Abstract
A pilot scale Upflow Anaerobic Filter (UAF) treating tannery wastewaters was operated for 160 days. The UAF was fed with low
COD/SO4
2- ratio (SO4
2- = 1810 mg L-1, CODtotal = 2530 mg L-1) for the investigation of sulphate and COD removal as a function
of substrates limitation and ammonia and sulphide inhibition. Sulphate-reducing bacteria (SRB) out-competed methanogenic
bacteria due to the low influent COD/SO4
2- ratio, the high concentration of sulphide and the presence of inhibiting compounds in
tannery wastewater. An average sulphate removal of 53% and an average COD removal of 42% were obtained. Ammonia and
sulphide concentrations were found to play a major role in the process, and their effect was quantified. A simplified mathematical
model was calibrated under semi-steady conditions and no substrate limitation, and used to describe sulphide and ammonia
inhibition. Half-inhibition constants for ammonia (KNH4) and sulphide (KHS) of 180 mg L-1 and 480 mg L-1, respectively, were
obtained. No improvements of the biodegradability between the untreated tannery wastewater and the UAF effluent were
observed through respirometric tests.