Evaluation of the treatability of a spearmint essential oil wastewater by up-flow anaerobic sludge blanket

Spearmint essential oil wastewater (SEOW) generally contains large amounts of organic matter, including oil and grease, chemical oxygen demand (COD), and phenolic compounds, and inorganic contents, and also has a strong aromatic odor and dark color. In this study, the pollutant removal performance of an up-flow anaerobic sludge blanket (UASB) reactor used for the treatment of SEOW was investigated. During the 102 days UASB operation at high sludge retention time and hydraulic retention time of 60 h, organic loading rate (OLR) was increased from 0.12 to 2.70 kg COD/m3.d through increasing influent SEOW concentration. With increasing OLR from 0.12 to 2.70 kg COD/m3.d, the concentration of COD, phenol and turbidity in the influent of UASB were increased to 6757.5±214.2 mg/L, 382.7±87.5 mg/L, and 336.1 NTU, respectively. At the highest OLR employed, the steady state average removal efficiencies of COD, phenol and turbidity were 71.8±1.9%, 63.1±6.0%, and 78%, respectively. The results of the present study indicate the good potential of the UASB in terms of pollutant removal performance for the treatment of SEOW. Nevertheless, the characterization of the effluent achieved by the UASB reactor showed that this wastewater requires post-treatment processes to meet Iran s Environmental Protection Organization standards for agricultural reuse.