Study On Treatment Of High Concentration Food Waste Leachate

Kitchen waste leachate is a complicated waste water with high concentration of organic matter, inorganic salt, ammonia nitrogen and various trace elements, which will make a serious impact on the environment if it is not timely and effectively treated.The kitchen wastes were collected from a student canteen at Jishou University to produce kitchen waste leachate in the laboratory in an anaerobic acidogenic reactor. The main purpose of this study was to investigate the change law of characteristics of kitchen waste leachate with fermentation time and the treatment efficiency of K2FeO4 and microbial fuel cell(MFC) on kitchen waste leachate.The main conclusions are as follows:(1)The concentration of COD and NH4+-N for formed kitchen waste leachate after reaction for 8 weeks is more than 140.6 g/L and 16.2 g/L.(2)K2FeO4 was synthesized using a new ultrasonic-assisted chemical method and the microstructure, morphology were investigated by X-ray diffraction(XRD), Fourier transform infrared(FT-IR) spectrum and scanning electron microscope(SEM).The treatment efficiency of COD and NH4+-N of kitchen waste leachate by K2FeO4 were discussed.Results show that as-prepared K2FeO4 presents a tetrahedral structure with a space group of D2h(Pnma).The yield of K2FeO4 was more than 68.2%with high purity of 98.3%.SEM demonstrated that the K2FeO4 particles were in a regular strip shape with some agglomeration between the particles.When 0.12 mol/L K2FeO4 was added to 100 mL kitchen waste leachate with initial COD concentration of 140.6 g/L and pH was adjusted to 8.7 for 24 min, the removal rate of COD and ammonia nitrogen was more than 80.4% and 75.9%, respectively. The mechanisms of removal of COD and NH4+-N by K2FeO4 were discussed. There is a synergistic effect of the strong oxidation of K2FeO4 and the flocculation of the new formed Fe(OH)3.(3)Electricigen F026 with good electrochemical activity were enriched and screened. F026 was closely related to genus Pseudomonas with 16 S rRNA gene sequence similarity value of 98.62%(Pseudomonas otitidis MCC10330T).Results of biological characteristics show that F026 grew well on 20-40oC with optimal temperature of 30-35 oC and the growth of the strain occurred in the pH range 5-9 with optimal pH 8-9, suggesting F026 is a promissing efficient electricigen for MFC.(4)The effects of substrate species and concentration on the electricity generation of MFC with F026 as electricigen in view of start-up time, time need to obtained stable open circuit voltage, electromotive force, internal resistance and power density were investigated. Experimental results showed that the substrate species and concentration greatly influenced the electricity generation of MFC probably due to their difference in structure. As results, it found that the white dextrin-fed MFC could be started up in shorter time with smaller internal resistance and smaller electromotive force and smaller power density. Under the same conditions, the soluble starch-fed MFC had larger electromotive force, larger power density, bigger internal resistance and longer time to be started-up. The results also indicated that an increase in the substrate concentration increased the time needed to reach constant OCV at low concentration of 2-6g/L for soluble starch and 2-8 g/L for white dextrin. While an opposite trend was observed at high concentration of 8-20 g/L for soluble starch and 10-20 g/L for white dextrin attributed to the substrate inhibition effect.(5)MFC was assembled using KMnO4 solution as catholyte, kitchen waste leachate as anolyte and F026 as electricigen. The electricity generation and COD removal efficiency of MFC were investigated. Iit was observed that maximum 1.14 V open circuit voltage(OCV) was obtained for the COD concentration of 50.0g/L. At optimum condition with external load of 105?, MFC gave 69.63 A/m3 of current density,16.42 W/m3 of power density and 58.7% of coulombic efficiency(CE) along with the substrate removal of 92.3% in terms of COD, suggesting the possibilities to reduce the quantity of kitchen waste leachate along with the production of bio-electricity.