Hybrid Cavitation/Constructed Wetland Reactors for Treatment of Chlorinated and Non-Chlorinated Organics

Abstract

Mitigation strategies can be implemented to decrease chlorinated and non-chlorinated organic exposures to biota of aquatic receiving systems thereby reducing associated risks. In this work, we investigated the concept of coupling a physical/chemical reactor (i.e. a cavitation reactor) with a biological reactor (i.e. a constructed wetland) in an effort to efficiently transform PCE, TCE, and petroleum in freshwater into non-toxic chemical forms or concentrations. Rates of TCE degradation due to cavitation ranged from 0.010 to 0.026 min -1 with corresponding half-lives of 69 to 27 min. Compared to controls, degradation of petroleum in water by cavitation was not detected in these experiments. After treatment in anaerobic wetland reactors, TCE and PCE decreased by more than 99% under two flow regimes (5-d and 20-d HRT). In reciprocating constructed wetland reactors receiving petroleum, mean COD, BOD 5 , and total Zn decreased by 90.0, 88.8, and 86.8 %, respectively, in wetland outflows compared to the initial conditions (96-h HRT). Percent survival (96-h) of D. magna and P promelas increased from zero percent in initial conditions to 80.1 (± 18.9) and 80.0 (± 21.4) %, respectively, after treatment in the constructed wetland reactors. The experimental results obtained in the laboratory-scale set-up and the theoretical model for the hybrid reactor concept will be used to obtain the intrinsic kinetic coefficients for the appropriate reactors. This kinetic information will be used to scale-up the hybrid reactor model concept for the same level of pollutant removal.