Biostability in distribution systems in one city in southern China：Characteristics, modeling and control strategy

This study investigated the bacterial regrowth in drinking water distribution systems receiving finished water from an advanced drinking water treatment plant in one city in southem China. Thirteen nodes in two water supply zones with different aged pipelines were selected to monitor water temperature, dissolved oxygen （DO）, chloramine residual, assimilable organic carbon （AOC）, and heterotrophic plate counts （HPC）. Regression and principal component analyses indicated that HPC had a strong correlation with chloramine residual. Based on Chick-Watson＇s Law and the Monod equation, biostability curves under different conditions were developed to achieve the goal of HPC 100 CFU/mL. The biostability curves could interpret the scenario under various AOC concentrations and predict the required chloramine residual concentration under the condition of high AOC level. The simulation was also carded out to predict the scenario with a stricter HPC goal （≤50 CFU/mL） and determine the required chloramine residual. The biological regrowth control strategy was assessed using biostability curve analysis. The results indicated that maintaining high chloramine residual concentration was the most practical way to achieve the goal of HPC ≤ 100 CFU/mL. Biostability curves could be a very useful tool for biostability control in distribution systems. This work could provide some new insights towards biostability control in real distribution systems.     

臭氧-生物活性炭组合工艺中最佳臭氧投加剂量的确定

在水处理过程中投加臭氧,可提高饮用水的可生物降解性.臭氧氧化后继的生物过滤,可以减少水中可生物降解有机物数量,提高饮用水的生物稳定性.试验表明,臭氧投加量2～8mg/L可使AOC-P17,AOC-NOX和BDOC分别增加20.9%～85.5%,42.1%～158.2%和21.4%～84.4%.臭氧投加量为3mg/L时,AOC和BDOC增加得最多,即3mg/L的臭氧投量为最佳投加剂量.生物活性炭滤柱(BAC)出水AOC浓度(乙酸碳)均低于50μg/L,在35.9～46.6μg/L之间,属于生物稳定性水质.     

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% ,不能保证饮用水的生物稳定性     

氯对模拟管壁生物膜的氧化特性研究

以载片上培养的大肠杆菌生物膜为对象,研究了氯对模拟管壁生物膜中大肠杆菌的灭活效果,同时考察氯氧化生物膜后水中生物可同化有机碳(AOC)、生物可利用磷(MAP)和细菌生长潜能(BRP)的变化情况.结果表明,氯可以有效灭活悬浮态的大肠杆菌,而对生物膜中的大肠杆菌的灭活效率远低于悬浮菌;在相同CT值下,较高浓度的氯对悬浮态和生物膜中大肠杆菌的灭活效果要高于低浓度的氯.氯对生物膜的氧化作用会使生物膜中物质溶出,增加了水中AOC和MAP浓度,如当氯的浓度为1.0 mg/Ｌ(CT值为100 mg·min/L)时,水中AOC由20.78 μg/L增加到120.17 μg/L,MAP含量由0.11 μg/L增加到0.17 μg/L;氯的氧化作用会增加水的细菌生长潜能（BRP）,BRP随着CT值的增加而增加,如当氯投量为1.0 mg/Ｌ(CT值为100　mg·min/L)时,BRP可达到1.10×10⁷ CFU/mL.     

Progress in quantitative research on the relationship between atmospheric oxidation and air quality

Atmospheric oxidizing capacity (AOC) is an essential driving force of troposphere chemistry and self-cleaning, but the definition of AOC and its quantitative representation remain uncertain. Driven by national demand for air pollution control in recent years, Chinese scholars have carried out studies on theories of atmospheric chemistry and have made considerable progress in AOC research. This paper will give a brief review of these developments. First, AOC indexes were established that represent apparent atmospheric oxidizing ability (AOIe) and potential atmospheric oxidizing ability (AOIp) based on aspects of macrothermodynamics and microdynamics, respectively. A closed study refined the quantitative contributions of heterogeneous chemistry to AOC in Beijing, and these AOC methods were further applied in Beijing-Tianjin-Hebei and key areas across the country. In addition, the detection of ground or vertical profiles for atmospheric OH·, HO₂·, NO₃· radicals and reservoir molecules can now be obtained with domestic instruments in diverse environments. Moreover, laboratory smoke chamber simulations revealed heterogeneous processes involving reactions of O₃ and NO₂, which are typical oxidants in the surface/interface atmosphere, and the evolutionary and budgetary implications of atmospheric oxidants reacting under multispecies, multiphase and multi-interface conditions were obtained. Finally, based on the GRAPES-CUACE adjoint model improved by Chinese scholars, simulations of key substances affecting atmospheric oxidation and secondary organic and inorganic aerosol formation have been optimized. Normalized numerical simulations of AOIe and AOIp were performed, and regional coordination of AOC was adjusted. An optimized plan for controlling O₃ and PM_2.5 was analyzed by scenario simulation.     

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 .     

Biological stability in drinking water: a regression analysis of influencing factors

Some parameters, such as assimilable organic carbon(AOC), chloramine residual, water temperature, and water residence time, were measured in drinking water from distribution systems in a northern city of China. The measurement results illustrate that when chloramine residual is more than 0.3 mg/L or AOC content is below 50μg/L, the biological stability of drinking water can be controlled.Both chloramine residual and AOC have a good relationship with Heterotrophic Plate Counts( HPC)(Iog value), the correlation coefficient was-0.64 and 0.33, respectively. By regression analysis of the survey data, a statistical equation is presented and it is concluded that disinfectant residual exerts the strongest influence on bacterial growth and AOC is a suitable index to assess the biological stability in the drinking water.     

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UV254进行了分析,结果表明,4个工艺对AOC的去除率分别是63.6%、-97.9% 、84.2%和94.7% ;对TOC的去除率分别是61%、6.6%、66.7%和75% ;对UV254的去除率分别是17.9%、25.6%、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.     

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 P17 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. ZJ2, Pseudomonas saponiphila 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°C) 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.     

饮用水生物稳定性控制指标体系研究

主要阐述了饮用水生物稳定性的主要控制指标AOC(可生物同化有机碳)、BDOC(可生物降解溶解性有机碳)、TP(总磷)、MAP(可生物利用磷)、BGP(细菌生长潜力)及其测定方法和AOC-T DWMS评价体系.利用层次分析法确定了在城市输水管网中各控制指标的重要性权,使城市饮用水的处理更具有针对性,保证城市饮用水的生物稳定性.