Wastewater Treatment of Tanneries Industry through Bio-ozone-biotreatment

This paper reports the results obtained during an investigation aimed at evaluating the laboratory-scale performance of an innovative process integrated with ozonation for the efficient treatment of tannery wastewater. In this process, biological degradation which carried out in a sequencing batch biofilm reactor (SBBR), is combined with chemical oxidation by ozone. The tannery wastewater treatment was carried out on a real primary effluent coming from a centralized plant treating wastewater produced by a large tannery district in Iran. SBBR performance both without and with ozonation, was assessed with very satisfactory results. The results showed that the integrated process was able to achieve high removal efficiencies for COD, TSS, surfactants and color with residual concentrations much lower than the current discharge limits. In particular, in the latter instance of the recorded COD and TSS average removals were (93%) and (99%) in phase I and (97%) and (99%) in phase II respectively. During the investigation biofilm properties (biofilm concentration and biofilm density) and flow dynamics aspects (head loss, shear stress, bed porosity) were also studied. Furthermore, the process was characterized by a very low sludge production (i.e., 0.1 kg dry sludge/m3 of treated wastewater) and high biofilm density (i.e. 87-122 gVSS/Lsludge) both contributing to a rather high biofilm concentration (i.e. 31-44 gTSS/Lfilter) with interesting repercussions on treatment costs (about 1.5 € per m3 of wastewater).