REMOVAL EFFICIENCY AND MECHANISM OF BDE-47 BY THE ZN-FE LDHS MODIFIED QUARTZ SAND-BIOFILM SYSTEM

In this paper, Zn-Fe layered double hydroxides (LDHs) modified quartz sand was prepared by coprecipitation method and cultivated with inoculation of Shewanella putrefaciens CN32 under aerobic, anaerobic and alternating conditions, to examine the biofilm formation process on LDHs modified matrix and its removal efficiency of BDE-47 as the target pollutant. The biotic and abiotic removal mechanisms of BDE-47 were further explored by monitoring variations of Fe²⁺ and H₂O₂ concentrations in the reaction systems. The results showed that LDHs coating would not affect the formation of biofilm on the surface of the modified quartz sand, but Zn-Fe LDHs modified matrix showed certain inhibitory effects on electron transport system activity of CN32 under aerobic condition, while the composition of extracellular polymer substance (EPS) of matrix biofilm changed with an increase in the proportion of polysaccharide under anaerobic condition. Total concentrations of EPS in the matrix biofilm reaction systems were significantly higher than those in the pure CN32 system under both aerobic and anaerobic conditions.The formation of matrix biofilm significantly improved the removal efficiency of BDE-47 in the reaction system (about 25%) under aerobic and anaerobic alternating condition. Under the alternating condition, the removal of BDE-47 in the first three cycles (within 72h) depended mainly on matrix adsorption; while 72h later, biofilm adsorption and biodegradation contributed jointly, and LDHs modified matrix exhibited greater boosting potential in the later stage. This study firstly demonstrated the biofilm formation characteristics of LDHs modified matrix and its potential for the removal of PBDEs from the aqueous phase, and provided new ideas for enhancing the biodegradation of PBDEs in constructed wetlands.