| In recent years, as the breeding scale of sturgeons expands gradually, the consequent water waste problem and the pollution caused by emission of aquaculture wastewater become obvious, which also retard the further development of sturgeon culture. In this article, the tail water in breeding of sturgeons was used to plant micro-alga, and the two-stage anaerobic fermentation based on coupling of planted micro-algae and aquaculture waste was researched in order to render important reference for resourceful utilization of sturgeon aquaculture wastewater and promotion and application of algae biomass conversion technology.Results of experiment of micro-algae cultivating in sturgeon aquaculture wastewater showed that when the light intensity was 4500 lux, light-dark ratio was 12 h to 12 h, and the inoculation of was 106/ml, chlorella and scenedesmus could absorb the pollutants in the sturgeon aquaculture wastewater such as NH4 +-N, NO2--N, NO3--N and PO43--P, and brought about the growth of algae cells; when the concentration of NH4 +-N, NO2-- N, NO3-- N and PO43--P in tail water was 0.93 ~ 4.22 mg / L, 0.11 ~ 0.24 mg / L, 8.75 ~ 12.10 mg / L and 0.08 ~ 0.41 mg / L, and cultivating for 8d later, chlorella and scenedesmus reached to 6~7.5 and 6~8 times than the initial biomass.In the process of micro-algae cultivation by using sturgeon tail water, when NH4+-N was 0.93, 2.33 and 4.22 mg /L, and the cultivation time of chlorella was 12 h, 24 h and 48 h, respectively, the removal rate of NH4+-N reached 100%, while after cultivating scenedesmus for 8d, the removal rate was 89.3%, 88.23% and 52.2%; when NO3--N in cultivating tail water is 10.96,11.38 and 12.10 mg/L, and 8d for chlorella cultivation, the removal rate of NO3--N reached 100%, while after 8d of scenedesmus cultivation, the removal rate of NO3--N is only 16.1%, 17.1% and 16.1%; when PO43-P concentration in tail water is 0.15、0.24 and 0.41 mg /L, and 4h, 5h and 8h of chlorella cultivation, the removal rate PO43--P was up to 100%, while the complete absorption for algae required 4d、6d and 8d in cultivation of scenedesmus. Using sturgeon tail water to cultivate chlorella have a better affect on purifying aquaculture wastewater than scenedesmus.Results of production of biogas from coupling of micro-algae and artificial solid waste by two-stage anaerobic fermentation showed that in acid hydrolysis p Hase, when the mass ratio of inoculated sludge, algae liquid and cultivated solid waste was 1:10:10, feed concentration was 6%,and p H is 7, after hydrolysis acidification for 4d at 35 ± 1 ℃,the VFA concentration of acidification material was 16504.6±200mg/L,under this conditions two-stage anaerobic fermentation acidified liquid could be obtained; in addition, after pre-trial of methanogenic p Hase started 10 d, the gas production of the system would come to a peak time and continued to 18 d, and the gas production basically ended after 22d; The experimental results of anaerobic fermentation of acidification material showed that if 20 g acidified liquid was added to the system every day after the methanogenic phase started 16 d, and the Hydraulic Retention Time was 10 d, gas production of this system remained stable after 23 d.The average daily gas production reached 537.5ml/d, VS gas production rate was 394.6 L/kg, and methane content of the gas was 82.2%, and material p H value during methanogenic phase remained between 7.63~7.77. Compared with the previous research, although the two-phase anaerobic fermentation VS gas yield was nearly close to single-phase anaerobic fermentation, the former one still continued gas production after 26 d, and the latter only lasted about 20d; furthermore, the methane content of two-phase anaerobic fermentation was 1.44 times that of single-phase anaerobic fermentation, which significantly improve quality of biogas. It could be seen that micro-algae cultivating with sturgeon tail water not only get algae biomass, but also purify water, meanwhile it could achieve the conversion of Environment-Enhancing Energy. |
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