Heating Energy Adjusting Of Biogas Fermentation Of Swine Wastewater

Anaerobic digestion is often considered effective alternatives for the treatment of swine wastewater.However,since swine wastewater is characterized by large volumes with low concentrations of organic matter concentration,it is difficult to raise the temperature of anaerobic digestion when heating energy is limited.The result is low efficiency of anaerobic digestion during winter.In this study,a scientific hypothesis of two-step heating mode with the same energy consumption for enhancing methane production efficiency was proposed to solve this problem.In order to confirm this hypothesis,tooking two-step heating strategy as an example,this paper verified the feasibility of two-step heating strategy to enhance biogas fermentation efficiency from theory and experiment,explored the factors that influence the increase in biogas fermentation efficiency,and studied the effects of the two-step heating strategy on anaerobic sludge characteristics.The main conclusions are as follows:(1)In theory,compared with the traditional heating mode(i.e.one-step heating),the two-step heating strategy could improve the fermentation temperature and biogas fermentation efficiency.The lower ratio of influent of digester 1 to that of digester 2(p)and the higher heating energy supplied to the wastewater(h)improved temperature increase of the two-step heating strategy.The lower p value and ambient temperature(T0)led to the greater efficiency of the biogas fermentation efficiency of the two-step heating strategy.(2)The temperature verification test with clear water as medium indicated that the temperature increase of the two-step heating strategy gradually increased with the decrease of p value.When the p value was 0.1,temperature rise of the two-step heating strategy was 4.61 ?.The temperature increase of the two-step heating strategy gradually increased with the increase of h value.The p value was 0.3,the h was 37.62 kJ L-1,temperature rise of the two-step heating strategy was 9.25 ?.However,temperature increase of the two-step heating strategy in the experiment was less than the theoretical value.The difference between the experimental value and the theoretical value is mainly due to the temperature loss caused by the heat dissipation of the tank and the pipeline,(3)The fermentation experiment of swine wastewater(p=0.5)as fermentation material showed that the two-step heating strategy increased the biogas(methane)yield,the biogas production increased by 4.70%?11.5%,and the methane production increased by 0.810%?11.6%.The organic loading rate and ambient temperature are the two main factors affecting the efficiency of the two-step heating strategy.(4)The two-step heating strategy increased the methane yield and the efficiency of methane production with the increase of organic loading rate.When the organic loading rate was 4 kg COD m-3 d-1,the improvement efficiency was 13.1%.As the decrease of the environment temperature,the methane yield and improvement efficiency of methane production increased.At T0 was 5 ?,the maximum efficiency of methane production was obtained as 14.7%.As the decrease of the p value,the methane yield and improvement efficiency of methane production increased.When the p value was 0.2,the improvement efficiency was 20.1%.The maximum volume biogas production rate(Rpmax)and semi-saturation constant(KLR)of the two-step heating strategy were higher than that of one step heating in terms of kinetic parameters of methane production.However,the experiment values of the methane yield and improvement efficiency of two-step heating strategy were significantly lower than the theoretical values.This is due to the low sludge concentration in the digester of two step heating strategy.Theoretical analysis did not take into account sludge loss problem caused by low hydraulic retention time.(5)In terms of sludge characteristics,the digester I(R2)of the two-step heating strategy had the best buffering property,while the digester II(R3)of the two-step heating strategy had the worst buffering property.The maximum specific methanogenic activity of R2 and R3 was 8.63 mL·gCOD-1·gMLVSS-1 and 8.57 mL·gCOD-'·gMLVSS-1,respectively,which was higher than 7.87 mL·gCOD-1·gMLVSS-1 of digester(R1)of one-step heating,indicating that the sludge activity of the two-step heating strategy is better than that of one-step heating.Microbial community structure analysis showed that the syntrophic oxidation in the digesters in two-step heating strategy was more active.