Technology for desalting and recycling salt-contained industrial wastewater containing calcium and magnesium and sulfate ions

Abstract

The invention discloses a technology for desalting and recycling salt-contained industrial wastewater containing calcium and magnesium and sulfate ions. The technology is characterized in that impurities are removed by pretreating; calcium and magnesium can be removed by resin softening; the obtained wastewater is further treated by reverse osmose, and the produced water is recycled; concentratedwater is treated by advanced oxidation to remove organic matters and then treated through a nanofiltration system to remove sulfate ions so as to obtain strong brine rich in monovalent cation salt; the strong brine is further concentrated by high-pressure reverse osmosis to obtain a regenerated liquid; the regenerated liquid is treated by resin softening again in order to be used for resin generating; the obtained strong brine is treated by nanofiltration and then is further concentrated by high-pressure reverse osmosis; the water produced by high-pressure reverse osmosis and the water produced by resin softening are mixed and then treated by reverse osmosis; calcium and magnesium in the wastewater can be removed by the resin softening, so that the pollution of a reverse osmosis membrane can be obviously reduced, and the running stability of a high reverse osmosis system can be greatly improved; the water production rate is beyond 95%; moreover, calcium and magnesium in the strong brine used for regenerating resin and sulfate ions in the concentrated water obtained in first-stage reverse osmosis are separated by nanofiltration, the recycling of the waste liquid in resin regenerating and the concentrated water obtained in reverse osmosis is achieved, as a result, the operation cost is decreased, and the drained strong brine of the whole system is less than 3%.

Description

technical field [0001] The invention relates to the field of advanced treatment of industrial wastewater, in particular to a process for desalination and reuse of salt-containing industrial wastewater containing calcium, magnesium ions and sulfate ions. Background technique [0002] In the production processes of coal chemical industry, petrochemical industry, electric power, steel and seawater desalination, etc., a large amount of saline wastewater will be produced. It is of great practical significance to treat these saline wastewater and realize the recycling of wastewater. At present, the salinity wastewater is generally reused by reverse osmosis-based membrane treatment, but when the calcium, magnesium and sulfate ions in the wastewater are high, it is easy to cause calcium sulfate scaling during the reverse osmosis operation, which is very difficult. It is difficult to clean with general cleaning solution, and the high calcium and magnesium ions and sulfate ions also l...

AI Technical Summary

Problems solved by technology

At present, the salinity wastewater is generally reused by reverse osmosis-based membrane treatment, but when the calcium, magnesium and sulfate ions in the wastewater are high, it is easy to cause calcium sulfate scaling during the reverse osmosis operation, which is very difficult. It is difficult to clean with general cleaning solution, and the high calcium and magnesium ions and sulfate ions also limit the product water recovery rate of the reverse osmosis system

Therefore, the water needs to be softened before entering the reverse osmosis system. Commonly used softening methods are chemical softening and cation exchange resin softening. Chemical softening needs to add a certain amount of chemical. The dosage of chemical should be strictly controlled, and the operating cost is high; Cation exchange resin is a mature softening method with stable performance. However, the capacity of ion exchange resin is limited. After saturation, it needs to be regenerated with a regenerant. The regenerant is generally a high-concentration sodium chloride solution. The cost of the regenerant is the softening of the cation resin. Main composition, at the same time, a certain amount of concentrated brine containing calcium and magnesium ions needs to be treated, which limits the economy and application of ion exchange resin softening process

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