Method and system for synergic production of fresh water from sewage plant secondary effluent and strong brine

Abstract

A method and system for synergistically producing fresh water from the secondary effluent of a sewage treatment plant and concentrated brine, the method comprising the following stages: (1) suction and cross-flow of the secondary effluent of the sewage treatment plant through a microfiltration membrane to remove suspended matter; The treated secondary effluent flows into one side of the forward osmosis membrane as the raw material solution, and the concentrated brine produced by seawater desalination flows into the other side of the forward osmosis membrane as the drawing solution, so that the secondary effluent is concentrated and the concentrated brine is diluted; (3) the diluted Concentrated brine passes through the reverse osmosis membrane to form fresh water, and the diluted concentrated brine is concentrated to the concentration of seawater and discharged into the sea; (4) Add iron salt dephosphorization agent to the concentrated secondary effluent, denitrification after dephosphorization Nitrogen removal treatment; the system includes a pretreatment tank, a forward osmosis separation tank, a desalinated water recovery tank and a concentrated water treatment tank. The invention can not only extract fresh water resources from the secondary effluent to realize zero discharge of waste water, but also can utilize concentrated brine discharged from seawater desalination, avoiding the influence of discharge on sea areas.

Description

technical field [0001] The invention relates to a method for producing fresh water by using forward osmosis membrane and reverse osmosis membrane technology, using concentrated brine from a seawater desalination plant and secondary effluent from a sewage treatment plant as raw materials, and belongs to the technical field of sewage treatment. Background technique [0002] In many coastal cities, most of the secondary effluent from urban sewage treatment plants is directly or indirectly discharged after advanced treatment reaches the first-level A or first-level B standard of the "Pollutant Discharge Standards for Urban Wastewater Treatment Plants" (GB18918-2002). Entering the sea, on the one hand, will cause potential pollution to the offshore marine environment, and on the other hand, it will also cause a great waste of fresh water resources. The advanced treatment methods of sewage mainly include coagulation / sedimentation / filtration method, ultrafiltration / reverse osmosis ...

AI Technical Summary

Problems solved by technology

[0004] Aiming at the problems of high energy consumption, easy membrane pollution and secondary pollution of concentrated brine produced by seawater desalination in the advanced treatment process used in the existing sewage regeneration and reverse osmosis process, the invention provides a secondary sewage treatment plant A method for synergistic production of fresh water from effluent and concentrated brine, which uses forward osmosis membrane and reverse osmosis membrane separation technology to combine sewage treatment and seawater desalination to synergistically produce fresh water

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