Nanofiltration of wastewater from the fishmeal industry

The wastewaters generated in fishmeal production, the average flow rates of which are 1100m3/h for a plant capacity of 100 ton fish/h, bear a high organic load, and therefore should not be discharged directly into the sea without a suitable treatment in order to prevent negative impacts in the environment. On the other hand, these effluents contain a significant amount of potentially valuable proteins. Nanofiltration (NF) reduces the organic load from the fish meal wastewaters and simultaneously promotes their partial desalination making possible water reuse in the plant. On the other hand, the proteins concentrated stream can be recycled directly into the fishmeal process, improving its quality and the economic profits from the raw material. Bearing in mind the high concentration of suspended matter in these effluents microfiltration pretreatment is recommended. An effluent from a fishmeal plant located in Talcahuano, Chile, has been characterized and microfiltrated. A ceramic multi-channel membrane Kerasep NanoNOlA (MWCO = 1 kDa, 19 channels, ID = 2.5 mm and L = 0.855m) was used in the NF experiments. The operating conditions have been optimized in total recycling mode and the subsequent concentration experiments have been carried out at 5 bar, 4m/s, ambient temperature and natural pH. The results of this work clearly show that NF is an efficient and ecologically suited environmental technology for decontamination and recycling of wastewaters generated in fishmeal production as it allows both recycling of water (permeate stream) and proteins (concentrate stream) into the fishmeal process beside the environmental pollution abatement. Although the membrane fouling is severe, the membrane can be easily cleaned through a basic washing.