Microbial community changes with decaying chloramine residuals in a lab-scale system

• Published in: Water research (Oxford) Vol. 47; no. 13; pp. 4666 - 4679
• Main Authors: Bal Krishna, K.C., Sathasivan, Arumugam, Ginige, Maneesha P.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01.09.2013; Elsevier
• Subjects: Ammonia - metabolism; Applied sciences; Bacteria - genetics; Bacteria - metabolism; Biodegradation, Environmental; Biodiversity; Biofilms; Bioreactors - microbiology; Chloramine decay; Chloramine residuals; Chloramines - metabolism; Clone Cells; Cluster Analysis; Colony Count, Microbial; Exact sciences and technology; Gene Library; Heterotrophic microbes; Kinetics; Laboratories; Microbial communities; Microbial Consortia - genetics; Molecular Sequence Data; Nitrification; Oxidation-Reduction; Phylogeny; Pollution; Polymerase Chain Reaction; RNA, Ribosomal, 16S - genetics; Water Microbiology; Water treatment and pollution; Chloramine residuals; Chloramine decay; Microbial communities; Heterotrophic microbes; Nitrification; Pseudomonadales; Chlorination; Heterotrophy; Metabolite; Nitrogen compounds; Tosylchloramide sodium; Water distribution; Pseudomonas; Methylobacterium; Bacteria; Pseudomonadaceae; Ureas; Reactor; Distribution network; Microbial community; Gram negative bacteria; Nitrobacteraceae; Sphingomonas; Real time system; Polymerase chain reaction; Ammonia; Urea; DNA; Nitrosomonas; Poison; Degradation product
• ISSN: 0043-1354; 1879-2448
• DOI: 10.1016/j.watres.2013.04.035

When chloramine is used as a disinfectant, managing an acceptable “residual” throughout the water distribution systems particularly once nitrification has set in is challenging. Managing chloramine decay prior to the onset of nitrification through effective control strategies is important and to-date the strategies developed around nitrification has been ineffective. This study aimed at developing a more holistic knowledge on how decaying chloramine and nitrification metabolites impact microbial communities in chloraminated systems. Five lab-scale reactors (connected in series) were operated to simulate a full-scale chloraminated distribution system. Culture independent techniques (cloning and qPCR) were used to characterise and quantify the mixed microbial communities in reactors maintaining a residual of high to low (2.18–0.03 mg/L). The study for the first time associates chloramine residuals and nitrification metabolites to different microbial communities. Bacterial classes Solibacteres, Nitrospira, Sphingobacteria and Betaproteobacteria dominated at low chloramine residuals whereas Actinobacteria and Gammaproteobacteria dominated at higher chloramine residuals. Prior to the onset of nitrification bacterial genera Pseudomonas, Methylobacterium and Sphingomonas were found to be dominant and Sphingomonas in particular increased with the onset of nitrification. Nitrosomonas urea, oligotropha, and two other novel ammonia-oxidizing bacteria were detected once the chloramine residuals had dropped below 0.65 mg/L. Additionally nitrification alone failed to explain chloramine decay rates observed in these reactors. The finding of this study is expected to re-direct the focus from nitrifiers to heterotrophic bacteria, which the authors believe could hold the key towards developing a control strategy that would enable better management of chloramine residuals. [Display omitted] •Microbial communities changed with chloramine residuals and nitrification.•Higher numbers of Pseudomonas, Methylobacterium &Sphingomonas were noted before the onset of nitrification.•Well known ammonia oxidising bacteria & two novel species were identified.•Microbial chloramine decay did not correlate with nitrification rates.•Novel strategies targeting specific microbial communities may be needed.