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Fish Processing Wastewater Treatment
Brines recovery membrane UF & NF system for fish processing industry
Water resources protection from pollution and exhaustion is one of the most important environmental targets. Fish processing requires large amounts of water. Fish processing wastewater has a high organic content, and subsequently a high chemical oxygen demand (СOD), because of the presence of blood, tissue, and dissolved protein. It also typically has a high content of nitrogen and phosphorus. Techniques for treating industrial wastewater in this sector include different processes and equipment combination.
Industrial production of the salted fish products based on the fish pickling in concentrated NaCl brines. Waste brine generated after the fish pickling is a complex biochemical system consists of concentrated NaCl solution, salt-soluble protein, tissular and bacterial enzyme.
The presentation covers the application of the hybrid membrane technology of ultrafiltration under vacuum (UFV) and low-pressure nanofiltration (NF) for concentrated brines treatment as well as the wastewater treatment plants (WWTP) design features based on these technologies. Progressive development of the membrane and vacuum technologies makes it possible to create compact high-performance water and wastewater treatment equipment with low power consumption and zero operating costs for the removable elements. Moreover, when required, it is possible to increase WWTP capacity due to modular-type construction.
The technical and economic advantages of WWTP built according to the hybrid technology:
Fish processing waste brine treatment process flowsheet
The pretreatment stage is represented only by rough mechanical waste brine filtration for the removal of particulate pollutants. The first main unit of WWTP is ultrafiltration under vacuum with the charged polymeric UF membranes with NMWCO from a 200 kDa to a 250 kDa. Ultrafiltration under vacuum is the most suitable choice for heavily polluted complex wastewaters from organic compounds such in the case of the fish processing waste brines. ultrafiltration under vacuum unit ensures treatment of wastewater with high salt concentration from organic compounds, oil products and suspended solids. In order to disinfect waste brines from bacteria, which can exist in concentrated salt solution, the NaClO disinfectant is dosed to UFV unit.
The ultrafiltration under vacuum unit consists of flat plate membrane module set plunged into the conical tank with wastewater. During the ultrafiltration under vacuum process wastewater level is automatically maintained under the membrane module set. For the continuous membranes surface treatment ultrafiltration under vacuum unit is equipped with agitating device and pressed air delivery system. Periodically, when the concentration of the pollutants achieved concentration design maximum, wastes are discharged into the sludge thickener. After the end of the thickening process solid wastes discard wastes are discarded to the off-site waste processing plants.
Table.1. The industrial WWTP working results:
Represented hybrid membrane technology of ultrafiltration under vacuum, low-pressure nanofiltration (NF) and sorption on activated carbon for concentrated brines treatment is highly recommended for implementation in the WWTP of fish processing industry by interested investors. These WWTP ensure fine waste brine treatment from suspended solids and organic substances according the State standards. The implementation of the represented technology is increase the cost-effectiveness and economic feasibility of industrial enterprises and gives opportunity of establishment of water recycling with NaCl utilization.