Effect Of Total Solids Concentration, Carbon Nitrogen Ratio And Hydraulic Rentention Time Of Dairy Cattle Manure On Biogas And Its Slurry Properties

With the improvement of living standards of society, people’s demand for dairy products is also growing. Therefore, the production scale and number of dairy farms are increasing and problems of cow manure pollution attendant should be taken seriously. Nowadays, proper dealing with cow manure has become a key to the appropriate emission standard and sustainable development. Anaerobic fermentation has low power consumption, low sludge production and it can eliminate odors, kill bacteria and pathogenic eggs as well as generating bio-energy——biogas, etc. So it is widely used in dairy farms. On the one hand, the process of anaerobic fermentation is affected by a number of factors. Above all the factors considered, Total Solid (TS), Carbon Nitrogen Ratio (C/N), Hydraulic Retention Time (HRT) have a greater impact and they are easily controlled, convenient and economically viable. On the other hand, it is relatively rare to analyze anaerobic fermentation of dairy manure comprehensively via analysis of TS, C/N and HRT. Therefore, in this thesis we used the combined method of sequencing batch and semi-continuous conditions to study the impact of TS, C/N and HRT on biogas production and nature of biogas slurry by anaerobic fermentation of dairy cattle manure and sought the optimum fermentation parameters of TS, C/N and HRT for efficient gas production and low emissions of biogas slurry, then provide a theoretical basis to the choice of parameters of fermentation process by dairy farms.With raw materials-dairy cattle manure, we used sequencing batch fermentation process, changing TS and C/N, to get dynamic curve of production rate of biogas, the cumulative production,biogas production rate of dry matter, the average methane content and the nature (pH, VFA, COD, TN, NH4+-N, TP) of biogas slurry in fermentation process. The results show that under the condition of25C/N, the anaerobic fermentation process is more stable and the process can start more quickly. With the TS range between2%-10%, the volume gas productivity rise from0.16m3/m3·d to0.54m3/m3·d gradually.Production rate of dry matter and the average methane content reach the peak236.46mL/g VS and68.59%respectively under the condition of C/N=25and TS=6%. Under this case, the COD, ammonia, TP removal rate of biogas slurry reached48.47%,80%and55%. Taking the biogas effects (biogas production rate of dry matte, the average methane content) and the nature of biogas (COD, TN, TP removal rate) as response indicators, we use Factor Sequence Generation method to further confirm that the sequencing batch fermentation effect is good and the nature of biogas is convenient for subsequent processing when TS=6%and C/N=25.Similarly, taking cow dung as fermentation raw materials and adopting semi-continuous fermentation method, fixed suitable fermentation liquid TS and C/N which selected from sequencing batch fermentation test and get different gas effect (methane gas production rate, cumulative gas production, production rate of dry matter and the average methane content) under different value of HRT and dynamic curve of the nature of biogas in the fermentation process (pH, VFA, COD, TN, NH4+-N, TP). The results show that throughout the test period, during the first50d the condition goes well but during the last10d, it appears acid suppression. In order to predict the biogas production of dairy cattle manure anaerobic fermentation process to facilitate the manual operation and regulation provide a theoretical basis for practical applications and the research foundation. TS=6%and C/N=25as sequencing batch fermentation conditions and TS=6%, C/N=25and HRT=20d as semi-continuous fermentation process conditions biogas dynamics situation analysis, which can well fit the curve of anaerobic fermentation of dairy cattle manure biogas production rate and cumulative biogas production.In summary, TS, C/N and HRT of dairy cattle manure have a significant effect on anaerobic biogas and its slurry properties, screened suitable fermentation parameters TS is6%, C/N is25and HRT is20d, is based on the Efficient biogas production and biogas slurry high COD removal rate, high TN removal rate, high TP removal rate as the criterion.In this thesis, because of the time limit, we only used dairy cattle manure as the raw material for fermentation and only considered the impact of TS, C/N, HRT by respectively. We will study more materials and more factors on biogas production and nature of biogas slurry in subsequent trials.