Comparison Of Monitoring Indicators Of Acidification Instability In AD Of FW And Study On Fluorescence Probe Method

The anaerobic digestion system will cause waste of resources when it is operated under low load,but acidification is likely to occur under high load.Monitoring of system operation indicators is especially important.At present,commonly used indicators have a certain hysteresis in the acidification warning of the system,so it is significant to look for more advanced monitoring indicators.EPS are closely related to microorganisms and can reflect the state of the system to a certain extent in a timely manner.The paper is based on the above questions,study on changes of content of EPS in anaerobic acidification,exploring its feasibility and advancement as an early warning indicator of acidification instability in anaerobic systems;combining a substance with fluorescent properties with the ingredients in the EPS to indicate the actual operating state of the system under certain reaction conditions,thereby regulating the system in time and avoiding complete rancidity and collapse.The main research content is as follows:Firstly,optimized the conditions for extracting EPS from cation exchange resin.The sum of the concentration of PN and PS in the EPS was used as the evaluation index and determined by single factor experiments.For the range of factor levels,selected 10,20,and 30 g(calculated at 15 gVS)as the three levels of resin addition;selected 100,150,and 200 r/min as the three levels of stirring rate;selected 1,2,and 3 h as the stirring three levels of time.Full factor analysis method was used to obtain a significant effect of the three factors,and the three factors had interactions and significant effects.The RSM was used to optimize the extraction conditions:20 g of resin(15 gVs),stirring rate was 150 r/min,stirring time was 2 h,total PN+PS content was 8.95 mg/gVS,close to the actual experimental results.Secondly,anaerobic batch experiments of food waste and anaerobic sludge,set different F/M ratios,monitoring at regular intervals.When the system of F/M=0.5,all of its monitoring indicators were stable and fluctuated,indicated that the system runs stably with low load and no acidification occurs.When the value of F/M of system were 2.0,3.0,4.0,the changes of its monitoring indicators all indicated that the system with high load will occur acidification when the reaction is performed for a certain period of time.The experimental results showed that the value of protein/polysaccharide(PN/PS)in the the value of F/M were 2.0,3.0,and 4.0,can alert acidification to a certain extent.The acidification instability time obtained as an indicator of acidification instability is better than other monitoring indicators.In advance,the fastest time can be 4 hours in advance,verifying the value of PN/PS as the feasibility and advancement of the monitoring indicators for the anaerobic digestion system of food waste.Finally,in order to avoid the loss of EPS extraction,to reduce the experimental operation time,to achieve the online detection of warning indicators as much as possible,the fluorescence probe was combined with the polysaccharide of the extracellular polymer(sodium alginate),and the method of fluorescence probe methodology was studied.The sodium alginate-degrading bacteria were isolated and purified,orthogonal experiment was used to optimize the fermentation conditions of sodium alginate degrading enzyme,and its optimum fermentation conditions were obtained:the optimal fermentation conditions were obtained:the temperature was 50?,the time was 48 h,and the inoculation amount was 6%.The physicochemical properties of the alginate degrading enzyme were studied.The optimum pH of the enzyme reaction was 7.5,and the optimum temperature was 40 ?.Michaelis-Menten kinetics fit gives the value of Km and Vmax of this enzyme.Zeta potential analysis and infrared spectroscopy showed that the diamino group in coumarin was combined with the carboxyl group of sodium alginate.The fluorescence properties of the reactants and conjugates were measured at an excitation wavelength of 366 nm and an emission wavelength of 390 nm respectively.Enzyme and sodium alginate had little effect on the fluorescence properties of coumarin.After 5 minutes of adding the enzyme,the measured fluorescence intensity of the system decreased,indicated that the coumarin fluorescent probe can reflect the changes of concentration of polysaccharide in EPS to some extent,it can provide methodological basis for follow-up applications.