Mitigation of benzoic acid-driven autotoxicity in waste nutrient solution using O

Area of Science:

• Environmental Science
• Agricultural Science
• Water Treatment

Background:

• Benzoic acid (BA), a root exudate, is a primary cause of plant autotoxicity in closed hydroponic systems, even at low concentrations.
• Plant autotoxicity negatively impacts germination and root development, hindering sustainable agriculture and hydroponic cultivation.

Purpose of the Study:

• To investigate the efficacy of ozone (O3) and ozone/hydrogen peroxide (O3/H2O2) oxidation treatments in mitigating benzoic acid-driven autotoxicity.
• To evaluate the degradation of benzoic acid, and the reduction in germination inhibition (GI) and root growth inhibition (RI) in waste nutrient solutions (WNS).

Main Methods:

• Waste nutrient solutions containing benzoic acid were treated with varying concentrations of O3 (1-8 mg L-1) and H2O2 (4, 8 mg L-1).
• Benzoic acid degradation rates, germination inhibition (GI), and root growth inhibition (RI) were measured.
• Operating costs for different treatment conditions were analyzed.

Main Results:

• Single O3 treatment showed limited benzoic acid degradation (up to 14.1%) and insignificant mitigation of germination inhibition.
• O3/H2O2 treatment significantly enhanced benzoic acid degradation (up to 24.8%) and substantially reduced GI (up to 7.69%) and RI (up to 0.88%).
• Optimal results for BA mineralization and phytotoxicity mitigation were observed at specific O3/H2O2 concentrations, with BA125 (1-8) showing high efficiency and cost-effectiveness.

Conclusions:

• Combined O3/H2O2 oxidation is a superior method for degrading benzoic acid and alleviating plant autotoxicity in hydroponic systems compared to O3 alone.
• The treatment condition BA125 (1-8) is recommended as the optimal treatment due to its high benzoic acid mineralization rate, effective autotoxicity mitigation, and favorable operating costs.
• This study provides a viable strategy for managing benzoic acid-driven autotoxicity, contributing to sustainable hydroponic practices.