Study On Treatment And Engineering Application Of Potato Starch Wastewater Based On Flat Ceramic Membrance

With the start of the strategy of becoming potato as the staple food and the increase in the demand for starch,the high viscosity and high degree of polymerization of potato starch is becoming more and more important in the Chinese market.The production of potato starch will produce a large amount of potato starch wastewater,especially high-concentration organic wastewater composed of protein liquid and starch extraction wastewater.The concentration of Chemical Oxygen Demand is high,and the main components of wastewater are protein and soluble starch,If the wastewater is discharged into natural water,it will destroy the ecological balance and cause water pollution.In this paper,the use of ceramic membranes for the separation of organic matter from high-concentration organic wastewater,on the one hand,it reduces the contaminant content of the wastewater,and on the other hand,the organics such as proteins are recycled as secondary resources.(1)Ceramic filter membrane reactor was simulated by using a commercial computational fluid dynamic code,Fluent(Fluent Inc.,Version 19.0),The media constructed in the reactor was modeled by the porous media and the wastewatersludge-air multiphase flow model of reactor were set up.The simulation results confirmed that under an aeration intensity of 0.6 m3/h,excessive aeration resulted in disturbance of the mud;when the aeration intensity is 0.2 m3/h,the reactor has excellent hydraulic conditions,and the fluid can be fully mixed and form a circular flow centered on ceramic filter membrane,which is conducive to the prevention and control of membrane fouling and the improvement of filtration efficiency;under different operating conditions,the internal flow velocity of the reactor is generally less than 0.025 m/s,but the flow velocity of the fluid near the inlet and outlet pipes and the aeration port is relatively large.The result can forecast the flow field under different conditions exactly and use this as a reference to design and fabricate a ceramic membrane reactor.(2)The potato protein from starch producing waste-water was extracted by alkali-solution and acid-isolation.The effects of p H and temperature on protein solubility and foaming properties were investigated.The results showed that the potato protein exhibited the lowest solubility and foaming around the isoelectric point p H 4.0,but the foam stability was higher.In the range of 5~65°C,the increase of the protein solubility temperature showed a trend of increasing first and then decreasing,and reached the best around 50°C.(3)Through relevant tests,the best operating conditions of the reactor were determined to be 20°C.p H 5.8 and aeration intensity of 0.2 m3/h.Under this condition,the reactor was operated to filter simulated potato starch wastewater.The COD concentration in the wastewater was decreased from 14800 mg/L to 5200 mg/L,the rejection rate was approximately 65%,and the protein concentration decreased from 6371.8 mg/L to 947.8 mg/L.the rejection rate was 83%~86%,the turbidity of effluent is less than 5 NTU,and the removal rate was up to 99%.The cleaning effect of different cleaning methods on the ceramic membrane was compared through experiments.The best cleaning agent was selected as 0.05% neutral protease.After backwashing at 130 L/(m2/h)for 5 min,the membrane flux recovered to 98.18%.And through the analysis of the phenomenon of ceramic membrane contamination,it was determined that the cleaning cycle is 100 min and the discharge cycle is 300 min.(4)Based on ceramic membrane reactor production ideas,combining with the engineering practice,the ceramic membrane separation equipment was optimized and made to treat industrial potato starch wastewater.In a single discharge cycle,protein concentration can be concentrated nearly 10 times,and the removal rate was 85%.The project economic analysis combined with 150 m3/d of high-concentration wastewater discharges resulted in an operating cost of approximately 3.828 RMB/m3,of which the pharmaceutical cost accounted for 53.03%.The benefits of resource utilization of effluent and concentrated liquid are 4.465 RMB/m3.The cost of using the "ceramic membrane separation equipment + UASB + SBBR" method to make wastewater achieving discharge standards is 4.728 RMB/m3.The results of this study show that ceramic membrane separation technology has excellent engineering application potential for the treatment of potato starch wastewater.