Research On Characteristics Of Typical Food Industry Wastewater Treatment By Biological Rotating Cage And Optimized Operation Management

Food industry wastewater has the characteristics of high organic matter,high suspended matter,high biodegradability and large fluctuation in water quality.It belongs to highly polluted and easily degradable industrial wastewater.The common treatment processes for this wastewater are mainly activated sludge method and biofilm method.The two methods both have engineering examples in practical applications.The high energy waste problem caused by the poor operation management mode is an urgent problem to be solved in the energy saving and consumption reduction of food industry wastewater treatment.The biofilm method has strong impact resistance and is suitable for long-generation cycle microbial growth,and is more suitable for food industry wastewater treatment.Due to its unique oxygenation and mixing method,the Rotating Biological Contactor(RBC)makes wastewater treatment more energy-saving and efficient.In order to improve the performance of the RBC,it can be filled with bio-fillers,providing more carrier area for biofilm to achieve higher wastewater treatment efficiency.The study analyzed the water quality characteristics of food industry wastewater and designed an integrated Biological Rotating Cage(RBC)wastewater treatment device.The reactor packing optimal filling ratio,biofilm performance,the wastewater treatment characteristics and biological community characteristics under a series of C:N load and different rotation speeds were studied.The energy consumption of the reactor at different speeds were analyzed to obtain the optimal operating parameters for the RBC.By analyzing the oxygen mass transfer characteristics in RBC,a physical oxygen mass transfer model based on the DO balance was constructed and verified.Then the model was used to explain the features and effects of the RBC,providingoptimal operating parameters.The main research content and results of this study are as follows:(1)Based on the typical characteristics of food industry wastewater quality,the food industry wastewater quality and treatment requirements were analyzed,and an integrated wastewater treatment device was designed and developed according to target parameters.And the device integrates a biological rotating cage reactor,a regulating tank,a secondary settling tank,a sludge drying tank,a dosing tank,a detection system and a control system.The device is designed with an effective reactor volume of 3 m³,a processing capacity of12 m³·d^-1,and a rotation speed of 1?7 r·min^-1,which can monitor sewage water quality in real time and control multiple parameters.(2)The rotating cage in the reactor is equipped with 40 packing grids,and each grid can be filled with 0.11 m³ packing.Introduce seed sludge and add nutrients to start the reactor to biofilm formation.After the film is mature,the six gradients of biofilm growth and biofilm wastewater treatment performance with filling ratios of 0.4?0.5,0.5?0.6,0.6?0.7,0.7?0.8,0.8?0.9 and>0.9 are explored.The results of the study showed that the mass of biofilm on the filler increased with the increase of the filling ratio,ranging from65.02 to 147.23 mg·grain^-1,but the thicker the biofilm,the lower the density,ranging from 68.10 to 59.79 mg·m^-3.Biofilm had better COD removal and denitrification ability,and the thicker the biofilm,the better the denitrification ability.Comprehensive comparison of the reactor filler filling ratio biofilm amount,biofilm structure and biofilm performance,the optimal reactor filling ratio is between 0.7?0.9.(3)After determining the optimal filling ratio of the filler,explore the pollutant removal ability and the evolution of the microbial community in the food industry wastewater with different C:N(C:N is 20,25,30,and 35).The research results show that the average removal rate of COD and NH4⁺-N is 99.18%and 86.27%when C:N?30,respectively.When C:N?35,the concentration of COD and NH4⁺-N effluent starts to rise,but the average removal rate of COD is still more than 90%.The removal capacity of NO3^--N and NO2^--N in the reactor is positively related to temperature,meaning that the higher the temperature,the lower the effluent concentration of NO3^--N and NO2^--N,which is lower than 4 mg·L^-1 and 0.05 mg·L^-1.The analysis of the microbial community structure shows that when C:N?30,the microbial diversity increases with the increase of C:N.When C:N?35,the COD load in the reactor is relatively large,resulting in a decline in the diversity of functional microbial communities and a decline in water quality.Therefore,the reactor is suitable for processing wastewater from food industry with C:N?30.(4)After probing the C:N capacity of the reactor during operation,explore the pollutant removal characteristics of the reactor at different speeds under low C:N food industrial wastewater,and optimize the operating parameters of the reactor to achieve the purpose of energy saving and consumption reduction.The experimental research results show that at the experimental speed(1.0?3.0 r·min^-1,the gradient is 0.5 r·min^-1),the operating speed of the reactor is positively correlated with the COD removal rate,and the average removal rate is 318.76?499.84 mg·L^-1·h^-1,theoretically the COD removal capacity of this reactor is 21.92(±1.0)?36.85(±1.7)kg COD·d^-1.The average removal rate of NH₄⁺-N by the reactor is 4.56?8.4 mg·L^-1·h^-1(the average removal rate of NH₄⁺-N at the speed of 2.0 r·min^-1 and 2.5 r·min^-1 is the largest,respectively 8.4 mg·L^-1·h^-1 and8.35 mg·L^-1·h^-1),theoretically the total amount of NH₄⁺-N removed per day is 0.3428?0.6114 kg.The more sufficient COD in the reactor,the lower the concentration of NO3^--N and NO2^--N in the effluent.Energy consumption analysis of the reactor shows that the higher the rotation speed,the higher the energy consumption.The energy consumption per unit mass COD(kg)removal is 0.11?0.17 k Wh·kg COD^-1,which is compared with the traditional process(the rotation speed is 1.0?3.0 r·min^-1),and the energy saving2.55%?90.69%.Comprehensive analysis of the removal rate and energy consumption of COD,NH4⁺-N,NO3^--N and NO2^--N at different speeds,the optimal operating rate of the reactor is determined to be 2.0?2.5 r·min^-1.(5)A physical oxygen mass transfer model was constructed according to the DO change rule of the reactor under the impermissible speed,which could explain the pollutant degradation rule and realize the optimization of operation.The thesis builds a model for the two oxygen processes of“air-solution”and“air-biofilm”from the microscopic view,and calculates the pollutant removal rate and the oxygen consumption of the poplar macroscopically,and compares the microscopic and macroscopic results to complete the model verification.The model is used to explain the linear relationship of the pollutant degradation rate with the rotation speed and the simulation gives a reactor operation plan that meets the requirements.