marketing Agreement (LGMA) has been training growers on new water treatment requirements intended to reduce the chances of another foodborne illness outbreak like the one that befell the area about a year and a half ago.
The LGMA, a program managed by the Arizona Department of Agriculture, sets food safety
standards that its members are required to follow in the field and processing plant. Most if not all growers in the area participate, as wholesalers and retailers look to buy from those that do.
The standards already included multiple rounds of testing for growers and harvesters when the E. coli outbreak tied to Yuma romaine lettuce was first reported in April 2018. It eventually led to five deaths and 210 illnesses, matching the seriousness of the 2006 outbreak tied to spinach from California.
The Food and Drug Administration’s environmental assessment of the Yuma outbreak found irrigation water was the “most likely” source of the bacterial contamination. It found no evidence that growers weren’t following the current food safety practices.
The Arizona LGMA and its counterpart in California have adopted additional water treatment requirements or “metrics” in response to the report, and Vicki Scott, a technical assistant to the Arizona LGMA who helped start the Yuma Safe Produce Council, has been leading classes and workshops about them since the spring.
She said the classes have proven very popular, with the smaller-scale events still drawing up to 60 people.
“So everybody’s busy trying to learn how to do that, they’re trying to determine which sort of chemical they’re going to use, and how they’re going to inject it into the water,” Scott said.
“All the chemical applicator (pesticide) guys, a lot of them have been just using municipal water since the outbreak, and others are going to be treating with each use, when they go to do a pesticide application they’ll be treating the water prior to application.
“Everybody is on board and trying to figure out how to get this implemented.”
The new requirements for water treatment apply only to crops that are watered by sprinklers on large beds, such as spinach, baby-leaf lettuce and some romaine lettuce. And it only applies for the final 21 days before the crops’ harvest, when research has shown there’s an additional risk of water landing on the edible parts of the plant and contaminating it.
Furrow irrigation is used for other crops, so water is absorbed into the soil, not directly applied to the plants.
Growers and applicators do have a few different options for treating their irrigation water, if they don’t decide to use drinking-quality water from a treatment plant or high-quality well water.
Chlorine-based products are what many Yuma growers are most familiar with, Scott said. The most common liquid form is sodium hypochlorite, which when dissolved in water becomes bleach. Calcium hypochlorite is sold as a powder or in tablet form, and is the product most commonly used to treat pool water.
There is also chlorine dioxide, which Scott said “has to be generated onsite and is a little bit more complex, it’s a combination of two chemicals right onsite.”
Filtration systems use reverse osmosis or sand filtration to treat the water, but must be used with one of the other compounds as a sanitizer, she said.
Ultraviolet light, followed by an ozone-based sanitizer, is being used for smaller batches of water such as for pesticide application, Scott added.
Scott has deployed several other local experts to talk about specific aspects of the new metrics, including Paul Mondragon of Ag Partners Southwest, a business that offers water treatment services.
Mondragon said many of the growers he’s worked with have gravitated toward the chlorine dioxide products, which require pumps and other equipment to mix two or sometimes three chemicals. “Chlorine dioxide is very effective, but it’s also a little bit complicated,” he said.
Paracetic acid or PAA, sold on the market as SaniDate, is another sanitizing compound that is often used, along with the other chlorine compounds.
He said his company is developing ultraviolet lightbased treatment systems, with several trial runs with lab-based data planned for the upcoming season.
“I think it will be potentially most effective, but it has its own complications, like you have to have power created onsite, through a large generator, but there’s its own benefit of no byproducts into the soil, no dangerous chemicals,” he said.
He said some of the residue left behind by chlorinetreated water, especially sodium, can damage the soil in large concentrations, and lead to crop damage.
According to the U.S. Centers for Disease Control, disinfection byproducts, created when chlorine reacts with naturally occurring chemicals or matter in water, have been shown to lead to health problems with long-term exposure. The Environmental Protection Agency currently regulates four categories of these byproducts in drinking water.
Mondragon said the new requirements will be an added cost and obstacle for growers who already have to work under a multitude of regulations intended to ensure food safety.
“The general public has no idea about the difficulty and the requirements that the grower has to put safe vegetables on people’s table. And everybody complains about price, they complain about this or that,” he said.
“But just the new metrics that are placed on the grower are enormous, and I wish more people would have respect for what the grower does, because he has a lot. And it’s now just one extra piece. It’s not the only one, it’s just one extra piece,” he said.
Scott said growers are just starting to get a handle on what the added cost will be, with the numbers she’s heard so far coming in anywhere from $60 to $120 per acre.
“It’s probably dependent on which chemical you’re using, and how much equipment you already have that could be used. I’m sure there’s a whole lot that factors into that. But it is definitely going to add to the bottom line of growing costs,” she said.
Since only the crops watered with overhead sprinklers are affected by the new regulations, the effect on the overall industry will be limited, she said.
The new metrics do create additional hurdles on growers, but everyone’s getting prepared for them, she said: “It’s going to be a big challenge. Everybody’s hard at it.”
“But just the new metrics that are placed on the grower are enormous, and I wish more people would have respect for what the grower does, because he has a lot.”