title: A comprehensive evaluation of re-circulated bio-filter as a pretreatment process for petroleum refinery wastewater.
abstract: Conventional biological treatment process is not very efficient for the treatment of petroleum refinery wastewater (PRW) that contains high-concentration of organic contaminants. Prior to biological treatment, an additional pretreatment process for PRW is required for the effluent to meet the discharge standards. While re-circulated bio-filter (RBF) has been applied as a pretreatment process in several PRW treatment plants, its effects have not been comprehensively evaluated. In this study, the parameters of operation, the changes in pollution indexes and contaminant composition in an engineered RBF have been investigated. We found that mainly highly active de-carbonization bacteria were present in the RBF, while no nitrification bacteria were found in the RBF. This indicated the absence of nitrification in this process. The biodegradable organic contaminants were susceptible to degradation by RBF, which decreased the Biological Oxygen Demand (BOD5) by 83.64% and the Chemical Oxygen Demand (CODCr) by 54.63%. Consequently, the alkalinity and pH value of RBF effluent significantly increased, which was unfavorable for the control of operating parameters in subsequent biological treatment. Along with the decrease of CODCr, the RBF effluent exhibited a reduction in biodegradability. 834 kinds of recalcitrant polar organic contaminants remained in the effluent; most of the contaminant molecules having complex structures of aromatic, polycyclic and heterocyclic rings. The results of this study showed that RBF could efficiently treat PRW for biodegradable organic contaminants removal; however, it is difficult to treat bio-refractory organic contaminants, which was unfavorable for the subsequent biological treatment process operation. An improved process might provide overall guarantees for the PRW treatment.
authors.affiliation: State Key Laboratory of Heavy Oil Processing, Beijing Key Laboratory of Oil and Gas Pollution Control, China University of Petroleum, Beijing 102249, China. Electronic address: daixiaoli2007@163.com.
authors.forename: Xiaoli
authors.initials: X
authors.lastname: Dai
authors.affiliation: State Key Laboratory of Heavy Oil Processing, Beijing Key Laboratory of Oil and Gas Pollution Control, China University of Petroleum, Beijing 102249, China.
authors.forename: Chunmao
authors.initials: C
authors.lastname: Chen
authors.affiliation: State Key Laboratory of Heavy Oil Processing, Beijing Key Laboratory of Oil and Gas Pollution Control, China University of Petroleum, Beijing 102249, China.
authors.forename: Guangxu
authors.initials: G
authors.lastname: Yan
authors.affiliation: State Key Laboratory of Heavy Oil Processing, Beijing Key Laboratory of Oil and Gas Pollution Control, China University of Petroleum, Beijing 102249, China.
authors.forename: Yu
authors.initials: Y
authors.lastname: Chen
authors.affiliation: State Key Laboratory of Heavy Oil Processing, Beijing Key Laboratory of Oil and Gas Pollution Control, China University of Petroleum, Beijing 102249, China. Electronic address: cupgsh@163.com.
authors.forename: Shaohui
authors.initials: S
authors.lastname: Guo
mesh_terms: D001673:Biodegradation, Environmental; D057919:Biological Oxygen Demand Analysis; D019652:Extraction and Processing Industry; D005374:Filtration / Q000295:instrumentation*; D058465:Nitrification; D010578:Petroleum; D014865:Waste Disposal, Fluid / Q000379:methods*; D062065:Wastewater / Q000737:chemistry*; D014873:Water Pollutants / Q000032:analysis / Q000378:metabolism
chemical_list: D010578:Petroleum; D062065:Wastewater; D014873:Water Pollutants
keywords: Comprehensive evaluation; Petroleum refinery wastewater; Pretreatment; Re-circulated bio-filter