Method and system for treating saline wastewater to zero discharge and recycling

Abstract

The invention discloses a method and system for treating saline wastewater to zero discharge and recycling. The method comprises the following steps: pretreating, and removing suspended substances, alkalinity, COD (chemical oxygen demand) and hardness in wastewater, including grids, a conditioning tank, flotation, composite separation and ion exchange. The system comprises a special membrane recycling unit and a low-temperature evaporation crystallizing unit, wherein the special membrane recycling unit is composed of an ultrafiltration unit, a common reverse osmosis unit and a special reverse osmosis unit, and can recycle more than 95% of clean water; and the low-temperature evaporation crystallizing unit is composed of an electrolytic oxidation device and a low-temperature evaporator. The concentrated solution generated by the membrane recycling unit is subjected to electrolytic oxidation to remove residual COD in the wastewater, and enters a WLST evaporation crystallizing system to obtain solid salt and condensed water by evaporation crystallization; and sludge is subjected to the WLSD unit for dehydration until the water content is smaller than 60%. After the wastewater is treated by the WLZD system, the zero discharge of wastewater is implemented, the total wastewater recovery rate is higher than 98%, and the recovered water and the solid salt can be reclaimed, thereby implementing decrement, recycling and hazard-free treatment.

Description

technical field [0001] The present invention relates to a treatment method of saline wastewater, more precisely, relates to a treatment method of saline wastewater which recovers water and solid matter separately after the saline wastewater is treated by a multi-stage treatment unit and its system. Background technique [0002] Water resources are basic natural resources and strategic economic resources, and are an important foundation for sustainable economic and social development, maintaining ecological balance, and maintaining a beautiful environment. According to the "World Water Resources Development Report" released at the 4th Water Resources Forum in Mexico City on March 22, 2006, the global water consumption increased by 6 times in the 20th century, and the growth rate was twice that of the population growth rate. 1.1 billion people are short of water, and 2.6 billion people cannot guarantee water sanitation; by 2030, the contradiction between the supply and demand...

AI Technical Summary

Problems solved by technology

2. Direct reuse, using brine as flushing water and other places that do not have strict water quality requirements, but this method has limited ability to digest brine

The former treatment method only concentrates the waste water and cannot realize the zero discharge of waste water. The recovery rate of this kind of waste water is generally below 60%, and there is still a large amount of concentrated liquid to be treated.

The latter method directly adopts evaporation and crystallization after pretreatment, which has a large scale of treatment and high investment and operation costs.

Due to the use of evaporation and concentration is a process of extracting clear water, the content of pollutants and salt in the residual water is getting higher and higher, and a strong bubble layer will be generated during the evaporation process, which will reduce the evaporation efficiency and make it difficult to achieve the predetermined goal

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