Improvement of the assimilable organic carbon （AOC） analytical method for reclaimed water

Microbial growth is an issue of concern that may cause hygienic and aesthetic problems during the transportation and usage of reclaimed water. Assimilable organic carbon （AOC） is an important parameter which determines the heterotrophic bacterial growth potential of water. Pseudomonas fluorescens P17 and Spirillum sp. NOX are widely used to measure AOC in drinking water. The AOC values of various reclaimed water samples determined by P 17 and NOX were compared with those determined by the new strains isolated from reclaimed water in this study. It showed that the conventional test strains were not suitable for AOC measurement of reclaimed water in certain cases. In addition to P17 and NOX, Stenotrophomonas sp. Z J2, Pseudomonas saponi- phila G3 and Enterobacter sp. G6, were selected as test strains for AOC measurement of reclaimed water. Key aspects of the bioassay including inoculum cell density, incubation temperature, incubation time and the pH of samples were evaluated for the newly selected test strains. Higher inoculum density （104 CFU.mL-1） and higher incubation temperature （25℃） could reduce the time required for the tests. The AOC results of various collected samples showed the advantages of the method proposed based on those five strains in evaluating the biologic stability of reclaimed water.

Significant increase of assimilable organic carbon(AOC)levels in MBR effluents followed by coagulation,ozonation and combined treatments:Implications for biostability control of reclaimed water

As water reuse development has increased,biological stability issues associated with reclaimed water have gained attention.This study evaluated assimilable organic carbon(AOC)in effluents from a full-scale membrane biological reactor(MBR)plant and found that they were generally stable over one year(125-216µg/L),with slight increases in warmer seasons.After additional tertiary treatments,the largest increases in absolute and specific AOCs were detected during ozonation,followed by coagulation-ozonation and coagulation.Moreover,UV254 absorbance is known to be an effective surrogate to predict the AOC changes during ozonation.Applying coagulation prior to ozonation of MBR effluents for removal of large molecules was found to reduce the AOC formation compared with ozonation treatment alone.Finally,the results revealed that attention should be paid to seasonal variations in influent and organic fraction changes during treatment to enable sustainable water reuse.

Variation in assimilable organic carbon formation during chlorination of Microcystis aeruginosa extracellular organic matter solutions

This study investigated the chlorination of Microcystis aeruginosa extracellular organic matter（EOM） solutions under different conditions, to determine how the metabolites produced by these organisms affect water safety and the formation of assimilable organic carbon（AOC）. The effects of chlorine dosages, coagulant dosage, reaction time and temperature on the formation of AOC were investigated during the disinfection of M.aeruginosa metabolite solutions. The concentration of AOC followed a decreasing and then increasing pattern with increasing temperature and reaction time. The concentration of AOC decreased and then increased with increasing chlorination dosage, followed by a slight decrease at the highest level of chlorination. However, the concentration of AOC decreased continuously with increasing coagulant dosage. The formation of AOC can be suppressed under appropriate conditions. In this study, chlorination at 4 mg/L, combined with a coagulant dose of 40 mg/L at 20°C over a reaction time of 12 hr, produced the minimum AOC.

Variability of micropollutants and microorganisms in water distribution system

The variation of water quality in water distribution system was investigated with assimilable organic carbon (AOC)and trihalomethanes(THMs) used as assessment indexes. Bacterium was identified in water distribution. The result showed that there were pathogenic parasites in water distribution system. The variation of AOC is related to chlorine residual and bacterium activity, and AOC concentration decreased first and then increased with the extension of water distribution system. The formation of THMs was related to the consumption of chlorine inside the distribution system, and THMs concentration increased with the extension of water pipe line.

供水管网中AOC、消毒副产物的变化规律

以西南L市的供水管网为研究对象 ,以可同化有机碳 (AOC)、三卤甲烷 (THMs)、卤乙酸 (HAAs)为评价指标 ,研究了不同季节给水管网中水质的变化情况。结果表明 :三卤甲烷在管网中只受余氯的影响 ,其含量一般随管道长度的增加而增加 ;卤乙酸和AOC在管网中的变化受余氯和微生物活性的影响 ,其含量一般随管网延伸而先增加后减少 ,温度越高则下降越快。温度和余氯是管网中控制消毒副产物和AOC浓度的重要因素。

生物测定饮用水中可同化有机碳(AOC)方法优化

在对可同化有机碳（AOC）生物测定中就测试菌的生长特性进行研究的基础上，对接种浓度、培养温度、培养时间与培养基种类等培养条件进行了比较，并确定了优化操作条件。提出了改进的产率系数计算方法，并测定了该AOC分析方法的适用范围（10～300μg乙酸碳／L）。对3种不同接种方法的比较研究发现，同时接种法试验时间短、操作简单，测定结果更接近实际值，是较为理想的方法。

控制配水管网中细菌再生长的AOC浓度研究

研究了配水管网中AOC浓度与细菌再生长的关系,以确定控制细菌再生长的AOC标准。结果表明:最大AOC浓度与最大HPC呈线性关系,当AOC<57μg/L时,管网水中的营养基质难以维持悬浮菌的生长;最大AOC浓度与AOC最大消耗量也呈线性关系,当AOC<43.8μg/L时AOC没有被消耗,即细菌不生长。结合已有的AOC控制标准,推断在采用加氯消毒的管网中,控制AOC<40μg/L能够确保饮用水的生物稳定性。

不同水处理工艺对地表水中AOC的去除效果

研究了以A江水、B河水为原水的常规处理工艺和以C湖水为原水的两种深度处理工艺对有机污染物的去除效果。对水样的AOC、TOC和UV2 54进行了分析 ,结果表明 ,4个工艺对AOC的去除率分别是 6 3 6 %、- 97 9%、84 2 %和94 7% ;对TOC的去除率分别是 6 1%、6 6 %、6 6 7%和 75 % ;对UV2 54的去除率分别是 17 9%、2 5 6 %、83 3%和 95 1% ,与深度处理工艺相比 ,常规处理工艺不能保证饮用水的生物稳定性。

不同水处理工艺对可同化有机碳(AOC)的去除特性研究

通过对不同水处理工艺出水中可同化有机碳(AOC)的测定,分析各处理工艺对AOC的去除特性.结果表明:常规工艺对AOC有一定的去除效果,生物活性滤池能有效去除AOC,并且生物预处理和深度处理都有助于去除AOC.须对不同原水中的有机物成分进行分析,以掌握各工艺对原水中有机物的去除规律.

饮用水中AOC测定的优化与改进

论文对目前可同化有机碳(AOC)测定方法中存在的检测时间长、效率低、前后接种测定值大于实际值,检测过程复杂等问题进行了部分改进。实验结果表明:采用接种温度28℃,接种液量30mL,接种时间P17:40h、NOX:60h,AOC-NOX修正值计算公式:y=0.1337x+7.9414,可使测定方法在时间上缩短1d,消除了缺氧和差值两个误差,试验结果更加准确。

臭氧—活性炭组合工艺对饮用水中AOC的去除

研究了以O3/GAC为主的饮用水深度处理工艺对AOC去除效果 ,结果表明 :原水 (某江水 )AOC浓度为 6 1 9μg乙酸碳 /L ;生物陶粒滤池对AOC的去除率为 54% ;O3 +GAC对AOC的去除率为 83.8% ;加氯消毒后AOC浓度增加 1 .38倍 ;常规水处理工艺对AOC的去除率为 4 3.7% 。

饮用水中AOC快速检测法

介绍了国内外AOC检测方法的发展。推荐一种应用发光菌快速检测AOC的方法 ,这种快速检测方法能在 2～ 3h之内完成检测。

Effect of different molecular weight organic components on the increase of microbial growth potential of secondary effluent by ozonation

Ozonation has been widely applied in advanced wastewater treatment. In this study, the effect of ozonation on assimilable organic carbon （AOC） levels in secondary effluents was investigated, and AOC variation of different molecular weight （MW） organic components was analyzed. Although the removal efflciencies were 47%-76% and 94%-100% for UV2s4 and color at ozone dosage of 10 mg/L, dissolved organic carbon （DOC） in secondary effluents was hardly removed by ozonation. The AOC levels increased by 70%-780% at an ozone dosage range of 1-10 mg/L. AOC increased significantly in the instantaneous ozone demand phase, and the increase in AOC was correlated to the decrease in UV254 during ozonation. The results of MW distribution showed that, ozonation led to the transformation of larger molecules into smaller ones, but the increase in low MW （〈1 kDa） fraction did not contribute much to AOC production. The change of high MW （〉100 kDa and 10-100 kDa） fractions itself during ozonation was the main reason for the increase of AOC levels. Furthermore, the oxidation of organic matters with high MWs （〉 100 kDa and 10-100 kDa） resulted in more AOC production than those with low MWs （1-10 kDa and 〈1 kDa）. The results indicated that removing large molecules in secondary effluents could limit the increase of AOC during ozonation.

可同化有机碳(AOC)检测方法的对比

水中可同化有机碳(AOC)浓度与异养菌总数(HPC)密切相关,高AOC含量会加速细菌的生长,由此引发水质劣变等问题。文中对比了平板涂布法、流式细胞术(flow cytometry,FCM)+纯菌接种与流式细胞术+土著菌接种检测AOC的方法,流式细胞术计数获得的P17、NOX和土著细菌标准曲线的判定系数R^2分别为0.729、0.957、0.921;平板涂布计数法的P17、NOX和土著细菌标准曲线的判定系数R^2分别为0.714、0.917、0.156。相较于平板涂布法,流式细胞术所测得的AOC标准曲线线性关系较好,所测结果稳定,且可对水中的全部细菌进行计数,克服了传统平板涂布法仅可检测水中活的且可培养的细菌的缺陷;在此基础上,使用土著细菌接种所表征的结果客观反映了水中细菌的存在状况。鉴于其计数快捷、可大批量检测、可区别计数、培养周期短,且误差小的特点,流式细胞术+土著菌接种检测AOC方法可为供水管理部门评判水质生物稳定性提供理论参考与技术支持。

不同净水处理工艺出水水质指标AOC、TOC、HPC的变化比较

为了解不同净水工艺处理水中可同化有机物(AOC)、总有机碳(TOC)、异养菌数(HPC)的变化,在取自两个不同水源的三家水厂进行了从进水到出厂水及管网水的各单元工艺出水的测定。结果表明对H江、Q水库而言,TOC高其相对应AOC也高。原水经加氯杀藻或厂内预氯化处理后AOC会有所增加,经过混凝、沉淀、砂滤处理后AOC有所降低,经臭氧活性炭的出水AOC也会有所减少。深度处理工艺出厂水较原水AOC有所减少,常规处理工艺则会出现反超现象。对深度处理水厂来说,经活性炭处理后出水HPC均较进水有所增加,但经加氯胺消毒的出厂水中HPC大为减少。深度处理水厂在处理过程中TOC随工艺过程逐步降低,其中经混凝、沉淀、过滤去除的TOC较后续臭氧活性炭去除的要多。不同出厂水质所引起的管网AOC、HPC的变化规律各不相同,一般水源水质好TOC低,且出厂AOC低,管网水HPC变化就小,三个指标是相关联的。

基于AOC去除技术的饮用水贮存生物稳定技术路线分析

贮存饮用水作为应急供水基础保障模式,因长期存放普遍存在生物稳定性降低、微生物超标的问题。基于生物稳定性,通过分析水质生物稳定性评价指标、影响因素,贮存水生物稳定的关键在于降低营养基质AOC浓度,辅以控制消毒剂剂量。对比总结可同化有机碳(AOC)在不同处理工艺中的变化规律发现:(1)常规工艺对AOC去除有限;(2)预处理工艺可改变AOC构成,增强水的可生化性,提高工艺整体去除率;(3)深度处理工艺中生物处理、NF、RO、活性炭等工艺对AOC去除作用明显。根据贮存饮用水需求确定技术指标要求,结合材料、抑菌、隔菌等贮存技术提出技术路线设计选配方法及可行路线:(1)使用与维管分离的生物处理;(2)深度处理+末端处理;(3)深度处理与低剂量消毒综合控制。

饮用水AOC检测方法的研究

介绍了国内外AOC检测方法的发展和改进,提出目前情况下适宜我国情况的AOC检测方法,并推荐一种应用发光菌快速检测AOC的方法。

提供生物稳定饮用水的最佳工艺

研究由预处理、常规处理和深度处理组合而成的 7种不同工艺对饮用水源水中可生物同化有机碳 ( AOC)的去除效果 .试验表明 :生物陶粒预处理对 AOC具有较高的去除率 ,达到 45%左右 ,如果在它之前先经过预臭氧化 ,生物处理的去除率可增大到 58.4% ;常规处理对 AOC的去除非常有限 ,去除率平均在 2 0 %左右 ;新活性炭单元因其吸附作用对 AOC的去除效果稳定在30 %左右 ,如和臭氧氧化连用 ,去除效果能提高到 50 %以上 ;包括了常规处理、生物预处理、预臭氧和臭氧活性炭的组合工艺对AOC的去除效果最好 ,达到 86% .因此臭氧氧化、生物炭和生物处理是提高饮用水生物稳定性的重要手段 ,并以本试验结果为依据提出了对于不同的水源水所采用的最佳工艺 .

饮用水生物稳定性控制指标探讨

结合给水管网中饮用水微生物再生长现象,分析了AOC作为反映饮用水生物稳定性的替代参数所存在的问题。根据饮用水处理系统中微生物营养的种类及特点,以及磷在微生物生长和代谢过程中的关键作用,提出同时检测和控制磷含量来保证饮用水生物稳定性的观点,并对磷和AOC共同作为饮用水生物稳定性控制指标的可行性进行了探讨。

臭氧-生物活性炭对有机物分子量分布的影响

测定了南方某水厂中试规模的臭氧-生物活性炭工艺不同处理阶段(原水、沉淀水、砂滤水、臭氧化水、生物活性炭出水)有机物(TOC和UV254)的分子量(MW)分布.分析了原水中生物可同化有机碳(AOC)的分子量分布.结果表明,AOC主要属于天然有机物(NOM)中MW<1kDa的部分.MW<1kDa的部分占可溶解性有机碳(DOC)的53%～67%,而AOC只占DOC的2.65%～5.91%,表明去除大部分DOC的臭氧-生物活性炭工艺并不能有效去除AOC.