Drainage water recirculation recovers 30–50% of fertiliser costs and significantly reduces environmental load. A breakdown of the DISMART UV approach and operational requirements for safe implementation.
Run-to-waste fertigation discards drainage water that still carries a meaningful share of the nutrients originally dosed into it. In most protected-crop operations, that drainage stream is 20–40% of what was applied — recirculating it is less a sustainability add-on than a direct line item on the fertiliser budget.
Why growers still run to waste
The reason is not economics — it is risk. Recirculated drainage water carries whatever pathogens, algae, or root-zone organisms were present in the substrate it drained from. Without adequate disinfection, recirculation becomes a distribution system for exactly the problems a grower is trying to avoid, which is why run-to-waste remains the default in operations that have not solved disinfection reliably.
What UV disinfection changes
UV treatment neutralises pathogen DNA without adding disinfectant residue to the nutrient solution, which matters because the treated water is going straight back into a fertigation line, not into a discharge point. The practical requirements are dose (UV intensity × exposure time) matched to the pathogen profile actually present, and pre-filtration — organic matter and particulates in raw drainage water shield pathogens from UV exposure and reduce lamp effectiveness over time, so filtration ahead of the UV stage is what keeps dosing calculations valid rather than theoretical.
The economics
Recovering 30–50% of fertiliser cost is the headline number, but it understates the case: recirculation also reduces the volume of nutrient-laden water leaving the site, which is increasingly the more expensive side of the equation as environmental discharge regulation tightens in protected-horticulture regions. The DISMART UV approach pairs the treatment stage with the same EC/pH monitoring used in closed-loop fertigation, so recirculated water re-enters the mixing tank at a known, controlled composition rather than as an unmeasured variable added back into the system.
Where this fits operationally
Recirculation is not a bolt-on to an existing fertigation setup — it needs pre-filtration, UV dosing sized to actual flow and pathogen load, and monitoring integrated with the dosing controller rather than run as a separate system. Treated as a full loop rather than three disconnected steps, it is one of the more directly measurable returns available in a protected-crop retrofit.