Purifying Sewage Water Hyacinth And Energy Utilization

Water hyacinth(Eichhornia crassipes),introduced into China in 1930's,spreads very quickly in recent years because of water eutrophication in watershed areas.It has become a social problem as it occpies waterway,disturbs aquatic ecosystem equilibrium and impacts local economics.This work follows the basic principles of ecological engineering for the control and utilization of water hyacinth.Firstly,the state-of-the-art growth pattern of water hyacinth was field investigated while the causes of rapid spread of the plant were probed at the laboratory.Based on the study,measures for water hyacinth control were proposed.Secondly, the efficiency of nutrient removals in the eutrophication water by water hyacinth harvest was calculated.Thirdly,anaerobic fermentation of water hyacinth for biogas production was developed for water hyacinth,at both laboratory and pilot scales.Main results of this study are concluded as follows.(1)Waste water from livestock could promote the growth rate of water hyacinth remarkably.The plants double in 5 days in livestock waste water with moderate concentrations (COD_crranged from 500 to 700 mg/L).(2)The plant has significant purification ability,the removal rates of COD,TN and TP in 30 days reach 66%-90%,70%-85%and 55%-60%,respectively.The purification rate of water hyacinth for moderate pollution livestock waste water is highly correlated with first order kinetics equation,and purification rate of COD and TN decreasing concentration of waste water,while the purification rate for TP is less affected by initial pollutant concentration in waste water.(3)The water hyacinth takes dissolved nutrient in water for photosynthesis and growth.It was estimated that the maximum surplus production of water hyacinth was about 0.056 kg/m²Â·a TN and 0.013 kg/m²Â·a TP.(4)Parameters such as inoculating ratio,chopping size,and temperature on anaerobic fermention of water hyacinth were tested and an optimum inoculating ratio 1:1(TS);The maximum yield of gas was 0.5316 m³/kg(TS) by weight of water hyacinth;Comparing with theapplication of middle temperature,higher temperature has no obvious advantage for biogas production;Water hyacinth anaerobic digestion general acidification time is 5-10 days.(5) Early water hyacinth anaerobic digestion,pH lower quickly,up to the lowest point. Subsequently,pH increased,with reaction of Methane-producing.The end of anaerobic digestion,pH stabilized,and the gas production procesd into stagnation.(6) Water hyacinth anaerobic digestion biogas is the flammable gas,the main component of the total volume of methane of around 60%.After anaerobic digestion,the elements of the using have almost no losses.Organic matter content is higher than human waste 5-6 times,the residue of fertilizer higher in nutrients,riching in organic matter and more of humic acid.