Non-Thermal Plasma Treatment of Dye-Contaminated Wastewater: A Sustainable Approach for Pollutant Degradation and Enhanced Plant Growth

The win–win situation of dye degradation and nitrogen fixation in wastewater using non-thermal plasma (NTP) were investigated in this study. Specifically, the feasibility of utilizing plasma-treated dye-contaminated wastewater for seed germination and plant growth was explored. Crystal Violet (CV) and Rhodamine B (RhB) dyes were used as model pollutants, while Sorghum bicolor (great millet) seeds were used to assess germination rates and plant growth responses. In untreated wastewater containing CV and RhB, approximately 45% of seeds germinated after three days, but no significant stem or root growth was observed after 11 days. Plasma treatment significantly enhanced dye degradation, with efficiency improving as treatment time and input power increased. After 16 min of plasma treatment at 1.3 ± 0.2 W input power, about 99% degradation efficiency was achieved for both CV (0.0122 mM) and RhB (0.0104 mM). This degradation was primarily driven by reactive oxygen and nitrogen species (RONS) generated by plasma discharge. When sorghum seeds were germinated using plasma-treated wastewater, the germination rate increased to 65% after three days—20% higher than with untreated wastewater. Furthermore, after 11 days, the average stem length reached 9 cm, while the average root length extended to 7 cm. These findings highlight NTP as a promising and sustainable method for degrading textile industry pollutants while simultaneously enhancing crop productivity through the reuse of treated wastewater.