Evaluation of Diethyl phthalate and Diallyl phthalate biodegradation mechanisms in the treatment of synthetic wastewater

Over the last few years, Phethalic Acid Esters (PAEs) have attracted a widespread attention due to their widespread production and use. These compounds are not only linked to endocrine disruption and cancer but also considered as emerging and hazardous pollutants. Large amounts of PAEs have been detected in industrial wastewaters. Given the widespread use of biological processes in industrial wastewater treatment, this study aimed to identify biodegradation pathways of PAEs and their potential metabolites. Two short-chain esters from phthalic acid esters including diethyl phthalate (DEP) and diallyl phthalate (DAP) were selected in the present study. We used the survey of metabolites in a moving bed biofilm reactor effluent to determine biodegradation pathways of designated esters at hydraulic retention times of 1 to 12 hours. Influent concentration of 100 mg/l was also considered throughout the study. Phthalic acid, mono-methyl phthalate, dimethyl phthalate and catechol were identified as the most noteworthy metabolites in biodegradation of both esters. The degradation pathway of both studied compounds was similar and involves either detachment of ester-chain or removal of methyl group, followed by few decomposition steps resulting in the production of benzene ring. The degradation can proceed further with ring cleavage and it ends with 2-hydroxy muconic semi-aldehyde. The main route for removal of studied compounds was de-esterification followed by demethylation. According to identifies degradation pathways and metabolites produced, biodegradation can be considered as a reliable treatment process for industrial wastewaters containing PAEs.