Performance enhancement of dissolved air flotation column in removing low concentrations of heavy fuel oil by adding powdered activated carbon

摘要

In this study, the effect of adding walnut shell-based powdered activated carbon (WS) to a bench-scale dissolved air flotation (DAF) column on oil removal was investigated. All experiments were conducted using synthetically prepared wastewater containing low but stable concentrations of heavy fuel oil. After comparing the effect of different WS doses from 0 (blank) to 40 mg/L at the saturator pressure of 5 bar and 10 min flotation time, 20 mg/L WS was chosen as the optimal concentration. In order to find the best flotation time for efficient use of WS capacity, experiments were repeated with and without 20 mg/L WS at longer flotation times. According to the obtained results, by adding WS, the removal efficiencies of oil and grease (O&G) and total petroleum hydrocarbons (TPH) after 60 min flotation time and without adding any coagulant, increased from 57.6 and 63.4% to 78.1 and 86.8%, respectively. By analyzing the samples taken at the flotation times of 10, 30, and 60 min, it was found that the most adsorbed TPH or nonpolar extractable hydrocarbons during the 60 min flotation time were removed during the first 10 min. Also, the TPH/O&G ratio was decreased, by increasing the flotation time.