Quantifying Uncertainties for Chlorine Residual Control in Drinking Water Distribution Systems

Author(s):  
T. Chang ◽  
M. A. Brdys ◽  
K. Duzinkiewicz
1998 ◽  
Vol 38 (8-9) ◽  
pp. 275-282 ◽  
Author(s):  
P. J. Ollos ◽  
R. M. Slawson ◽  
P. M. Huck

Laboratory reactors operated under conditions relevant for drinking water distribution systems were used to examine the impact of support surface, chloramine residual, biodegradable organic matter (BOM) concentration, shear, and temperature on the growth of heterotrophic microorganisms. In terms of both heterotrophic bacterial growth-supporting and corrosion characteristics, mild steel and stainless steel/polycarbonate substrata bracket metallic pipe materials, such as ductile iron. Results of gradually increasing disinfectant dosage studies suggest that a 0.5 mg/L free or combined chlorine residual on polycarbonate surfaces, and 0.5 mg/L free chlorine or 2.0 mg/L combined chlorine residual on ductile iron substrata would be needed to reduce biofilm HPC numbers to approximately 103 CFU/cm2. Regression analysis suggests low or very low correlation between biofilm and suspended HPC numbers.


2020 ◽  
Vol 41 (S1) ◽  
pp. s255-s255
Author(s):  
Ayodele T. Adesoji ◽  
Adeniyi A. Ogunjobi

Background: Multidrug-resistant bacteria can lead to treatment failure, resulting in infectious diseases being transferred through nonpotable water. Aminoglycosides are an important class of antibiotics that are abused in Nigeria. Few studies have investigated aminoglycoside-modifying genes (AMGs) that are likely responsible for resistance in Nigeria bacteria isolates. Therefore, we aimed to characterize AMGs from isolates in drinking water distribution systems (DWDS) in southwestern Nigeria. Methods: Multidrug-resistant bacteria (n = 181) that had been previously characterized by 16S rDNA sequencing and that were positive for resistance to at least 1 aminoglycoside antibiotic were selected from 6 treated and untreated water distribution systems. Strains were PCR genotyped for 3 AMGs: aph(3)c, ant(3)b and aph(6)-1dd. Results: Of 181 MDR bacteria tested, 69 (38.12%) were positive for at least 1 of the AMGs. The most common was ant(3)c (27.6%), followed by aph(3")c (18.23%). Both aph(3)c and ant(3")b were found in 7.73% of tested isolates, ant(3)b was most commonly found in Alcaligenes spp (50%). Furthermore, aph(3")c was most commonly detected in Proteus spp (50%). Other genera positive for AMGs included Acinetobacter, Aeromonas, Bordetella, Brevundimonas, Chromobacterium, Klebsiella, Leucobacter, Morganella, Pantoae, Proteus, Providencia, Psychrobacter, and Serratia. Conclusions: High occurrence of ant(3)c and aph(3)c among these bacteria call for urgent attention among public health workers because these genes can be easily disseminated to consumers if present on mobile genetic elements like plasmids, integrons, and transposons.Funding: NoneDisclosures: None


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