Aerobic Granular Sludge Reactors for the Treatment of Chlorinated Aromatic and Aliphatic Compounds

Due to their toxicity even at low concentration and their widespread use in several anthropic activities, chlorinated organic pollutants have been considered an environmental priority to deal with. Compared to non-chlorinated compounds, the presence of strong C-Cl bound in their molecular structure makes them resistant to biological degradation and persistent in both water and soils. In this study, two Granular sludge Sequencing Batch Reactors (GSBR) were run for the biological treatment of synthetic wastewater containing a mixture of 1,2,4-trichlorobenzene and 2,4-dichlorophenol (1,2,4-TCB and 2,4-DCP) and 1,2-dichloroethane (1,2-DCA), respectively, using readily biodegradable carbon sources as the primary (growth) substrates. For 1,2,4-TCB and 2,4-DCP degradation, GSBR-1 was operated as a Sequencing Batch Bubble Column (SBBC) reactor, while GSBR-2 was started-up and properly configured in order to minimize 1,2-DCA losses due to volatilization. Performance of both GSBRs in terms of 1,2,4-TCB, 2,4-DCP and 1,2-DCA removal efficiencies were evaluated throughout the research: toxic compounds were completely removed and granules were successfully maintained in the reactors. The treatment of a mixture of highly toxic 1,2,4-TCB and 2,4-DCP and the possibility to treat volatile chlorinated compounds by aerobic granules are of novelty and will contribute in extending the potential applications of the aerobic granular sludge technology.