# Degradation of Trace Organic Contaminants by a Membrane Distillation--Enzymatic Bioreactor
## 4 Conclusions  
Performance of an enzymatic bioreactor integrated with the MD system (MD-EMBR) was examined for the removal of 13 phenolic and 17 non-phenolic compounds. Based on permeate quality, MD-EMBR achieved 90-99% TrOC retention. Degradation of TROCs varied (40-99%) depending on their molecular properties (electron withdrawing functional groups electron donating functional groups and phenolic moiety). High degradation (above 90%) of TROCs containing EDGs in their chemical structure was observed in the MD-EMBR, while those containing EWGs in their molecular structure were moderately degraded (40-75%). Degradation of TROCs was further improved by adding three redox-mediators, namely syringaldehyde (SA), violuric acid (VA) and 1-hydroxybenzotriazole (HBT). VA at 0.5 mM concentration was found to be the most effective mediator for improving the degradation of phenolic and non-phenolic TROCs. Moreover, it was observed that the degradation of non-phenolic compounds in lacase-mediator system was strongly influenced by the tested  
Figure 6: Permeate flux during the operation of MD-EMBR with and without the presence of redox-mediators. Box-and-whisker plot shows the interquartile range; median (horizontal line in the box); min and max (whiskers); average (small square in the box); and 1 and 99% percentiles (cross above and below the whiskers). Operating conditions for MD-EMBR: Temperature of the enzymatic bioreactor and the permeate tank were kept at 30 and 10 \({}^{\circ}\)C, respectively; cross-flow rate of water from enzymatic bioreactor and distillate was 1 L/min (corresponding to cross-flow velocity of 9 cm/s); the initial TrOC concentration and lacase activity was 20 \(\mu\)g/L and 95–100 \(\mu\)M\({}_{\text{(DMP)}}\)/min, respectively; and each mediator was added at 0.25 or 0.5 mM concentration in separate runs.  
concentration of the redox-mediators. Despite an increase in the toxicity of the reaction mixture caused by SA, the final effluent of the MD-EMBR was nontoxic.  
The following are available online at [[http://www.mdpi.com/2076-3417/7/9/879/s1](http://www.mdpi.com/2076-3417/7/9/879/s1)]([http://www.mdpi.com/2076-3417/7/9/879/s1](http://www.mdpi.com/2076-3417/7/9/879/s1)), Table S1: Physicochemical properties of the selected trace organic contaminants (TrOCs), Table S2: Physicochemical properties of the selected redox-mediators, Figure S3: Impact of mediator concentration (0.25 and 0.5 mM) on the degradation of after an incubation time of 12 h in the MD-EMBR. Error bars indicate the standard deviation of duplicate samples. Degradation of these TrOCs did not improve by increasing mediator concentration, Figure S4: Permeate flux obtained during the operation of enzymatic membrane distillation (MD-EMBR) with and without the addition of redox mediators.  
This research has been conducted with the support of the Australian Government Research Training Program Scholarship. Novozymes Pty. Ltd., Australia is thanked for the provision of enzyme solution. This study was partially funded by the GeoQuEST Research Centre, University of Wollongong, Australia.  
[PERSON] conceived and led the project. [PERSON] and [PERSON] planned the experiments in consultation with the coauthors. [PERSON] conducted the experiments. [PERSON], [PERSON] and [PERSON] analyzed TrOC and toxicity samples. [PERSON] and [PERSON] analyzed the data and prepared the manuscript with the contribution of [PERSON], [PERSON], [PERSON], [PERSON] and [PERSON] to specific sections.  
The authors declare no conflict of interest.