Research On Anaerobic Fermentation And Nitrogen Fixation Technology For Filtrating Swine Wastewater

Swine wastewater has high levels of suspended solids,organic matter,and nitrogen.Traditional anaerobic fermentation treatment of swine wastewater generally has the problems of long fermentation cycle,low productivity,and unstable anaerobic fermentation system.The paper starts from the practical problems of industrialization of the technology for treating swine wastewater by anaerobic fermentation,and proposes that straw filtration of swine wastewater is firstly implemented to remove suspended solids in wastewater to achieve the purpose of intensified pretreatment.After pretreatment,The content of insoluble impurities is significantly reduced,which provides convenience for subsequent anaerobic fermentation.Then,the anaerobic fermentation is optimized by changing the hydraulic retention time to improve the fermentation efficiency.Finally,the struvite precipitation method is used to fix the nitrogen in the biogas slurry after anaerobic fermentation.（1）The crushed corn straw with a particle size of 10-16 mm is used to strengthen the pretreatment of swine wastewater.The changes in p H,chemical oxygen demand（SCOD）,ammonia nitrogen（TAN）,TS,and VS before and after filtration are investigated.Determine the methane production potential of wastewater before and after filtration.The results showed that the removal rates of TS and VS in the filtered wastewater reached47.55%and 51.06%,but the removal effect of dissolved chemical oxygen demand and ammonia nitrogen content was not obvious.The removal rates were 15.22%and 7.95%.The filtrate was subjected to anaerobic fermentation.When the anaerobic fermentation reached 11 days,90%of the gas production was basically completed,while the control group only completed 60%;and the methane production potential of the filtrate was reduced by 60%compared with the control group,which effectively relieved the subsequent anaerobic fermentation pressure of swine wastewater.（2）The filtrate was treated with a full-mixed anaerobic fermentation reactor.The test results show that the effect of changing the hydraulic residence time on the p H of the anaerobic fermentation substrate is not obvious,the p H range is always between 7.5-8.0,and no acidification occurs;when the hydraulic residence time of the full-mixed anaerobic fermentation reactor is 5 d At this time,the removal rate of SCOD is only13.37%,and when the hydraulic retention time is 15 d and 25 d,the SCOD removal rate in the filtrate is above 60%;as the hydraulic retention time increases,the full-mixed anaerobic fermentation will be caused.The organic matter concentration in the reactor substrate decreased,resulting in a decrease in biogas production from 6721.89 m L to3536.65 m L when the reactor was operating stably;a fully mixed anaerobic fermentation reactor was used to treat swine wastewater.When the hydraulic retention time was 15 d,methane production The efficiency was 239.17 m LCH₄/g VS,and the removal rates of VS and SCOD were 23.74%and 60.94%,respectively.（3）High-throughput sequencing of the inoculum and three groups of substrates with stable anaerobic fermentation at different hydraulic retention times revealed that Firmicutes and Bacteroidetes are the dominant flora in the bacterial community,Methanosarcina and Methanosaeta occupies a prominent position in the archaeal community.When the hydraulic retention time is 5 d,the unclassified archaea（unclassifiedunk?norank?d?Cha Archaea）accounted for the largest proportion,reaching43.62%.The change of hydraulic retention time had a significant effect on the bacteria and archaea in the full mixed anaerobic fermentation,which was the main reason for the microbial difference between the treatment groups.（4）On the basis of previous anaerobic fermentation,the struvite sedimentation treatment is performed on the anaerobic fermentation biogas slurry with the optimal hydraulic retention time.The nitrogen and phosphorus removal rate is the index of investigation n(Mg²⁺):n（NH₄⁺）、n(PO₄^3-):n（NH₄⁺）and p H are the influencing factors.Three factors and three levels orthogonal experiments are designed.Design8.0 was used for analysis and optimization.After optimization of the experimental parameters,the molar ratio n(Mg²⁺):n(PO₄^3-):n（NH₄⁺）=1.02:1.06:1,the p H was 9.6,and the ammonia nitrogen（TAN）The removal rate reached 86.66%.In summary,the enhanced pre-treatment of swine wastewater through straw filtration and anaerobic fermentation can effectively shorten the anaerobic fermentation cycle and increase the rate of methane production.Finally,combined with struvite sedimentation method can effectively achieve swine wastewater.The removal of organic matter and the fixation of nitrogen and phosphorus are beneficial to the resource utilization of swine wastewater,and provide technical guidance for the actual project construction and operation.