【作者】 梁涛；

【导师】 马军；

【作者基本信息】 哈尔滨工业大学 ， 市政工程， 2009， 博士

【摘要】 可生物同化有机碳（Assimilable Organic Carbon,简称AOC）是可生物降解有机物中能被微生物转化成其自身菌体的部分。AOC可反映饮用水的生物稳定性,即水中可生物降解有机物支持异养菌生长的潜力。生物不稳定的饮用水将给管网和管网水质带来严重影响,因此关于给水处理过程中AOC变化规律的研究具有重要的现实意义。本课题中AOC测定采用LeChevallier法,接种方式为荧光假单胞菌—P17菌株和螺旋菌—NOX菌株分别接种。绘制产率标准曲线,发现在高浓度(大于200μg·L^-1乙酸碳)时得到的P17产率系数小于低浓度的产率系数,高低浓度的产率系数分别为7.5×106和1.4×107cfu·mL^-1。NOX菌的产率曲线中高低浓度的产率系数保持一致,约为7.1×108cfu·mL^-1左右。通过江水超滤膜过滤进行AOC不同分子量分布的测定,发现AOC主要以分子量小于1ku的有机物为主体,占AOC总量的43%。松花江原水AOC较高,而且随季节变化波动较大。夏季最高可达2714μg·L^-1;冬季最低为452μg·L^-1。以松花江水为水源水的S水厂常规给水处理各单元过程中,混凝单元对AOC去除率最高,春季和冬季的去除率达到30%左右,夏季和秋季可达到60⁸0%;过滤单元对AOC的去除不稳定;加氯消毒后AOC增加20%左右。整个常规给水处理工艺中,以AOC-NOX为代表的羧酸类物质只占AOC的10%左右,经消毒后这一比例才略有上升。常规给水处理工艺抗AOC冲击负荷较低,出厂水AOC随原水变化而波动,最低达到400μg·L^-1,属于生物不稳定饮用水。AOC在管网内的消耗随温度变化,温度越高消耗越快,总消耗量都在300μg·L^-1以上,说明管网内有可能存在细菌再繁殖问题。考察了不同水体、混凝剂、混凝剂投量、pH值和钙离子浓度等混凝条件下AOC变化规律和水质变化情况。研究发现,江水混凝过程中硫酸铝在高投量下对AOC的去除率最高达24.5%,而相同投量下氯化铁混凝的去除率可以达到65.9%。人工配水混凝在低投量下铝、铁混凝剂对AOC的去除率分别为71.8%和93.0%。氯化铁混凝剂在去除AOC和其它混凝效果方面均优于硫酸铝。在中性和弱酸性pH值条件下混凝AOC的去除率最高,达到86.1%,碱性条件下混凝AOC反而增加了29.1%。复合铝铁混凝剂对AOC的影响有限,增加Ca2+离子浓度可使AOC去除率从54.1%上升到80.4%。分别选取了高锰酸钾、臭氧和次氯酸钠三种预氧化剂来研究AOC在预氧化过程中的变化规律。三种预氧化方法混凝后的AOC随预氧化剂投量增加而增长,AOC最高增长率分别为61.5%、86.9%和81.1%。三种预氧化过程中混凝前AOC的增长率分别为23.6%、33.5%和17.7%。臭氧预氧化产物中AOC-NOX所代表的羧酸类物质较多,占AOC的40%;高锰酸钾和次氯酸钠氧化后水体中能被P17菌利用的基质增加。在三种预氧化剂的预氧化中,AOC/TOC（有机物的生物可同化性）分别从8.2%增加到14.0%、16.7%和10.8%。高锰酸钾和臭氧预氧化过程中TOC的变化主要是由其中BDOC的变化而引起的;而次氯酸钠预氧化中TOC增长了5.2%,主要来自于AOC的增加。在三种预氧化过程中,不能被生物降解的有机物（NBDOC）都没有随氧化剂投量的增加而变化。臭氧和高锰酸钾都是在投量低于1.0mg·L^-1时的助凝效果较好,而次氯酸钠是在投量高于1.0mg·L^-1时有微弱助凝效果。选取了三种不同载体—陶粒、硅胶和沸石负载TiO2,以考察AOC所代表的小分子物质在臭氧多相催化氧化过程中的变化规律。臭氧催化氧化比单纯的臭氧氧化能更彻底地将大分子有机物氧化成小分子有机物。陶粒、硅胶和沸石负载TiO2等三种催化氧化条件下,将AOC从大约300μg·L^-1分别增加到674μg·L^-1、847μg·L^-1和882μg·L^-1,AOC/TOC从初始的4.7%分别升高到30.5%、33.2%和46.0%,明显地提高了水中有机物的可生物降解性。增加臭氧投量,催化氧化可使小分子有机物部分被矿化,水中AOC下降13.0%。以AOC-NOX所代表的羧酸类物质在催化氧化过程中明显增加,占总AOC的90%以上,改变了AOC的组成比例。与未改性时相比,改性后TiO2催化氧化出水的AOC降低了17.9%,对催化剂的进一步改进可能使有机物的可生化性控制在一个合理的范围。更多还原

【Abstract】 Assimilable Organic Carbon （AOC） is the fraction of organic carbon that is most easily consumed by microorganisms, resulting in a proliferation of microbial cells. It has been regarded as one of the most important quality parameters for microbiological stability in drinking water treatment and distribution systems. Removal of AOC during the production of drinking water not only deprives heterotrophic bacteria of nutrients indispensable for their survival and multiplication in the water phase, but also limits bacterial colonization in drinking water distribution system.AOC was analysed by a modification of the LeChevallier method. The maximum growth of Pseudomonas fluorescens P17 and Spirillum sp. strain NOX which were inoculated into duplicate water samples respectively was converted to the amount of AOC. The yield factor of strain P17 at high concentration remains below the level expected on the yield factors observed at low concentrations, and the Y value of strain NOX does not decrease. Yield factors for the test strains were taken from standardization calibration curves experiments and were 7.5×106 and 1.4×107 cfu·mL^-1 for strain P17 at high and low concentration and 7.1×108 cfu·mL^-1 for strain NOX. The AOC concentration of raw water was fractionated into seven fractions by ultrafiltration, and the AOC of molecular weight less than 1ku is the largest proportion, reaching 43%.The AOC in Songhua River source is always at a high level and ranged from 452μg·L^-1 to 2714μg·L^-1, depending on the season, with the highest value in summer and the lowest in winter. Coagulation was the most effective step on the AOC removal in the conventional treatments of S plant, with the removal rate of about 30% in spring and winter, and 60⁸0% in summer and autumn. The effect of AOC removal by filtration was not stable, and the AOC was enhanced about 20% by chlorine disinfection. AOC-NOX constituted about 10% proportion of AOC in conventional water treatment, and the ratio was enhanced by chlorine in disinfection. The AOC in the effluent of the plant depends on the concentration of influent, and the AOC in the effluent (more than 400μg·L^-1), was above the limits for biostability. The AOC declined to above 300μg·L^-1 along the distribution system, depending on the temperature. Most likely, biofilm processes played an important role in AOC uptake, and multiplication of bactecia in distribution systems posed a potential health threat to citizen.The variation of AOC under different coagulation conditions was investigated, including coagulant dosages, pH value, poly aluminum iron sulphate coagulant, waters from different source and Ca2+ iron concentration. It was found that the removal rate of AOC during alum coagulation in raw surface water was only about 24.5% at high coagulant dosage. Higher removal rate of AOC with the case of FeCl3 coagulation （about 65.9%） was observed under the same dosages. The removal rates of AOC during alum and iron coagulation of the synthetic water were 71.8% and 93.0% at low coagulant dosages, and the case of coagulation with FeCl3 also resulted in a better coagulation effect. It indicated that the pH of coagulation is a very influential parameter for the removal of AOC. The highest AOC removal rate after coagulation was obtained at initial pH 6.5 and 7.0, reaching 86.1%; AOC was increased to 29.1% after coagulation when the water is in alkaline condition. Poly aluminum iron sulphate coagulant had limited effect on the AOC value and enhancing Ca2+ concentration increased the removal of AOC from 54.1% to 80.4%.Three oxidants were selected in studying the variation of AOC in preoxidation process, including potassium permanganate, ozone and NaClO. AOC was increased by 61.5%, 86.9% and 81.1% respectively with the increase of oxidant dosages after coagulation. The AOC was increased by 23.6%, 33.5% and 17.7% only in preoxidation before coagulation. More AOC-NOX, which represents carboxylic acids, was formed and constituted about 40% of AOC during O3 preoxidation, while permanganate and NaClO preoxidation increased the substrate available for strain P17. The AOC/TOC ratio, which indicated assimilation ability of organic carbon, was increased from 8.2% to 14.0%, 16.7% and 10.8% in the three preoxidations respectively. The variation of TOC during permanganate and O3 preoxidation resulted from the variation of BDOC, and AOC increase was responsible for TOC increase by 5.2% during NaClO preoxidation process. The concentration of NBDOC changed little with the increase of oxidant dosages in the three preoxidation processes. Permanganate and O3 preoxidation exhibited better coagulation effect with the dosage less than 1.0mg·L^-1, while better condition efficientcy was achieved at higher NaClO dosages.The variation of AOC was investigated during catalytic oxidation with titanium dioxide nano-particles loaded on several selected carriers in ozonation such as cerami, silica gel and zeolite. Catalytic ozone oxidation is more effective than ozonation alone for the degradation of large molecular weight fractions of organics into lower molecular size. The AOC increased to 674μg·L^-1, 847μg·L^-1 and 882μg·L^-1 from 300μg·L^-1 by the catalytic ozonation in the presence of cerami/TiO2, silica gel/TiO2, zeolite /TiO2 respectively; and the proportion of AOC in TOC could increase to 30.5%、33.2% and 46.0% from 4.7%, respectively. The catalytic oxidation greatly enhanced the biologradability of organics in water. With ozone dosage increased, AOC reduced 13.0% because some of the low molecular sized organic carbon was mineralized. In these processes, AOC-NOX mostly consisting of carboxyl acid increase rapidly, resulting in the increase of the proportion of AOC-NOX in AOC to 90% and the majority of AOC turned over from AOC-P17 to AOC-NOX. The AOC was less （17.9%） in modified catalytic oxidation than TiO2 catalytic oxidation, and it is assumed that advanced modification could reduce AOC efficiently to a reasonable level.更多还原