Advanced Treatment of Laundry Wastewater by Electro-Hybrid Ozonation-Coagulation Process: Surfactant and Microplastic Removal and Mechanism

Laundry wastewater is supposed to be one of the most important sources of surfactants and microplastics in the wastewater treatment plant. Consequently, the aim of the study was evaluating the performance and mechanism of the electro-hybrid ozonation-coagulation (E-HOC) process for the removal of surfactants and microplastics. In this study, the efficiency of the E-HOC process for surfactant and microplastic removal was examined at different current densities and ozone dosages. Under the optimal reaction conditions (current density 15 mA center dot cm(-2), ozone dosage 66.2 mg center dot L-1), both the removal efficiency of surfactant and microplastic can reach higher than 90%. Furthermore, the mechanism of surfactant and microplastic removal was investigated by electron paramagnetic resonance (EPR) and Fourier transform infrared spectroscopy (FT-IR). The results showed that the E-HOC (carbon fiber cathode) system can produce more reactive oxygen species (ROS), which can significantly improve the removal of the contaminants. In addition, the shape, size and abundance of the microplastics were analyzed. It was found that the shape of the microplastics in laundry wastewater is mainly fiber. Microplastics less than 50 mu m account for 46.9%, while only 12.4% are larger than 500 mu m. The abundance of microplastics in laundry wastewater ranges between 440,000 and 1,080,000 items per 100 L. The analysis of microplastics by FT-IR showed that most of the microplastics in laundry wastewater were polyethylene, nylon and polyester. These results indicated that the E-HOC process can effectively remove surfactants and microplastics from laundry wastewater.

Automated summary

This study evaluated the performance and mechanism of the electro-hybrid ozonation-coagulation (E-HOC) process for the removal of surfactants and microplastics from laundry wastewater. The results showed that under optimal conditions, the E-HOC process could achieve a removal efficiency of over 90% for both surfactants and microplastics. The E-HOC system was found to generate more reactive oxygen species (ROS), which greatly improved the removal of contaminants. Additionally, the analysis of microplastics in the wastewater revealed that they mainly consisted of fiber-shaped particles, with smaller particles (<50 μm) accounting for 46.9% and larger particles (>500 μm) only accounting for 12.4%. The abundance of microplastics in the laundry wastewater ranged from 440,000 to 1,080,000 items per 100 L. FT-IR analysis further identified polyethylene, nylon, and polyester as the predominant types of microplastics in the wastewater.