Biokinetic behaviour of autochthonous halophilic biomass at different salinity: comparison between activated sludge and granular sludge systems

Abstract

The main goal of this study was the evaluation of the impact of increasing salinity on halophilic biomass in forms of flocculent and granular sludge for the treatment of hypersaline fish-canning wastewater, focusing on the metabolic behavior of autotrophic biomass. For this purpose, two sequencing batch reactors, one with aerobic granular sludge (GSBR) and the other with flocculent activated sludge (SBR) were monitored. In both reactors, a halophilic biomass was cultivated from a real saline wastewater collected from a fish-canning industry. The salt concentration was stepwise increased (2 gNaCl L-1) from 30 gNaCl L-1 to 50 gNaCl L-1. Therefore, ammonia and nitrite uptake rates for granular and flocculent biomass were evaluated at each salinity increase. Both AUR and NUR tests revealed a high metabolic activity despite the extreme salinity environment. AUR ranged between 4.6 mgNH4-N gVSS-1 h-1 and 3.10 mgNH4-N gVSS-1 h-1 in the GSBR showing, on the whole, a decreasing trend with salinity increasing. In the SBR instead, AUR was mainly affected by the biomass ageing, while a slight dependency of salinity was observed only above 46 gNaCl L-1 when it started in decreasing. The nitrite uptake rate did not show any significant connection with the increasing salinity.