【作者】 元新艳；

【导师】 王琳；

【作者基本信息】 中国海洋大学 ， 环境工程， 2008， 博士

【摘要】 针对目前生物除磷脱氮工艺中出现的硝化菌与聚磷菌泥龄的不协调、反硝化与释磷过程对碳源的竞争、厌氧区硝酸盐成分对释磷的影响、沉淀固液分离时富磷污泥的释磷作用及出水中存在少量富磷污泥颗粒导致出水TP提高等问题,提出两级序批式MBR工艺(两级SBMBR)。两级SBMBR工艺以优化除磷脱氮为目的,通过运行条件的控制,将聚磷菌与硝化菌分别控制在两级反应器中优势生长,形成先除磷(同时去除大部分有机物)、后脱氮的运行模式,实现去除有机物的同时,高效除磷与脱氮,并有效控制膜污染,为工程实践提供参考和设计依据。两级SBMBR工艺具有以下特点:①解决自养硝化菌与异养细菌之间泥龄的矛盾,同时又可使最终排水端反应器中为非富磷污泥,再通过膜的高效截留,从而可充分降低出水的TP浓度,最终达到优化除磷与脱氮的效果;②在一级反应器中去除大部分有机污染物,在二级反应器中进一步去除难降解有机物,提高有机物去除率;③降低有毒物质对脱氮的冲击,提高脱氮的稳定性;④序批式、空曝、间歇抽滤出水相结合的运行方式,可以有效控制膜污染。采用两级SBMBR工艺,以青岛崂山区凉泉社区生活污水为处理对象,采用试验与机理分析相结合的研究方法,全面系统地研究了两级SBMBR工艺分级优化除磷脱氮的可行性、处理效能、混合液特性及对膜污染的影响。1、从SBMBR1(除磷级)除磷及去除有机物总体效能、周期除磷特性及除磷机理,SBMBR2(脱氮级)脱氮的总体效能及脱氮动力学等方面对两级SBMBR进行了研究。研究得出:通过运行泥龄的控制(SBMBR1为5~7d ,SBMBR2为25~30d),两级SBMBR能够将聚磷菌与硝化菌分别控制在两级反应器中优势生长,从而将除磷(同时去除有机物)与脱氮这两个相互矛盾的生物处理过程分别控制在两级反应器中优化完成。在系统稳定运行阶段,出水COD、TN、TP、NH3-N平均值分别为25.75mg/L、12.33 mg/L、0.46mg/L、2.71 mg/L,满足城市景观环境用水水质要求;综合考虑沉淀期间POAs的释磷作用及沉淀效率,确定SBMBR1最佳沉淀时间为20min;通过周期试验确定硝化速率常数k1=0.21,反硝化速率常数k2=0.22,反硝化速率要高于硝化速率。2、通过实验室测定及扫描电镜观察,对比分析了SBMBR1(除磷级)、SBMBR2(脱氮级)混合液污泥特性。试验发现:在混和液物理特性和生物特性方面,两级反应器均表现出了不同。从外观观察SBMBR1反应器中的活性污泥呈浅黄色,随着运行时间的增加,污泥粒径逐步增加,SV、SVI值逐步下降,呈现出较强的颗粒特征,沉降性能良好;SBMBR2污泥呈土黄色,污泥絮体被高强度的曝气所产生的切应力所打碎,污泥粒径迅速降低,絮体较为细碎,和水相混合成均一粘稠的溶液,看不到泥水分界面;低泥龄、高负荷运行,使得SBMBR1可以保持较高的微生物活性,MLVSS/MLSS值、SOUR值均高于SBMBR2;两级反应器活性污泥中均有大量的菌胶团,长杆菌、短杆菌和球菌是构成主体,但SBMBR1活性污泥中含有大量固着型原生动物如累枝虫等,还存在着一定数量的丝状菌,生物相要比SBMBR2丰富。3、借助原子力显微镜、扫描电镜、透射电镜等手段对平板膜污染现象进行观测和分析,并通过膜表面污染物EPS测定、污染膜表面能谱分析,得出平板膜表面污染物的组成。经过110多天的运行之后,SBMBR2反应器内膜表面形成了导致过膜压力升高的粘稠的污染层,污染后平板膜的粗糙度与清洁膜相比增加了20倍左右,膜表面污染层的最大厚度为1695.74nm。通过达西公式对平板膜的阻力分布进行了表征,得到平板膜自身固有阻力占总阻力的38.24%,沉积阻力占总阻力的53.09%(其中凝胶极化阻力为43.09%)、内部污染阻力占总阻力的8.67%,得出膜表面形成的凝胶层是导致膜过滤性能下降的主要原因。膜污染主要是由有机物污染、微生物污染、无机物污染造成,膜表面有机污染物含量为417.69mgEPS/g.MLSS,蛋白质:多糖=3.5:1,蛋白质为优势污染物;膜表面及膜孔内部生物污染以球菌、杆菌为主;膜表面无机污染物主要是Fe、Na、Zr、Rb、Ca等化合物在膜表面和膜孔内形成的硬垢。4、对SBMBR2反应器中膜污染影响因素进行了研究,通过优化操作方式、投加PAC等措施延缓膜污染。得出:污泥浓度的增加会加剧膜污染的速度;EPS、SMP因膜的截留在反应器内积累,是形成凝胶层的主要影响因素;混合液中,大分子物质占到了61%,大大高于进水与出水,是引起膜污染的主要原因。序批式运行方式与间歇抽滤、空曝相结合的膜运行方式,可以减缓浓差极化,有效降低沉积污染及凝胶层污染,膜比流量下降速率与连续流MBR相比明显降低,系统在运行100多天后,过膜压差仅增加了0.12bar;投加适量PAC,污泥粒径增加,上清液SMP降低,膜的过滤性能明显得到改善,当PAC投加量为1g/L时,膜比流量提高了70%,周期内膜通量衰减速率也有所降低,上清液中蛋白质和多糖含量分别降低了14%、12%,有助于延缓膜污染。对污染膜组件的清洗采用物理清洗与化学清洗相结合的形式,空曝2小时、400ppm次氯酸钠清洗2小时、200ppm次氯酸钠溶液浸泡20小时后膜比通量恢复至81.51%。更多还原

【Abstract】 The two-stage sequencing batch membrane bioreactor (TSBMBR) process was put forward to face with the problems in biological nitrogen and phosphorous removal, like different sludge age between nitrification and phosphorous bacteria, competition for carbon during denitrification and phosphorous release process, influence of nitrate on the phosphorous release in anaerobic zone, phosphorous release during sedimentation process, sludge with high phosphorous concentration in the effluent which can cause high TP concentration in effluent and etc. The two-stage sequencing batch membrane bioreactor (TSBMBR) process was aim to optimize the removal of nitrogen and phosphorous. With the control of operation parameters, phosphorous bacteria and nitrification bacteria can be controlled in two-stage reactors. Phosphorous and large amount of COD could be removed in the first stage, and nitrogen could be removed in the second stage, which could in a whole realize the simultaneous removal of COD, nitrogen and phosphorous. The membrane fouling can also be mitigated effectively. This operation can provide references for application and design. The characteristics of two-stage sequencing batch membrane bioreactor (TSBMBR) process can be summarized as follows:①Dissolve the contradiction between autotrophic nitrification bacteria and heterotrophic bacteria and enable the sludge in the reactor that provides effluent is not P-rich type, and with the effective separation of membrane, the concentration of TP in the effluent can be completely reduced. And the optimal nitrogen and phosphorous removal can be obtained;②Large amount of COD can be removed by the first stage of reactor and the refractory biodegradable organics can be furthered removed in the second stage reactor, hence the removal efficiency of COD can be improved;③Reduce the toxic shock loading to nitrification bacteria and enhance the stability of denitrification;④Combine sequencing bath and intermittent suction operation modes together to mitigate membrane fouling effectively.TSBMBR process was applied to treat wastewater of Liaoquan residential area, Laoshan district, Qingdao. Experiment and mechanical analysis were combined to systematically research on the feasibility of TSBMBR in removing phosphorous and nitrogen, the removal efficiency, solution characteristics and influence on membrane fouling.1. The research on TSBMBR includes removal efficiency of phosphorous and organic pollutants in SBMBR1 (phosphorous removal stage), phosphorous removal characteristics and mechanism in one cycle and removal efficiency of nitrogen and denitrification dynamics in SBMBR2 (nitrogen removal stage). Through the control of sludge age (5~7d i n SBMBR1,25~30d in SBMBR2), phosphorous bacteria and nitrification bacteria were the dominant species in each stage. Therefore, the contradiction between phosphorous removal and nitrogen removal can be optimized in two chambers separately. After the stable operation of system, COD, TN, TP and NH3-N average concentration in the effluent was 25.75mg/L, 33 mg/L,0.46mg/L and 2.71 mg/L, which could meet the Criteria of Scenic Environment Using Water. Concerning the phosphorous release effects in sedimentation period of PAOs and sedimentation efficiency, the optimal sedimentation time in SBMBR1 was 20 min. Through the periodic experiment, the nitrification rate constant K1 equaled to 0.21 and the denitrification rate constant K2 equaled to 0.22. That is to say, the denitrification rate is higher than nitrification rate.2. Lab experiments and SEM observation were performed to analyze the sludge characteristics in SBMBR1 and SBMBR2. From biological and physical point of view, the sludge characteristics in two stages are totally different. The sludge in SBMBR1 was light yellow and with the time passed by, the sludge size gradually increased and the SV, SVI value gradually decreased. The sludge in SBMBR1 presented granular characteristics and settled very well. The sludge in SBMBR1was brown and the sludge flocs was smashed by the shear force due to high intensity of aeration. The sludge size decreased and the sludge flocs blended with water forming ropy solutions, and there was no distinguish interface between water and sludge. Low sludge age and high loading operation enabled the sludge in SBMBR1 keeping higher sludge activity and the MLVSS/MLSS ratio and SOUR values of SBMBR1 were higher than SBMBR2. Both in SBMBR1 and SBMBR2, there were large amount of zoogloea, bacillus, coryneform of bacteria, and pediococcus. However, in SBMBR1 there were also a lot of Protozoa like epistylis and etc. A certain amount of filamentous bacteria can also be found in SBMBR1. The biological species in SBMBR1 were much more abundant than that in SBMBR2.3. Membrane fouling on flat-sheets membrane was observed and analyzed with AFM, SEM and TEM. After the measurement of membrane surface EPS and membrane surface ETX analysis, the pollutants composition on the surface of flat-sheets membrane was calculated. After 110 days operation, pollutants layer formed on the membrane surface in SBMBR2, which could induce the increase of trans-membrane pressure (TMP). The roughness of fouled membrane surface was 20 times higher than the new membrane and the thickest height of membrane pollutant layer was 1695.74nm. Darcy’s Law was used to analyze the resistance distribution on the membrane surface, the resistance of membrane (Rm) accounted for 38.24% of total resistance, the cake resistance (RC) accounted for 53.09% of total resistance (43.09% of which was gel polarization resistance), and the pore blocking resistance(Rp) accounted for 8.67% of total resistance. The gel lay caused by concentration polarization on the membrane surface was the main reason of the reduction of membrane permeability. The membrane pollutants were composed of organic pollutants, biological pollutants and inorganic pollutants. The organic pollutants represented by EPS on the membrane surface were 417.69EPSmg/g.MLSS, and the protein/polysaccharide ratio was 3.5. Protein was the predominant pollutants. The biological pollutants on the membrane surface are mainly bacillus and pediococcus and the inorganic pollutants were scales mainly composed of Fe, Na, Zr, Rb and Ca compounds inner and outer the membrane.4. The influential factors of membrane fouling in SBMBR2 were also investigated. Membrane fouling was mitigated through optimizing operation parameters and dosing PAC. The increase of sludge concentration could increase the membrane fouling velocity. EPS and SMP accumulated in the reactor were the main formation reason of gel layer. In reactor solutions, substances with high molecular weight accounted for 61%, which was much higher than the value in the influent and effluent. This is the main reason of membrane fouling. The Combination of sequencing bath and intermittent suction operation modes could mitigate membrane fouling effectively, the velocity of which was much lower than the non-stop MBR. After operation for more than 100 days, the TMP only increased 0.12bar. After the dosing of PAC, the sludge size increased, and the SMP in the supernatant reduced, and the membrane filterability was mitigated dramatically. With the dosage of PAC reached 1g/L, the specific membrane flux enhanced 70% and the membrane flux reduction rate in one cycle was also reduced. The protein and polysaccharide concentration in the supernatant was also reduced by 14%, and 12%, which was beneficial for the mitigation of membrane fouling. The combination of physical and chemical cleaning was performed on the cleaning of fouled membrane. After aeration for 2 hr, 400 mg/L sodium hypochlorous cleaning for 2 hr, and then 200 mg/L sodium hypochlorous marinating for 20hr, the specific membrane flux recovered to 81.51%.更多还原