Anaerobic degradation of dimethyl phthalate in wastewater in a UASB reactor

Over 99% of dimethyl phthalate (DMP) and 93% of chemical oxygen demand (COD) were effectively removed in a continuous upflow anaerobic sludge blanket (UASB) reactor from a wastewater containing 600 mg/L DMP at 8 h of hydraulic retention time (HRT), corresponding to a loading rate of 3 g-COD/(L d). Each gram of sludge, expressed as volatile suspended solids (VSS), had a maximum specific methanogenic activity (SMA) of 24 mg-CH4/(g-VSS d) using DMP as the sole carbon source. The sludge yield was estimated as 0.08 g-VSS/g-COD. During anaerobic degradation, DMP was de-esterified, first to mono-methyl phthalate (MMP) and then to phthalate, before being de-aromatized and subsequently converted to CH4 and CO2. The maximum specific degradation rates of DMP, MMP and phthalate were 415, 88 and 36 mg/(g-VSS d), respectively. Analysis based on polymerase chain reaction (PCR) and denaturing gradient gel electrophoresis (DGGE) showed a gradual shift of microbial population with the increase of DMP loading.