For P5, the combination of POD assisted phytopolymerization and phytooxidation, and rhizomicrobial degradation completely eliminated 500 mg/L of phenol in wastewater within 800 h, while the natural attenuation of phenol by microbes in wastewater alone will take as long as 2.36 years considering a degradation rate of 3x10-4 r- 1. The same reaction mechanism was also true for P1 to P4, but at different reaction rates (see Figure 7d). Nevertheless, the phenol degradation rate in this study is slower than that reported in a previous study. Singh et al. (2008) reported that after four days, vetiver grass in aseptic Murashige and Skoog liquid medium decreased phenol at an initial concentration of 500 mg/L by 76%. Conversely, in our study of the same time period vetiver grass degraded just 25% of the phenol at the same initial concentration. This is presumably because our study was conducted using real wastewater with COD, organic load (such as total petroleum hydrocarbon), and inorganic reducing species; the actual pollutant loads are not available for aseptic Murashige and Skoog liquid medium. These organic and inorganic reducing loads consume the oxidative capabilities of H2O2 and POD and might compete with phenol degradation. As seen in Figure 6f, the wastewater samples started with negative ORP, which required the consumption of an oxidant such as H2O2 to become positive 500 h later.