Process Optimization And Resource Utilization Of Halophilic Bacteria In Treating High Salt Wastewater From Glucosamine Production

The industrial production wastewater of glucosamine not only has a large discharge volume,but also has the characteristics of high salt and high COD,making it one of the more difficult to treat industrial wastewater.Due to its high salt content and poor biodegradability,the traditional activated sludge biological treatment technology has poor removal efficiency.Halophilic bacteria not only have high adaptability to salt,but also have simple nutritional requirements,which can achieve rapid and effective treatment of high salt wastewater.However,there is limited research on the treatment of high salt wastewater from glucosamine production by halophilic bacteria.This study focuses on glucosamine wastewater and optimizes the environmental conditions for the treatment of high salinity wastewater by halophilic bacteria.At the same time,it explores the physiological and metabolic characteristics of halophilic bacteria under batch and continuous flow treatment,as well as the preparation of the bioactive substance ectoin from this wastewater.The main research findings are as follows:(1)Firstly,univariate experiments was conducted to investigate the halophilic bacterium H.elongate optimized the cultivation conditions for the treatment of simulated wastewater from glucosamine production.The research results showed that the optimal conditions for halophilic bacteria to treat simulated wastewater were 37℃,initial pH was 8.0,and salinity was 6%.Furthermore,the maximum specific growth rate of halophilic bacteria was 0.1041 h-1 through batch cultivation on a 5 L stirred tank.After 24 hours of cultivation,the degradation rate of glucosamine in the simulated wastewater reached 88%,and the yield of ectoin reached 705 mg/L.In addition,the metabolic changes of wastewater treatment under different dilution rates were investigated during the continuous flow treatment process.The results showed that with the increase of dilution rate,the concentration of halophilic bacteria,the rate of carbon dioxide release,and the production of ectoin showed an increasing trend.When the dilution rate is 0.06 h-1,the highest degradation rate of glucosamine in wastewater reaches over 90%.A lower dilution rate helps to improve the removal effect of ammonia nitrogen.(2)Research reports and genomic data from this halophilic bacterium suggest that the glyoxylic acid cycle is also a key pathway in metabolic processes.In the process of glucosamine production,a large amount of acetic acid waste acid water is produced during the product concentration.In order to realize the synergistic treatment of the two kinds of wastewater,the effects of sodium acetate on the growth of bacteria,degradation of residual glucosamine and metabolism of ectoin were investigated in the halophilic treatment of simulated wastewater.The experimental results showed that when the initial sodium acetate dosage was 200 mg/L,the removal rate of glucosamine in the simulated wastewater was up to 77.47%,which had little effect on the synthesis of ectoin.When the concentration of sodium acetate was higher than 300 mg/L,the growth of bacteria was inhibited obviously,which affected the treatment effect of glucosamine wastewater.When sodium acetate was added at the stable stage,the yield of ectoin reached 550 ± 10 mg/L,which increased by about 15.27%compared with the control group.The addition of sodium acetate at the stable stage may promote the synthesis of oxaloacetic acid,the precursor of ectoine synthesis,through the glyoxylic acid pathway.In addition,in the process of continuous treatment of simulated wastewater,the degradation rate of glucosamine increased after the addition of sodium acetate,up to 94%.The concentration of ectoine increased from 450 mg/L to 498.39 mg/L with the addition of sodium acetate,which led to an increase in biomass and product yield while decreasing the concentrations of COD and ammonia nitrogen in the effluent.(3)Based on the metabolism of halophilic bacteria in simulated wastewater,the characteristics of treatment of glucosamine mother waste-liquid by halophilic bacteria were studied in combination with response surface design,degradation kinetics model and observation of bacteria morphology.The optimized process conditions are as follows:the optimal dilution ratio of mother waste-liquid is 5 times,the optimal treatment temperature(37 ℃)and the initial pH(8.0),the removal rate of glucosamine from mother waste-liquid wastewater reaches 67%.In the treatment of mother waste-liquid in 5 L stirred reactor,the maximum specific growth rate of H.elongata in the 5-times diluted mother waste-liquid reached 0.1805 h-1,which was 73.3%higher than that of the simulated wastewater(0.1041 h1),which may be related to the existence of inorganic salts or a small amount of nitrogen source substances in the waste mother waste-liquid.The degradation kinetics experiment showed that the degradation trend of glucosamine in mother waste-liquid by H.elongata was consistent with the second-order kinetic equation.The results of scanning electron microscopy showed that the morphology of H.elongata in logarithmic stage was quite different from that in glucosamine mother waste-liquid and simulated wastewater,showing a long rod shape.Simultaneously,cotreatment of waste acetic acid and glucosamine mother liquor by H.elongata resulted in a 35%increase in ectoin yield,with a final concentration of 1890.35 ± 10 mg/L,compared to the control group.The above results indicate that H.elongata can treat glucosamine to produce high-salt wastewater,which provides a possibility for treating high-salt wastewater.