Simultaneous methanogenesis and denitrification of pretreated effluents from a fish canning industry

A lab-scale hybrid upflow sludge bed-filter (USBF) reactor was employed to carry out methanogenesis and denitrification of the effluent from an anaero bic industrial reactor (EAIR) in a fish canning industry. The reactor was i nitially inoculated with methanogenic sludge and there were two different o perational steps. During the first step (Step I: days 1-61), the methanogen ic process was carried out at organic loading rates (OLR) of 1.0-1.25g COD l (- 1) d (- 1) reaching COD removal percentages of 80%. During the second step (Step II: days 62-109) nitrate was added as KNO3 to the industrial eff luent and the OLR was Varied between 1.0 and 1.25 g COD l (- 1) d (- 1). Tw o different nitrogen loads of 0.10 and 0.22 g NO3--N l (- 1) d (- 1) were a pplied and these led to nitrogen removal percentages of around 100% in both cases and COD removal percentages of around 80%. Carbon to nitrogen ratio (C:N) in the influent was maintained at 2.0 and eventually it was increased to 3.0, by means of glucose addition, to control the denitrification proce ss. From these results it is possible to establish that wastewater produced in a fish canning industry can be used as a carbon source for denitrificat ion and that denitrifying microorganisms were present in the initially meth anogenic sludge. Biomass productions of 0.23 and 0.61 g VSS: g TOC fed for Steps I and II, respectively, were calculated from carbon global balances, showing an increase in biomass growth due to denitrification. (C) 2000 Else vier Science Ltd. All rights reserved.