Oxidation of simazine: biological oxidation of simazine and its chemical oxidation byproducts

Batch biodegradation studies were conducted to assess the biodegradability of single s-triazines. s-Triazines tested included simazine, a widely used herbicide, and its products resulting from oxidation with ozone, ultraviolet (UV) light, and combined ozone and UV light oxidation. Degradation rates for each s-triazine were calculated as μM N/hr. Rates ranged from 0 to 10.3 μM N/hr. s-Triazine degradation rates were a function of the ring substituents and followed the order of hydroxy ⪢ amino ⪢ chlorine ≥ ethylamino. Chemical oxidation methods capable of oxidizing the more persistent simazine substituent groups (chlorine and ethylamine) to more easily biodegraded substituents (amine and hydroxy) proved attractive in enhancing the s-triazine mineralization of simazine. When simazine was pretreated with combined ozone and UV, the s-triazine biodegradation rate was increased by an order of magnitude. s-Triazine biodegradation rates also were enhanced with ozone and UV pretreatment but not to the same extent.