关键词: 臭氧, 微纳米气泡, 循环井, 地下水, 三氯乙烯

Abstract:

To investigate the degradation performance, influencing factors and reaction mechanism of trichloroethylene (TCE) by catalytic ozonation coupled circulating well technology, this study takes TCE, a typical pollutant in groundwater, as the target contaminant. Ozone micro-nano bubbles (O3-MNBs) were combined with groundwater circulating well (GCW) remediation technology. Volcanic rock was added into the circulating well as an ozonation catalyst, and systematic research was carried out through batch tests in a simulation tank. The results showed that the O3-MNBs coupled GCW system achieved superior TCE removal efficiency compared with single O3-MNBs treatment or independent GCW treatment. The optimal operating conditions were determined as follows: catalyst dosage of 15 g, ozone flow rate of 150 mL/min, and aeration rate of 1.200 cm3/h for the circulation well. The coupled system exhibited excellent degradation performance toward TCE wastewater at low concentrations (6.25-25.00 mg/L), while its treatment capacity was slightly limited for high-concentration TCE wastewater (37.50 mg/L). A negative correlation was observed between groundwater flow velocity and TCE degradation rate. Volcanic rock acts as a composite polymetallic catalyst containing Al2O3, Fe2O3, CaO and other metal oxides, which can efficiently trigger the generation of reactive free radicals from ozone and further enhance TCE degradation. TCE is degraded via two pathways: Direct oxidation by ozone molecules and indirect oxidation by ozone-derived reactive free radicals, and is ultimately almost completely mineralized into non-toxic and harmless end products.

Key words: ozone, micro-nanobubbles, groundwater circulation well, groundwater, trichloroethylene