Treatment of waste gas contaminated with dichloromethane using photocatalytic oxidation, biodegradation and their combinations

The treatment of waste gas (WG) containing dichloromethane (DCM) using advanced oxidation processes (AOPs) [UV and UV-TiO2], biological treatment (BT), and their combination (AOPs-BT) was tested. AOP tests were performed in an annular photo-reactor (APHR), while BT was conducted in a continuous stirred tank bioreactor (CSTBR). The effects of gas flow rate (Q(gas)), inlet DCM concentration ([DCM](i)), residence time (tau), photocatalyst loading (PH-C-L) and % relative humidity (% RH) on the AOPs performance and the removal of DCM (%DCMr) were studied and optimized. The UV process exhibited %DCMr <= 12.5 % for tests conducted at a [DCM](i) <= 0.45 g/m(3), Q(gas) of 0.12 m(3)/h and tau of 27.6 s, respectively, and < 4 % when the [DCM](i) >= 4.2 g/m(3). The UV-TiO2 achieved a %DCMr >= 71 +/- 1.5 % at Q(gas) of 0.06 m(3)/h, [DCM](i) of 0.45 g/m(3), tau of 55.2 s, PH-C-L of 10 g/m(2), and %RH of 50, respectively. The BT process removed similar to 97.6 % of DCM with an elimination capacity (EC) of 234.0 g/m(3).h. Besides, the high %DCMr of similar to 98.5 % in the UV-BT and 99.7 % in the UV-TiO2-BT processes confirms AOPs-BT as a promising technology for the treatment of recalcitrant compounds present in WG.

Automated summary

The study found that factors such as gas flow rate, dichloromethane concentration, residence time, photocatalyst loading, and relative humidity significantly affect the efficiency of DCM removal through UV and UV-TiO2 processes, while biological treatment also showed promising removal performance. The AOPs-BT technology is confirmed to be effective in treating recalcitrant compounds present in waste gas.