Study On The Efficiency Of Submerged Ceramic Plate Membrane Bioreactor For Coal Chemical Wastewater Treatment

Modern coal chemical industry is an important method to utilize coal in clean and efficient ways,which is conductive the dependence of resources on foreign countries and maintaining energy security in China,but water is a limiting factor for its development.Coal chemical wastewater with the characteristics of large amount and complex quality contains phenols,polycyclic aromatic hydrocarbons,long-chain alkanes,heterocyclic compounds and other organic compounds,which has certain inhibitory effects on activated sludge.Combining the characteristics of high sludge concentration of MBR and high flux and strength of ceramic flat-plate membrane,the treatment effect of the reactor on coal chemical wastewater,membrane fouling and influence factor were investigated in this experiment.Laboratory test results showed that when MLSS?7500 mg/L and HRT=24,COD,ammonia nitrogen,total phenol,turbidity of effluent were less than 31.40 mg/L,3.03mg/L,3.76 mg/L,0.4 NTU,respectively,which met the first-class standard of comprehensive sewage discharge?GB8978-2002?.Biodegradation played the leading role and microfiltration membrane enhanced its effect.When HRT is 21 h,DO is 3.2⁴.0mg/L and pH is 7.1⁷.5,the removal efficiency of pollutants is better.The effect of sludge concentration on the treatment efficiency is not obvious in low organic load of sludge.Activated sludge is the main part of MBR.High throughput sequencing showed that the microorganisms on the mixed solution and membrane were mostly aerobic bacteria,and the content of organic degradation bacteria and nitrifying bacteria was higher.The dominant bacteria changed in different growth environments.The total number of bacteria in the mixed solution was more,and the bacteria on the membrane had higher biodiversity.Membrane fouling and replacement are important factors limiting the wide use of MBR.TMP reaches 40 kPa after 66 days at a flux of 5 L·m^-2·h^-1 because backwashing can effectively slow down the membrane fouling process.After the operation,the resistance of cake layer and concentration polarization resistance accounted for 50.08%and 48.87%of the total resistance respectively,while the inherent resistance and internal resistance only accounted for a small part.The process of membrane fouling is complex.The membrane properties,the nature of feed and the hydrodynamic environment of membrane are the basic factors determining membrane fouling.The ceramic membrane showed high hydrophilicity through the comparison of contact angle and clear flux,which makes it more superior in organic wastewater treatment.The concentration of EPS and SMP decreased gradually from the initial stage to the later stage of operation.The growth rate of TMP changed inapparently when MLSS is between 5000 and 10000 mg/L and increased rapidly when MLSS is more than 12000 mg/L.When the aeration is 200 mL/min and the pumping-stopping ratio is7:3,the pollution rate is slower.SEM observation showed that NaClO and NaOH had better effect as chemical cleaning agents.The combination of NaClO and citric acid is most suitable for wastewater quality,economic and safety.In the pilot study of ceramic plate membrane bioreactor,the removal rate of COD was 37.42%,the concentration of ammonia nitrogen was less than 4.46 mg/L,and the turbidity was stable below 1 NTU and chemical washing cycles exceed 5 days at flux of30 L·m^-2·h^-1 which reached the goal of the pilot study.