| The food waste has the characteristics of high content of moisture and organic,it is easy to orrupt and stink.If it can not be handled properly,it will has an adverse impact on people's normal life and environment.At the same time,food waste is a kind of waste that contain a huge amount of resources,which has great utilized value.It is an effective technology to deal with food waste by using anaerobic digestion technology because it can recycle its resources.However,due to the fact that food waste contain high proportion of protein,salt as well as organic matter,anaerobic digestion of food waste is often prone to salt inhibition,ammonia inhibition and overloading inhibition because anaerobic digestion system is sensitive to the change of environmental factors.In order to investigate to instability characteristics of anaerobic digestion system in salt inhibition,ammonia inhibition and overloading inhibition,this study uses food waste to perform the bacth experiments of mesopHilic anaerobic digestion,to investigate the effects of inhibition factors on daily gas production,biogas production rate,substrate conversion ratio and state parameters.In addition,using First-order Exponential model,Modified Gompertz model and Logistic function to fit the biogas production process,acoording to the parameters of model,to further explain the kinetics features of anaerobic digestion system in salt inhibition,ammonia inhibition and overloading inhibition.The results are as follows:(1)In salt inhibition experiment,when the concentration of Na+ was 2000,4000,6000,8000 and 10000,15000 and 20000 mg·L-1,the methane production rate was 94.46%,92.75%,84.10%,81.03%,77.80%,15.53% and 10.55% of control group respectively.It can be seen that the increase of Na+ can reduce the biogas production performance of anaerobic digestion of food waste.(2)In ammonia inhibition experiment,with the increase of TAN,the methane production rate of ananerobic system will gradually decline.When the concentration of TAN was 1500,3000,4500,6000 and 8000,10000 and 20000 mg·L-1,the methane production rate was 84.67%,70.98%,63.76%,58.46%,58.02%,55.66% and 5.74% of control group respectively.(3)In OLR inhibition experiment,when OLR was 2.5,5,10 and 15 g VS·L-1,the stability of the anaerobic system is good,all the methane production rate were above 95.21% of theoretical methane production.When the OLR was 20 g VS·L-1,there is a obivious inhition in the system,which the methane production rate was drop to 36.02% of theoretical methane production.(4)With the increase of Na+ concentration and TAN concentration,there will be a pHenomenon of biogas stagnation in the anaerobic digestion system.The higher the concentration of Na+ and TAN,the longer the stagnation period of biogas production,(5)In anaerobic digestion system,compared with VS removal rate,the change of COD removal rate is similar to the trend of methane production rate.The COD removal rate is a better indicator of efficiency of conversion of organic substrates to methane.(6)Modified Gompertz model can fit very well with the methane production of overload inhibition(R2?0.96),and Logistic model presents the best agreement in the fitting process of ammonia inhibition(R2?0.97)and salt inhibition(R2?0.99),which have biogas stagnation in the reaction process.(7)The easiest and first instability process in the anaerobic digestion system is the methane production process.The rate of methane production is always the lowest in salt inhibition,ammonia inhibition and overload inhibition tests.In addition,the Rmax of inhibition system is decreasing with the increase of inhibitor concentration,indicating methane production was severely inhibited when the anaerobic digestion was inhibited.(8)In overload inhibition system,k/Rmax' failed to show the monotone changing with inhibitor concentration,but in those reactors whose methane production rate was less than 50%(OLR=20 g·L-1),their k/Rmax' were much higher that those in normal operation.Therefore,the performance of anaerobic digestion system can be judged through the k/Rmax'. |
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