| Chongqing is situated along the Changjiang River citrus belt,where produces 250,000 tons orange juice every year which leave the equal weight of peel at the same time,ranking the first orange juice producer in Asia each year.The current main destination for those peel is being buried in landfills, which will not only covers more and more area of valuable land resources,but also causes second contamination to the land due to the sour liquid leakage soon after.This study focused on fermenting the citrus peel by aerobic pre-treatment and optimized fermentation,a way turning the organic carbon in biogass and keeping using it in a large amount way.Because of the acid elements in citrus skin,the acidity of the fermentation would reach pH 1 which will kill the majority of f microbe for the fermentation if the citrus skin is put into the course. According to reports,the composition of orange skin in the process of anaerobic fermentation residue,such as volatile fatty acids(VFA) under the formic acid,acetic acid,propionic acid,butyric acid,pentanoic acid,hexanoic acid and their isomers is an important intermediate product reflecting the operation of the anaerobic reaction.In a well-functioning of the anaerobic reactor,VFA in the acetic acid can be a high proportion,while for a bad state of reactor operation,metacetonic acid and butanoic acid concentrations rise.Studies have shown that the accumulation of acid generation and anaerobic digestion of biological seriously affected the normal operation of treatment systems.The emergence of a large number of acid producing metacetonic acids led to low efficiency,and thus cause lower pH in anaerobic methane-producing reactorand influence the activity of methanogenic bacteria by ending it up of the failure of production of methane.In this study,by aerobic pretreatment to the citrus peel aiming at rising the solution pH,followed by optimizing anaerobic methane fermentation,directional control of the fermentation will be most conducive to the production of methane direction.There was is no current research in this field so far.In addition,the paper also examined the promoters' effect to the methane gas yield.The main conclusions are as follows: 1.We screened filiform white-rot fungus from a citrus fruits orchard's pile of fill.The orthogonal test aiming for optimizing this species for decomposing the citrus reticulata cedrat dregs ahead of the methane experiment indicated that under this strain single factor,in 25 days,this strain decomposed 30%of the fresh citrus residure.It also showed:the best combination condition for it decomposing the citrus dregs is bran 2g.60%of water in citrus peel dregs,initial period pH3,and 0.2g ammonium sulfate.Has the return to original state sugar quantity(μg/g) the average to achieve 517μg/g;Xylose 120.8μg/g;The cellulose+cellulose decomposition measures 0.96g;The even weightlessness achieves 67%;Suffices to enhance the citrus reticulata cedrat dregs pH to enhance effectively from pH1 to pH4,has made the advantageous preparation to the next step anaerobic fermentation.The enzyme vitality test indicated:The hypha cover citrus reticulata orange peel dregs the 8th day to the 26th day,the AVI vigor must be higher than CMC and FPA far.AVI achieves in a big way in the raise 13th day of enzyme vigor,the 17th day later,enzyme activity directly excited drop.And CMC in the entire raise period does not have the change nearly,has maintained steady. After citrus reticulata cedrat dregs pretreatment carries on anaerohic produces the methane to ferment,the experiment indicated that before alter the processing citrus reticulata cedrat dregs produces the methane ultimate output not to process,enhances 20%,the methane content enhances 26%;The COD value can effective reduce achieves 27%;Around the fermentation returns to original state the sugar quantity to reduce 20%.2.Pre-processing the results of the two fungi:In accordance with pre-treatment from the joint after the decomposition of reducing sugar,OD value of the deal with weight loss(%),to deal with before and after the pH value and,ultimately,the efficiency criteria for gas analysis,co-pretreatment of the white-rot Bacteria+F160+and the white-rot fungus Aspergillus niger joint processing of citrus skin 25 days after the anaerobic fermentation residue,when the best choice.3.The present study,gas chromatogram was used to analyze and determine the type of produced organic acid during anaerobic fermentation of citrus skin residue after different pretreatment.Then by adjusting volume loading,pH value,ORP value,and other conditions to control the production of acetic acid,which is beneficial for the production of methane.Experimental results showed that at the first 10 days when citrus skin residue was used to produce methane after different pretreatment, the pre-processing acid was mainly acetic acid.But 25 days later,various degrees of propionic acid were generated,and acid production reached the maximum.The white-rot fungus combining with Aspergillus niger pretreatment produced acetic acid,propionic acid,butyric acid,the amount was 2.88×10-6,0.28×10-6,0.51×10-6g(per luml content),respectively,and other pretreatments did not generate butyric acid.When continuous flow was used to control acid production,at start-up phase when loading volume,ORP,and pH was adjusted to[kg.COD.(m3.d)-1],-400 mV,5.6, respectively,the production of acetic acid is maximum;at control phase when other conditions unchanged,adjusting the ORP value to -230 mV,the production of acetic acid can be significantly increased by 73%;then at the stable stage,adjusting pH value to 6.7,acetic acid production remained stable at 7.6×10-6g,until the end of gas production.4.Accelerator experiments show that:the process of anaerobic fermentation in trace elements and charcoal can enhance the activity of methane bacteria to enhance gas production.The optimum ratio of Fe3+:Ni+:charcoal for the 2:1:5,voted to increase the absolute amount of 0.61%(as opposed to the dry weight of raw materials).Domesticated species of the higher microbial biomass than the domestication of the former increased 27.3%.5.The best parameters' test of exploring the citrus skin residue's anaerobic fermentation showed.that: the process of the citrus skin residue from biological pre-treatment to anaerobic fermentation can be carried out from the following steps,which can improve the methane production rate of the citrus skin residue effectively,and the methane production is 62%more than which of only using fresh fruit residue directly to take anaerobic fermentation.1) Taking 60%moisture content of the citrus skin's waste residue as the main raw materials,first inoculated 3%(the ratio of total weight of the bacteria re-suspension and the citrus skin residue.g:g) of white-rot fungi in the constant temperature of 25℃to culture and decompose 7-10 days.2) Then inoculate 3%(the ratio of the total weight of the Aspergillus niger's re-suspension and citrus skin residue.g:g) of Aspergillus niger in the constant temperature of 23℃to take aerobic decomposition for 20 days;3) Add 5-10%(based on the citrus skin residue of pretreatment,the ratio of the dry weight of people and livestock feces and the total wet weight of the production of aerobic decomposition plus people and livestock feces.g:g) of people and livestock feces to the production of aerobic decomposition of having taken pre-processing step of 1) and 2),take the anaerobic fermentation with the concentration of the raw materials which is 6—8%(the ratio of the dry weight of the production of aerobic decomposition plus people and livestock feces and the total wet weight of those ones) of the effective reaction volume and inoculate 2%(the ratio of the dry weight of old sludge and the total wet weight of the production of aerobic decomposition plus people and livestock feces plus the old sludge plus water.g:g) of microbial composite inoculum for two-phase anaerobic fermentation to control the production process of acetic acid.In the fermentation stage of production of the organic acids,maintain the fermentation pH value as 5.0:in the stage of producing methane by anaerobic fermentation,maintain the fermentation pH value as 6.8,and keep the fermentation temperature being maintained at 20-35℃.Then it was fermented for 30 days.6.Inoculation procedures showed that,after the domestication,the form of sludge and its dominant microbial flora were changed,and that domestication had played a important role in those changes. The sludge began to adjust to it gradually,because of the characteristic of material had changed;the dominant microorganisms in the sludge had changed,and the sludge accumulated the characteristic of the microbial floras which matched the skin of the citrus slag.At the end of domestication,we could get inoculum which was able to apply to anaerobic digestion of the citrus skin residue.
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