Experimental Study On Distillation Treatment Of Folic Acid Wastewater

Folic acid wastewater is a kind of industrial wastewater with high COD,high NH₃-N,high chromaticity and high salinity.Direct discharge will cause serious environmental pollution.Chemical and biochemical treatment methods explored have the problems of complicated process,unstable effect and high cost.Considering the differences in the physical properties of various substances in the wastewater,distillation was tried to treat folic acid production wastewater in this paper,and its treatment effect and separation mechanism were studied.Besides,the operating parameters of the distillation process were optimized through the experiment which designed by response surface method for laying the foundation for the development of production wastewater distillation treatment technology.Main results obtained from the study are as follows:（1）Raw folic acid waste water produced by a chemical and pharmaceutical factory in the high-tech zone of Xi’an,Shaanxi Province was distilled.The quality of the condensate obtained was good.Moreover,most of the pollutants in the wastewater were left in the concentrated.（2）Adjusting initial pH value of the wastewater and then distilling,the changing of the COD and ammonia nitrogen concentration of the condensate were observed.The influence of the pH value on the water quality is as follows.The lower the pH was,the higher the COD concentration of the condensate will be.As the pH increased,the COD concentration of the condensate decreased rapidly.The effect of pH on the concentration of ammonia nitrogen was just the opposite.（3）By reducing the pressure,the ammonia nitrogen and COD removal rate of the distillation process were effectively improved.The main mechanism is:vacuum distillation reduces the boiling point as well as the ammonia nitrogen and volatile fatty acids produced by thermal decomposition of nitrogen-containing complex organic compounds in folic acid wastewater.Ultimately,the volatilization of ammoniacal nitrogen and volatile fatty acids were reduced.Meanwhile,the concentration of ammonia nitrogen and COD in the condensate were also reduced.（4）With the help of Design-Expert 8.0 analysis software,the Box-Behnken design method was used to design the response surface test to optimize the working conditions in the rotary evaporation process.Then,the best treatment effect can be obtained and the corresponding condition parameters can be recorded.The effluent satisfies the municipal pipe network takeover standard stipulated in the"Water Quality Standards for Wastewater Discharge into Urban Sewers"（GB/T31962-2015）.