Use of a hybrid membrane bioreactor for the treatment of saline wastewater from a fish canning factory

A new pilot scale hybrid biofilm-suspended biomass membrane bioreactor was used to treat two wastewater streams generated in a fish canning factory. During a first stage, wastewater generated during tuna cooking with brine was treated. COD and N content were between 7.8–11.8 g COD/L and 1.2–1.8 g N/L, respectively. Salt concentration was up to 84 g/L. COD removal efficiency was affected by salinity, but after 73 operating days adaptation of the sludge to the hypersaline conditions took place. COD efficiency of 92% was obtained after adaptation of the sludge to the salinity.During a second stage, wastewaters generated during tuna cooking by steam injection were treated. HRT was fixed at 5 d. Organic loading rate was up to 4 kg COD/m3 d. COD concentration in the permeate was lower than 100 mg/L throughout this period. Salt concentration below 15 g/L did not affect nitrification. NLR was gradually increased up to 0.7 kg N/m3 d. Total nitrogen concentration in the permeate was lower than 100 mg N/L, and nitrate was below 65 mg N/L during the whole experimental period. Moreover, very low nitrate concentrations of less than 1 mg N/L were observed during the period in which a NLR up to 0.55 kg N/m3 d was applied.