Reviews - Field Studies - Lab Studies - HAAs - HANs - HAMs - HNMs - Halobenzoquinones

Single DBP - Other

(See also: DBP Degradation, Chloramine Models)

 

Major Reports & Review Papers on DS Nitrification
Citation Notes Abstract

   

 

Field Studies: Distribution Systems and Simulated Systems
Citation Notes Abstract

Schrantz, K. A., J. G. Pressman, et al. (2013). "Simulated distribution nitrification: Nitrification Index evaluation and viable AOB." Journal American Water Works Association 105(5): 55-56.

  Laboratory-scale annular reactors were used to evaluate the impact of simultaneously increasing temporal influent monochloramine (NH2Cl) concentrations (0.0 to 3.2 mg chlorine [Cl-2]/L) and chlorine-to-nitrogen mass ratios (0:1 to 3.2:1) on nitrification, allowing evaluation of the recently proposed Nitrification Index (NI) for chloraminated drinking water distribution system operation control. Nitrification was severely affected with a 1.5 mg Cl-2/L NH2Cl residual, becoming undetectable when the NH2Cl residual reached 3 mg Cl-2/L. The calibrated NI was successful in simulating nitrification occurrence. In addition, temporal biofilm sample results demonstrated that viable ammonia-oxidizing bacteria were (1) dominated by Nitrosomonas europaea related species for an NH2Cl residual less than approximately 0.4 mg Cl-2/L, (2) dominated by N. oligotropha-related species for an NH2Cl residual between 0.4 and 1.5 mg Cl-2/L, and (3) not detected once the NH2Cl residual was maintained at approximately 3 mg Cl-2/L.
Pressman, J. G., W. H. Lee, et al. (2012). "Effect of free ammonia concentration on monochloramine penetration within a nitrifying biofilm and its effect on activity, viability, and recovery." Water Research 46(3): 882-894.
  Chloramine has replaced free chorine for secondary disinfection at many water utilities because of disinfection by-product (DBP) regulations. Because chloramination provides a source of ammonia, there is a potential for nitrification when using chloramines. Nitrification in drinking water distribution systems is undesirable and may result in degradation of water quality and subsequent non-compliance with existing regulations. Thus, nitrification control is a major issue and likely to become increasingly important as chloramine use increases. In this study, monochloramine penetration and its effect on nitrifying biofilm activity, viability, and recovery was investigated and evaluated using microelectrodes and confocal laser scanning microscopy (CLSM). Monochloramine was applied to nitrifying biofilm for 24 h at two different chlorine to nitrogen (Cl-2:N) mass ratios (4:1 [4.4 mg Cl-2/L] or 1:1 Cl-2:N [5.3 mg Cl-2/L]), resulting in either a low (0.23 mg N/L) or high (4.2 mg N/L) free ammonia concentration. Subsequently, these biofilm samples were allowed to recover without monochloramine and receiving 4.2 mg N/L free ammonia. Under both monochloramine application conditions, monochloramine fully penetrated into the nitrifying biofilm within 24 h. Despite this complete monochloramine penetration, complete viability loss did not occur, and both biofilm samples subsequently recovered aerobic activity when fed only free ammonia. When monochloramine was applied with a low free ammonia concentration, dissolved oxygen (DO) fully penetrated, but with a high free ammonia concentration, complete cessation of aerobic activity (i.e., oxygen utilization) did not occur and subsequent analysis indicated that oxygen consumption still remained near the substratum. During the ammonia only recovery phase, different spatial recoveries were seen in each of the samples, based on oxygen utilization. It appears that the presence of higher free ammonia concentration allowed a larger biomass to remain active during monochloramine application, particularly the organisms deeper within the biofilm, leading to faster recovery in oxygen utilization when monochloramine was removed. These results suggest that limiting the free ammonia concentration during monochloramine application will slow the onset of nitrification episodes by maintaining the biofilm biomass at a state of lower activity.
Krishna, K. C. B., A. Sathasivan, et al. (2012). "Evidence of soluble microbial products accelerating chloramine decay in nitrifying bulk water samples." Water Research 46(13): 3977-3988.  

The discovery of a microbially derived soluble product that accelerates chloramine decay is described. Nitrifying bacteria are believed to be wholly responsible for rapid chloramine loss in drinking water systems. However, a recent investigation showed that an unidentified soluble agent significantly accelerated chloramine decay. The agent was suspected to be either natural organic matter (NOM) or soluble microbial products (SMPs). A laboratory scale reactor was fed chloraminated reverse osmosis (RO) treated water to eliminate the interference from NOM. Once nitrification had set in, experiments were conducted on the reactor and feed waters to determine the identity of the component. The study showed the presence of SMPs released by microbes in severely nitrified waters. Further experiments proved that the SMPs significantly accelerated chloramine decay, probably through catalytic reaction. Moreover, application of common protein denaturing techniques stopped the reaction implying that the compound responsible was likely to be a protein. This significant finding will pave the way for better control of chloramine in the distribution systems.

Lee, W. H., D. G. Wahman, et al. (2011). "Free Chlorine and Monochloramine Application to Nitrifying Biofilm: Comparison of Biofilm Penetration, Activity, and Viability." Environmental Science & Technology 45(4): 1412-1419.
  Biofilm in drinking water systems is undesirable. Free chlorine and monochloramine are commonly used as secondary drinking water disinfectants, but monochloramine is perceived to penetrate biofilm better than free chlorine. However, this hypothesis remains unconfirmed by direct biofilm monochloramine measurement. This study compared free chlorine and monochloramine biofilm penetration into an undefined mixed-culture nitrifying biofilm by use of microelectrodes and assessed the subsequent effect on biofilm activity and viability by use of dissolved oxygen (DO) microelectrodes and confocal laser scanning microscopy (CLSM) with LIVE/DEAD BacLight. For equivalent chlorine concentrations, monochloramine initially penetrated biofilm 170 times faster than free chlorine, and even after subsequent application to a monochloramine penetrated biofilm, free chlorine penetration was limited. DO profiles paralleled monochloramine profiles, providing evidence that either the biofilm was inactivated with monochloramine's penetration or its persistence reduced available substrate (free ammonia). While this research clearly demonstrated monochloramine's greater penetration, this penetration did not necessarily translate to immediate viability loss. Even though free chlorine's penetration was limited compared to that of monochloramine, it more effectively (on a cell membrane integrity basis) inactivated microorganisms near the biofilm surface. Limited free chlorine penetration has implications when converting to free chlorine in full-scale chloraminated systems in response to nitrification episodes.
Krishna, K. C. B. and A. Sathasivan (2010). "Does an unknown mechanism accelerate chemical chloramine decay in nitrifying waters?" Journal American Water Works Association 102(10): 82-90.
  Most chloraminated water distribution systems experience accelerated chloramine loss after the onset of severe nitrification. It is commonly believed that nitrification (largely the nitrite and pH changes induced by nitrification) is the major cause of chloramine loss. The experiments described in this article showed that nitrite and pH or other known mechanisms are not sufficient to explain the decay observed in severely nitrifying bulk waters. By separating the microbial and chemical decay using the microbial decay factor method, the authors found that an unknown mechanism-suspected to be soluble microbial products-was responsible for accelerated chloramine decay. It is necessary to understand the basic mechanisms of accelerated chloramine decay in nitrified waters before control mechanisms are implemented. The findings of this study suggest that water providers dealing with accelerated chloramine decay should target the production and control of soluble microbial products released by microbes in addition to nitrification.

 

Lab Studies
Citation Notes Abstract
Wahman, D. G. and G. E. Speitel (2013). The Reaction of Monochloramine and Hydroxylamine: Implications for Ammonia Oxidizing Bacteria in Chloraminated Drinking Water. Water Quality Technology Conference, Long Beach, CA, AWWA.    
Krishna, K.C.B., A. Sathasivan, and D.C. Sarker. 2012. Evidence of soluble microbial products accelerating chloramine decay in nitrifying bulk water samples. Water Research 46:3977-3988.
SMPs caused "auto-catalytic" decomposition of chloramines The discovery of a microbially derived soluble product that accelerates chloramine decay is described. Nitrifying bacteria are believed to be wholly responsible for rapid chloramine loss in drinking water systems. However, a recent investigation showed that an unidentified soluble agent significantly accelerated chloramine decay. The agent was suspected to be either natural organic matter (NOM) or soluble microbial products (SMPs). A laboratory scale reactor was fed chloraminated reverse osmosis (RO) treated water to eliminate the interference from NOM. Once nitrification had set in, experiments were conducted on the reactor and feed waters to determine the identity of the component. The study showed the presence of SMPs released by microbes in severely nitrified waters. Further experiments proved that the SMPs significantly accelerated chloramine decay, probably through catalytic reaction. Moreover, application of common protein denaturing techniques stopped the reaction implying that the compound responsible was likely to be a protein. This significant finding will pave the way for better control of chloramine in the distribution systems.
Pressman, J. G., W. H. Lee, et al. (2012). "Effect of free ammonia concentration on monochloramine penetration within a nitrifying biofilm and its effect on activity, viability, and recovery." Water Research 46(3): 882-894.
  Chloramine has replaced free chorine for secondary disinfection at many water utilities because of disinfection by-product (DBP) regulations. Because chloramination provides a source of ammonia, there is a potential for nitrification when using chloramines. Nitrification in drinking water distribution systems is undesirable and may result in degradation of water quality and subsequent non-compliance with existing regulations. Thus, nitrification control is a major issue and likely to become increasingly important as chloramine use increases. In this study, monochloramine penetration and its effect on nitrifying biofilm activity, viability, and recovery was investigated and evaluated using microelectrodes and confocal laser scanning microscopy (CLSM). Monochloramine was applied to nitrifying biofilm for 24 h at two different chlorine to nitrogen (Cl-2:N) mass ratios (4:1 [4.4 mg Cl-2/L] or 1:1 Cl-2:N [5.3 mg Cl-2/L]), resulting in either a low (0.23 mg N/L) or high (4.2 mg N/L) free ammonia concentration. Subsequently, these biofilm samples were allowed to recover without monochloramine and receiving 4.2 mg N/L free ammonia. Under both monochloramine application conditions, monochloramine fully penetrated into the nitrifying biofilm within 24 h. Despite this complete monochloramine penetration, complete viability loss did not occur, and both biofilm samples subsequently recovered aerobic activity when fed only free ammonia. When monochloramine was applied with a low free ammonia concentration, dissolved oxygen (DO) fully penetrated, but with a high free ammonia concentration, complete cessation of aerobic activity (i.e., oxygen utilization) did not occur and subsequent analysis indicated that oxygen consumption still remained near the substratum. During the ammonia only recovery phase, different spatial recoveries were seen in each of the samples, based on oxygen utilization. It appears that the presence of higher free ammonia concentration allowed a larger biomass to remain active during monochloramine application, particularly the organisms deeper within the biofilm, leading to faster recovery in oxygen utilization when monochloramine was removed. These results suggest that limiting the free ammonia concentration during monochloramine application will slow the onset of nitrification episodes by maintaining the biofilm biomass at a state of lower activity.
     

HAAs
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Haloacetonitiles
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Haloacetamides
(related info may be found in: DBP Analysis and Non-regulated DBP pages)
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Halonitromethanes
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Halobenzoquinones
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Single Studies in VariousTreatment Scenarios
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Large DBP Studies with some Degradation Data
Citation Notes Abstract