Tannery wastewater treatment by periodic biofilm system: process performances and biofilm characterisation

The paper reports the results obtained treating real tannery wastewater by a integrated process in which ozone was dosed in the recirculation stream of a periodic submerged filters (SBBR). Process performances resulted very satisfactory with COD, ammonia and TSS average removals, (96%), (99%) and (98%) respectively. The process was characterized by very low specific sludge production (0.05 kgVSS/kgCODremoved). Biomass in the SBBR, that has grown as granules, was characterised by different measurements (biomass concentration, extracellular polymeric substances, cellular protein and biomass density). Biomass density resulted very high, i.e. 170 gTSS/Lbiomass, and this permitted to achieve a biomass concentration such high such as 40 gTSS/Lbed. Such biomass concentration didn't cause any decrease of biomass metabolic activity as proved by its high total protein content (40% of organic matter), a parameter frequently used as an indicator of microorganisms activity.