Research On Biogas Production And Microcystin Biodegradation In Biogas Fermentation Of Blue Algae From Dianchi Lake

In order to realize the effective treatment of blue algae and solve the limitationof microcystins on comprehensive utilization of blue algae from Dianhi Lake, thispaper aimed to establish biogas fermentation system of blue alage and explore thedegradation rule of microcystins with different fermentation conditions, increase therate of microcystins degradation.This paper mainly carried on4aspects: the biogas fermentation experimentalstudy of different inoculum with blue algae; the biogas fermentation experimentalstudy of different treatment with blue algae; the biogas fermentation experimentalstudy of blue algae with different fermentation temperature; the biogas fermentationexperimental study of different adding amount of blue algae.The experimental results showed: using mixture fermentation residue (blue algaeand other raw material fermentation residue) as inoculum, using blue alage afternatural placed7d as raw materials, microcystins can be degraded effectively in thebiogas fermentation system. The degradation process of microcystins included threeperiods: rapid degradation period, fluctuation period and stable period. The gaspotential of raw material can increased with increase of fermentation temperature forbiogas fermentation experiment of blue alage at the room temperature,20degree,25degree,30degree,35degree. The fermentation temperature mainly had effect ondegradation of microcystin during its rapid degradation stage. The higher thetemperature, the higher the degradation rate. The final concentration of microcystinwas range from26.98ng/mL to41.81ng/mL. At35degree, the biogas potential ofblue algae was not affected by the addition of raw materials (10%,20%,30%,40%,50%,60%,70%). The initial concentration of microcystin had a strong influence onthe final degradation level of microcystins. The general trend was that the higher theinitial concentration, the lower the amount of degradation. It can reach1.86ng/mLand the rate of microcystin degradation was98.52percent. It made microcystinconcentration of1ng/mL (national hygiene standards) possible in biogas fermentationsysterm. In the process of biogas fermentation of blue algae, the pH was changed during rapid degradation and fluctuating period of microcystin concentration. Thisstage was main process of biogas production as well. It showed a tendency towardstabilization to microcystin concentration, biogas production and pH value.Through the above results, microcystin degradation can be reached lower level at35degree in biogas fermentation experiment of adding40%blue algae. At the sametime, microcystins can be degraded effectively and biogas can be producted in thebiogas fermentation system. The safety assurance can be provided for thecomprehensive utilization of biogas residues, such as fertilizer, feed and so on.