Method and system for extracting fresh water from sewage with synergy of forward osmosis and electrodialysis

Abstract

The invention provides a method and system for extracting fresh water from sewage with synergy of forward osmosis and electrodialysis. The method comprises the three stages: secondary effluent pretreatment, forward osmotic membrane separation and drawing liquid regeneration; in the secondary effluent pretreatment stage, suspended solids are removed from secondary effluent of an urban sewage treatment plant by utilizing a mechanical filtering function of micro-filtration membrane holes; in the forward osmotic membrane separation stage, the secondary effluent is concentrated, NaCl aqueous solution is diluted; in the drawing liquid regeneration stage, fresh water is collected and the concentrated NaCl aqueous solution is recycled. The system comprises a secondary effluent pretreatment tank, a forward osmotic separation tank and a drawing liquid regenerator. According to the method and system for extracting the fresh water from the sewage with the synergy of the forward osmosis and the electrodialysis, the forward osmosis technique and the electrodialysis technique are combined; on one hand, the fresh water resource can be recycled from the diluted drawing liquid, and one the other hand, the regeneration and utilization of the drawing liquid can be achieved; therefore, the stable and high concentration of the drawing liquid on one side of the drawing liquid in the forward osmotic separation process is ensured, high membrane flux is ensured, and the scaling possibility in the electrodialysis process is reduced.

Description

technical field [0001] The invention relates to a method for producing fresh water by applying forward osmosis and electrodialysis technology and using secondary effluent of a sewage treatment plant as a raw material, belonging to the technical field of sewage treatment. Background technique [0002] In view of the current situation of shortage of fresh water resources, the effluent of sewage treatment plants can be reused for daily miscellaneous purposes, industrial production or agricultural production process after advanced treatment, which can alleviate the problem of water resource shortage to a certain extent, and has good social benefits and environmental benefits. At present, the advanced treatment methods adopted by sewage treatment plants are mainly coagulation / sedimentation / filtration method or ultrafiltration / reverse osmosis treatment technology. The effluent water quality obtained by coagulation / sedimentation / filtration method is not good enough to provide user...

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Problems solved by technology

[0004] Aiming at the problem that the existing sewage treatment technology cannot provide good water quality, in order to effectively extract fresh water resources from sewage, realize the regeneration and reuse of sewage, and alleviate the problem of shortage of fresh water resources, the present invention provides a method that can be recovered from the secondary effluent of sewage plants. A method for extracting fresh water from sewage in cooperation with forward osmosis and electrodialysis of fresh water, and providing a system for realizing the method at the same time

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