Development And Application Of Liquid Compound Microbial Agent For Aerobic Composting

The existed research and practice had confirmed that aerobic composting was one of the effective ways to achieve the resource,reduction and harmlessness of surplus sludge.At present,the research of composite microbial agents for compost has become a research hotspot in this field.The preparation process of solid microbial agents was complicated and costly.However,the liquid composite microbial agents had the advantages of simple preparation method,low production cost and convenient use.At the same time,there were problems such as short storage time,unsatisfactory use effects,and easily inactivated microorganisms.The surplus sludge from sewage treatment and corn straw were used as compost raw materials in this study,and the strains preserved in our research team were selected.Through the study of the effect of composition strains and the compounding ratio on the compost,an aerobic composting composite microbial agent with the dominant indigenous microorganisms was studied.Combining with the research on physiological-biochemical characteristics and identification of degradation function for the selected strains,the fermentation conditions of the strains was optimized,which could achieve high cell density and high spore rate culture.It also could improve the microbial preservation activity and reduce the cost of preparation.Through the single factor and response surface optimization study of thickeners,emulsifiers and antioxidants,we could obtain the prepare method of liquid composite microbial agent.Furthermore,the stability of the liquid microbial agent that obtained after 30 days and the actual compost effect were studied.The above research could provide a useful reference for the preparation and industrial application of compound microbial agents for composting surplus sludge.It had the important academic significance and practical value.The main research contents and results were as follows:（1）The development for the formula of aerobic compost compound microbial agent.Using the strains that preserved in the laboratory to carry out the research,the effect of strain composition and compounding ratio on the composting.The results showed that the composting effect of the composite microbial agent that consisting ZX5,ZX6,GX2,GX5,and GX9 was better,which could effectively improve the conversion efficiency of organic in the heap,shorten the time to reach high temperature,extend the duration of high temperature,speed up the composting process and improve the sanitary condition.When the amount of fungicide was0.3%,the reactor reached the period of high temperature at 16 hours,when compared with the blank control,which was 6 hours ahead of time and the high temperature duration was 72 hours.The cellulose and lignin degradation rates in the reactor were 35.76%and 20.62%,respectively.When the composting was end,the C/N of the pile was 15.86,the number of fecal coliform was4 MPN/g and the mortality of roundworm was 96.54%,the maturity and composting quality were better.（2）The optimization for the fermentation process of microbial strains that used in combination of agents.First,the optimization research of medium and fermentation conditions by shaker culture.The results showed that the best carbon sources for ZX5,ZX6,and GX2 were sucrose,glucose and sucrose,respectively,and the best carbon sources for GX5 and GX9 were soluble starch.The best nitrogen sources for ZX5 and ZX6 were both yeast powder,the best nitrogen sources for GX2 was odium nitrate,and the best nitrogen for GX5 and GX9 were both ammonium chloride.The research results of the 3 L fermenter expanded culture showed that after batch fed fermentation,the viable count of ZX5 was 9.30×10⁹ CFU/mL,and the spore rate was 61.2%.The viable count of ZX6 was 7.70×10⁹ CFU/m L,the spore rate was 43.7%.The viable count of GX2 was 1.80×10¹⁰ CFU/mL,and the spore rate was 66.6%.The viable count of GX5 was 1.58×10¹⁰ CFU/mL,and the spore rate was 88.9%.The viable count of GX9 was 1.31×10¹⁰ CFU/mL,and the spore rate was 89%.When the pH was 6.8,the culture temperature was 50oC and the stirring speed was 150 r/min,the spore rate of GX2 was the highest,and it could reached 84.1%.（3）The research on the preparation technology of liquid compound microbial agents.The research result of the single factor optimization showed that the number of viable bacteria that added with gum arabic was higher than that of agar and sodium alginate,and with the increase of the added amount,the survival rate of the strain increased first and then decreased.Compared with Tween-80 and lauric acid monoglyceride,the number of viable bacteria that added Tween-20 was higher.The survival rate of strains that added ascorbic acid was higher than that of tea polyphenols and BHT.The optimization research results of three-factor and three-level response surface showed that the best preparation conditions for the liquid microbial agents were the addition of 0.401%gum acacia,0.090%Tween-20 and 0.042%ascorbic acid.The order that affected the survival rate of the strains was ascorbic acid,Tween-20 and gum Arabic.Under the above optimal conditions,after the liquid composite microbial agent was stored for30 days,the survival rate of the strain was 63.9%and the number of viable bacteria was 1.86×10¹⁰ CFU/m L.（4）The research on the composting effect of liquid compound microbial agent.Taking the fresh liquid composite microbial agent as a control,the composting effect of the inoculum that stored after 30 days was studied.The results showed that the composting performance of the liquid composite microbial agent was relatively stable after being stored for 30 days,which could entered the high temperature period at 24 hours,the duration of the high temperature period was 5 days,the maximum temperature reached 61.5oC,and the degree of harmlessness was higher.The degradation rates of hemicellulose,cellulose and lignocellulose that added by the 30 days liquid composite microbial agent was higher,which were 58.23%,34.2%,and19.67%,respectively.In addition,the 30 days addition of liquid microbial agents had a relatively high degree of maturity,all of them could reach the maturity standard with the C/N of 17.05 and GI value of 153.2%.