Vetiver plantlets in aerated system degrade phenol in illegally dumped industrial wastewater by phytochemical and rhizomicrobial degradation.

Abstract

This research evaluated the feasibility of using vetiver plantlets (Vetiveria zizanioides (L.) Nash) on a floating platform with aeration to degrade phenol (500mg/L) in illegally dumped industrial wastewater (IDIWW). The IDIWW sample was from the most infamous illegal dumping site at Nong Nae subdistrict, Phanom Sarakham district, Chachoengsao province, Thailand. Laboratory results suggested that phenol degradation by vetiver involves two phases: Phase I, phytopolymerization and phyto-oxidation assisted by root-produced peroxide (H2O2) and peroxidase (POD), followed by phase II, a combination of phase I with enhanced rhizomicrobial degradation. The first 360-400h of phenol degradation were dominated by phytopolymerization and phyto-oxidation yielding particulate polyphenols (PPP) or particulate organic matter (POM) as by-products, while phenol decreased to around 145mg/L. In Phase II, synergistically, rhizomicrobial growth was ∼100-folds greater on the roots of the vetiver plantlets than in the IDIWW and participated in the microbial degradation of phenol at this lower phenol concentration, increasing the phenol degradation rate by more than three folds. This combination of phytochemical and rhizomicrobiological processes eliminated phenol in IDIWW in less than 766h (32days), while without the vetiver plantlets, phenol degradation by aerated microbial degradation alone may require 235days. To our knowledge, this is the first that systematically reveals the complete phenol degradation mechanism by vetiver plantlets in real aerated wastewater.