Quantification of the bacterial community of drinking water-associated biofilms under different flow velocities and changing chlorination regimes

Abstract

Microbial growth in drinking water distribution systems (DWDS) depends on a great number of factors, and its control represents a great challenge for management of these engineering systems. The present case study assessed the influence that a pair of factors-water chlorination and flow velocity-had on the biofilms formed in a model DWDS in 626 days. The culturable bacteria number and biomass of the biofilms developed under the flow velocities of 0.3 m/s, 0.5 m/s, 0.7 m/s and 1 m/s were determined during three consecutively applied regimes of water chlorination to 0.05 mg/l (in 380 days), 0.42 mg/l (in 46 days) and 0.14 mg/l free chlorine (in 200 days). The results demonstrated that biofilm formation was a prolonged process directly depended on flow velocity at drinking water chlorination to 0.05 mg/l. The increase in the water chlorination to 0.42 mg/l chlorine resulted in both the reduction in culturable bacteria number and biomass removal, but the bacteria killing and the biofilm removal were distinct processes. The biocide action of chlorine was faster and more effective than its biomass removal effect. The chlorine decreasing from 0.42 to 0.14 mg/l resulted in increasing the biofilm HPC densities, although the biomass removal process was still continuing. The study carried out contributes for better understanding the biofilm behavior in DWDS and demonstrates that biofilm formation could be managed within a DWDS through operational decisions on parameters that can be changed and controlled as flow velocity and chlorination to safeguard drinking water quality.

Effect of Drinking Water Distribution System Design on Antimicrobial Delivery to Pigs

“…Low velocity water flows that occur in pipe sections of over-sized pig building WDSs also influence biofilm growth [ 40 ]. Studies have shown that, when compared to WDSs with high velocity water flows (>0.3 m/sec), those with low velocity flows have lower hydrodynamic shear forces at the internal surface of their pipes, which leads to growth of thicker, less dense and less stable biofilms [ 41 , 42 , 43 ]. Further to this, low velocity water flows through pipes lead to higher concentrations of antimicrobial-resistant bacteria (ARB) and a higher prevalence of antimicrobial-resistant genes (ARGs), and different microbial community compositions than are found in pipes with higher velocity water flow [ 44 , 45 , 46 ].…”

Effects of the chlorination and pressure flushing of drippers fed by reclaimed wastewater on biofouling

“…The copyright holder for this preprint this version posted July 17, 2020. ; https://doi.org/10.1101/2020.07.17.208074 doi: bioRxiv preprint of colonisation rather than using them separately (Mathieu et al, 2014;Tsvetanova, 2020).…”

Optimization of Quantitative Analysis of Biofilm Cell from Pipe Materials

“…Due to the fact that the study of biofilms in real DWDS is complicated, many reactors and laboratory simulated DWDS have been developed for this purpose [4,[35][36][37][38][39]. These devices enable the formation of a biofilm under controlled physicochemical and microbiological conditions that ensure operational conditions similar to those prevailing in DWDS.…”