Research On Development Of The Membrane-chemical Reactor For Removal Of Deleterious Metals From Wastewater And Related Mechanism

The industrial wastewater containing various deleterious metal ions often does great harm to the human and nature environment due to its complex components and great toxicity, and these metal elements could not be degradated naturally by organisms and may be accumulated through the food chain. So it is necessary to conduct intensive research on development of the equipments for removal of deleterious metals from wastewater and related mechanism, and this will be significant to promote the development of cleaner production. The technique of the treatment of wastewater containing 241Am/Pb by coagulation-microfiltration process were studied,and the optimization of structure and operational parameters of membrane reactor was conducted by measuring the velocity of flow using laser doppler anemometry (LDA).The test for treatment of radioactive wastewater containing 241Am involved two steps. The first one was the cold test, the tap water was used to replace the raw radioactive wastewater and the ferric chloride was dosed as coagulant to study the anti-fouling capcity of the membrane and to provide operational parameters for hot test. The second step was the hot test, in which the removal efficiency of 241Am by the integrated coagulation-microfiltration device was studied. During the cold test, the volume of the treated wastewater was 5177.6 L, the total volume of concentrated sludge was 28 L,and the turbility of the effluent was under 0.5 NTU. In the hot test, it was found that the quality of the effluent was poor without the pretreatment to the raw radioactive wastewater. However, after the organics and surfactants in the raw wastewater were removed with pretreatmtmt by adjusting the pH of the influent to 2~4 and dosing KMnO4, the the activity of 241Am of the effluent could meet the discharge standard. As the activity of 241Am in the influent was 890~11900 Bq/L, that of the effluent was less than 1Bq/L. The decontamination factor (DF) was up to 47600.The test for removal of lead from lead storage battery production wastewater by coagulation-microfiltration process was divided into two parts, coagulation jar test and continuous test, NaOH and lime were used as the precipitants. In the continuous test with NaOH as the precipitant, the volume of the treated wastewater was 1596.8L, the total volume of concentrated sludge was 1.28 L,and the condensing factor was 1247.5. The total Pb in the effluent was 0.001~0.052mg/L, the turbutity was lower than 0.2 NTU. In the continuous test with lime as the coagulants, the volume of treated wastewater was 1401.6 L, the total volume of concentrated sludge was 1.60 L and the condensing factor was 876. The total Pb in the effluent was 0.001~0.14 mg/L, the turbutity was lower than 0.4 NTU. Theconcentration of SO42- in the membrane reactor had significant effect on the menbrane flux. It was found that the presence of the ferrous ions was helpful to the removal of lead.The membrane fouling characteristics was studied based on the character of mixture liquid and operational conditions in membrane separation, and the measures to control membrane fouling were offered. There was a critical mixed liquor suspended solid (CMLSS) in the process for removal of deleterious metal from wastewater by chemical coagulation-microfiltration, the CMLSS was inflenced by the degree of membrane fouling, the size distribution of the MLSS, shearing force on the membrane surface and operational condition. The total resistance consisted of membrane resistance, the membrane fouling resistance and the concentration polarization resistance. The corresponding valid anti-fouling measures could be adopted based on the different composition of the membrane resistances.The influence of the baffle-plate and the aeration strength in the membrane reactor on the velocity of flow of mixed liquor nearby membrane surface was researched by measuring the velocity of flow with LDA, and the structure and operational parameters of membrane reactor were optimized based on the test results. The rising time everaged velocity and impulsive velocity of mixed liquid nearby membrane surface were all increased with setting up the baffle-plate, and the turbulent fluctuation of mixed liquor was increased with the corrugated plate.