title: Occurrences and behaviors of naphthenic acids in a petroleum refinery wastewater treatment plant.
abstract: Naphthenic acids (NAs) are one class of compounds in wastewaters from petroleum industries that are known to cause toxic effects, and their removal from oilfield wastewater is an important challenge for remediation of large volumes of petrochemical effluents. The present study investigated occurrences and behaviors of total NAs and aromatic NAs in a refinery wastewater treatment plant, located in north China, which combined physicochemical and biological processes. Concentrations of total NAs were semiquantified to be 113-392 μg/L in wastewater from all the treatment units, and the percentages of aromatic NAs in total NAs was estimated to be 2.1-8.8%. The mass reduction for total NAs and aromatic NAs was 15±16% and 7.5±24% after the physicochemical treatment, respectively. Great mass reduction (total NAs: 65±11%, aromatic NAs: 86±5%) was observed in the biological treatment units, and antiestrogenic activities observed in wastewater from physicochemical treatment units disappeared in the effluent of the activated sludge system. The distributions of mass fractions of NAs demonstrated that biodegradation via activated sludge was the major mechanism for removing alicyclic NAs, aromatic NAs, and related toxicities in the plant, and the polycyclic NA congener classes were relatively recalcitrant to biodegradation, which is a complete contrast to the preferential adsorption of NAs with higher cyclicity (low Z value). Removal efficiencies of total NAs were 73±17% in summer, which were higher than those in winter (53±15%), and the seasonal variation was possibly due to the relatively high microbial biotransformation activities in the activated sludge system in summer (indexed by O3-NAs/NAs). The results of the investigations indicated that biotransformation of NA mixtures by the activated sludge system were largely affected by temperature, and employing an efficient adsorbent together with biodegradation processes would help cost-effectively remove NAs in petroleum effluents.
authors: †Laboratory for Earth Surface Processes, College of Urban and Environmental Sciences, Peking University, Beijing 100871, People's Republic of China.
authors: Beili
authors: B
authors: Wang
authors: †Laboratory for Earth Surface Processes, College of Urban and Environmental Sciences, Peking University, Beijing 100871, People's Republic of China.
authors: Yi
authors: Y
authors: Wan
authors: ‡Chinese Academy of Sciences, State Key Laboratory of Environmental Aquatic Chemistry, Ecoenvironmental Science Research Center, Beijing 100085, People's Republic of China.
authors: Yingxin
authors: Y
authors: Gao
authors: †Laboratory for Earth Surface Processes, College of Urban and Environmental Sciences, Peking University, Beijing 100871, People's Republic of China.
authors: Guomao
authors: G
authors: Zheng
authors: ‡Chinese Academy of Sciences, State Key Laboratory of Environmental Aquatic Chemistry, Ecoenvironmental Science Research Center, Beijing 100085, People's Republic of China.
authors: Min
authors: M
authors: Yang
authors: §Petrochina Ji Dong Oilfield Company, Tangshan, 063200 Hebei, People's Republic of China.
authors: Song
authors: S
authors: Wu
authors: †Laboratory for Earth Surface Processes, College of Urban and Environmental Sciences, Peking University, Beijing 100871, People's Republic of China.
authors: Jianying
authors: J
authors: Hu
mesh_terms: D002264:Carboxylic Acids / Q000032:analysis*; D002681:China; D020847:Estrogen Receptor Modulators / Q000032:analysis; D010084:Oxidation-Reduction; D010578:Petroleum / Q000032:analysis*; D012621:Seasons; D014865:Waste Disposal, Fluid; D062065:Wastewater / Q000737:chemistry*; D018508:Water Purification / Q000379:methods*
chemical_list: D002264:Carboxylic Acids; D020847:Estrogen Receptor Modulators; D010578:Petroleum; D062065:Wastewater; C046170:naphthenic acid