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Paper industry wastewater has become a major source of environmental pollution , threats to people's production and life , as well as life and health . According to statistical data presentation , the national pulp and paper industry wastewater effluent emissions accounted for about 10% -12% of the total , ranking third ; effluent chemical oxygen demand (CODcr) about the country's total emissions of 40 % -45% , ranking first. Black liquor contains large amounts of cellulose, pigments and inorganic salts , can make the water turn black and produce a special odor ; their BOD load of up to 5000 ~ 40000g / L, consume a lot of oxygen in water , so that deterioration of water quality ; papermaking wastewater in the large number of alkaline material , the pH of the entity sharp rise , damage to the water balance of the environment . In the papermaking process lye soaked section of black liquor generated waste lye is a major component of COD , the COD load of waste lye is about 20000-30000g / L, semi- cellulose content : ≤ 18.39g / L Chroma : ≤ 550 times . Nanofiltration for papermaking waste lye in the night have a good treatment effect , the use of black liquor nanofiltration membrane technology for recycling of waste lye , can effectively remove most of the COD, but can be directly recycled lye for soaking section , in full compliance with the standard back , resulting in a concentrated liquid waste lye can be provided for the power plant flue gas desulfurization alkaline material, not only effectively utilize the black liquor concentrate , but also for the disposal of black liquor concentrate to provide a new way. After a nanofiltration membrane separation technology enrichment , effectively trapping live most COD, color , hemicellulose . COD removal efficiency of ≥ 95%, water production : ≥ 37.5 m3 / d, lye recovery rate : ≥ 75%, water production alkali content : 20% -23 % , producing water semi- cellulose content : ≤ 3g / L, chroma : ≤ 7 times , lye dosing pharmaceutical investment in the paper industry is relatively large an expense , so the spent caustic treatment, recovery and utilization is an energy saving benefits the country works.
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