Using Hydroponic Bioreactors to Assess Phytoremediation Potential of Perchlorate

Studies on plant-mediated decontamination of polluted waters commonly rely on hydroponic bioreactor systems for the rapid screening of different plant species and the investigation of the phytoremediation mechanisms. This chapter describes the use of ebband-flow and sealed root-zone hydroponic bioreactors (some mounted with dissolved oxygen, pH, and E_H probes) to investigate, under aerobic and anaerobic rhizosphere conditions, respectively, the phytoremediation potential of the new and emergent contaminant perchlorate. The experimental data show slower kinetics and higher fraction uptake and phytodegradation of perchlorate by plants grown under predominantly aerobic root-zone conditions. Meanwhile, for plants grown in sealed (predominantly anaerobic) root-zone hydroponic systems, the bulk solution chemistry is influenced by the plant photosynthesis and respiration cycles, and both phytodegradation and rhizodegradation are the predominant phytoprocesses. In ongoing research, various approaches are being developed to minimize the undesired uptake and slow phytodegradation process and enhance the favorable and rapid rhizodegradation process. Additionally, planted soil bioreactor experiments that simulate phytoremediation of perchlorate under natural field conditions are described.