| Coal chemical wastewater contains many kinds of organic pollutants, high COD, pollute the water ecological environment seriously, poses certain threat to the health of human beings, animals and plants. Because it has the characteristics of high concentration of pollutants and being difficult to degrade, using a single treatment method is often difficult to meet the national emission standards, so it often need to be preprocessed before the Advanced treatment. Although the effect of some treatment methods is good, the economic costs of them are high,which are not suitable for large-scale using in actual production. Therefore, exploring a kind of treatment method for coal chemical wastewater which is economical,practical and obvious effects.It can not only resolve the problem of coal chemical industrial wastewater being difficult to meet the national emission standards, but also has a very wide range significance of ecological and economic for protecting human water environment and promoting the sustainable development of water resources.The study taked the coal chemical wastewater in a Beijing coal chemical plant as the research object, the main research contents were:(1) Introduced coal chemical wastewater's source, characteristics and the current situation of treatment status; According to the selected coal chemical wastewater, appropriate treatment methods were adopted, then did research about them.(2) According to the characteristics of high concentration and difficult degradation for coal chemical wastewater,choosed the method of acidification+composite flocculation to pretreat the wastewater.Filtered the wastewater, explored the best conditions of acidification deposition, selected three kinds of flocculants which were polymeric ferric sulfate (PFS), polyaluminium chloride(PAC) and alum(KAl(SO4)2·12H2O),using them compositing with Coagulant polyacrylamide (PAM) respectively to determine the best pretreatment of coal chemical wastewater.(3) Since the coal chemical wastewater after pretreatment still existed some refractory materials, water quality standards was difficult to reach water quality,choosed DS A electrochemical process for the advanced treatment of the wastewater. Selected the best DSA anode from four kinds of electrode(Ti/TiO2-Ta2O5-IrO2-SnO2?Ti/TiO2-IrO2-RuO2-SnO2? Ti/TiO2-Ta2O5-IrO2?Ti/TiO2-IrO2-RuO2)in the lab,and used titanium plate as cathode,did electrolysis of orthogonal test based on single factor experiment,attained the optimal combination of orthogonal experiment.In order to optimize the experimental results, researched electrodes arrangements on the optimum conditions of orthogonal test, selected the best electrodes arrangement corresponding to best treatment effect,and used the electrodes arrangement to do advanced treatmenting for coal chemical wastewater after pretreatment.(4) Reasearched the cost analysis and degradation mechanism of the treatment technology of acidification-composite flocculation-DSA electrochemical process for coal chemical wastewater.Through the research and analysis of the experimental results, attained the main conclusions:(1) When the coal chemical wastewater was pretreated, the flocculation effect of PFS was better than PAC and alum under the condition of using inorganic flocculant independently. The flocculant compounding effect of PFS+PAM was better than PAC+PAM, alum+PAM and any other inorganic flocculant single using.(2) The best pretreatment scheme of coal chemical wastewater was:Filtered the wastewater, adjusted pH=3 and filtered the wastewater again; In the condition of pH=8, the mass ratio of PFS compounded with PAM was approximate 50:1.At this time, the removal rates of COD,ammonia, volatile phenols, and color reached 77.83%,83.70%,69.01% and 95.71% respectively.(3) For the deep treatment of the coal chemical industry wastewater, the best dimensionally stable anode(DSA) was Ti/TiO2-Ta2O5-IrO2-SnO2 anode selected by single factor experiment, and also the best single factor experimental parameters were obtained. On the basis of single factor experiment, some representative factors were chosen for the orthogonal experiment. The influence order of various factors on the removal rate of COD was voltage> electrolytic time> pH> NaCl electrolyte additives. The optimal experimental parameters of the orthogonal experiment were:voltage of 5.5V, NaCl electrolyte addition amount of 2g/L, pH value at 6, electrolytic time of 3h on the condition of Ti/TiO2-Ta2O5-IrO2-SnO2 anode and polar plate distance of 1 cm.(4) In order to optimize the experimental effect, under the condition of the best experimental parameters of the deep treatment of orthogonal experiment, the effect of polar plate arrangement on the coal chemical industry wastewater deep treatment was researched. The results showed that the best plate arrangement for polar plate of the deep treatment of the coal chemical industry wastewater by DSA electric catalytic oxidation was complex polar plate arrangement, and the experiment condition could be concluded that The Ti/TiO2-Ta2O5-IrO2-SnO2 anode was connected to the positive electrode, titanium cathode was connected to the cathode and the middle of them arranged by Ti/TiO2-Ta2O5-IrO2 complex polar plate. After the pretreated coal chemical industry wastewater COD was further treated by the best deep treatment scheme, ammonia nitrogen, volatile phenol and chroma removal rate arrived at 98.41%,99.64%,99.85% and 99.64%, respectively, reaching of integrated wastewater discharge standard GB8978-1996 tertiary, secondary and tertiary, primary level of emission standard.(5) To choose the best deal, coal chemical wastewater pretreatment solution of acidification-composite flocculation economic which cost was low, only 1.4903 yuan/ton of wastewater, economical and practical technology, reduced the depth of the subsequent processing of the load. In the pretreatment process PFS could provide a large number of hydroxyl complexation ion, and PAM composite with PFS could make rapid condensation, floc particles accelerated flocculation precipitation of body, improved the effect of purification; the depth treatment scheme DSA electrochemical method was with low energy consumption,0.0281 kW·h/g, the economic costs was 62.61 yuan/ton wastewater, economical and practical technology, provides a good reference value for practical production. Deep processing mainly was through indirect oxidation, DSA electrode and complex pole plate arrangement increased electrode effective specific surface area, enhanced the electron transition.This topic uses the new technology of acidification flocculation-DSA electrochemical to treat coal chemical wastewater, the treatment cost is low, the maneuverability is strong, the technology is practical, provides a good reference value for practical production. |
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