Effect of chloramine concentration on biofilm maintenance on pipe surfaces exposed to nutrient-limited drinking water

• Published in: Water S. A. Vol. 34; no. 3; pp. 373 - 380
• Main Authors: Kim, Yeong-Kwan, Park, Se-Keun
• Format: Journal Article
• Language: English
• Published: Pretoria Water Research Commission (WRC) 01.07.2008; Water Research Commision
• Subjects: Biofilm; Biological and medical sciences; Earth sciences; Earth, ocean, space; Exact sciences and technology; Fundamental and applied biological sciences. Psychology; GAC; HPC; Hydrology; Hydrology. Hydrogeology; Low-nutrient water; Monochloramine residual; Physiological substrate utilisation profile; plates; bacteria; density; Heterotrophy; concentration; chlorine; nutrients; pipes(igneous rocks); Ammonia; Rotaliacea; foraminifera; prokaryotes; substrates; Ratio; drinking water; Inhibition; Invertebrata; Protista; maintenance; pipes; organic carbon; Community; Rotaliina; communities
• ISSN: 0378-4738; 0378-4738
• DOI: 10.4314/wsa.v34i3.180632

This study addresses the effect of specific monochloramine concentration on biofilm density and bacterial functional potential in nutrient-limited water. The efficacy of monochloramine residual maintenance on biofilm density was studied at a range of 0.5 to 2.0 mg / ℓ, using a 3 : 1 (w / w) dosing ratio of chlorine to ammonia, with the provision of low-nutrient water (0.18 mg / ℓ as total organic carbon, 0.055 mg / ℓ as biodegradable dissolved organic carbon, and 10.5 µg / ℓ as assimilable organic carbon) using a granular activated carbon (GAC) filter. Biofilm density was monitored using biofilm bacteria counts and analysis of the physiological substrate utilisation profiles in Biolog gram-negative (GN) micro-plates. The monochloramine residuals were maintained stable in the low-nutrient water pipes, which contributed to the inhibition of biofilm density. Increasing the monochloramine residual from 0.5 to 2.0 mg / ℓ suppressed the total cells and heterotrophic plate count (HPC) bacteria in the biofilms by about 1 and 2 log units, respectively. The biofilm HPC densities were more sensitive to monochloramine residual, and the reduction in biofilm HPC densities expressed as log CFU / cm2 showed an exponential relationship with the increase in monochloramine residual. The Biolog micro-plate-based community-level assay showed that the biofilm communities occurring at 3 levels of chloramination were distinguished by the differences in their substrate utilisation potentials. The functional / metabolic potential of the biofilm community?s ability to utilise specific substrates was much lower at higher monochloramine concentration. Results suggest that the maintenance of a consistently high-level monochloramine residual in the low-nutrient water system led not only to a reduction in biofilm density on pipe surfaces but also depressed potential functional / metabolic ability of the biofilm community.