Treatment of tannery wastewater in a sequencing batch reactor

The aim of the research was to study the treatability of tannery wastewater by a sequencing batch reactor (SBR) compared with a continuous flow full s cale reactor. The experimental work presented in this paper was carried out on a laboratory scale anoxic-aerobic SBR fed with tannery wastewater comin g from a full scale continuous flow treatment plant located in S. Miniato ( Pisa, Italy). After a long acclimation period, a complete and stable nitrif ication has been developed. The denitrification was always performed withou t any additional carbon source with good results when influent COD/TKN rati o was higher than 8 and with a higher rate compared to that obtained in the continuous plant. When high effluent nitrate occurred, it was due only to stoichiometric (not kinetic) limitations. The organic substrate removal occ urred mainly during the anoxic period and a high affluent COD (refractory) was often present at the end of the process. This research has shown the su itability of the industrial wastewater (particularly tannery wastewater) tr eatment by SBR because of its several advantages compared to the continuous reactors: i.e. a higher versatility and the possibility to work with highe r loads (smaller volumes), by selecting through thr cyclic concentration gr adients, a biomass resistant to the presence of inhibiting substances (ofte n encountered in industrial wastewaters). (C) 1999 IAWQ Published by Elsevi er Science Ltd. All rights reserved.