【作者】 吴桂萍；

【导师】 陆晓华； 张爱清；

【作者基本信息】 华中科技大学 ， 环境工程， 2007， 博士

【摘要】 随着膜技术及膜工艺的发展,膜材料成本的降低,膜分离技术与其它废水处理技术的组合工艺受到水处理界的广泛关注。但膜抗污染性能差、寿命短导致成本高、膜反应器型式单一等问题,阻碍了膜技术在废水处理中的大规模应用。本文以拓展膜技术在废水处理中的应用潜力及范围为目的,选用性能优越的有机膜材料-聚醚砜(PES),对溶液相转化制备PES微孔膜过程中各工艺条件对成膜结构及性能的影响进行系统研究,制备出性能优良、结构可控的均质PES平板微孔膜和PES平板复合膜。对一体式中空纤维膜生物反应器(SH-MBR)、一体式平板膜生物反应器(SF-MBR)、一体式转盘膜生物反应器(SR-MBR)的污水处理效果和抗污染性能进行了研究;将膜分离技术引入光催化反应器构建一体式膜分离-光催化反应器,并对其可行性进行了考察;将膜分离技术与催化臭氧氧化技术结合起来进行洗车场废水处理回用的中试研究。得到主要结果如下:(1)聚合物浓度、添加剂种类和含量对PES均质膜结构和性能有很大的影响。制膜液中聚合物浓度增大,膜的厚度增大,孔隙率降低,膜中指状大孔结构减少,海绵状孔结构增加。添加剂PVP含量0-10%时,起到致孔的作用;PVP含量提高至10%以上时,膜中指状孔消失,孔径减小,随着PVP含量增加,膜的亲水性提高。非溶剂水的加入,使膜厚度及孔隙率变小,膜孔径增大,水通量增大。TiO2的加入提高了膜的强度、水通量及抗污染性能。在以上制膜规律的基础上,得出制备性能良好的PES微孔膜的工艺条件如下:PES浓度:11-15wt%,PVP添加剂:5-10wt%,水添加剂:3-5wt%,纳米TiO2:0.3-0.5wt%,凝固浴为水,凝固浴温度:30oC左右,铸膜液的温度:30oC左右。在此工艺条件下可制备出表面孔径0.5-2μm,孔隙率为80%左右,水通量为400-600L/m2. h的PES平板均质膜。(2)在制备PES均质膜工艺条件的基础上成功制备了PES/无纺布平板复合膜,并考察了制膜也组成、工艺条件对膜结构和性能的影响,结果表明:聚合物浓度、添加剂种类和含量、PES/SPES共混比例、SPES磺化度对PES/聚酯无纺布平板复合膜的结构和性能也有较大的影响。一定量SPES的加入有利于膜水通量和亲水性的提高,SPES磺化度提高,膜的亲水性有所改善,但是水通量下降。研究得出制备性能良好的PES复合膜的工艺条件如下:PES/SPES=80/20(wt),SPES磺化度5.2%,聚合物浓度10-13%,添加剂PVP含量3-8%,添加剂非溶剂水含量6%左右,纳米TiO2的加入量0.3-0.5wt%,凝固浴温度30oC。在可控条件下制备出高强度的PES/聚酯无纺布平板复合膜,水通量250-1400L/m2. h,亲水性良好。(3)将PES平板复合膜用于SF-MBR和SR-MBR,并对SH-MBR、SF-MBR、SR-MBR的污水处理效果和抗污染性能进行了考察。三种膜生物反应器出水水质好,COD去除率均>90%。SH-MBR工艺及SF-MBR工艺的最佳组合操作条件相同为:TMP=20kPa,抽/停8min/2min。PES平板复合膜用于MBR处理污水能达到与商业化生产的聚丙烯中空纤维膜相同的分离效果,且其水通量比PP中空纤维膜更稳定。对SR-MBR的研究发现,膜组件转动产生膜面流速可有效防止可逆污染的发生。在一定范围内增大膜组件转速、气水比及周期内停抽时间可有效改善SR-MBR的抗污染性能。SR-MBR工艺的最佳组合操作条件为:转速25r/min,TMP=25kPa,抽/停9min/1min,气水比15:1。SR-MBR可长期稳定运行,其稳定通量高达61 L/m2.h ,是SH-MBR,SF-MBR稳定通量的6倍左右。(4) PVDF平板复合膜具有较强的抗紫外辐射性能,适合用于光催化-膜分离反应器。浸渍法制备的负载TiO2的活性碳(TiO2/AC)表现出比TiO2, TiO2-AC更好的光催化活性和防止膜污染性能。光催化-膜分离反应器中,膜不仅能有效分离光催化剂,还可在一定程度上实现对待降解产物的截留,促使其在反应系统中进一步降解,保证出水水质。用光催化-膜分离反应器降解水溶液中苯酚时,膜对苯酚的平均截留率为19.3%,对COD的平均截留率为18.7%。光催化-膜分离反应器具有传统的悬浮光催化体系和固定薄膜式光催化体系都不具备的优点,用于有机废水的处理是可行的。(5) TiO2/AC催化臭氧氧化降解有机物COD的能力明显优于单独臭氧氧化和AC催化臭氧氧化,TiO2/AC作催化剂能明显提高臭氧的利用效率。膜分离-催化臭氧氧化组合工艺用于洗车场废水处理的中试研究,结果表明:系统出水水质好,符合生活杂用水标准,处理量30t/d的洗车场废水处理回用工程吨水造价为2315元,吨水运行费用为0.97元/吨,低于目前的商业用水水费,环境和经济效益佳,具有广阔的应用前景。更多还原

【Abstract】 Recent years, due to the development of membrane technology and membrane process, the combined processes of membrane separation and other technologies have attracted great attention in the field of wastewater treatment and reuse. Although membrane filtration offers many advantages over conventional separation processes, some drawbacks, such as membrane fouling, high cost and scarcity of membrane reactor formations, limited it’s broadly application in wastewater treatment. This paper focuses on the extension of the potential application and field of membrane process. Polyethersulfone, a kind of excellent membrane material, was chosen to prepare flat homogeneous PES microporous membrane and flat composite PES membrane by solution phase inversion method. The influences of various technical conditions on membrane structures and properties were studies. The flat homogeneous PES microporous membrane and flat composite PES membrane with good performances and controllable structures were prepared. The performances of the PES flat composite membrane were investigated during the process of applications in membrane bioreactor (MBR). The performances of anti-foul and pollutants removal efficiencies of submerged hollow-fiber membrane bioreactor (SH-MBR),submerged flat membrane bioreactor (SF-MBR) and submerged rotating membrane bioreactor (SR-MBR) were investigated. A hybrid membrane bioreactor (H-MBR) was developed to enhance the nitrogen and phosphorus removal, and its performance was investigated too. Photocatalytic membrane reactor, which combines both the advantages of classical photoreactor in which the catalyst is in suspension and membrane processes where separation at molecular level takes place, was designed to degrade organic pollutants in wastewater. Its feasibility was evaluated too. A pilot scale car washing wastewater was treated and reused by the combined process of membrane filtration and catalytic ozonation. The main conclusion of this thesis are as follows:(1) The structures and properties of membrane were affected by the polymer concentration and the type and content of the additive. With the increase of the polymer content, the fingerlike macrovoid structures converted to spongy pore gradually, and porosity of the membrane decreased. With the increase of the proportions of PVP from 0% to 10%, fingerlike pore developed sufficiently. When the contents of PVP exceeded 10%, fingerlike pore began to fade away and pore size became smaller. The hydrophilic performance of the membrane was improved by the addition of PVP. Water, used as a kind of nonsolvent additive, made the thickness and porosity of membrane decreased. Pore size and water flux increased with the increase of water content in casting solution. The addition of TiO2 improved the mechanical properties, water flux and anti-foul property of membrane. Based on the above studies, the preparation conditions of membrane with excellent performance were optimized as follows: PES concentrations varied from 11wt% to 15wt%, the content of PVP was 3-8wt%, the content range of water additive was 3-5wt%, the content of nano-TiO2 was from 0.3wt% to 0.5wt%, coagulation baths was water, the temperatures of casting solutions and coagulation baths were about 30oC, respectively. Under the optimal conditions, the homogeneous mricroporous PES membranes were prepared. The pore diameter on the top layer and porosity were 0.5-2μm and approximate 80%, respectively. The range of the water flux was 400-600 L/h.m2.(2) Polymer concentrations, the type and content of additive, the proportion of polyethersulfone to sulfonated polyethersulfone (PES/SPES) and the sulfonic rate of SPES had more obvious effect on the PES flat composite membrane structures and properties. Suitable addition of SPES could improve water flux and hydrophilic performance of the membrane. Increasing SPES sulfonic rate was propitious to hydrophilic performance of the membrane, but it was made against to the water flux. The preparation conditions of membrane with excellent performance were optimized as follows: PES/SPES=80/20(wt), the sulfonic rate of SPES was 5.2%, polymer concentrations varied from 10wt% to 13wt%, the content of PVP was 5-8wt%, the content of water additive was about 6wt%, the content of nano-TiO2 was from 0.3wt% to 0.5wt%, coagulation baths was water, the temperatures of casting solutions and coagulation baths were about 30oC, respectively. Under the optimal conditions, PES flat composite membranes were prepared. The pore diameter on the top layer and porosity were 0.5-2μm and approximate 80%, respectively. The range of water flux and contact angel were 250-1400 L/h.m2 and 65o-75o, respectively.(3) SH-MBR using PP hollow-fiber membrane and SF-MBR using PES flat composite membrane were used to treat sewage. The qualities of effluent of these two MBRs were excellent, the removal efficiencies of COD were higher than 90%. The optimal operation parameters of SH-MBR and SF-MBR were same: TMP=20kPa, 8min/2min.(4) A novel type of submerged rotating membrane bioreactor (SR-MBR), in which a rotatable rounded flat sheet membrane module fixed on the axes and moved by an electromotor, was used to treat synthetic sewage. Thus, an innovative membrane module, which is fixed on the axes and rotated by an electric motor was developed instead of the traditionally immobile membrane module to enhance filtration capacity and fouling prevention ability. The results indicated that the cross-flow velocity produced by the rotation of the membrane module, could help to prevent reversible fouling in the operation. The fouling prevention ability increased proportionately with increasing the rotation speed of the membrane module, ratio of aeration intensity to permeate flux (A/F) and stoppage time in an intermittent permeation cycle until their critical values were reached after which further increases would have little effects. The critical values for rotation speed, A/F and stoppage time were 60 r.min-1, 15 and 1 min for every 10 min cycle, respectively. Under this optimal condition, SR-MBR remained stable for a long time continuously running, and its equilibrium flux reached 61 L/h.m2, which was about 6 times of that of SH-MBR and SF-MBR.(5) Microorganism in H-MBR was more active than that in SMBR. The removal efficiencies of COD, NH3-N and TN reached to 92%, 80% and 70% respectively. The TP removal efficiency of H-MBR was not enough, only about 60%, when the TP concentration of the influent ranged from 5-6 mg/L. Declined the influent TP concentration to 3 mg/L, the TP concentration of the effluent became less than 1 mg/L, and the removal efficiency of TP reached 70% above.(6) The membrane which prepared by polyvinylidenefluoride (PVDF) was stable to UV irradiation. It was suitable to be used in the photocatalytic membrane reactor. The photocatalytic activity of TiO2-mounte activated carbon (TiO2/AC) catalyst was better than that of TiO2 and TiO2-AC photocatalysts. The selected membrane had the capability to retain the catalyst and to reject the partially degraded organic species. The removal efficiencies of phenol and COD were increased 19.3% and 18.7% due to the membrane separation. The photocatalytic membrane reactor combines both the advantages of classical photoreactor in which the catalyst is in suspension and membrane processes where separation at molecular level takes place seems very attractive.(7) The removal efficiencies of phenol solution were studied by TiO2/AC, activated carbon catalytic ozonation and ozonation alone. Results shows, TiO2/AC can well improve the efficiency of catalytic ozonation, and enhance the utilization of ozone. The pilot scale car washing wastewater was treated by the combined process of membrane filtration and catalytic ozonation. The results indicated that the qualities of effluent were better than the standards of reuse water, and the costs of this combined process and run fee were low. The cost of the engineer for 30t/d car washing wastewater treatment and reuse was 2315RMB per 1m3 wastewater. And the operation cost was as low as 0.97 RMB per 1m3 water. This membrane separation– catalytic ozonation combined process holds broadly applied potential in car washing wastewater treatment and reuse.更多还原