Toxic and inhibitory effects of trichloroethylene on hydrolysis acidification with phenol and benzoic acid co-metabolism

Abstract

Hydrolysis acidification (HA), an efficient biological pretreatment technology, has demonstrated significant potential in degrading toxic and recalcitrant compounds. In this study, the reaction efficiency was utilized to investigate the toxic and inhibitory effects of trichloroethylene (TCE) on HA during the co-metabolism of phenol and benzoic acid. Results indicated that high TCE concentrations exerted an inhibitory effect on HA, with an EC₅₀ value of 75 mg/L. Phenol and benzoic acid as co-metabolized substrates for HA exhibited a unique response to the toxicity of TCE, that increasing concentrations of phenol and benzoic acid enhanced the dechlorinating degradation of TCE by promoting secretion of extracellular polymeric substance (EPS), however, causing partial cell death. At a TCE concentration of 75 mg/L, when the concentrations of phenol and benzoic acid were 375 mg/L, the dechlorination efficiencies of TCE were 58.53 % and 49.71 %, the acid yields were 60.35 and 50.93 mg COD/g VSS, the EPS concentrations were 40.16 and 33.77 mg COD/g VSS, the DNA concentrations in solution were 10.45 and 10.97 mg COD/g VSS(significantly higher than blank control group: 8.97 mg COD/g VSS), respectively. This enhancing effect was consistently observed across various concentrations of phenol and benzoic acid, and dechlorination degradation of TCE has also been effectively improved. The unique toxic response may be attributed to the compact structure of granular sludge and the increased secretion of EPS, which likely served as protective barriers for cells against TCE toxicity.