| Title |
Effects of Phosphate Addition on Biofilm Bacterial Communities and Water Quality in Annular Reactors Equipped with Stainless Steel and Ductile Cast Iron Pipes |
| Author |
Hyun-Jung Jang1,2, Young-June Choi1, Hee-Myong Ro2, and Jong-Ok Ka2,3* |
| Address |
1Division of R&D for Water, Waterworks Research Institute, Seoul 143-820, Republic of Korea, 2Department of Agricultural Biotechnology, Seoul National University, Seoul 151-742, Republic of Korea, 3Research Institute for Agriculture and Life Sciences, Seoul National University, Seoul 151-742, Republic of Korea |
| Bibliography |
Journal of Microbiology, 50(1),17-28, 2012,
|
| DOI |
|
| Key Words |
biofilm, phosphate, disinfection by-products, drinking water distribution system, stainless steel pipe, ductile cast iron pipe |
| Abstract |
The impact of orthophosphate addition on biofilm formation
and water quality was studied in corrosion-resistant
stainless steel (STS) pipe and corrosion-susceptible ductile cast
iron (DCI) pipe using cultivation and culture-independent
approaches. Sample coupons of DCI pipe and STS pipe
were installed in annular reactors, which were operated for
9 months under hydraulic conditions similar to a domestic
plumbing system. Addition of 5 mg/L of phosphate to the
plumbing systems, under low residual chlorine conditions,
promoted a more significant growth of biofilm and led to a
greater rate reduction of disinfection by-products in DCI pipe
than in STS pipe. While the level of THMs (trihalomethanes)
increased under conditions of low biofilm concentration,
the levels of HAAs (halo acetic acids) and CH (chloral hydrate)
decreased in all cases in proportion to the amount of
biofilm. It was also observed that chloroform, the main species
of THM, was not readily decomposed biologically and
decomposition was not proportional to the biofilm concentration;
however, it was easily biodegraded after the addition
of phosphate. Analysis of the 16S rDNA sequences of 102
biofilm isolates revealed that Proteobacteria (50%) was the
most frequently detected phylum, followed by Firmicutes
(10%) and Actinobacteria (2%), with 37% of the bacteria
unclassified. Bradyrhizobium was the dominant genus on
corroded DCI pipe, while Sphingomonas was predominant
on non-corroded STS pipe. Methylobacterium and Afipia
were detected only in the reactor without added phosphate.
PCR-DGGE analysis showed that the diversity of species in
biofilm tended to increase when phosphate was added regardless
of the pipe material, indicating that phosphate addition
upset the biological stability in the plumbing systems. |
