Recycling contaminated irrigation water after treatment with a two-stage woodchip bioreactor in greenhouse systems

Irrigation return flow or drain water from greenhouse production often contains elevated concentrations of nitrate, phosphate, and pesticide residues, posing environmental risks if discharged or recycled without treatment.
This study evaluated two commercial-scale, sequential non-aerated (NAE) – aerated (AE) woodchip bioreactor systems operating at 30-min and 60-min hydraulic retention times (HRT) to assess nutrient retention and pesticide removal based on redox conditions.
Both systems operated at low dissolved oxygen (DO) levels in the NAE stages (30-min, 2.42 mg L^‑1; 60-min, 2.49 mg L^‑1) and high DO in the AE stages (30-min, 6.7 mg L^‑1; 60-min, 7.0 mg L^‑1). Total nitrogen (N) recycling increased under 30-min HRTs (91.1±11.5%, 2.89 kg day^‑1 in AE effluent vs. 2.63 kg day^‑1 in NAE influent) compared to 60-min operation (81.5±20.0%, 2.96 kg day^‑1 in the AE effluent vs. 2.41 kg day^‑1 in the NAE influent). Phosphate-phosphorus (P) was completely recycled in both systems.
Pesticide loads in the effluent decreased for dinotefuran (30-min: 12.0-24.3% removal; 60-min: 0.9-100.0% removal) and cyazofamid (30-min: 6.0-100.0% removal; 60-min: 24.5-100.0% removal) following AE treatment, with generally greater removal observed at the longer HRT. These results demonstrate that NAE–AE configurations can support fast water flow through woodchip bioreactors to simultaneously recycling nutrients and reducing pesticide loads in irrigation return water.

XI International Symposium on Irrigation of Horticultural Crops

H. Gonzalez, G. Reguera, J.S. Owen, R.T. Fernandez

drain water, irrigation return flow, nutrient recycling, pesticide remediation, water recycling

https://doi.org/10.17660/ActaHortic.2026.1468.50