Tetracycline degradation by ozonation, and evaluation of biodegradability and toxicity of ozonation byproducts

Abstract

Tetracycline was exposed to ozone by bubbling at different pH levels, and the acute toxicity of ozonation byproducts was tested by luminescent bacteria (Vibrio qinghaiensis sp.-Q67). Residual tetracycline in the solutions was detected by high performance liquid chromatography (HPLC). The results indicated that tetracycline was immediately degraded by ozonation and the degradation was favored at higher pH. Tetracycline (20 mg L−1) was completely degraded after 5 min of ozonation. However, total organic carbon (TOC) hardly decreased even though the ozonation time was extended to 40 min, suggesting that the ozonation process could not mineralize tetracycline. The luminescent bacteria assay indicated that the toxicity of the tetracycline solution was changed after ozonation. Chemical oxygen demand (COD) dropped by 15%, and the BOD5/COD ratio increased from 0·09 to 0·26, suggesting that the biodegradability of tetracycline was enhanced after 20 min of ozonation treatment.

Degradation of tetracycline in aqueous media by ozonation in an internal loop-lift reactor

“…The gentle increase of COD removal efficiency during the reaction process may result from the intermediates formed which were more stable than tetracycline under the experimental conditions. The similar phenomenon was reported by Wu et al [27] when tetracycline was degraded by ozone. They found that only 15% COD of tetracycline was removed by the first 5 min and the COD removal was not increased by extending the reaction time to 20 min.…”

“…The intermediates were further oxidized with the progress of ozonation, which led to the increasing D. magna mortality [50,51] and the inhibition ratio reached 95%. The similar tendency was reported by Wu [27] and Beltrán [52] when tetracycline and sulfamethoxazole were oxidized by ozone, respectively. They found the more toxic by-products were formed during ozonation process compared with the target pollutants.…”

“…Then the BOD 5 /COD ratio decreased slightly afterwards. This indicated that tetracycline was firstly oxidized to the intermediates with higher biodegradability than tetracycline itself [27], but further degradation of the intermediates could not improve the biodegradability. Moreover, the BOD 5 /COD ratio during the whole reaction time was higher than that of the tetracycline.…”

“…In particular, ozonation is capable of oxidizing organic compounds to simpler and more easily biodegradable compounds [15][16][17], such as procaine penicillin G [17], amoxicillin [18,19], ceftriaxone sodium [20], macrolide [21], sulfonamide [21,22], penicillin [23] and tetracycline [7,[24][25][26][27]. However, almost all the researches were performed in conventional bubble column reactors.…”

Comparison between continuous and intermittent ozonation for remediation of soils contaminated with polycyclic aromatic hydrocarbons

“…The acute toxicities of the soil extracts were tested by the luminescent assay of V. qinghaiensis sp.-Q67 kit in accordance with our previous method (Wu et al 2010). The toxicity assays were performed in triplicates.…”