Every option on this page is in commercial use on farms, and every one of them is the right answer somewhere. The purpose here is to describe what each one is actually good at, what it costs to run, and where it fails — including where onsite generation fails, which is the part most supplier comparisons leave out.
About claims on this page
EcoloxTech generators produce a hypochlorous acid solution on site. They are regulated by the EPA as devices, are not registered disinfectants, and we make no efficacy claims for them or for the solution they produce. The only EcoloxTech product with disinfection claims is HOCl-AS200 (EPA Reg. No. 101112-1), used according to its label. Research cited here describes published studies of hypochlorous acid and electrolysed water under their own test conditions; it is not a claim for any product.
Framing the comparison
Comparisons go wrong when they compare a chemical against a piece of equipment. The useful frame is: what is the treatment for, what does it have to survive, and who has to handle it?
| Question | Why it decides the answer |
|---|---|
| Is a residual needed downstream? | Rules out the non-residual technologies immediately for line and emitter work |
| What is the organic load? | High load punishes chlorine chemistry and rewards oxidisers less affected by it |
| What is the source water chemistry? | Hardness, iron and pH change the economics of every option, including generation |
| Who is handling it, and where? | Concentrated chemistry on a farm means storage, PPE, spill response and training for a seasonal workforce |
| How far is the depot? | Freight on dilute liquid chemistry is a real cost and a real vulnerability at peak season |
| Is a documented claim required? | If a buyer scheme or a rule requires a registered product, no generated solution answers it |
Sodium and calcium hypochlorite
Delivered bleach and cal hypo are the incumbent almost everywhere, and for good reason: they are cheap per unit of available chlorine, universally understood and available from any agricultural supplier.
| Sodium hypochlorite (bleach) | Calcium hypochlorite (cal hypo) | |
|---|---|---|
| Form | Liquid, typically 10-12.5% trade strength | Solid granule or tablet, around 65-70% available chlorine |
| Strength over time | Degrades in storage, faster when warm. Farm storage in summer is a real problem | Stable in storage if kept dry and cool |
| Freight | Shipping mostly water. Expensive relative to the active | Shipping the active. Much cheaper per unit delivered |
| pH effect | Strongly alkaline; raises pH, which shifts the chemistry away from hypochlorous acid | Also alkaline; adds calcium, which matters in hard water and drip systems |
| Handling | Corrosive liquid, splash and decanting risk, containment needed | Oxidiser. Serious incompatibility and fire hazards if contaminated or wetted improperly |
| Scale risk in drip | Moderate | Calcium contribution can worsen scaling and emitter fouling in hard water |
The honest comparison against onsite generation is this: hypochlorite is cheaper per unit of chlorine at the point of purchase, and onsite generation removes the freight, the storage, the degradation and the concentrated-chemical handling. Which of those matters more depends on how remote the operation is, how much water it treats and what its safety and insurance profile looks like. A farm two hours from a depot at peak season values delivery independence differently from one on the edge of a city.
There is also a pH point that growers with drip systems feel directly. Both hypochlorites raise pH, and the hypochlorous acid fraction of free chlorine falls as pH rises. Operations injecting bleach into alkaline irrigation water frequently end up also injecting acid to compensate — two chemicals, two injection points, two sets of handling. Onsite generation produces a solution at a pH range that does not require that correction, which is a practical simplification rather than a performance claim.
Peracetic acid
PAA has become the default in a lot of post-harvest produce washing, and the reasons are substantive. It performs comparatively well in high organic load, does not form the same chlorinated by-products, is effective across a wider pH range, and breaks down to acetic acid, water and oxygen.
Its costs are equally real. It is expensive. Concentrated PAA is aggressive: vapour is a genuine respiratory hazard, handling requires PPE and engineering controls, and storage has ventilation and incompatibility requirements that a produce shed frequently does not meet. Residual is short-lived, which is fine in a wash tank and useless in an irrigation line. And its smell in an enclosed packhouse is a recurring worker-relations issue that nobody puts in the brochure.
Where PAA is the right answer — a high-organic-load wash system where by-product formation is a concern and the operation has the handling infrastructure — it is genuinely the right answer, and we will say so. Where onsite generation competes better is the broader case: the same equipment serving wash water, surfaces, tool dips and irrigation, without a concentrated chemical on site.
Chlorine dioxide
Chlorine dioxide performs well across a wide pH range, is effective against biofilm, and produces a different by-product profile from free chlorine. In agriculture it shows up mainly in water systems and some post-harvest applications.
The complications are generation and control. It is usually made on site from precursors, which means either a two-part chemical system or a generator of its own, with the associated handling and monitoring. Gas-phase chlorine dioxide is hazardous and has explosive limits at higher concentrations. Monitoring is less familiar to farm staff than free chlorine testing. For large operations with technical staff it is a legitimate option; for a mid-sized farm it usually adds complexity that the food safety programme cannot absorb.
Copper ionisation and copper-based products
Copper ionisation is common in greenhouse recirculation specifically, and it has a distinct profile: it persists, it is effective against algae, and it does not decay the way an oxidiser does.
The limits are equally distinct. Copper accumulates — in the nutrient solution, in the substrate and potentially in the discharge — and crops vary widely in tolerance. Copper toxicity in a recirculating system is a real and reported failure mode, and monitoring accumulated copper is an additional routine. It is also slower-acting than an oxidiser against many organisms. Growers who use it well tend to use it as part of a programme rather than alone, and they monitor copper levels as diligently as they monitor EC.
Ozone
Ozone is a powerful oxidiser generated on site, leaves no chemical residue and is used in some produce washing and water treatment. Its weaknesses in this sector are practical: very short half-life so effectively no downstream residual, significant capital and electrical cost, off-gassing that requires containment and monitoring in enclosed spaces, and material compatibility issues with some seals and plastics.
In a recirculating greenhouse, ozone is a serious contender for in-loop treatment. In an irrigation main serving a block of drip line, it cannot do the job at all, because there is nothing left by the time the water reaches the emitters.
UV and physical treatment
UV is widely used in greenhouse recirculation and is genuinely good at what it does: it inactivates organisms passing through the chamber, adds no chemistry, changes no nutrient formulation and leaves nothing behind.
“Leaves nothing behind” is also the limitation. UV treats water at a point; it does nothing to the line downstream, nothing to biofilm on the pipe wall and nothing to an emitter. Its performance also depends heavily on transmittance, so a nutrient solution with high organic content or colour degrades the dose delivered — and lamp fouling reduces it further without any obvious symptom. UV dose is engineering, not chemistry: it requires correct sizing, flow control and lamp maintenance to mean anything.
Slow sand filtration deserves a mention because in horticulture it is a well-established and low-cost biological treatment for recirculated water, effective against several important pathogens including Phytophthora and Pythium. It is slow, it requires space and management of the biological layer, and it provides no residual. For growers with the space it is a legitimate primary treatment, often combined with something else for the line.
Heat treatment is the remaining physical option: effective and non-selective, with an energy cost that only makes sense at certain scales and with heat recovery.
Side by side
| Option | Downstream residual | Handling burden | Best at | Main limitation |
|---|---|---|---|---|
| Onsite HOCl generation | Yes | Salt, water, electricity | Serving several applications from one system without concentrated chemistry on site | Capital cost; demand and pH still govern performance; no efficacy claims |
| Sodium hypochlorite | Yes | Corrosive liquid, storage, freight | Low upfront cost, universal availability | Degrades in storage; raises pH; freight on water |
| Calcium hypochlorite | Yes | Oxidiser solid, incompatibilities | Freight and storage stability | Calcium contribution; oxidiser hazards; dissolution handling |
| Peracetic acid | Short | Significant: vapour, PPE, storage | High organic load wash water, by-product profile | Cost; hazard; odour; no line residual |
| Chlorine dioxide | Yes | Generation system, precursors | Wide pH range, biofilm | Complexity; gas hazards; less familiar monitoring |
| Copper ionisation | Persistent | Low routine, high monitoring | Greenhouse recirculation, algae | Accumulation and crop toxicity; slower action |
| Ozone | Negligible | Generation and off-gas control | In-loop treatment with no residue | No downstream residual; capital and energy; containment |
| UV | None | Lamp maintenance | Recirculating loops, no chemical addition | Point treatment only; transmittance and fouling sensitive |
| Slow sand filtration | None | Space and biological management | Low-cost primary treatment in horticulture | Slow; space; no residual |
Where onsite generation is the wrong choice
Four situations, stated plainly.
- Low water volume. Below a certain throughput the capital cost cannot be recovered against a small chemical bill, whatever the per-litre arithmetic says.
- A required registered-product claim. If a buyer scheme, a customer specification or a rule requires an EPA-registered disinfectant with a documented claim, a generated solution does not satisfy it. Use HOCl-AS200 per its label.
- Difficult source water with no appetite for pre-treatment. Hardness and iron that would need conditioning are a reason to solve water chemistry first, or to stay with delivered chemistry.
- No one to own it. A generator is plant equipment. It needs a named owner, a service arrangement and a monitoring routine. Operations that cannot staff that are better served by a delivered product and a simple dosing pump.
The counterpart is the situation where it is the strongest option: a multi-application site — wash water, surfaces, tool dips, irrigation — far enough from a depot that freight and delivery reliability matter, with enough volume to justify the capital and someone on staff to run it.
Switching without losing a season
Farms change treatment badly more often than they choose badly, and the pattern of a good transition is predictable. Run parallel: keep the incumbent chemistry available through the first full season, because a harvest is not the time to discover a gap. Start with one application rather than the whole site — usually the packhouse wash, where monitoring is already in place and the effect is measurable — and add irrigation once the first one is stable.
Commission out of season if the calendar allows it. An installation commissioned three weeks before peak harvest will be validated during peak harvest, by people who have no time to do it, and the set points will be guesses. Commissioned in the quiet period, the same system arrives at harvest with measured demand, trained staff and a filled-in log.
And measure the incumbent before you switch. A grower who has recorded chemical consumption, residual readings and maintenance hours for a season under the old system has a genuine comparison; one who has not is left arguing from impressions. That baseline costs nothing but attention, and it is unrecoverable once the change is made.