Research On Kinetics Of COD Degradation In CASS Plus Filler Process Treating Mustard Tuber Wastewater

The mustard wastewater treatment is difficult because it contains high salt,high nitrogen and phosphorus,and high concentrations of organic matter.At present,the treatment of mustard wastewater is still based on biochemical methods,but it is limited by the degree of salt suppression,There are only a limited number of companies that can operate normally up to standard emissions.Based on the production commissioning operation of a chemical dephosphorization-two-phase anaerobic-CASS plus packing process in a mustard wastewater treatment station in Chongqing,this study systematically studied the COD degradation of CASS plus packing units and established a fixed salinity kinetic model of COD degradation.The CASS filling unit is enriched with suspended and attached salt-tolerant microorganism,and the biological population is complex and diverse.This project analyzes the COD degradation process of CASS plus packing system,taking into account the influencing factors such as temperature,water quality and quantity change,mass transfer efficiency and so on.After reasonable simplification,the COD degradation kinetics model was established based on Grau model,MSK model and material balance,and the kinetic parameters were obtained by graphical method through monitoring data.It is found that the Grau second-order model and the MSK kinetic model can better reflect the COD degradation process of the CASS filling system,accurately predict the COD concentration of effluent,and the MSK model has better simulation effect than the Grau model.Actual production commissioning operation data indicates:(1)The two-phase anaerobic treatment unit has strong impact load resistance capacity,which ensures the stability of the inlet water quality of the CASS filling unit;(2)Based on the Grau second-order model and MSK model,the COD degradation kinetics model was established with salinity-inhibited of 1.5%,and the simulation effect was better.When the temperature is in the range of 10°C-15°C,the kinetic parameter K of the Grau second-order model is 0.168d^-1,and the kinetic parameters K_B and U_max of the MSK model are:4.056g/L and 3.333g/L respectively;When the temperature is in the range of15°C-20°C,the kinetic parameter K of the Grau second-order model is 2.685 d^-1,and the kinetic parameters K_B and U_max of the MSK model are 6.785 g/L and 5.000 g/L respectively.(3)The temperature affects the microbial activity.Within the operating temperature range of the project,the higher the temperature,the higher the microbial activity and the greater the COD degradation rate.The conclusions of this study can be used to guide the design and operation of mustard wastewater or similar high-salt wastewater treatment projects.