Biological degradation of the phenoxy acid herbicide 2,4-dichlorophenoxyacetic acid (2,4-D).

摘要

A bench-scale study was performed to investigate the biodegradation potential of a phenoxy acid herbicide (2,4-dichlorophenoxyacetic acid or 2,4-D) under various experimental conditions. This study included two main phases. During the first phase, the effect of hydraulic retention time (HRT) and the presence or absence of supplemental substrate was explored using sequencing batch reactors (SBRs). In the second phase, batch reactors were used to investigate the effect of temperature, pH, and seed type on 2,4-D degradation.;In the beginning, two identical two-liter liquid volume SBR units were employed. SBR 1 was fed with a mixture of phenol and 2,4-D and SBR 2 with a mixture of dextrose and 2,4-D. A long acclimation period (over 80 days) was observed in both SBR 1 and SBR 2 before the first signs of 2,4-D degradation were recorded. In order to achieve a sustainable 2,4-D degradation pattern, it was found that, the initial substrate concentration, biomass concentration, and HRT have to be carefully selected.;After achieving steady state operation, an additional SBR unit was introduced (SBR 3) identical to the other two with 2,4-D as the sole source of carbon and energy. All three systems were able to degrade more than 95% of the 2,4-D concentrations applied at an HRT range of 12 to 48 hrs. Even though the use of supplemental substrate resulted in lower 2,4-D-specific removal rates, better system stability in terms of good settling characteristics and superior floc formation was achieved in the corresponding reactors. (Abstract shortened by UMI.).