Effects Of Sturgeon Culturing Water Purification And Biogas Production By Microalgae

In recent years, sturgeon farming has been developed rapidly in China. However, intensiveculture of sturgeon discharged large amount of nutrients into aquatic ecosystems and lead tofresh water resources exhausted, environmental pollution and increasing of production costsand so on. Therefore, sturgeon culturing water purification and utilization is the key for thedevelopment of sturgeon culture. In this paper, sturgeon culturing water purification andbiogas production were studied, which aims at to provide the necessary reference for thesturgeon culturing wastewater purification and resource utilization for large-scale application.Experiments on water purification properties of microalgae were carried out. Experimentalresults indicated that NH4+-N and PO43--P could be removed effectively by Chlorella vulgaris.The removal efficiency of NH4+-N would be above90%when its concentration was kept at2.0~6.0mg/L; Meanwhile, when the concentration of PO43--P was0.590mg/L, the removalefficiency could reach to94.6%; Maximum specific removal rate of NH4+-N and PO43--P were2.657mg/(L· d) and0.445mg/(L· d), respectively; Additionally, algal cell density wouldincrease from1.33×107/mL to2.61×107/mL by72h when the concentration of NH4+-Nincreased from0.8to10.0mg/L. In addition, experiments on culturing of Scenedesmus inartificial sturgeon culture wastewater were carried out. Results indicated that removalefficiency of NH4+-N, NO2--N, NO3--N and PO43--P were around95%,90%,93%and96%,respectively, when initial NH4+-N concentration was0.6,0.8and1.0mg/L after6days ofcultivation. When initial NH4+-N concentration was0.6,0.8and1.0mg/L, the removal rate ofCOD were32.2%,34.7%and35.5%, respectively, and algal cell biomass increased from2.01×106/mL to4.30×106,4.64×106and4.87×106/mL after6days of cultivation.Design a small runway pool-type photobioreactor for the cultivation of microalgae in thelaboratory. In this part, Scenedesmus was cultivated in sturgeon culture wastewater, nutrientremoval efficiency of Scenedesmus under different concentrations of wastewater were studied.Experimental results indicated that nitrogen and phosphorus could be removed effectively byScenedesmus. The removal efficiency of NH4+-N, NO3--N and PO43--P and total inorganicnitrogen were around20.8%,40.6%,98.4%and34.5%, respectively. Meanwhile, algal cellbiomass increased from1.98×105,2.14×105, and2.29×105/mL to2.11×106,3.73×106and5.56×106/mL after18days of cultivation. Therefore, culturing of Scenedesmus in sturgeonculture wastewater would be promising in water purification and the harvesting of algalbiomass.Microalgae and aquaculture waste anaerobic fermentation biogas production test resultsshow that the direct use of Scenedesmus anaerobic fermentation, gas production, gas production rate and methane content of the biogas were228.5mL,78.0mL/gVS and42.3%.Adding aquaculture wastes could increase gas production obviously. When inoculatedsludge, Scenedesmus and aquaculture solid waste ratio was1:1:1, the total gas production,gas production rate and methane content of the gas produced were4412.5mL,499.7mL/gVSand47.4%. The removal rate of COD were84.0%. Thermal hydrolysis, ultrasound treatmentScenedesmus can increase gas production, and the highest increase was achieved for thethermal hydrolysis. The gas production lasts for27days. The total gas production, gasproduction rate and methane content of the gas produced were3854.0mL,492.2mL/gVS,49.6%. The removal rate of COD were86.6%. In addition, proportion of sludge couldsignificantly increase gas production and gas production rate, and increasing the amount ofinoculation can accelerate the progress of the reaction, when inoculated sludge, Scenedesmusand aquaculture waste ratio is1:1:1.5, the Scenedesmus and aquaculture waste anaerobicfermentation of total gas production and gas production rates were3654.5mL and478.3mL/gVS, and the methane content of the gas produced reach the highest ratio of57.2%, gasproduction continuing for26d.