Feasibility Study On Coagulation Biochemical Fenton Treatment Of Winter Melon Processing Wastewater

Since ancient times,clothing,food,housing,and transportation have been the basic needs of human life.With the gradual improvement of people’s living requirements,the raw materials for food are becoming increasingly abundant,which also leads to the complexity of food processing wastewater.Among them,the quality of winter melon processing wastewater produced by moon cake processing plants using winter melon as raw material is more complex,with characteristics such as high COD,high SS,and high chroma.For such wastewater,there are few reports in China on research and treatment methods.Therefore,it is particularly necessary to explore processes that can achieve good treatment effects for such wastewater.This study focuses on the wax gourd processing wastewater in food processing wastewater.The wastewater is taken from the actual production wastewater of a mooncake processing factory in Jingzhou City,Hubei Province.The operation effect of the combined process of pretreatment-biochemical treatment-deep oxidation treatment on the actual wastewater is investigated to explore whether the effluent quality can meet the discharge standard.Through experimental research on the selection of pre-treatment microfiltration machines,operating conditions of coagulation process,biofilm formation period of biochemical reaction,stable operation effect of biochemical reaction,and operating parameters of deep oxidation,the following conclusions are drawn:(1)The pre-treatment process involves removing SS from the wastewater through a medium grid and a rotary drum grid machine(with a gap of 1 mm).SS is reduced to about210～300 mg/L,turbidity is about 50 NTU,and suspended solids removal rate is about83%.By comparing the removal effects of PAC and PFS on pollutants in wastewater,PFS was selected as the suitable flocculant for the wastewater.The single factor experiment shows that when the p H is 7,the dosage of PFS and PAM is about 500 mg/L,and the dosage of PAM is about 2 mg/L,respectively,the optimal treatment effect is achieved.Using RSM to predict the optimal reaction conditions,the dosage of PFS is 479.710 mg/L,the dosage of PAM is 1.853 mg/L,and the p H is 6.999.At this time,the COD removal rate is 27.212%,the turbidity removal rate is 42.547%,and the TP removal rate is about80% according to the experimental data.(2)The two-stage sludge acclimation method is adopted,and the period from the cultivation system to adapt to the wastewater quality is about 56 days.During the stable operation of the system,the COD in the effluent is about 800 mg/L,and the removal rate is stable to about 85%.The ammonia nitrogen in the effluent is about 22 mg/L,and the removal rate is stable to about 74%.The TP in the effluent is about 1.25 mg/L,and the removal rate is stable to 72%.Through three-dimensional fluorescence spectroscopy analysis,the types of dissolved organic compounds in wastewater are reduced,leaving only hydrophobic acids and fulvic acids,which are difficult to degrade by conventional biochemistry,and the fluorescence intensity of DOM in wastewater is greatly reduced.(3)Through a single factor experiment affecting the biochemical treatment effect,it was shown that the optimal reaction conditions and effects of biochemical treatment were: under the conditions of HRT of 36 hours,nitrification liquid reflux ratio of 250%,DO concentration of 4 mg/L,and temperature of 25 ℃,the system had the best treatment effect on pollutants,with effluent COD,ammonia nitrogen,and TP concentrations reaching 662 mg/L,13.5 mg/L,and 0.94 mg/L,respectively,with removal rates of 91.2%,82.2%,and 81.8%.In addition,through biochemical treatment,the chromaticity decreases from about 80 times that of the influent water to below 50 times.(4)Through experimental research on the factors affecting the effect of Fenton,it was found that the suitable conditions were hydrogen peroxide to ferrous iron dosage ratio of 1-2,p H of 3-4,and reaction time of 0.5 to 1.5 h.Using RSM to model fit the three influencing factors of Fenton reagent dosage ratio,initial reaction p H,and reaction time with COD removal rate,it was found that the order of significance of COD removal rate was p H>dosage ratio>reaction time,and there was an interaction between the three factors.The optimal reaction conditions were predicted as follows: the dosage ratio was1.502,the p H was 3.594,the reaction time was 0.897 h,and the COD removal rate was67.598%.Through experimental verification,the relative deviation was less than 3%.(5)Through the combined process,the wastewater quality changes from COD to12000 mg/L,ammonia nitrogen to 70 to 90 mg/L,TP to 20 to 30 mg/L,SS to 1000 to1200 mg/L,p H to 3 to 4,and chromaticity to about 300 times.The effluent decreases to a stable COD of less than 500 mg/L,ammonia nitrogen to less than 25 mg/L,turbidity of about 20 NTU,TP to about 1 mg/L,and chromaticity of less than 50 times.In addition to TP,the effluent meets the Class III standard in Table 4 of the Comprehensive Wastewater Discharge Standard(GB 8978-1996),while the slightly higher concentration of TP is due to the fact that the biochemical reaction device has not yet been equipped with a sedimentation tank.