Reducing Heavy Metals in Commercial Cannabis with Ozonated Water

July 25, 2019

Conscientious growers who have been careful to sell what they thought was safe, uncontaminated cannabis products are being blindsided by California regulations.

Over the last few years, California and other states have been continuing to lower the bar for legal access to marijuana. As of July 2019, 10 states and Washington, D.C. have fully legalized the recreational use of marijuana. Dozens more have legalized the use of marijuana for medicinal use. The result is that in 2018, American marijuana companies generated $9 to $10 billion in sales in 2018, and will exceed that figure in 2019.

Given that the full value of the American cannabis industry—legal and black market combined—is believed to be approximately $50 to $55 billion, there is still immense growth potential for the industry.

But, there’s a problem.

Many marijuana growers are running into issues with state product testing requirements for pesticides, chemicals, fungi, but most of all, heavy metals.

When California fully legalized marijuana in 2018, it also tightened safety requirements for commercially sold cannabis products. As of July 1, 2018, all marijuana sold in the state must meet strict testing requirements.

Throughout 2018, all marijuana products were required to be tested for potency, as well as the presence of a variety of contaminants, including:

  • Pesticides
  • Microbial impurities (E. coli, Salmonella, and a variety of fungi)
  • Solvents
  • Processing chemicals and foreign materials

The stakes for passing these tests are quite serious. If a batch of cannabis goods fails to past any regulatory compliance testing, it cannot be sold. Failed goods must either be destroyed, or the owner must grow through a lengthy and costly remediation process. When testing requirements first went into effect, 20% of goods failed product testing. While cannabis growers quickly got their acts together, the failure rate was still quite high—around 14% by the end of 2018.

But then growers were hit with another complication, as beginning in 2019, the state of California implemented a third tier of required laboratory testing for the presence of mycotoxins—poisons produced by certain types of fungi—and heavy metals, particularly cadmium, arsenic, lead, and mercury.

Many growers have been very careful to utilize green, ‘eco-friendly’ ways of controlling pests and fertilizing their crops, which has allowed them to avoid issues with tests for fungi, pesticides, solvents, and other chemicals. But growers are already running into serious issues when it comes to fungal and heavy metal contamination.

But heavy metal contamination is proving to be a particularly vexing issue for growers. Many commercially available fertilizers have measurable levels of heavy metals. Even organic growers run into trouble, as organic fertilizers like bat guano and fish oil are also often contaminated with heavy metals. Some labs have seen heavy metal levels 10 to 20 times the maximum allowed by law.

Conscientious growers who have been careful to sell what they thought was safe, uncontaminated cannabis products are being blindsided by California regulations. And the issue isn’t limited to the state of California. States that have recently implemented or are currently implementing the mandatory testing of heavy metals and mycotoxins include Arizona, Colorado, Connecticut, Massachusetts, Minnesota, Nevada, Oklahoma, and Washington.

The trend is clear. Commercial marijuana growers will not be able to sidestep the complications imposed by lab testing for heavy metals and other contaminants by simply ignoring the California market. As states adopt and formalize standards for the legal sale of marijuana products, they will also impose increasingly state product testing requirements.

Growers must find a way to reduce levels of heavy metals and other contaminants in their crops. But how?

Ozone water purification systems make it simple and cost effective to reduce heavy metal levels in cannabis and other cultivated crops.

Water purity and filtration is crucial in any agricultural operation. But this particularly the case with the cultivation of marijuana and other crops and indoor crops. This is in part because marijuana is particularly vulnerable to fungal infestations—water supplies contaminated with fungal spores or bacteria can devastate a crop.

But traditional large-scale approaches to reducing heavy metal levels are inappropriate for agricultural applications. For instance while wastewater treatment plants—and some home and well water treatment systems—sometimes use reverse osmosis, this wastes a great deal of water. More critically, it also produces a waste stream with very high concentrations of heavy metals, which requires careful disposal. Other systems rely on ion exchange technologies, but these systems tend to be high maintenance and also filter out beneficial minerals, such as calcium, which are crucial to healthy plant development.

Chemical-based approaches, such as chlorinating irrigation water, can be used to reduce the presence of toxic heavy metals. This is because chlorine is an oxidizer. When a heavy metal is oxidized, it forms a less soluble and bioavailable chemical compound—typically in the form of a metallic oxide or hydroxide. But high levels of heavy metals require correspondingly high levels of chorine, higher than what is typical in municipal drinking water. Such levels of chlorine are toxic to both plants and beneficial soil organisms, which makes chlorination an unworkable solution for cannabis cultivation and other agricultural activities.

This is where ozone water treatment comes in. Ozone is an extremely powerful oxidizer, far more powerful than chlorine. When water is treated with ozone, which significantly increases the levels of dissolved oxygen in the water, bacteria, fungi, and other harmful organisms are immediately sanitized and broken down. In addition, harmful heavy metals and other minerals are also oxidized, precipitating them out of the water as harmless chemical compounds.

In the case of a cannabis cultivation or other agricultural applications, while irrigation water has high levels of dissolved oxygen, this water can reduce high levels of heavy metals introduced into the soil via the use of organic fertilizers and other contaminated soil treatment products.

One of the benefits of ozone water treatment is that while ozone is extremely powerful, it is also short-lived. When ozone is dissolved in water that is 70 degrees Fahrenheit has a half-life of less than 20 minutes. This means it does its job, killing harmful organisms and oxidizing heavy metals, and then rapidly breaks down and dissolves into water and surrounding air.

If your cannabis cultivation business or other agricultural operation is looking for a non-toxic, cost-effective way to reduce the levels of heavy metals and other harmful contaminants in your crops, ask us about our agricultural ozone water treatment systems. Our systems can be scaled up for operations of any size, and shipped to your location ready to install as a complete turnkey system. Contact Watson Well to learn more!

California Groundwater Association
National Groundwater Association