| With the development of national economy,the amount of food waste in our country has been increasing year by year.At the same time,the Environmental requirements improving,the treatment of food waste has gradually become the research focus of people.According to the characteristics of food waste,anaerobic digestion technology has obvious advantages.However,the inhibition caused by high concentration of ammonia nitrogen and grease is now a problem encountered in anaerobic biological treatment,and its inhibition mechanism remains controversial.In this study,the novel controlled internal circulation(CIC)anaerobic reactor was used to treat food waste,the processing efficiency and the optimization of process parameters of the reactor was investigated.Then through the static small bottle test and the reactor continuous experiment,the effect of different concentration of oil and ammonia nitrogen on the treatment efficiency of the CIC anaerobic reactor and the recovery measures were studied.In addition,the physico-chemical characteristics of anaerobic granular sludge,and the succession of microbial community in the reactor was analyzed.The major conclusions were as follows:1.Research on the process efficiency and parameters optimization of the CIC reactor.The treatment efficiency of the CIC reactor was studied by controlling hydraulic retention time,temperature and reflux ratio.Combining with single factor test and engineering practice for the future application,the optimal operation parameters of the CIC anaerobic reactor for the treatment of food waste was determined:wastewater CODcr 5000mg/L,hydraulic retention time HRT was 16h,the temperature was 25?,reflux ratio was R=3.Under the operation parameters,the concentration of CODcr in the effluent was about 650mg/L,and CODcr removal rate was above 87%.It was showed that the CIC anaerobic reactor was running in good condition.2.In the anaerobic digestion inhibition test of grease,the static small bottle test results showed that when the grease concentration of 2g/L,the removal efficiency of anaerobic system began to be inhibited.With the increase of grease concentration,the inhibition effect was more apparent.The CODcr removal rate reduced from 94%to 27%,and the content of VFA increased from 5mmol/L to 9mmol/L at grease concentration lOg/L.The CIC reactor continuous anaerobic digestion test showed that the grease concentration of 3g/L had a certain inhibitory effect on the reactor.With increasing grease concentration,the removal efficiency of the CIC reactor dropped significantly.The CODcr removal rate dropped from 94%to 70%,the content of VFA increased from 10mmol/L to 25mmol/L above,and the content of ALK decreased from 102mmol/L to 60mmol/L.At the same time,when the grease concentration increased from lg/L to 3g/L,the protein content in the LB-EPS of anaerobic granular sludge increased from 44.89mg/gVSS to 71.57mg/gVSS.And the protein content in LB-EPS of anaerobic granular sludge reduced to 57.16mg/gVSS at the grease concentration 7g/L(R=4).At the same time,when the grease concentration increased from lg/L to 3g/L,the polysaccharide content increased from 23.58mg/gVSS to 57.96mg/gVSS,and then reduced to 26.04mg/gVSS at the grease concentration 7g/L(R=4).With the grease concentration increasing,the 3D-EEM spectra analysis of EPS showed humic acid and ultraviolet fulvic acid substances was increased,and the coenzyme F420 had stronger absorption peak.It was indicated that the toxicity of grease on microorganisms was enhanced,and the inhibition for the CIC anaerobic reactor was obvious.3.In the anaerobic digestion inhibition test of ammonia nitrogen,the static small bottle test results showed that as the ammonia nitrogen increased to 1000mg/L,the CODcr removal efficiency was on obvious influenced.But it had significant effects on the NH3-N removal,the removal rate decreased from 40.6%to 7.9%.The CIC reactor continuous anaerobic digestion test showed that when the ammonia concentration increased from 500mg/L to 1500mg/L in the influent,the CODcr removal rate decreased from 90%to 76%,and the NH3-N removal rate also decreased from 20%to 6%.With increasing concentration of ammonia nitrogen,the protein content in the LB-EPS increased from 38.86mg/gVSS to 75.64mg/gVSS,and the polysaccharide content increased from 50.34mg/gVSS to 68.16mg/gVSS.The 3D-EEM spectra showed that the coenzyme F420 absorption peak gradually disappeared,and the toxic substances of benzene ring increased in the FTIR spectra.It was indicated that with the increase of ammonia nitrogen concentration,the removal efficiency of the CIC reactor was significantly reduced,ammonia nitrogen caused certain toxicity on the microorganisms inside the reactor,and the microbial activity was inhibited.4.For the restorative measures study of inhibition,the measures of increasing the inner circulate and adding biochar had be adopt to relieve the inhibition of grease and ammonia nitrogen,respectively.Results showed that the recovery experiment of grease inhibition,when the grease concentration was 3g/L,the removal efficiency of the CIC reactor could be back to the initial state by increasing reflux ratio.However,when the grease concentration increased to 7g/L,even the reflux ratio was increased to 4,the CIC reactor was still hard to recover.At the conditions,the removal rate of CODcr was 70%,and the content of VFA was more than 25mmol/L.In the recovery test of ammonia nitrogen inhibition,after adding biochar to the CIC reactor at ammonia nitrogen concentration 1500mg/L,the CODcr removal rate increasd from 76%to 90%,and the NH3-N removal rate increased from 6%to 18%.The characteristics of anaerobic granular sludge analysis showed that the protein content in the LB-EPS increased to 58.96mg/gVSS,and the polysaccharide content also increased to 68.16mg/gVSS.Meanwhile,the UV-vis spectra showed that the polysaccharide and protein had stronger absorption peak,the EEM spectra analysis showed that the coenzyme F420 absorption peak reappeared.At the same time,the polysaccharide and protein absorption peak strengthened in the FTIR spectra.It was illustrated that after adding the biochar,the performance of the anaerobic granular sludge significantly was improved,methanogens were increased,and the inhibitory effect of ammonia nitrogen on the CIC reactor was reduced.5.High-throughput sequencing results showed that in the anaerobic digestion inhibition test of grease,under the conditions of grease concentration was 3g/L and the reflux ratio was 2,the the Chaol and shannon index were highest in the CIC reactor.But the index was lowest at grease concentration 7g/L.In archaea community structure analysis,the microbial structure was similar at grease concentration 3 g/L and 7g/L.When the grease concentration in the influent increased from lg/L to 7g/L,Methanobacteriaceae reduced from 57.21%to 34.4%.For the bacteria,the community structure was similar under the condition of lg/L and 3g/L.The bcteroidetes was predominant.With grease concentration increasing from lg/L to 7g/L,the abundance of bacteroidetes increased from 29.42%to 52.08%.It was speculated that bacteroidetes could better adapt to the high concentration of grease environment.In anaerobic digestion inhibition test of ammonia nitrogen,the microbial species diversity was the lowest under the ammonia nitrogen concentration was 1500mg/L,and it was highest after adding the biochar.When the ammonia nitrogen concentration increased to 1500mg/L,the abundance of Methanobactiaceae decreased from 66.3%to 30.9%,while Methanotrichaceae increased from 32.31%to 46.84%.It could deduce that Methanobacteriaceae was sensitive of ammonia nitrogen,and Methanotrichaceae could adapt to the high concentration of ammonia nitrogen.For the bacteria,when the ammonia nitrogen concentration increased to 1500mg/L,the abundance of Clostridiales increased from 2.47%to 28.4%,Lactobacillales increased from 0.11%to 27.62%.After adding the biochar,the abundance of Methanotrichaceae reduced from 62.92%to 46.84%and Methanobacteriaceae reduced from 30.9%to 17.9%,while Methanoregulaceae increased from 4.83%to 17.09%.In the analysis of bacteria,the abundance of the unclassified bacteria,Clostridiales and Lactobacillales decreased,while the abundance of Bacteroidales and Anaerolineales increased. |
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