On-site treatment of dye-bath wastewater with a two-stage polymer extraction and biological regeneration process.

In this study, we propose a two-stage process consisting in an extraction stage, realized by contacting the dye bath stream with absorptive polymers, followed by polymer regeneration in a two-phase partitioning bioreactor (TPPB). TPPBs consist of a cell-containing aqueous phase and a sequestering/partitioning phase (generally polymer beads when applied to liquid streams decontamination) able to reduce the aqueous concentrations of toxic substrates to which the biomass is exposed. Restoring the thermodynamic equilibrium, following the substrate consumption, determines the pollutant release to the cells based on metabolic demand (Quijano et al., 2009). The two-stage process, previously applied to soil decontamination (Tomei et al., 2013), is well suitable for dye removal because, given the different optimal operating conditions characterizing the extraction and regeneration stages, allows the separate optimization of the performance of each stage. A possible practical application of the proposed process is the on-site polymer extraction for dye removal achievable in very short times (of the order of hours) and the subsequent bioregeneration of the contaminated polymer beads utilized in more extraction cycles. Objective of this study is to investigate and optimize the operating conditions of the two-stage process applied to the decolourization of a contaminated stream containing the reactive azo dye Remazol Red (RR).