Full metadata
Title
Impact of Temperature and Electrochlorination on Biofilms and Legionella Growth on Different Pipe Materials
Description
Megapolitan cities have emerged due to unprecedented urban migration. These changes strain urban resources, especially water distribution and treatment systems. The recent rise of Legionella cases linked to water distribution systems highlights this issue.Bacterial growth and biofilm formation are influenced by factors, such as type and concentration of residual disinfectant, pipe material, water temperature. Experiments were conducted in identical model water distribution systems (WDSs) constructed of three different pipe materials: galvanized steel, copper, and cross-linked polyethylene (PEX) operated under a continuous flow rate of 15 L/min. Each model WDS includes 11 steel coupons screwed to the water distribution pipes. City of Tempe (Arizona) municipal water was used in the experimentation, with no nutrients added. Following biofilm growth, coupons were removed and processed by scrubbing biofilm into
phosphate-buffered saline (PBS). Reasoner's 2A (R2A), Trypticase Soy Agar (TSA), Brilliant, and buffered charcoal yeast extract (BCYE) agar media were used to examine biofilm samples for heterotrophic plate counts (HPC), metabolically active bacteria, E coli,
and Legionella. Simultaneously, water samples from the reservoirs of model WDSs were also collected and examined for the same bacteria.Next, an electrochlorination cell maintained free chlorine residuals in unheated PEX and copper model WDSs. These two systems maintained free chlorine residuals for one week and evaluated biofilm and bacterial kinetics. Higher water temperature increased biofilm development. Bacterial counts in biofilms were higher on new (fresh) coupons compared to the old coupons. Heterotrophic and metabolically active bacteria behaved similarly. Only control and heating systems in copper water reservoirs have Legionella spp. Biofilms
formed less on copper systems than steel and PEX systems. Initially, PEX had more HPC than copper. After electrochlorination, HPC concentration in the PEX system rapidly declined to non-detect, whereas in the copper system dropped to 0.54 log CFU/mL.
Thus, higher temperature increases biofilm growth on all pipe materials and reservoirs bacterial concentration. Electrochlorination is a potential biofilm and microbial disinfection method. This thesis topic investigated how these parameters affect the model distribution system bacterial populations and biofilm growth.
Date Created
2022
Contributors
- Kolahi Kouchaki, Bita (Author)
- Abbaszadegan, Morteza (Thesis advisor)
- Alum, Absar (Committee member)
- Perreault, Francois (Committee member)
- Arizona State University (Publisher)
Topical Subject
Resource Type
Extent
54 pages
Language
eng
Copyright Statement
In Copyright
Primary Member of
Peer-reviewed
No
Open Access
No
Handle
https://hdl.handle.net/2286/R.2.N.171558
Level of coding
minimal
Cataloging Standards
Note
Partial requirement for: M.S., Arizona State University, 2022
Field of study: Civil, Environmental and Sustainable Engineering
System Created
- 2022-12-20 12:33:10
System Modified
- 2022-12-20 12:52:47
- 1 year 11 months ago
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