Optimization Of Process And Operation Parameters Of Organic Wastewater Treatment By Self-forming Dynamic Membrane Bioreactor

Dyeing and livestock breeding wastewater with high amount emission are hard to treatment.Membrane bioreactor(MBR)provides a good effect in the treatment of the wastewaters with less land occupation,high solid liquid separation efficiency,strong load impact resistance,and stable outlet water quality.However,in the process of high concentration organic wastewater treatment by MBR method,the problem of membrane fouling is difficult to be effectively controlled and resolved.So the dynamic membrane bioreactor(DMBR)has been concerned and studied by the majority of researchers because of low cost,low resistance,easy cleaning and recovery.However,in the process of operation,the dynamic membrane has the same membrane fouling problem.Therefore,the dynamic membrane fouling and the control strategy are hot spots in the field of wastewater treatment.This paper studies the morphological changes of dynamic membrane in the first,middle and late stages.It was found that the gel layer on the surface of the dynamic membrane increased;the porosity of the dynamic film substrate narrowed and the retention ability became stronger during the formation of dynamic membrane.More important,the trend of exogenous protein were also the same with the morphological changes of the dynamic membrane,which indicating that the extracellular protein content is the leading role in the formation of dynamic membrane gel layer.In addition,the effects of activated sludge characteristics,aeration intensity,flux and water head on the dynamic membrane were analyzed.It was found that increasing the sludge concentration could shorten the time of dynamic membrane reaching stable state.However,the excessive sludge concentration would increase the membrane fouling.Moreover,increasing the aeration rate will slow down the formation of the dynamic membrane,which is conducive to the suppression of the pollution of the dynamic membrane.On the other hand,the high aeration intensity will affect the formation of dynamic membrane.Increasing the water head can accelerate the dynamic membrane formation,also facilitate the transmembrane pressure difference of the dynamic membrane,and then accelerate the membrane fouling.The critical flux of the membrane module used in this experiment is about 20.8～20.9 L/(m2·h).The optimal operating parameters for preventing the dynamic membrane fouling were obtained.These parameters were:12 g/L of sludge concentration,2 L/min of aeration rate,less than 20.5 L/(m2·h)of membrane flux,2.5 cm of water head.The dynamic membrane process was applied to treat actual living wastewater under the optimum operating parameters.The results indicated that the removal rate of COD was 77.5～81.1%and the removal rate of ammonia nitrogen was 2.0～80.8%with only aerobic process.The removal rate of COD was 54.6～70.7%and the removal rate of ammonia nitrogen was 30.8～90.2%with only anaerobic process.The removal rate of COD was 80.0～90.7%,and the removal rate of ammonia nitrogen was 73.7～94.8%with anaerobic-aerobic series process.The removal rate of COD was 90.394.0%,and the removal rate of ammonia nitrogen was 54.2%～99.9%with anaerobic-aerobic recycling process.The removal rate of COD and ammonia nitrogen in anaerobic-aerobic recyclingprocess was better than that of anaerobic-aerobic series process.Under the optimum operating parameters,the dynamic membrane process was applied to treat simulated dyeing wastewater.The changes of chroma and COD in the process were analyzed.The chroma removal rate was 78.3～94.3%and the COD removal ratewas 70.4-92.0%in anaerobic-aerobic series process.The chroma removal rate is 83.8～89.6%and the COD removal rate is 80.5～93.8%in anaerobic-aerobic recycling process.The COD removal rate of the effluent of anaerobic aerobic recycling process was slightly better than that in series process.The effluent quality of circulating process is also more stable than that of the series process.When treating simulated livestock wastewater under the optimum operating parameters with anaerobic-aerobic series process,the removal rate of COD was 78.8～92.7%,and the removal rate of ammonia nitrogen was 82.3～87.2%.The removal rate of COD was 75.2～89.4%,and the removal rate of ammonia nitrogen was 84.8～92.3%when treating simulated breed wastewater with anaerobic-aerobic recycling process.The COD removal rate of the anaerobic-aerobic recycling process is similar to that of the series process,but the water quality of the system is more stable and the system adaptation period is shorter.The ammonia nitrogen removal rate of the anaerobic-aerobic recycling process is higher than that of the series process,but the system adaptation period is a little longer.In the process of operation,anaerobic reactor dynamic membrane is more susceptible to be polluted than that of aerobic reactor.In the recycling process,the speed of membrane fouling of anaerobic reactor was quicker than that in series process,and the membrane blockage rate of aerobic reactor was greater than that in series process.