Modeling of chlorine effect on floc forming and filamentous micro-organisms of activated sludges

被引:35
作者
Caravelli, A
Contreras, EM
Giannuzzi, L
Zaritzky, N [1 ]
机构
[1] Natl Univ La Plata, CONICET, Fac Ciencias Exactas, CIDCA, RA-1900 La Plata, Argentina
[2] Natl Univ La Plata, Fac Ingn, RA-1900 La Plata, Argentina
关键词
filamentous bulking; Sphaerotilus natans; Acinetobacter anitratus; chlorination model;
D O I
10.1016/S0043-1354(02)00601-2
中图分类号
X [环境科学、安全科学];
学科分类号
08 ; 0830 ;
摘要
Chlorination is the most economical, non-specific method to control the excessive growth of filamentous microorganisms causing bulking in activated sludge systems in the treatment of food industrial wastewaters; it was one of the first methods used to control filamentous bulking and is still widely employed. Considering that chlorination affects both floc-forming and filamentous micro-organisms and leaves undesirable disinfection by-products, it is necessary to define the adequate doses to control bulking, minimizing the effect on floc-forming bacteria. In the present work the effect of biomass concentration and type of micro-organism on chlorine decay kinetics was evaluated; the inactivation of either a filamentous (Sphaerotilus natans) or a floc-forming (Acinetobacter anitratus) micro-organism due to chlorination was also analyzed. For chlorine decay assays, the samples were treated in a batch system with sodium hypochlorite ranging between 9.8 and 56.6mg Cl-2 (gVSS)(-1). Respirometric assays were used to evaluate the effect of chlorine on micro-organisms respiratory activity; in these cases, sodium hypochlorite doses ranged between 2.5 and 18 MgCl2 (gVSS)(-1). A model that allowed. to predict simultaneously chlorine consumption and respiratory activity decay for both microorganisms as a function of time was proposed. The model includes three coupled differential equations corresponding to respiratory inhibition, readily organic matter oxidation by chlorine and chlorine decay. The rate of chlorine decay depended on both, type and concentration of the micro-organisms. in the system. Chlorine consumption rate due to S. natans was 2-4 times faster than A. anitratus. Using the proposed model initial critical chlorine doses (the lowest initial dose that leads to a total inhibition of the respiratory activity) were calculated for both micro-organisms and values of 11.9 MgCl2 (gVSS)(-1) for S. natans and 4.5 MgCl2 (gVSS)(-1) for A. anitratus were obtained. These critical doses indicated that in non flocculated pure cultures, floc-former bacteria A. anitratus was more susceptible to chlorine action than S. natans. (C) 2003 Elsevier Science Ltd. All rights reserved.
引用
收藏
页码:2097 / 2105
页数:9
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