Study On Anaerobic Digestion Of Water Hyacinth

With the development of industry and agriculture and improvement of people's living standard, the environment pollution was worse day by day, especially the eutrophication of the water body. It is the effective way of resourceful utililization that the water hyacinth is used in water restoration and biogas production by anaerobic fermentation. Through the analysis of the characteristics of its anaerobic digestion and the research of the CSTR technology, the paper provides a proper testimony for the basic research and resourceful utilization of the water hyacinth. The main contents are as follows:The whole plant, leaves, and root of water hyacinth respectively were studied by batch anaerobic fermentation experiment, with the purpose of exploring the potential of gas production and the conversion rate of anaerobe in different parts of the water hyacinth. The results showed that stems and leaves had good biogas production characteristics, with 443.71ml/TS(total solid) and 538.35mlg/VS (volatile solid). TS biogas production were 15.16% and 41.01% higher than whole plant and root. VS biogas production were 17.87% and 42.25% higher than whole plant and root. TS and VS decomposition rate of stem was the highest, biological conversion rate of stem was up to 80.64%, the whole plant was 64.48%, the roots were at least 45.35%. Therefore, the water hyacinth's stems and leaves had a better fermentation efficiency than the whole plant and root.The characteristics of anaerobic digestion of water hyacinth were studied in the batch anaerobic digestion. In terms of studying anaerobic fermentation of water hyacinth growing in the water of different concentration of nitrogen and phosphorus, the experiments carried out on the water hyacinth growing in the 3 different nitrogen and phosphorus concentrations of man made water bodies (eutrophication of the lake water, an emission of A, a discharge B). The results showed that: the growth and gas production of water hyacinth were positively correlated with water nitrogen and phosphorus concentrations. The higher the concentration of nitrogen and phosphorus in the water, the better growth of water hyacinth and the more gas production potential. The biogas production potential of water hyacinth which growing in eutrophicated lake water, an emission of A, a discharge B were respectively:326ml/gTS(378ml/gVS); 375ml/gTS (430ml/gVS); 395ml/gTS(455ml/gVS). TS, VS, cellulose and hemicellulose degradation rate is as same as the biological conversion rate. The study indicated that the different nutritional characteristics of water hyacinth in different water bodies made different biogas production, in which the lignin content of water hyacinth degradation was the greater impacting factor.The different inoculation ratio was studied in the mesophilic anaerobic batch fermentation of water hyacinth, with water hyacinth and the VS proportion of inoculated sludge were 1:0,1:0.5,1:1,1:1.5. The purpose was to explore the effect of different inoculation ratio on the anaerobic fermentation. The results showed that: the larger inoculum size, the faster the fermentation, the more gas production peak advanced. Later in the fermentation, there were no obvious differences between processing and methane gas production. Denitrification reaction occurred and produced nitrogen under anaerobic conditions in 1:0 treatement. The highest nitrogen content was 90.55%. Considered the efficient use of integrated water hyacinth and volumetric gas production rate, VS ratio 1:0.5 was the best choice.Using water hyacinth for methane production in 10L CSTR(continuous stirring tank reator) was studied in the mesophilic by the semi-continuous feeding way. The organic loading rate was increased step by step from 0.5 gVS/L.d to 2.8 gVS/L.d. The results showed that: 3 days was the best time of acidification of water hyacinth; and CSTR operation stability was enhanced after feeding acidification of water hyacinth. Adding trace elements (Fe, Co, Ni) did not improve the rate of raw's gas production and methane content; low-speed agitation is in favour of the good mixture of raw. In the operational phase, with the increase of organic loading rate, biogas production and volumetric gas production rate increased, but raw gas production rate and VS degradation were reduced.the highest volume of biogas production rate was 0.83 m3/m3 .d.Considering the efficient use of water hyacinth and the volume of biogas production rate, the 1.5gVS/L.d organic loading rate was taken.