ANAEROBIC TREATMENT OF FISHERY WASTE-WATER USING A MARINE SEDIMENT INOCULUM

The effluent generated by the Chilean fishmeal industry during hydraul ic unloading of fish from ships is high in organic load. After recycli ng and primary treatment to remove fats and proteins, the effluent con tains 4-6 kg COD m(-3) and high salt content (an average of 1.85 kg SO 4= m(-3) and 16.2 kg Clm(-3)). Marine sediments and fresh pig manure w ere assayed as anaerobic inocula to purify this saline effluent. The m arine inoculum adapted better and faster at 37 degrees C, Showing a hi gher final methanogenic/sulphate-reducing bacteria ratio of 0.0025. Sp ecific methanogenic activity at 37 degrees C was 0.065 kg CH4 COD (kg VSS day)(-1), corresponding to 1.3 kg COD (kg VSS)(-1) in 20 days. Met hane production was inhibited at COD/SO4= ratios lower than 0.5. A 50% inhibition of the activity was found at 0.22 kg H2S m(-3), 53 kg Na()m(-3) and 10 kg SO4= m(-3) respectively; however, at the concentratio n range in the effluent neither was inhibitory. Kinetic parameters wer e obtained at 18 and 37 degrees C in mixed flow reactors. At those tem peratures, mu(max) values were 0.267 and 0.479 days(-1), while K value s for the Chen and Hashimoto model were 2.964 and 1.476, and the growt h yield factor (Y) was 0.19 kg VSS (kg COD)(-1). The activation energi es were estimated as 3.06 kJ mol(-1) for mu(max) and 27.51 kJ mol(-1) for K. showing that the saline wastewater treatment has a lower temper ature dependence than the non-saline one. It was concluded that, under these conditions of high organic load, fishery effluent can be anaero bically treated. (C) 1997 Elsevier Science Ltd.