Treatment Of Molecular Sieve Production Wastewater Through Two-staged A/O Process

Zeolite molecular sieve is a kind of catalyst with high shape selectivity.It is widely used in the heterogeneous catalysis process of methanol to olefin,alkylation,propylene epoxidation,etc.The wastewater produced in the production process of molecular sieve catalyst belongs to hardly-degradable industrial wastewater which is characterized often contains complex composition,high concentration of organic matter.At present,the research on the treatment of this kind of industrial wastewater is relatively limited,especially in the research of biochemical treatment.This thesis takes the SPAO-34 molecular sieve catalyst production wastewater provided by a company as the research object,and conducts a small laboratory test on the pretreatment process of membrane pretreatment based on the two-stage A/O process.The operation of the unit and the removal of pollutants have been monitored for a long time to analyze the feasibility of the combined process.In addition,the wastewater that has not undergone physical and chemical pretreatment is directly treated with a system that has undergone long-term actual wastewater domestication,and its treatment effect is explored and compared with the combined process.The main conclusions are as follows.（1）Chemical precipitation-two-stage A/O process is used to treat molecular sieve catalyst wastewater.After chemical precipitation treatment,5.9%of COD and 23.1%of ammonia nitrogen can be removed,mainly for the removal of SS and TP,and the average TP of wastewater is3500±176mg/L,the average concentration after chemical precipitation is 50±10mg/L,and the removal rate is as high as 98.6%,which greatly reduces the load of subsequent biochemical treatment.After the system is stable in the biochemical section,the average COD removal rate of the effluent is 91.2%,and the highest is 94.2%.Among them,the first stage A/O plays the main role of decarburization,accounting for 91.3%of the total removal rate,and the second stage A/O plays an auxiliary role.The ammonia nitrogen concentration of the influent of the two-stage A/O process is 114.7-198.4mg/L,with an average of 157.9mg/L.The NH₄⁺-N concentration of the effluent has increased compared with the influent,and TN concentration of the influent is 1600-2500mg/L,the average is 1771.6mg/L,and the average TN concentration of the effluent is 890.5mg/L.Because the removal rate of NH₄⁺-N is not high,the TN removal rate is 56.6%.Comprehensive physical and biochemical treatment results,the combined system can create conditions for the subsequent advanced treatment process to remove the pollutants of the molecular sieve catalyst wastewater,and can meet the requirements of membrane feeding.（2）By comparing the removal effect of the two-stage A/O process on the raw water under high and low influent load conditions,it can be found that under the same conditions,the pollutant removal performance of the two-stage A/O process is better than that of the low-load influent.High-load influent,the average removal rate of COD during the operation period is 91.4%.The removal of COD from wastewater by higher-load reactors cannot be maintained at a high level for a long time.The early removal rate can reach 89.3%,and the system is about 100 days,the removal rate began to gradually decline.（3）Inspecting the performance of the two systems for nitrogen and phosphorus removal,it was found that despite long-term special waste water domestication,the reactor still could not achieve the ideal nitrogen and phosphorus removal effect.Since nitrification has been suppressed to a greater extent,the ammonia nitrogen in the effluent of the system is higher than the influent.The two sets of reactors have the highest removal rates of total nitrogen only 23.3%and 44.6%,and the highest removal rates of total phosphorus are 50.0%and 48.8%,and the removal rate showed a downward trend in the later period.During the operation of the reactor,with the accumulation of pollutants in the wastewater,the sludge status（sludge volume,sedimentation,dewatering,etc.）of each unit gradually became worse,and sludge swelling appeared to varying degrees,Aging,mud running,etc.The group with relatively low water ingress load is slightly better than the other group.