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.

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. OLR up to 1.4 kg COD/m3 d was applied. Total nitrogen (TN) in the influent was between 1.2 and 1.8 g/L. Most of the TN was hydrolyzed to ammonia in the reactor. However, nitrification was not observed throughout the first stage. This was a result of the very high saline concentration of the wastewater. Fouling cause operational problems of operation in this system, and probably a longer experimental period might be necessary in order to estimate the effects of the salts on the membrane life. Biomass yield of only 0.03 g-VSS/g-COD was estimated. During a second stage, the wastewater generated during tuna cooking by steam injection was treated. HRT was fixed at 5 d. One of the main characteristics of the hybrid MBR is the high capacity and efficiency that were obtained, even considering that biomass concentration was below 2–4 g TSS/L throughout most of the period. Organic loading rate was up to 4 kg COD/m3 d. COD concentration in the permeate was lower than 100 mg/L. 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. Biomass yield during this period was around 0.12 g-VSS/g-COD.