摘要
膜-生物反应器(MBR)应用过程中产生的膜污染问题一直是膜法水处理研究中的热点。投加絮凝剂来改善MBR混合液性质,减缓膜污染的发生,是解决上述问题的有效途径之一。但絮凝剂的种类对改善膜污染的效果及其作用机理尚未明确。本研究从常用的三大类絮凝剂中,各取具有代表性的三种常用絮凝剂:Al_2(SO_4)_3·18H_2O(AS)、聚丙烯酰胺(PAM)、聚合硫酸铁(PFS)对此进行研究。采用污泥比阻力值作为表征混合液过滤性能的指标,初步确定了三种絮凝剂的最佳剂量范围。PFS:500mg/L左右; PAM:20mg/L左右; AS:400mg/L左右。
在此基础上,将三种絮凝剂在各自最佳剂量范围内投加到MBR系统内,分别考察了过滤期内EPS、SMP、上清液胶体TOC、上清液TOC、RH以及膜污染速率的变化。实验结果表明,恒通量过滤期分为两个阶段:慢速发展期和TMP突变。过滤时,膜污染速率Γ45值的大小主要取决于慢速发展期的长短。絮凝剂投加以后,与对照MBR系统相比膜污染速率明显放缓,不同絮凝剂对减缓膜污染速率大小不一,依次为:PFS > PAM > AS。根据各絮凝剂对Γ45值增加的大小,修正了三种絮凝剂的最佳剂量:PFS:600mg/L,PAM:20mg/L,AS:450mg/L。
絮凝剂-MBR系统与对照MBR相比,上清液DOC含量变化不大,SMP和上清液胶体TOC含量有所下降,而EPS和RH却明显升高。絮凝剂对液相中SMP的去除主要是通过对减少液相中胶体TOC实现的,不同絮凝剂对SMP和胶体TOC的去除能力为:PFS > PAM > AS,而对EPS和RH的增加能力为:PFS > AS > PAM。
采用相关性分析和多元回归等统计方法对投加不同絮凝剂的MBR系统中,过滤期内EPS、SMP、上清液胶体TOC、RH和Γ45值等指标的变化进行分析。结果表明,Al_2(SO_4)_3·18H_2O、聚丙烯酰胺和聚合硫酸铁对减缓膜污染速率的关键污染因子分别为EPS、SMP和RH。Al_2(SO_4)_3·18H_2O主要是通过电和絮凝作用,将液相中与膜污染相关的大分子转移到絮体表面,同时刺激微生物产生更多EPS,从而增加絮体表面疏水性的方式减缓膜污染,但絮凝剂能力有限。其对减缓膜污染的能力可以用EPS的增加量进行表征;聚丙烯酰胺主要以架桥絮凝作用,将液相中与膜污染相关的大分子转移到絮体表面,从而减缓膜污染。虽然,PAM对絮体疏水性增加能力不如硫酸铝,但对液相中大分子的絮凝能力比硫酸铝强,因此,对减缓膜污染速率的综合能力表现为比硫酸铝更强,而且这种能力可以用SMP减少量进行表征;聚合硫酸铁主要以高价正电荷强烈吸引液相中与膜污染相关的大分子,将其絮凝转移到絮体表面,同时其中的铁盐强烈刺激微生物产生大量EPS,从而增加絮体表面疏水性的方式减缓膜污染。其对减缓膜污染速率的能力强,且可以用RH增加量对此能力进行表征。
Membrane fouling is the hot topic today in membrane bioreactor (MBR) field. The method that flocculants added into the mixed liquor in order to ameliorate filterability of MBR sludge and mitigate membrane fouling is an effective solution to the problem of“Membrane Fouling”. However, the effect and mechanism of flocculants remain largely unkown. In this study, three types of flocculants (aluminium sulphate, polyacrylamide and polymeric ferric sulfate) were selected, and they belong to respectively the three kinds of flocculants (monomer, inorganic polymer and organic polymer). Adopt sludge specific resistance as index of filterability of MBR sludge, and the results showed that the optimum dosages of the three types of flocculants is 400mg aluminium sulphate (AS), 500mg polymeric ferric sulfate (PFS) and 20mg polyacrylamide (PAM) per liter waste sludge.
On this basis, three types of flocculants were added into MBR with the optimum dosage, and the influence of flocculants on EPS, SMP, colloid-TOC, RH and on membrane fouling in MBRs was investigated. The experimental results indicate that the period of filtration with constant flux divided into two phases which include slow stage and sudden rise in TMP. The membrane fouling rate (Γ45) of MBRs is dependent on slow stage. The membrane fouling rate of flocculant added MBR is longer than controlled trials noticeably, and different flocculants have different effects on the membrane fouling rate. Three types of flocculants arranged according toΓ_(45) is PFS > PAM > AS, and the optimum dosages of the three types of flocculants is PFS 600mg/L, PAM 20mg/L and AS 450mg/L.
Compared with controlled MBR, the concentration of supernatant DOC (dissolved organic carbon) changed little, the concentration of SMP (Soluble microbial product) and supernantant colloid TOC (total organic carbon) dropped noticeably, and then concentration of EPS (extracellular polymeric substances) and RH (relative hydrophobicity) increased. The removal of SMP is dependent on supermantant colloid TOC, and the ability of SMP and supermantant colloid TOC removals of different flocculants is that PFS is the best one, and PAM is better than AS. Three types of flocculants arranged according to the ability of EPS and RH increases is PFS > AS > PAM.
The collected data of EPS, SMP, supermantant colloid TOC, RH andΓ45 were analyzed by multiple regression analysis, and the results show that the key factor of mitigate membrane fouling rate of aluminium sulphate (AS) is EPS, SMP for polymeric ferric sulfate (PFS) and RH for polyacrylamide (PAM). AS largely depend on charge neutralization to remove SMP and supermantant colloid TOC from liquid, and meanwhile, AS force microorganism to produce more EPS. With the growth of EPS, the relative hydrophobicity of sludge increase, and therefore, the membrane fouling rate was dropped. EPS can express AS’s capacity for membrane fouling. PAM reduce large molecule from liquid by bridging action. The ability of flocculation of PAM is better than AS. So, PAM can largely improve membrane fouling in MBRs, and SMP can express its capacity for membrane fouling. High valence positive charge of PFS can strongly absorb large molecule in liquid, and transfer to the surface of the sludge. Meanwhile, PFS stimulate microorganism to produce more extracellular polymeric substances, thus the relative hydrophobicity of sludge increased. The ability of mitigate membrane fouling PFS is the best, and relative hydrophobicity (RH) can express its capacity for membrane fouling.
引文
[1]刘颖,高艳玲,吕立宏. MBR技术在污水处理中的应用[J].沈阳大学学报,2006(18):2~4.
[2]张忠祥,钱易.废水生物处理新技术[M].第一版.北京:清华大学出版社,2004年. 509~523.
[3]邢传宏,钱易, Tardieu Eric.超滤膜-生物反应器处理生活污水及其水力学研究[J].环境科学, 1997, 18(5): 17~19
[4]李红兵,顾国雄,谢维民.中空纤维膜-生物反应器处理生活污水的特性[J].环境科学, 1999, 20(2): 53~56
[5]郑祥.膜-生物反应器的技术经济分析[J].给水排水, 2002, 28(3): 105~108
[6] Yang Wenbo, Cicek N, IIg J. State-of-art of membrane bioreactors: Worldwide research and commercial applications in North America, J. Membr. Sci. 2006,201~211.
[7]徐铜文.膜化学与技术教程.合肥:中国科学技术大学出版社, 2003.
[8]安树林.膜科学技术实用教程.北京:化学工业出版社, 2005
[9]甘一萍白宇.污水处理厂深度处理与再生利用技术[M].第一版.北京:中国建筑工业出版社,2010年. 310~315.
[10] Yamamoto K. Tannery wastewater treatment using a sequencing batch membrane reactor[J]. Wat. Sci. Tech. 1991, 23:16~39.
[11]张军,聂梅生等. MBR在污水处理与回用工艺中的应用[J].环境工程. 2001,19(5):9~11.
[12] Jefferson B, Laine A T, Judd S J, et al. Membrane bioreactors and their role in wastewater reise[J]. Wat. Sci. Tech. 2000,41(1):197~204.
[13] Brindle K,Stephenson T. The application of membrane biological reactors for the treatment of wastewater. Biotechnol Bioeng. 1996, 49(6):601~610.
[14] Kimura S. Japan’s aqua renaissance’90 project. WAt Sci Tech,1991,23:1573~1582.
[15] Mallevialle J, Odendaal P E, Wiesner M R. Water treatment membrane processes. McGraw-Hill, 1996.
[16] Stephenson T, Judd S, Jefferson B, et al. Membrane bioreactor for wastewater treatment. London: IWA Publishing,2000.
[17] Ueda T, Hata K,Kikuoka Y. Treatment of domestic sewage from rural settlements by a MBR. Wat Sci Tech. 1996, 34(9):189~196.
[18]高以烜,叶凌碧.膜分离技术基础.北京:科学出版社,1989.
[19]顾国维,何义亮.膜-生物反应器在污水处理中的研究和应用[M].北京:化学工业出版社,2002.
[20]张燕波,刘振鸿.膜-生物反应器中膜污染形成机理分析[J].环保科技. 2009, 15(1):33~36.
[21]余亚琴,徐微. MBR中膜污染类型随温度变化初探[J].安全与环境工程. 2008, 9(3):4~7.
[22] Cheryan M. ultrafiltration and microfiltration handbook. PA:Technomic Publishing Company, Lancaster, 1998.
[23] Bader M S H, Veenstra J N. Analysis of concentration polarization phenomenon in ultrafiltration uner turbulent flow conditions. J Membr Sci. 1996,114: 139~148.
[24] Sablani S S, Goosen M F A, Al-Belushi R, et al. Concentration polarization in ultrafiltration and reverse osmosis: a critical review. Desalination. 2001, 141: 269~289.
[25]霍守亮等.膜-生物反应器在污水处理中膜污染及其防治.工业水处理. 2004, 24(8).
[26]刘研萍等.膜-生物反应器的污染及防治.工业水处理. 2004, 24(6).
[27]胡玉平等.膜-生物反应器膜污染机理及其防治.净水技术,2004,23(1).
[28]周政杰等.膜生物反应器(MBR)中膜污染防治方法的研究进展[J]. 2010,37(7): 63~65.
[29] Kang I-J, Yoon S-H,Lee C-H. Comparison of the filtration characteristics of organic and inorganic membranes in a membrane-coupled anaerobic bioreactor. Wat Res, 2002, 36: 1803~1813.
[30] L. Defrance, M.Y. Jaffrin, Comparison between filtrations at fixed transmembrane pressure and fixed permeate flux: application to a membrane bioreactor used for wastewater treatment, J. Membr. Sci. 1999, 152: 203~210.
[31] M. Meireles, P. Aimar, V. Sanchez. Effects of protein fouling on the apparent pore size distribution of sieving membranes. Journal of Membrane Science,1991,56(1):13~28.
[32] Baniel, A, Eyal, A, Edelstein, D, Hajdu, K, Hazan, B., Lian, Y. and Zamir, E. Porogen derived membranes. 1. Concept description and analysis. J. Mem. Sci. 54: 271~284
[33] Choo K H, Lee C H. Effect of anaerobic digestion broth composition on membrane peme ability[J]. Wat Sci Tech,1996,34(9): 173~179.
[34] Magara Y, Itoh M. The effect of operational factors on solid/liquid separation by ultra-membrane filtration in a biological denitrification system for collected human excreta treatment plants. Wat Sci Tech, 1991, 23: 1583~1590.
[35] A. Brookes, B. Jefferson, G. Guglielmi, S.J. Judd, Sustainable flux fouling in a membrane bioreactor: impact of flux and MLSS, Sep. Sci. Technol. 2006, 41:1279~1291.
[36] S. Rosenberger, H. Evenblij, S. te Poele, T. Wintgens, C. Laabs, The importance of liquid phase analyses to understand fouling in membrane assisted activated sludge processes-six case studies ofdifferent European research groups, J. Membr. Sci. 2005, 263: 113~126.
[37] Sato T, Ishii Y. Effects of activated sludge properties on water flux of ultrafiltration membrane used for human excrement treatment. Wat Sci Tech. 1991, 23: 1601~1608.
[38] Shimizu Y et al. Effect of particle size distribution of activated sludge on cross-flow micro-filtration flux for submerged membrane. J. Ferment. Bioeng. 1997, 83(6):583~589.
[39] Bai R, Leow H F. Micro-filtration of activated sludge wastewater—the effect of system operation parameters. Separ Purif Technol, 2002, 29:189~198.
[40] Laspidou CS, Rittmann BE. A unified theory for extracellular polymeric substances, soluble microbial products, and active and inert biomass[J]. Water Research, 2002, 36: 2711~2720
[41] Chang I-S, Kim S-N. Wastewater treatment using membrane filtration—effect of biosolids concentration on cake resistance. Process Biochem. 2005, 40: 1307~1314.
[42] Ahmed Z, Cho J, Lim B-R. Effects of sludge retention time on membrane fouling and microbial community structure in a membrane bioreactor[J]. Journal of Membrane Science, 2007, 287(2): 211~218.
[43]刘锐,黄霞等.膜-生物反应器中溶解性微生物产物的研究进展.环境污染治理技术与设备. 2002, 3(1): 1~7.
[44] C.A. Ng, D. Sun, J. Zhang, H.C. Chua, W. Bing, S. Tay, A. Fane, Strategies to improve the sustainable operation of membrane bioreactors, in: Proceedings of the International Desalination Association Conference, Singapore, 2005.
[45] B Lesjean, S Rosenberge. Correlation between membrane fouling and soluble/colloidal organic substances in membrane bioreactors for municipal wastewater treatment [C]. Proceeding of IWA Special Conference: Water Environment-Membrane Technology, Seoul, 2004: 525~534.
[46] B. Espinasse, P. Bacchin, P. Aimar, On an experimental method to measure critical flux in ultrafiltration, Desalination. 2002, 146: 91~96.
[47] L. Defrance, M.Y. Jaffrin. Reversibility of fouling formed in actibated sludge filtration, J. Membr. Sci. 1999, 157: 73~84.【ghr1】
[48] Ueda, T., Hata, K., Kiknoka, Y. and Seino, O. Effects of aeration on suction pressure in a submerged bioreactor. Wat. Res. 1997, 31(3): 489~494.
[49]Liu R, Huang X, Wang C, et al. Study on hydraulic characteristics in a submerged membrane bioreactor process. Process Biochem. 2000, 36: 249~254.
[50] Magara Y. and Itoh M. The effect of operational factors on solid/liquid separation byultra-membrane filtration in a biological denitrification system for collected human an excreta treatment plan[J]. W a Sci Tech. 1999, 23: 1583.
[51] Masse A, Sperandio M, Cabassud C. Comparison of sludge characteristics and performance of a submerged membrane bioreactor and an activated sludge process at high solids retention time[J]. Water Research, 2006, 40(12): 2405~2415.
[52] Lee W, Kang S, Shin H. Sludge characteristics and their contribution to microfiltration in submerged membrane bioreactors [J]. Journal of Membrane Science, 2003, 216(1-2): 217~227.
[53] Zhang JS, Chuan CH, Zhou JT, et al. Effect of sludge retention time on membrane bio-fouling intensity in a submerged membrane bioreactor [J]. Separation Science and Technology, 2006, 41(7): 1313~1329.
[54] Fangang Menga, So-Ryong Chae, Anja Drews. Recent advances in membrane bioreactors(MBRs): Membrane fouling and membrane material[J]. Water Research, 2009, 43(1): 489~512.
[55] Xie Y J, Yu H Y, Wang S Y, et al. Improvement of antifouling characteristics in a bioreactor of polypropylene microporous membrane by the adsorption of Tween 20[J]. Journal of Enviromental Sciences, 2007, 19: 1461~1465.
[56] Yu H Y, Xie Y J, Hu M X, et al. Surface Modification of plyropylene Microporous Membrane to Improve Its Antifouling Property in MBR: CO2 Plasma Treatment[J]. Journal of Membrane Science, 2005, 254: 219~227.
[57]许晓鹏,郑领英.聚砜超滤膜的表面改性[J].水处理技术, 1993, 19(6): 330~335.
[58] Yu H Y, Xu Z K, Lei H, et at. Photoinduced graft polymerization of acrylamide on polypropylene microporous membranes for the improvement of antifouling characteristics in a submerged membrane-bioreactor[J]. Separation and Purification Technology. 2007, 53: 119~125.
[59] Ng C A, Sun D, Fane A G. Operation of membrane bioreactor with powdered activated carbon addition [J]. Separation Science and Technology, 2006, 41(7): 1447~1466.
[60] Hu A Y, Stuckey D C. Activated carbon addition to a submerged anaerobic membrane bioreactor: effect on performance, trans-membrane pressure and flux [J]. Journal of Environmental Engineering-ASCE, 2007, 133(1): 73~80.
[61]罗红等.应用投加粉末活性炭的膜-生物反应器处理生活污水的研究[J].重庆环境科学. 2002, 3: 28~31.
[62] Lee J C, Kim J S, Kang I J, et al. Potential and limitations of alum or zeolite addition to improve the performance of a submerged membrane bioreactor [J]. Waters Science and Technology. 2001, 43(11):59~66.
[63] Sofia A, Ng W J, Ong SL. Engineering desingn approaches for minimum fouling in submerged MBR[J]. Desalination, 2004, 160: 67~74.
[64] Bouhabila E H, Aim R B, Buisson H. Fouling characterization in membrane bioreactors. Separ Purif Technol, 2001, 22-23: 123~132
[65]章非娟.水污染控制工程实验.北京:高等教育出版社, 1988.
[66]浏上善弘等.卫生工学研究论文集. 1987, 23: 239.
[67] Harada H, Momonoi K, et al. Application of anaerobic UF membrane reactor for treatment of a wastewater containing high strength particulate organics. [J]. Wat. Sci. Tech. 1994,30(12): 307~319.
[68] Huang X, Liu R, Qian Y. Behaviour of soluble microbial products in a membrane bioreactor[J]. Process Biochem. 2001, 36(5): 401~406.
[69] P. Le-Clech, V. Chen, T.A.G. Fane. Fouling in membrane bioreactors used in wastewater treatment. Journal of Membrane Science. 2006, 284(1~2): 17~53.
[70] M. Rosenberg, D. Gutnick, E. Rosenberg, 1980. Adherence of bacteria to hydrocarbons: a simple method for measuring cellsurface hydrophobicity. FEMS Microbiology Letters 9(1): 29~33.
[71]纪婧.絮凝剂对减缓膜污染-生物反应器膜污染速率的效果和机理研究[D].上海:上海交通大学,2009.
[72] D.N. Petsev, V.M. Starov, I.B. Ivanov. Concentrated dispersions of changed colloidal particles: sedimentation, ultrafiltration and diffusion[J]. Colloids and Surfaces-Physicochemical and Engineering Aspects,1993,81:65~81.
[73]刘开敏,龙海.铝盐和聚合硫酸贴除氟效果研究[J].广州化工, 2009,37(7):96~98.
[74]牛芳,章军.聚合硫酸铁在处理黄河水中的实际应用[J].宁夏电力, 2005,增刊:267~269.
[75]罗慧.阳离子型聚丙烯酰胺的絮凝性能研究[J].应用化工, 2006,35(11):864~866.
[76] Chang I-S, Lee C-H. Membrane filtration characteristics in membrane-coupled activated sludge system-the effect of physiological states of activated sludge on membrane fouling. Desalination, 1998, 120:221~233.
[77] FIELD RW, WUD, HOWELLJA, et al. Critical flux concept for microfiltration fouling[J]. Journal of Membrane Science, 1995, 100: 259~272.
[78] MORGAN JW, FORSTER CF, EVISON L M. A comparative study of the nature of biopolymers extracted from anaerobic and activated sludges[J]. Water Res, 1990, 6: 743~750.
[79]刘锐,黄霞.膜-生物反应器中溶解性微生物产物的研究进展[J].环境污染治理技术与设备. 2002, 3(1): 1~7.
[80] Namkung E, Rittmann B E. Effects of SMP on biofilm-reactor performance [J]. J. Environ. Eng.Div. ASCE, 1988, 114(1): 199~210.
[81] Rittmann B E, Bae W, Namkong E, et al. A critical evaluation of microbial product formation in biological processes [J]. Water Sci Tech., 1987, 19(3~4): 517~528.
[82]张海丰等.膜生物反应器中溶解性微生物代谢产物的产出[J].中国环境科学, 2007, 27(4): 539~542.
[83]蔡春光,刘军深,蔡伟民.胞外多聚物在好氧颗粒化中的作用机理[J]. 2004, 24(5): 623~626.
[84]章文波,陈红艳.实用数据统计分析及SPSS 12.0应用.北京,人民邮电出版社, 2009.144~159.
[85]耿文燕.投加混凝剂对膜-生物反应器膜污染控制与机理研究, [学位论文],北京,中国地质大学, 2006
[86] Meng, F.G., Zhang, H.M., Yang, F.L. Identification of activated sludge properties affecting membrane fouling in submerged membrane bioreactor. Separation and Purification Technology. 2006, 51(1): 95~103.