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

Abstract

The invention provides a method and system for synergic production of fresh water from sewage plant secondary effluent and strong brine. The method comprises the following phases: (1) suction and cross flow filtration are carried out for secondary effluent of the sewage plant to pass through a micro-filtration membrane, and suspensions are removed; (2) pretreated secondary effluent flows to one side of a forward osmosis membrane and is used as a feed solution, strong brine generated from seawater desalination flows to the other side of the forward osmosis membrane and is used as a draw solution, and the secondary effluent is condensed and strong brine is diluted; (3) diluted strong brine passes through a reverse osmosis membrane to form fresh water, and diluted strong brine is condensed till the concentration is equal to the salt content of seawater and discharged to sea; (4) a ferric salt agent for removing phosphate is added into the condensed secondary effluent, after phosphate removal, denitrification treatment is carried out for nitrogen removal; the system comprises a pretreatment pool, a forward osmosis separation pool, a desalted water recycling tank and a concentrated water treatment pool. A fresh water resource can be extracted from the secondary effluent, in order to realize zero discharge of the waste water; strong brine discharged from seawater desalination can be utilized, in order to avoid influence of discharge on marine site.

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

Images