Surfactants removal from industrial laundry wastewater using combined bio-oxidative and physical/chemical processes

Aim of this work is the evaluation of bioxidization phases efficiency in the treatment of surfactants discharged from textile industries. We have quantified, in wastewaters coming from industrial dye-works or laundries, the removal of COD and TS reachable using classic oxidization phases with respect to treatments provided by final phases of clariflocculation or clariflotation. The analyzed data from dye-works present a decisive increase, both in COD and in TS removal, using coagulants in final sedimentation phases. COD outfalls concentrations can permit discharge in surfaces waters using classic bioxidization phases, while, only using flocculants in sedimentation, TS output values, (varying from 2 to 5 mg/l) are not far from Italian law limits for discharge in public sewers. The case study, a bioxidization scheme with final flotation applied to a laundry wastewater, reveals that most part of COD reduction is carried out in the aeration phase. TS removal has been realized with the same efficiency both in oxidization and in flotation phase, so, taking in account ingoing values, it appears that oxidization plays the main role in TS absolute abatement. In case of treatment limited to equalization and oxidization phases, averaged removal efficiency reach 64,5 % and 70 % respectively for COD and TS. In this case output values are far to allow discharge in public sewers and appear similar to the standards adopted by sewer service managers for accepting discharge with increased fee payment.