System and method for realizing zero discharge of wastewater and recovery of saltpeter

The invention discloses a system and a method for realizing zero discharge of wastewater and recovery of saltpeter. The system comprises a membrane concentration pretreatment unit, a membrane concentration unit, an evaporation salt extraction pretreatment unit and an evaporation salt extraction unit which are arranged along a water supply direction. The method comprises the steps of pretreatment, membrane concentration, deep treatment and evaporation salt extraction treatment on the wastewater. According to the system, the pretreatment unit is introduced, so that the membrane treatment unit can operate stably, the service life of the membrane treatment unit is prolonged, the treatment efficiency of the membrane treatment unit is improved, and the system has the advantages of reasonable design, low energy consumption, low equipment investment and maintenance cost, low operation and maintenance difficulty, high saltpeter recovery rate, high saltpeter product purity, low carnallite yield and the like; zero emiss