【作者】 欧金次仁；

【导师】 邱江平；

【作者基本信息】 上海交通大学 ， 生态学， 2011， 硕士

【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:Al₂（SO₄）₃·18H₂O（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,Al₂（SO₄）₃·18H₂O、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。Al₂（SO₄）₃·18H₂O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。更多还原

【Abstract】 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 toΓ₄₅ 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.更多还原