Recovery process for wastewater with high salt COD (chemical oxygen demand)

Abstract

Disclosed is a recovery process for wastewater with high salt COD (chemical oxygen demand). Wastewater with sodium chloride, sulfate, calcium ions, magnesium ions, nitrate, COD ions and the like is adopted as a raw material which is then vapored and concentrated to produce fresh water and a nearly-saturated solution in a condition that concentration is controlled by an antiscale agent; the nearly-saturated solution is subjected to clarification for solid-liquid separation to obtain calcium sulfate sediment and sulfate brine clarified liquid; the brine clarified liquid is subjected to a salt and sulfate separation process to obtain the sodium chloride, the sulfate, the fresh water and high-COD salt-making mother liquid; the salt-making mother liquid is subjected to high-temperature spray evaporation to obtain mixed abraum salt with the COD, the sodium chloride, the sulfate, nitrate and the like; circulating filtering liquid with ingredients similar to that of the salt-making mother liquid is adopted to separate the COD from inorganic salt including the sodium chloride, the sulfate, nitrate and the like in the mixed abraum salt through a vertical separator; the inorganic salt including the sodium chloride, the sulfate, nitrate and the like obtained at the bottom can be dissolved by the fresh water and then subjected to comprehensive utilization, COD filtering cakes in overflowingliquid are utilized as fuel, and the filtering liquid can be utilized cyclically.

Description

technical field [0001] The invention belongs to the technical field of sewage treatment, in particular to a high-salt COD waste water recycling process. Background technique [0002] COD is chemical oxygen demand. It is the amount of oxidant consumed when a certain strong oxidant is used to treat water samples under certain conditions. It is an indicator of the amount of reducing substances in water. Reducing substances in water include various organic matter, nitrite, sulfide, ferrous salt, etc. Therefore, chemical oxygen demand (COD) is often used as an indicator to measure the content of reducing substances in water. Known processes for producing inorganic salts from high-salt COD wastewater include: 1) After complex pretreatment, the wastewater is concentrated by membrane methods (reverse osmosis, electrodialysis, etc.), evaporated, and crystallized to separate inorganic salts, but the mother liquor for salt production contains COD High, large amount of miscellaneous s...

AI Technical Summary

Problems solved by technology

Known processes for producing inorganic salts from high-salt COD wastewater include: 1) After complex pretreatment, the wastewater is concentrated by membrane methods (reverse osmosis, electrodialysis, etc.), evaporated, and crystallized to separate inorganic salts, but the mother liquor for salt production contains COD High, large amount of miscellaneous salts; 2) Wastewater is concentrated by evaporation (distillation, flash evaporation, etc.) after complex pretreatment, and evaporated and crystallized to separate inorganic salts, but the same salt-making mother liquor contains high COD and large amount of miscellaneous salts

The above-mentioned processes all have problems such as large amount of pretreatment water, high processing requirements, large equipment, high COD content in the salt-making mother liquor, large amount of miscellaneous salt and difficult to use, high production cost, and long process flow, etc.

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