Photosonolysis of TCA, TCE, and PCE in Flow-Through Reactor System

Photosonolysis of 1,1,1-trichloroethane (TCA), trichloroethylene (TCE), and tetrachloroethylene (PCE) in water was investigated using a cup-horn, flow-through reactor system. Water containing titanium dioxide was deliberately contaminated with a mixture of volatile organic compound (VOC)-TCA, TCE, and PCE-and individual VOC. These solutions were irradiated with ultraviolet light (UV) and ultrasonic waves (US), independently and concurrently (UVUS). The values of the first-order degradation rate constant and the removal efficiency for the VOC were evaluated for the UV, US, and UVUS treatments. The results showed that the concurrent use of UV and US increased the VOC degradation rate and removal efficiency beyond the additive effect of UV and US, suggesting that the UVUS effect on the decomposition of the VOC is synergistic under certain conditions. TCE and PCE were more readily degraded than TCA, suggesting that double-bond cleavage is one of the initial degradation pathways. With the reactor specifications used, the photosonolysis process can produce water meeting the drinking water standard (MCLs of 5 µg/L) for TCE and PCE with a removal efficiency of approximately 90%.