Research On The Harmless Treatment Of Cyanobacteria’s Fermentation After Being Pressured

In order to reduce the pollution of cyanobacteria bloom in the lake, the method of salvage is used to concentrate the cyanobacteria to the algae station. And then coagulating sedimentation is used to enrich cyanobacteria after being pressured. This research focus on the treatment of enriched cyanobacteria after being pressured in order to get harmless disposal and resource utilization method. This research adopts anaerobic fermentation and aerobic composting to remove microcystic toxins that are harmful to human health, and anaerobic fermentation can produce biogas as energy material, after fermentation, the biogas slurry can be used as organic fertilizer. And aerobic composting can form solid fertilizer. In this paper, we mainly study on whether pressure can promote fermentation process; the optimum conditions of anaerobic fermentation of cyanobacteria, with activated sludge; under the optimal conditions, the cyanobacteria’s anaerobic fermentation process; the aerobic composting of cyanobacteria, adding wheat bran and activated sludge, remove microcystic toxins. The main results are as follows:(1) At the same temperature (35℃), the same TS content (3.7%), the same weight of cyanobacteria (19Kg) as fermentation substrate conditions, we compared the anaerobic fermentation of without pressure group of cyanobacteria and after pressure group of cyanobacteria,without inoculated sludge.The result is that pressure treatment is beneficial to anaerobic fermentation. Without inoculation sludge anaerobic fermentation’s harmless cycle is 18 days, gas production cycle is 28 days. After 18 days,the biogas production is rarely. So the hydraulic retention time (HRT) of anaerobic fermentation’s reactor is 18 days, subsequent fertility is maintained.(2) At different temperature(33 ℃,35 ℃,38 ℃) and different inoculation sludge ratio (1:8、1:6、1:4), the same TS content (3.65%) and with the same weight cyanobacteria slurry as fermentation substrate conditions, the optimum conditions of pressurized cyanobacteria’s anaerobic fermentation is that best temperature is 35 ℃, best sludge inoculation TS ratio is 1:6. During the anaerobic fermentation of cyanobacteria,most microcystic removal within 25 days, the 49th day removal rate reached more than 99%, close to 100%, so at 35 ℃ and with 1:6 inoculated sludge TS ratio, the most economical harmless disposal cycle is 25 days.(3) At optimal conditions (35 ℃, sludge inoculation ratio is 1:6), we contrast anaerobic fermentation of without pressure group.composed of natural cyanobacteria (TS=3.01%), and pressurized group,concentrated by precipitation pool (TS=5.87%).We verify the pressure is beneficial to anaerobic fermentation. The most economic cycle of pressurized cyanobacteria’s anaerobic fermentation is 30 days. Within 30 days, most biogas are produced, and most microcystic is removed, fertilizer can be reserved.(4) At 35℃,we compared the aerobic composting of cyanobacteria, mixed with wheat bran and activated sludge. We find that adding wheat bran is conducive to rapid degradation of microcystic, and can improve the removal rate. And adding activated sludge is beneficial to the rapid degradation of microcystic, but on the removal rate has no significant effect. The vast most microcystics are removed within 16 days. So the most economical harmless cycle is 16 days.