Abstract
The paper presents the results of an analysis of a two-stage pilot plant for the removal of toluene and benzene from the exhaust air of an industrial wastewater treatment plant (WWTP). The two-stage air process combines a water scrubber and a biotrickling filter (BTF) in sequence, and treats air stripped from the liquid phase compartments of the WWTP. During the experimental period, the pilot plant treated an airflow of 600 Nm3h-1. Average concentrations of the waste air stream entering the water scrubber were 10.61 mg Nm-3 benzene and 9.26 mg Nm-3 toluene. The water scrubber obtained medium-high removal efficiencies (averages 51% and 60%, for benzene and toluene, respectively). Subsequent passage through the BTF allowed a further reduction of average concentrations, which decreased to 2.10 mg Nm-3 benzene and to 0.84 mg Nm-3 toluene, thereby allowing overall average removal efficiencies (REs) of 80% and 91% for benzene and toluene, respectively. Results prove the benefits obtained from a combination of different removal technologies: water scrubbers to remove peak concentrations and soluble compounds, and BTFs to remove compounds with lower solubility, due to the biodegradation performed by microorganisms.
Highlights
Benzene and toluene are typical components of oil and its derivatives
This paper presents the results of a two-stage process pilot application, combining water absorption with biotrickling filtration for the treatment of exhaust air stripped from the liquid process units of an oil refinery wastewater treatment plants (WWTPs)
Wash water used in the scrubber in this application was WWTP effluent; it contained small concentrations of bacteria that, in time, could colonize the scrubber that worked not just as a pure physical absorption system, and, in part, as a bioreactor itself
Summary
Benzene and toluene are typical components of oil and its derivatives Such compounds are abundantly present in refinery wastewater as well as in wastewaters from chemical and petrochemical industries. It has been observed that with specific biological reactors, and in the presence of specially-acclimated biomass, these compounds can be removed extremely quickly from waste streams, with negligible stripping from the liquid to air phase, even in the presence of continuous aeration (Capodaglio et al, 2010) These compounds are found in the exhaust air of mechanical-biological waste treatment plants (Schiavon et al, 2015a), in landfill biogas (Raboni et al, 2015), and in vehicles’ exhaust gases (Faber et al, 2013). Due to the toxic behavior of these compounds, it is essential to minimize their release into the environment and, into the atmosphere, in order to protect workers and the general public health
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