Research And Engineering Application Of Sweet Potato Starch Wastewater Treatment Process Based On Chitosan Flocculation Pretreatment

This study is based on the research and comprehensive demonstration project of integrated agricultural non-point source pollution control and water quality improvement in the middle and lower reaches of the Shaying River in the Huaihe River water project(project number 015ZX07204-007),taking sweet potato starch wastewater as the research object,comparing the research status at home and abroad,Through a single factor test,a comparative study on the traditional chemical flocculant and biological flocculant chitosan,screening chitosan as a flocculant for the treatment of sweet potato starch wastewater,and a pilot test study,on the basis of good results,use Chitosan flocculation-anaerobic-aerobic-advanced treatment combined process was used to treat sweet potato starch wastewater,and the feasibility of chitosan treatment of sweet potato starch wastewater and resource utilization was discussed from three aspects of protein recovery for the production of aquaculture feed.(1)Being dependent on the water quality characteristics of sweet potato starch wastewater.PAC and chitosan were selected for flocculation experiment of sweet potato starch wastewater.Through the analysis of experimental results,the traditional polymer flocculant PAC has a better removal effect on total phosphorus,while the biological flocculant chitosan has a better removal effect on total phosphorus,while the removal effects of total nitrogen and COD are also more obvious.Afterwards,an orthogonal experiment was conducted on the treatment of sweet potato starch wastewater with chitosan.The results showed that when the wastewater p H was 10,the dosage of flocculation was 48mg/L(that is,the dosage of chitosan per 1L of wastewater was 48mg),and the sedimentation The time is 45min,and the three influencing factors of chitosan flocculation to treat sweet potato starch wastewater are the order from primary to secondary:settling time>p H>dosage.The effluent COD removal rate of wastewater is 42.8%.TP removal rate is 69.2%,and TN removal rate is 39.2%.(2)Sweet potato starch wastewater contains a large amount of protein,which can be consulted by flocculation and precipitation of chitosan.The optimal flocculation parameters of protein recovery are set by experiments,and the amino acid components in the precipitate and chitosan are analyzed.It can recover 46.8%of free protein in wastewater at a p H range of 9?10,dosage of 48mg/L,precipitation still time of 40min,protein recovery rate curve is basically consistent with turbidity removal curve,turbidity removal rate can reach 84%,the remaining protein in the wastewater can be removed by the process,and the recovery of various types of amino acids mainly contains essential amino acids,and the lysine content is relatively high.(3)Based on chitosan as a flocculant for the treatment of sweet potato starch wastewater,coagulation sedimentation and coagulation air flotation processes were selected at the beginning of the primary stage,and an experimental investigation was conducted.As a pretreatment process of chitosan flocculation treatment of sweet potato starch wastewater,and the pilot test research and engineering application of chitosan treatment of sweet potato starch wastewater,the operating parameters of the pilot project were determined through the experiment:flocculation tank The p H is9?10,the flow rate of starch wastewater treatment is 10m~3/h,the flow rate of the 0.6%chitosan solution is 80L/h,and the speed of the first-level second-level three-level flocculation tank mixer is 120 r/min,120 r/Min,40 r/min,and the initial sedimentation tank residence time is 2h,good results can be achieved,the pretreatment effluent water quality is stable,and the average removal rates of COD,total phosphorus,and total nitrogen are 26.45%,60.01%,and 31.66%,respectively.(4)Since the"Twelfth Five-Year Plan"water project has higher requirements for the discharge of sweet potato starch wastewater,on the premise of determining the good effect of chitosan flocculation pretreatment,choose an improved IC reactor-an improved oxidation ditch-Two-stage ecological pond combined process to treat sweet potato starch wastewater and carry out on-site debugging to explore the effect and applicability of the combined process on the treatment of rural sweet potato starch wastewater The monitoring of the water quality of the combined process in the last 14days shows that the combined removal rate of COD,ammonia nitrogen,total phosphorus and total nitrogen by the combined process is 99.7%,95.1%,93.1%and93.5%,and the effect is good.