| With the water pollution problems become more serious in our country,the country’s requirements for sewage treatment are becoming more stringent.This requires appropriate improvements based on traditional wastewater treatment processes to obtain more economical and efficient methods.Biofilm method is one of the most important methods in the field of sewage treatment.It is widely used due to its excellent shock resistance capacity and high efficiency.In the biofilm process,the biofilm filler plays a decisive role in the process effect Therefore,it is very important to find a carrier material with good biocompatibility,strong corrosion resistance,low cost and easy availability,and environmental protection.it is very important to find carrier materials with good biocompatibility,strong corrosion resistance,low cost and environmental protection for broadening the application scale of biofilm method in engineering field.Excessive soybean stalks can cause serious pollution problems and threaten human life and health if its disposal methods are unreasonable,such as incineration Therefore,how to rationally realize the comprehensive utilization of straw and broaden the field of straw resource utilization according to the characteristics of straw is one of the problems that need to be solved in China todayIn this paper,soybean straws were used as biofilm carrier to construct a double-cell switching biofilm system to treat simulated domestic sewage.The reactor in the experiment consists of four independent single cells(numbered sequentially from the influent to the effluent).Conversion of anoxic/aerobic function of reaction tank is realized by controlling the alternating aeration of pool I and pool II,and the III pool is always in an aerobic state Combining soybean straw with polyethylene mesh and suspension ball to build packing module.In this paper the microbial adhesion of soybean straw and the feasibility of its use as carriers were explored.The optimal operation mode of the reaction system was discussed,the characteristics of the reaction system were analyzed,and the pollutant removal effect under the optimal operation mode was optimizedAfter the packing module is placed in the reaction tank,the COD content in the leachate can reach 750 mg/L,indicating that the straw can provide sufficient carbon source for the reaction system during the film hanging process,which can save operation cost.The inoculated sludge was cultured and added to the reaction cell for membrane-hanging experiments.The whole process was divided into static and dynamic membrane-hanging.The removal effect of the pollutants was measured at the dynamic film-hanging stage.When the removal rate of COD and ammonia nitrogen in the reaction system was finally stabilized at 86%and 80%,it was confirmed that the film was completed.After the completion of microbial,the weight of the carriers increased significantly and the amount of suspended sludge in the reaction tank was very small,which indicated that the straw had good microbial adhesion performance,and it was very feasible to use the soybean straw as a biofilm filler.The experiment explored the changes in the removal efficiency of COD,ammonia nitrogen,total nitrogen,phosphorus in the reaction system when operating in repeated aeration mode.The results showed that the removal rate of pollutants in the reaction system would be reduced by the influence of switching aeration,but the decrease was not significant and then there was a trend of recovery.This indicated that the biofilm system had a certain impact load resistance capacity,and also showed the feasibility of operating the system by switching aeration mode.The optimal operation mode of the reaction system was discussed by changing the length of the alternate aeration.In the aeration mode in which O/A/O was switched to A/O/O,the reaction system was operated for 5 days,10 days,and 15 days,respectively.The experimental results showed that the reaction system could achieve the best effect on the removal of COD and ammonia nitrogen when the length of the alternating aeration was 15 days,which could reach 90%and 85%respectively.And the removal rate of total nitrogen could also reach about 55%.After 30 days in the unfavorable environment where the reaction system was at a low temperature and no nutrient source,the removal ability of the contaminant could be restored in only 5 days.It showed that the microorganisms in this system had strong viability and good tolerance to adverse environments.Aiming at the problem of high NO3--N content in effluent and unsatisfactory removal effect of total nitrogen when treating simulated domestic sewage under the optimal operation mode.The improvement was made by increasing the reflux of the nitrifying liquid without changing other conditions.The results showed that the system had a significant increase in the removal rate of total nitrogen,which could reach more than 70%.In the later stage of operation,the average concentrations of COD,ammonia nitrogen and total nitrogen in the effluent were 37mg/L,5.81mg/L and 8.68mg/L,respectively,which could meet the first-class standard of urban sewage discharge standards.Therefore,using straw as filler for sewage treatment can not only recycle straw,but also achieve the effect of environmental protection and improve the economic value of straw.It has certain reference value for the field of sewage treatment technology and agricultural waste recycling. |
