Evaluation of biofilm development on various pipelines in the domestic hot water system

Huijin Zhang; Yanling Yang; Xing Li; Yongwang Liu; Li Zhao

doi:10.2166/ws.2017.138

Evaluation of biofilm development on various pipelines in the domestic hot water system

Water Science & Technology Water Supply ◽

10.2166/ws.2017.138 ◽

2017 ◽

Vol 18 (2) ◽

pp. 638-647 ◽

Cited By ~ 3

Author(s):

Huijin Zhang ◽

Yanling Yang ◽

Xing Li ◽

Yongwang Liu ◽

Li Zhao

Keyword(s):

Microbial Communities ◽

Biological Diversity ◽

Growth Characteristics ◽

Hot Water ◽

Plate Count ◽

Biofilm Growth ◽

Domestic Hot Water ◽

Biological Safety ◽

Biofilm Development ◽

Dominant Bacteria

Abstract Biological safety of hot water is important, and it is affected by pipeline material to a certain degree. Polypropylene random (PPR), polyvinyl chloride (PVC) and stainless steel (SS) are the common materials for pipelines in domestic hot water systems (DHWS), and biofilm growth characteristics, and biofilm microbial communities and biological diversity on the walls of pipelines are affected by the pipeline materials to a certain extent. In this paper, the effects of different materials on the growth characteristics and diversity of microbial communities were studied. The results showed that after about 60 days, the bacteria of the biofilm on the wall of pipelines completed a microbial growth cycle. Compared with PPR and SS, a greater amount of the total number of bacteria, Escherichia coli and heterotrophic plate count (HPC) attached to the PVC pipeline. Although the types of bacteria on the pipelines were similar, the proportions of species were different. Proteobacteria were the dominant bacteria at the phylum level on all the walls of the PPR, PVC and SS pipelines, and the dominant bacteria at the genus level changed before and after the exfoliation of biofilm. Some potential pathogens, such as Pseudomonas and Legionella, were detected in biofilm, so effective biofilm disinfection should be considered to ensure biological safety in DHWS.

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Investigation into biofilms in a local drinking water distribution system

Biofilms ◽

10.1017/s1479050505001614 ◽

2005 ◽

Vol 2 (1) ◽

pp. 19-25 ◽

Cited By ~ 18

Author(s):

J. Y. Hu ◽

B. Yu ◽

Y. Y. Feng ◽

X. L. Tan ◽

S. L. Ong ◽

...

Keyword(s):

Distribution System ◽

Distribution Systems ◽

Water Distribution ◽

Water Distribution System ◽

Water Distribution Systems ◽

Plate Count ◽

Residual Chlorine ◽

Biofilm Growth ◽

Water Plant ◽

Biofilm Development

Biofilm growth within a water distribution system could lead to operational problems such as pipe corrosion, water quality deterioration and other undesirable impacts in water distribution systems. With the high ambient temperatures experienced in Singapore, the operating environment in water distribution systems is expected to be more conducive to biofilm development. We have recently conducted a survey on biofilms potentially present in a local water distribution system.The survey results indicated that residual chlorine (±standard deviation) decreased from 1.49±0.61 mg/l (water plant outlets) to 0.82±0.21 mg/l (block pipes) or 0.18±0.06 mg/l (unit pipes), respectively. Consumed chlorine, instead of residual chlorine, was found to be correlated with biofilm bacterial population. Assimilable organic carbon (AOC) level was 160±66 μg acetate C/l, and AOC:PO4-P:NO3-N was about 8:13:1. Carbon source seemed to be the limiting nutrient for bacterial growth. The concentration of iron increased from <0.04 mg/l (water plant outlets) to 0.22±0.10 mg/l (all sites). All samples showed negative results in a coliform test. The average heterotrophic plate count (HPC) for the suspended bacteria was 20 colony-forming units (c.f.u.)/ml (2 days, 35 °C) or 290 c.f.u./ml (8 days, 35 °C). The average HPC for the biofilm bacteria was 6500 c.f.u./cm2 (2 days, 35 °C) or 29000 c.f.u./cm2 (8 days, 35 °C). High HPC values in samples B2a, B2b and B3a (representing biofilm samples at site 2 from block/unit pipes and biofilm samples at site 3 from block pipes, respectively) illustrated that the relevant sample sites had a higher probaboility of biofilm growth.

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Effects of culvert length and flow rates of raw water transport on biofilm development and water quality

Water Science & Technology Water Supply ◽

10.2166/ws.2021.205 ◽

2021 ◽

Author(s):

Ruikang Xue ◽

Tinglin Huang ◽

Gang Wen ◽

Junle Yan ◽

Qian Liu

Keyword(s):

Water Quality ◽

Water Transport ◽

Cell Number ◽

Water Transfer ◽

Plate Count ◽

Raw Water ◽

Long Distance ◽

Biofilm Growth ◽

Flow Rates ◽

Biofilm Development

Abstract Long-distance water transfer projects are important for water allocation. To enhance our understanding of biofilm growth and changes in water quality during raw water transfer, raw water through long-distance non-full culvert at flow rates of 1.4−2.0 m/s was studied.The results revealed that: (1) the biofilm total cell number (TCC) and heterotrophic plate count (HPC) were the highest at a flow rate of 1.5 m/s, which were 3.7E + 04 cells /cm2 and 1.1E + 03 CFU/cm2, respectively; (2) proteobacteria had the highest relative abundance (RA) among all samples, and the RA in biofilm (78.85%) was higher than that in water (48%−59%); (3) when the pollutants and biofilm were partially shed, the total phosphorus (TP), permanganate index (CODMn), and dissolved organic carbon (DOC) increased by 0.011, 0.36, and 0.5 mg/L at most, respectively; and (4) dissolved oxygen (DO) was sufficient during non-full flow water transport and nitrification occurred. The highest removal rates of ammonium nitrogen (NH+4-N) and nitrous nitrogen (NO2--N) reached 27.16% and 66.76%, respectively. At the flow rates of 2.0 m/s, the efficiency decreased to 10.47% and 41.25%, respectively, due to the shedding of biofilm.

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