| Organic chloramines can form as inorganic chloramines or free chlorine reacts with organic nitrogen in drinking water systems. Organic chloramines may serve as intermediates for disinfection by-products (DBPs) and affect microbial inactivation in distribution system. Organic chloramines also interfere with conventional N,N-diethyl-p-phenylenediamine (DPD) analysis of combined chlorine residuals. This interference can be lead to the overestimation of active disinfection residuals. Although biological materials are major sources of organic nitrogenous compounds in water treatment system, previous research on organic chloramines formation has mainly focused on disinfectants reactions with simple amino acids. Therefore, it is hypothesized that organic chloramines form when biofilms react with free chlorine or monochloramine.;The disinfection efficacy of organic chloramines were evaluated on E. coli, bacteriophages (PR 772 and MS2), and Pseudomonas fluorescence and compared against free chlorine and monochloramine. All inactivation data and inactivation rate constants reveal that free chlorine exhibits greater rates of inactivation than monochloramine and inactivation in the presence of organic chloramines is essentially none existent.;The influence of organic chloramines during nitrification event was studied in batch and pipeloop systems. Nitrification was induced by adding Nitrosomonas europaea (ammonia oxidizing bacteria: AOB) in a laboratory pipeloop system. Working in batch modes with planktonic AOB, addition of free chlorine and monochloramine inhibited nitrification by AOB inactivation. Addition of organic chloramines (1 mg Cl2/L) in batch and pipeloop experiments led to nitrification. Thus, AOB can actively oxidize ammonia to produce nitrite and nitrate in the presence of organic chloramines. This result showed that nitrification continuously occurred in the presence of organic chloramines.;Free chlorine or monochloramine added to extracted extracellular polymer substances (EPS) from wastewater biomass and heterotrophic plate count (HPC) bacteria. Extracted EPS contained organic nitrogen rich compounds and combined amino acids were present. Organic chloramines were quantified by a colorimetric method using DPD and MonochlorF methods. Organic chloramines formed quickly with free chlorine and decayed slowly over a given period of time. With monochloramine, the amount of formed organic chloramines was lower but the organic chloramines decayed slower. This research showed that biofilms/biomass can be a source of organic nitrogen to form organic chloramines. |
