Biodegradation And Utilization Of N-methyl-2-pyrrolidone

With the continuous advancement of industrialization,industrial wastewater produced by large factories has become a water pollution situation in China's cities,which has brought challenges to the field of environmental pollution control in China.The pollutant concentration of industrial wastewater is high and the composition is complex.Its large discharge will lead to the deterioration of surrounding water quality and soil.Its biological toxicity will further accumulate with the food chain,and has an impact on human health.Most industrial wastewater is treated by advanced oxidation combined with biodegradation,that's why the treatment cost is high.Some industrial wastewater with good biodegradability will adopt the combination of aerobic and anaerobic activated sludge.Nitrogen containing heterocyclic organics are common typical organic pollutants in industrial wastewater.Most of the research focuses on substances with high toxicity and poor biodegradability.It is important to treat high concentration nitrogen containing heterocyclic organics wastewater with low toxicity and good biodegradability.In this study,N-methyl-2-pyrrolidone(NMP),a nitrogen-containing heterocyclic organic compound commonly found in chemical industry wastewater,was selected as the object substance.Aerobic and anaerobic activated sludge capable of degrading NMP and denitrifying activated sludge capable of denitrification using NMP as electron donor were acclimated respectively.This paper explores the biodegradation of NMP under different treatment methods and its application as an electron donor in denitrifying sludge,designs the relevant process flow and discusses the relevant mechanism.The main research results of this paper include:(1)The characteristics of NMP production wastewater were explored,and different treatment methods of NMP were compared.NMP production wastewater has high biodegradability,in which NMP accounts for more than 70% of organic matter content(calculated by TOC).After acclimation,aerobic activated sludge can realize the efficient biodegradation of NMP.Under the anaerobic condition with nitrate,the degradation rate of NMP is better,and the oxygen degradation is increased by 7.5%.The degradation process is hydrolysis,deamination and oxidation.The presence of intermediate product monomethylamine affects its mineralization effect.The acceleration mechanism of nitrate is electron transfer and tricarboxylic acid cycle.(2)The feasibility of NMP as denitrification electron donor was explored,and the relevant process flow was designed.Through the calculation of theoretical chemical oxygen demand and effective electron number,it is proved that NMP is theoretically feasible as an electron donor for denitrification.When C/N is 5,the denitrification rate of NMP as electron donor was 17.07 mg N/(g MLSS·h),which had significant advantages over glucose.In the denitrification process with NMP as electron donor,the optimum C/N is 4.By adding "nitrification-denitrification" treatment in the follow-up,the ammonia nitrogen produced in the degradation process of NMP can be treated,and the ammonia nitrogen concentration after treatment meets the emission standard.(3)Bacillus tropicus can biologically enhance the denitrification process with NMP as electron donor.When Bacillus tropicus bacterial solution(5% dry weight ratio)was added to the activated sludge system,the nitrate reduction rate was 14.81 mg N/(g MLSS·h),which was 28.67% higher than that of the group without bacteria.(4)The microbial community of denitrifying sludge domesticated by NMP was analyzed.The richness and diversity of denitrifying sludge with NMP as electron donor were higher than those with glucose as electron donor.The microbial communities of the two groups of sludge have little difference at the phylum level,and have great difference at the family and genus levels.Most of the denitrifying sludge with glucose as electron donor are common denitrifying bacteria,and the denitrifying sludge with NMP as electron donor has the highest abundance,which is not only related to denitrification.It is also related to the intermediate products and electron transfer in the degradation of NMP.