Study On Duckweed Used For Wasetwater Purificaiton And Biogas Fermentation

Duckweed was the floorboard of the duckweed division (Lemnaceae) plants. In recent years, because ofits high starch content, high reproductive rate, simple ways of cultivation and harvest and other features,duckweed was considered of one kind of excellent plant for sewage purification and biomass energyproduction, which had important ecological value and energy value. On the basis of previous research,the thesis focused on its growing ability and resource utilization ways, included as: i) influence oflivestock wastewater concentration on growth of common duckweed (Lemna minor); ii) study onpotential biogas production of duckweed; iii) study on dry anaerobic digestion using duckweed mixedwith cow dung. The purpose of study was to ensure the main effective of the whole process to theenvironment. The conclusions of whole paper were as follow:I. The results indicated that the duckweed presented the highest purification capability in1%wastewater,followed by5%wastewater. Polynomial regression analysis showed that the highest fixation of carbonand energy would be obtained under3.4%wastewater, in which ammonia nitrogen and TP were26mg/Land3.4mg/L, respectively. This study would provide the basis for the optimization of aquaculturewastewater-duckweed culture system with high biomass accumulation and pollutant removal rate.II. In the fermentation potential experiment using duckweed as substrate at35℃as previewing study,the results showed that biogas production rate could be achieved up to0.23L/gVS, even more.Comparably, the process of biogas production used mixed substrates performed better.III. For the experiment of dry anaerobic digestion under mesophilious conditions using duckweed mixedwith cow dung, the substrate ratios had been mainly investigated., which the substrate ratio was1:0.33,1:0.5,1:0.67and1:1respectively. The result showed that under mesophilious temperature and30days HRT, the better results of volumetric gas production rate with0.50L/(L·d) and material productionrate with0.33L/gVSwere achieved by1:0.67substrate ratio.