Plasma-Activated Water: The Emerging On-Farm Sanitizer and Growth Tool You’ve Probably Never Heard Of

For decades, agriculture has leaned on chemicals like chlorine, peracetic acid, and quaternary ammonium to sanitize irrigation systems, protect young plants, and wash produce. A new entrant—plasma-activated water (often abbreviated PAW)—promises similar benefits with fewer residues and on-demand generation. While still early in its commercial rollout, the technology is gaining traction in greenhouses, nurseries, hydroponics, and postharvest operations seeking to reduce chemical inputs without sacrificing biosecurity.

What Plasma-Activated Water Is—and How It’s Made

Plasma-activated water is produced by exposing air and water to “cold plasma,” a partially ionized gas generated at near-room temperature. When plasma interacts with water and the surrounding air, it forms a cocktail of short-lived and longer-lived reactive oxygen and nitrogen species (often called RONS). Common constituents include hydrogen peroxide (H2O2), ozone (O3), nitrite (NO2−), nitrate (NO3−), and other oxidants. The mixture elevates the water’s oxidation-reduction potential (ORP) and modestly acidifies it, both of which contribute to antimicrobial activity.

Commercial and pilot systems typically use one of three approaches to generate PAW:

• Dielectric barrier discharge (DBD): A high-voltage field energizes air across a dielectric material in contact with or adjacent to water.
• Atmospheric plasma jets: A focused plume of ionized gas is directed into a passing water stream or a small batch tank.
• Gliding arc or corona discharge reactors: Scalable reactors that treat flowing water with ionized air in-line.

Unlike electrolyzed water systems that require added salt to generate hypochlorous acid, PAW uses air and water, producing a chlorine-free oxidant blend. The reactive mix gradually reverts to more benign species (mostly nitrate/nitrite and oxygen-containing compounds), which means it is generated on-site and used promptly rather than stored.

Where It Fits on the Farm

Plasma-activated water is not a silver bullet, but several early applications stand out:

• Irrigation system hygiene: Periodic PAW pulses through drip lines and emitters help disrupt biofilms and suppress microbial buildup without high residual chlorine. Growers report cleaner lines and fewer clogging events.
• Hydroponics and recirculating systems: In greenhouses, on-demand PAW can be dosed into reservoirs to manage microbial load, complementing filtration and UV. Because the oxidants decay, it reduces concerns about persistent residues in root zones.
• Nursery and propagation: Using PAW to sanitize trays, tools, and benches offers broad-spectrum disinfection with minimal corrosion compared to some chemical sanitizers.
• Seed priming and surface sanitation: Short soaks or mists with carefully controlled PAW have been studied for improving germination in certain crops and reducing seed-borne pathogens. Results vary by species and water chemistry, so small trials are essential.
• Postharvest rinse water: PAW can be used in single-pass or recirculated wash water to lower microbial counts on produce surfaces and equipment, potentially reducing reliance on chlorine-based chemicals. As with any wash, process control and monitoring are critical.

Chemistry and Control: What to Measure

Because PAW’s effectiveness comes from its reactive species, monitoring and control replace the simple “dose and forget” mindset of some traditional chemicals. Practical parameters include:

• ORP (oxidation-reduction potential): A quick proxy for oxidizing strength. Many systems target elevated ORP relative to source water during treatment windows.
• pH: PAW often becomes mildly acidic during generation. Knowing pH helps avoid phytotoxicity when used on sensitive tissues.
• Hydrogen peroxide concentration: Spot checks with test strips or sensors give insight into oxidant levels; useful for repeatability.
• Nitrite/nitrate levels: Indicative of nitrogen species formed; important for both efficacy and nutrient accounting in closed-loop systems.
• Contact time and temperature: Oxidation kinetics depend on both; higher temperatures can accelerate reactions and decay of reactive species.

Vendors increasingly bundle in-line sensors and simple dashboards to automate dosing or trigger alarms when oxidant levels drift.

Energy Use and Economics

Cold plasma generators draw electrical power to create reactive species. Actual consumption depends on target oxidant levels and flow rate, but field pilots commonly report energy use in the sub–kilowatt-hour to low single–kilowatt-hour range per cubic meter treated. For a greenhouse treating 20 cubic meters per day, that can translate to roughly a few to a few dozen kilowatt-hours daily, a modest cost compared to other sanitation inputs.

Capital costs vary with capacity, integration (in-line vs. batch), and controls. Entry systems suited for small greenhouses or nurseries are typically priced lower than industrial postharvest units sized for wash lines. Maintenance involves electrode inspection or replacement, gas pathway cleaning, and periodic calibration of sensors. Because the “consumable” is air and electricity, many growers evaluate PAW as a replacement or partial substitute for chlorine-based chemicals, factoring in avoided chemical purchases, reduced corrosion, and potential quality or shelf-life benefits in postharvest settings.

How It Compares to Conventional Sanitizers

Every sanitizer has trade-offs. Here’s how PAW lines up against common options:

• Chlorine/hypochlorous acid: Widely available, effective, and well-understood, but can create chlorinated byproducts in organic-rich water, requires careful pH control, and may corrode metals. PAW avoids chlorine chemistry and decays to non-chlorinated species.
• Peracetic acid (PAA): Strong oxidizer with broad antimicrobial action and rapid breakdown, but can be pungent and requires careful handling. PAW aims for similar on-demand oxidizing benefits with no chemical deliveries.
• UV treatment: Excellent for clear water and certain pathogens, but effectiveness drops with turbidity and offers no residual effect. PAW provides a short-lived residual in-system and can be complementary to UV.

In practice, many adopters blend approaches—for example, filtration plus UV to reduce load, with PAW for polishing and residual control.

Crop Safety and Efficacy: What We Know

Academic and industry studies have documented significant microbial reductions on surfaces, in irrigation loops, and on produce when PAW is appropriately dosed. Seed priming results are more variable: some crops show improved germination and vigor, while others show no effect or even stress at high oxidant levels.

Three practical rules of thumb emerge from early adopters:

• Start low, step up: Begin with conservative oxidant targets and short contact times; increase gradually while monitoring plant response and microbial counts.
• Water chemistry matters: High organic load consumes oxidants quickly; filtration and basic water quality management greatly improve consistency.
• Freshness counts: Use PAW soon after generation, or recirculate through a generator to maintain target oxidant levels.

Safety, Materials, and Integration

As with any oxidizing process, worker safety and materials compatibility deserve attention. Systems should be ventilated to manage any ozone or nitrogen oxide off-gassing during generation. Materials in contact with treated water—especially elastomers and certain metals—should be verified for oxidant exposure. Many growers integrate PAW systems with existing pumps, filters, and storage tanks; in-line injection with backflow prevention and automated shutoffs is common.

Regulatory Considerations

Regulations vary by country and use case. In some jurisdictions, making antimicrobial or pesticidal claims for water treatment technologies triggers specific approvals or device registrations. Organic programs may treat PAW differently from electrolyzed water or conventional sanitizers. Producers should confirm local compliance for intended uses (irrigation sanitation versus direct produce contact, for example) and ensure worker safety protocols match occupational standards for oxidizing agents.

Getting Started: A Practical Adoption Playbook

1. Define the job: Is the priority biofilm control in drip lines, hydroponic reservoir hygiene, seed sanitation, or postharvest washing? Each use has different dosing and monitoring needs.
2. Baseline your water: Test source water for pH, alkalinity, organic load, and turbidity; fix basic issues (filtration, sediment) first.
3. Pilot on a contained loop: Start with a small, well-instrumented subset—one bay’s irrigation line, a single reservoir, or a side-stream on a wash line.
4. Instrument and log: Track ORP, pH, temperature, and an indicator of oxidant concentration, plus microbial counts at critical points. Document crop response.
5. Dial in runtime and dose: Adjust generator power, flow rate, and contact time to hit targets under real operating conditions.
6. Train and standardize: Develop simple SOPs for operators, including daily checks, sensor calibration, and safety practices.

What’s Next: Smarter Control and New Combinations

The next wave of PAW systems is focusing on tighter control and integration. Expect to see closed-loop dosing based on ORP and inline peroxide sensing, predictive maintenance for plasma reactors, and modular units sized for smaller farms and vertical racks. On the treatment side, researchers are exploring hybrid approaches—combining PAW with UV, ultrasonics, or fine filtration—to cut energy use while boosting consistency. There’s also growing interest in tailoring the reactive species profile (for example, favoring nitrogen species for seed priming) by adjusting gas composition and power settings.

Bottom Line

Plasma-activated water gives growers and packers a new tool: an on-site, chlorine-free oxidant source that can sanitize systems, supplement postharvest washes, and potentially boost early plant performance when carefully applied. It won’t replace every sanitizer, and it brings its own learning curve in monitoring and control. But for operations looking to trim chemical deliveries, reduce corrosion, and modernize water hygiene, PAW is a compelling technology to trial—especially in closed or recirculating environments where water quality control pays dividends every day.