Treatment of refinery wastewater using Arthrobacter chlorophenolicus A6 in an upflow packed bed reactor

Abstract

In this study, refinery wastewater collected from Guwahati, India, was treated in an upflow packed bed reactor (PBR) with immobilized Arthrobacter chlorophenolicus A6. The wastewater was initially characterized using standard methods. The toxicity of the wastewater was determined using aerobic mixed microbial consortia following the resazurin toxicity assay. As the chemical oxygen demand (COD) level in the raw refinery wastewater was very low (190 mg l−1), the raw wastewater was spiked with a mixture of substituted phenol at different concentrations. The batch shake flask experiment revealed that the COD removal efficiency was found to be less when the raw refinery wastewater was not spiked with nutrient. On the other hand, when supplemented with nutrients in the form of mineral salt medium, more than 98% COD removal was achieved. The PBR was operated by varying the influent phenolic concentration in the range of 250–350 mg l−1 and at a hydraulic retention time of 12.5 h. Results indicated that more than 99% pollutant removal and 94% effluent toxicity removal were achieved at a combined pollutants loading rate of 1707 mg l−1 d−1. However, at higher pollutants loading rate, the reactor performance was found to be unstable, due to the transient accumulation of toxic intermediate products such as chlorocatechol and nitrocatechol.