Activated sludge combined with powdered activated carbon ( PACT process ) for the petroleum industry wastewater treatment : A review

ISSN: 2410-9649 S. Jafarinejad / Chemistry International 3(4) (2017) 268-277 iscientic.org. 269 www.bosaljournals/chemint/ editorci@bosaljournals.com surrounding environment, and water reuse issues, the petroleum industry wastewaters need treatment with appropriate treatment technologies (Ghorbanian et al., 2014). Process wastewater pretreatment, primary treatment, secondary treatment, and tertiary treatment or polishing are general classifications of petroleum industry wastewater treatment (U.S. EPA, 1995; Benyahia et al., 2006; IPIECA, 2010; European Commission and Joint Research Center, 2013; Goldblatt et al., 2014; Jafarinejad, 2017a,b). In secondary treatment, dissolved oil and other organic pollutants may be consumed biologically by microorganisms (U.S. EPA, 1995; Jafarinejad, 2016c; 2017a,b). In real, organic matter can be oxidized into simple products (CO2, H2O, and CH4) under aerobic, anaerobic or semi aerobic conditions by microorganisms (naturally occurring, commercial, specific groups, and acclimatized sewage sludge). A C:N:P ratio (100:5:1) may be appropriate for growth of microorganisms (Ishak et al., 2012; Jafarinejad, 2017a,b). Biological treatment processes can be classified into two categories:  Suspended growth processes such as activated sludge process (ASP), powdered activated carbon treatment (PACT) process, sequencing batch reactors (SBRs), continuous stirred tank bioreactor (CSTB), membrane bioreactors (MBRs), and aerated lagoons; and  Attached growth processes such as trickling filters (TFs), fluidized bed bioreactor (FBB), and rotating biological contactor (RBC) (EPA, 1997; IPIECA, 2010; Ishak et al., 2012; Jafarinejad, 2017a,b). Treatment of petroleum industry wastewater by a conventional process such as activated sludge may be hindered by the presence of recalcitrant organic compounds; therefore, tertiary treatments for wastewater polishing are required. Powdered activated carbon (PAC) adding to the activated sludge process can lead to a higher quality of treated wastewater, a more stable system and the production of reusable water (Campos et al., 2014). In this study, history, principles, mechanisms, and advantages of powdered activated carbon treatment (PACT) process, selection of carbon, typical configuration of a refinery wastewater treatment plant (WWTP) consisting of the PACT process, and application of the PACT technology for the petroleum industry wastewater treatment have been reviewed. HISTORY OF THE PACT PROCESS PACT system has been developed (U.S. Patent 3,904,518) by DuPont in the early '70s (Sublette et al., 1982; Campos et al., 2014). Robertaccio et al. (1972) and Robertaccio (1973) have reported on pilot scale treatment of wastewater from DuPont's Chambers Works plant in Deepwater, New Jersey (Sublette et al., 1982) and in real, the first installation was in New Jersey. Synergistic treatment improvements and lower costs in comparison with the sequential treatment processes have been seen (Heath, 1986; Foy and Close, 2007). In the 1980s, DuPont sold the patent to Zimpro. DuPont and Zimpro have designed most of the PACT systems in the world (Foy and Close, 2007). In real, according to Meidl (1992), Dupont, General Electric, Ciba-Geigy, Koch refining, Unocal, Exxon, Tenneco, Alcoa, BP oil, Bostik, Nalco, Tosco and others are some major users of the PACT technology (Meidl, 1992). Some researches was carried out and published on the theory of PACT technology in the 1970s. This process was a proprietary technology, therefore, there is limited published information on the application of this process (Foy and Close, 2007). PRINCIPLES OF THE PACT PROCESS Activated carbon (both PAC and granular activated carbon (GAC)) has been utilized for a long time in water and wastewater treatment due to its large surface area for adsorption (Tri, 2002; Jafarinejad, 2015; 2017a). PAC has a diameter of less than 200 mesh (Tri, 2002). Activated sludge treatment with PAC or PACT process is similar to the conventional activated sludge process, but in this process, PAC is added directly into the aeration tank or mixed with the influent of this tank. The removal of contaminants is achieved and enhanced by a combination of biodegradation and adsorption (Tri, 2002; IPIECA, 2010; Jafarinejad, 2017a). A schematic of a typical PACT process is shown in Fig. 1. Most of the PAC is recycled with the activated sludge, but the system needs a continuous makeup of fresh carbon (IPIECA, 2010; Jafarinejad, 2017a). According to Tri (2002) and Jafarinejad (2017a), the PACT process could generally remove organic compounds more efficiently than what would be expected from either biodegradation or adsorption alone. The dosage of PAC and the mixed-liquor-PAC-suspended-solids concentration are related to the sludge age as follows: