Scale-up of fluidized bed reactor for treatment of commercial laundry wastewater plus domestic sewage: optimization of operational conditions

Abstract

The LAS (alkylbenzene linear sulfonate) is the most widely used surfactant worldwide. Its presence in the environment damages the public and environmental health. Among the reactors setups applied for the LAS removal has been obtained satisfactory results with application of the fluidized bed reactor (FBR). To date, most of these studies were performed in bench scale (volume close to 1 L) to diluted commercial laundry wastewater. The purpose of the present study is the scale-up of the FBR. Moreover, it is intended to treat commercial laundry wastewater in combination with domestic sewage, in order to evaluate the actual composition of what is usually discharged into the environment. In order to evaluate the influence of the presence of ethanol as a co-substrate in LAS degradation kinetics, kinetic parameters of degradation of the anionic surfactant will be obtained through bath tests in the presence and absence of that alcohol. The fluidized bed reactor will be operated in enlarged scale in four operating phases differentiated by the HRT: 18h, 14h, 12h and 8h for LAS concentration (dilution of the commercial laundry in domestic sewage) determined according to the results of the kinetics tests. The greatest challenges in scaling - ups is the difficulty of maintaining the mass transfer. The upflow velocity has a direct influence on this parameter, therefore, it will be tested over two expansion/fluidization velocities (vf) of the bed, besides that one established in all steps (1,3vmf), for the HRT in that phase with highest LAS removal efficiency . Through hydrodynamic tests is intended to measure the flow regime and identify flow anomalies to different HRT and flow velocities applied. Physico-chemical characterization of laundry wastewater and domestic sewage will be performed prior their use in the bath tests and reactor feeding. Periodic monitoring analyzes of the influent and effluent of the reactor will be done, such as COD, pH, alkalinity, volatile organic acids, total volatile solids and LAS. Biomass sample will be taken fot the HRT with the highest LAS removal efficiency , including the tree different flow velocities. Kinetic tests as well as inoculation of the reactor in enlarged scale will be made with biomass from activated sludge systems. It is an original research, since it is intended to identify in scale-up a lower HRT (hydraulic retention time) than those used by researchers from the Laboratory of Biological Processes Group (LPB) of the EESC-USP.