Category Archives: Distribution Systems

Opportunistic premise plumbing pathogen occurrence, China

Liu L, Xing X, Hu C, Wang H. One-year survey of opportunistic premise plumbing pathogens and free-living amoebae in the tap-water of one northern city of China. Journal of environmental sciences (China). 2019 Mar;77:20-31. doi: 10.1016/j.jes.2018.04.020.

In this study, qPCR was used to quantify opportunistic premise plumbing pathogens (OPPPs) and free-living amoebae in 11 tap water samples collected over four seasons from a city in northern China. Results demonstrated that the average numbers of gene copies of Legionella spp. and Mycobacterium spp. were significantly higher than those of Aeromonas spp. (p < 0.05). Legionella spp. and Mycobacterium spp. were 100% (44/44) positively detected while P. aeruginosa and Aeromonas spp. were 79.54% (35/44) and 77.27% (34/44) positively detected. Legionella pneumophila was only detected in 4 samples (4/44), demonstrating its occasional occurrence. No Mycobacterium avium or Naegleria fowleri was detected in any of the samples. The average gene copy numbers of target OPPPs were the highest in summer, suggesting seasonal prevalence of OPPPs. Average gene copy numbers of OPPPs in the taps of low-use-frequency were higher than in taps of high-use-frequency, but the difference was not significant for some OPPPs (p > 0.05). Moderate negative correlations between the chlorine concentration and the gene copy numbers of OPPPs were observed by Spearman analysis (rs ranged from -0.311 to -0.710, p < 0.05). However, no significant correlations existed between OPPPs and AOC, BDOC, or turbidity. Moderate positive correlations were observed between the target microorganisms, especially for Acanthamoeba spp., through Spearman analysis (p < 0.05). Based on our studies, it is proposed that disinfectant concentration, season, taps with different-use frequency, OPPP species, and potential microbial correlations should be considered for control of OPPPs in tap water.

Contaminants in drinking water stored in plastic cisterns, Brazil

de Oliveira Moura T, Oliveira Santana F, Palmeira Campos V, de Oliveira IB, Medeiros YDP. Inorganic and organic contaminants in drinking water stored in polyethylene cisterns. Food chemistry. 2019 Feb 1;273:45-51. doi: 10.1016/j.foodchem.2018.03.104.

This work evaluated the presence of contaminants in stored rainwater in 36 polyethylene tanks installed in two rural communities of the semiarid of Bahia, Brazil. Carbonyl compounds were analyzed by High Performance Liquid Chromatography (HPLC-UV), BTEX (Benzene, Toluene, Ethylbenzene and Xylenes) by gas chromatoghaphy (GC-FID), and trace elements by inductively coupled plasma optical emission spectrometry (ICP-OES). Seven carbonyl compounds were quantified including acrolein (<3-115 µg L-1), which is considered a potent mutagenic agent, above the potability limit in 75% of the cases. Trace elements such as copper, zinc, barium, aluminum and lead, more frequently found, were also quantified, and lead (<0,56-99 µg L-1) was above the tolerable limit for drinking water of 10 μg L-1 in 73% of the cases. The results show that the stored water in polyethylene cisterns in the Brazilian semiarid region does not present satisfactory conditions for human consumption.

Mn and Al deposits in drinking water distribution systems

Li G, Ding Y, Xu H, Jin J, Shi B. Characterization and release profile of (Mn, Al)-bearing deposits in drinking water distribution systems. Chemosphere. 2018 Jan 9;197:73-80. doi: 10.1016/j.chemosphere.2018.01.027.

Inorganic contaminants accumulation in drinking water distribution systems (DWDS) is a great threat to 2 without well crystalline form. The relative abundance of Mn and Fe in deposits changed with their distance from the water treatment plant. Compared with iron in corrosion scales, Mn and Al were more labile to be released back into bulk water during unidirectional flushing process. A main finding of this work is the co-release behavior of Mn and Al in particulate form and significant correlation exists between these two metals. Dual control of manganese and aluminum in treated water is proposed to be essential to cope with discoloration and trace metal contamination in DWDS.

Controlling Copper and PEX Drinking Water Pipeline Biofilms

Inkinen J, Jayaprakash B, Ahonen M, Pitkänen T, Mäkinen R, Pursiainen A, Santo Domingo JW, Salonen H, Elk M, Keinänen-Toivola MM. Bacterial community changes in copper and PEX drinking water pipeline biofilms under extra disinfection and magnetic water treatment. Journal of applied microbiology. 2017 Dec 9. doi: 10.1111/jam.13662.

AIMS: To study stability of biofilms and water quality in pilot scale drinking water copper and PEX pipes in changing conditions (extra disinfection, magnetic water treatment MWT).

METHODS AND RESULTS: Next-generation sequencing (NGS) of 16S ribosomal RNA genes (rDNA) to describe total bacterial community and ribosomal RNA (rRNA) to describe active bacterial members in addition to traditional microbiological methods were applied. Biofilms from control copper and PEX pipes shared same most abundant bacteria (Methylobacterium spp., Sphingomonas spp., Zymomonas spp.) and average species diversities (Shannon 3.8-4.2) in rDNA and rRNA libraries whereas few of the taxa differed by their abundance such as lower total Mycobacterium spp. occurrence in copper (<0.02%) to PEX (<0.2%) pipes. Extra disinfection (total chlorine increase from ca. 0.5 to 1 mg l-1 ) affected total and active population in biofilms seen as decrease of many bacterial species and diversity (Shannon 2.7, P < 0.01, rRNA) and increase of Sphingomonas spp. as compared to control samples. Further, extra disinfected copper and PEX samples formed separate clusters in unweighted non-metric multidimensional scaling plot (rRNA) similarly to MWT-treated biofilms of copper (but not PEX) pipes that instead showed higher species diversity (Shannon 4.8, P < 0.05 interaction).

CONCLUSIONS: Minor chlorine dose addition increased selection pressure and many species were sensitive to chlorination. Pipe material seemed to affect mycobacteria occurrence, and bacterial communities with MWT in copper but not in PEX pipes.

SIGNIFICANCE AND IMPACT OF THE STUDY: This study using rRNA showed that chlorination affects especially active fraction of bacterial communities. Copper and PEX differed by the occurrence of some bacterial members despite similar community profiles.

Impact of water quality on corrosion of cast iron pipes

Hu J, Dong H, Xu Q, Ling W, Qu J, Qiang Z. Impacts of water quality on the corrosion of cast iron pipes for water distribution and proposed source water switch strategy. Water research. 2017 Oct 31;129:428-435. doi: 10.1016/j.watres.2017.10.065.

Switch of source water may induce “red water” episodes. This study investigated the impacts of water quality on iron release, dissolved oxygen consumption (ΔDO), corrosion scale evolution and bacterial community succession in cast iron pipes used for drinking water distribution at pilot scale, and proposed a source water switch strategy accordingly. Three sets of old cast iron pipe section (named BP, SP and GP) were excavated on site and assembled in a test base, which had historically transported blended water, surface water and groundwater, respectively. Results indicate that an increasing Cl or SO42- concentration accelerated iron release, but alkalinity and calcium hardness exhibited an opposite tendency. Disinfectant shift from free chlorine to monochloramine slightly inhibited iron release, while the impact of peroxymonosulfate depended on the source water historically transported in the test pipes. The ΔDO was highly consistent with iron release in all three pipe systems. The mass ratio of magnetite to goethite in the corrosion scales of SP was higher than those of BP and GP and kept almost unchanged over the whole operation period. Siderite and calcite formation confirmed that an increasing alkalinity and hardness inhibited iron release. Iron-reducing bacteria decreased in the BP but increased in the SP and GP; meanwhile, sulfur-oxidizing, sulfate-reducing and iron oxidizing bacteria increased in all three pipe systems. To avoid the occurrence of “red water”, a source water switch strategy was proposed based on the difference between local and foreign water qualities.

Partial Lead Service Line Replacement Should be Avoided

Deshommes E, Laroche L, Deveau D, Nour S, Prévost M. Short- and Long-Term Lead Release after Partial Lead Service Line Replacements in a Metropolitan Water Distribution System. Environ Sci Technol. 2017 Aug 9. doi: 10.1021/acs.est.7b01720.

Thirty-three households were monitored in a full-scale water distribution system, to investigate the impact of recent (<2 yr) or old partial lead service line replacements (PLSLRs). Total and particulate lead concentrations were measured using repeat sampling over a period of 1-20 months. Point-of-entry filters were installed to capture sporadic release of particulate lead from the lead service lines (LSLs). Mean concentrations increased immediately after PLSLRs and erratic particulate lead spikes were observed over the 18 month post-PLSLR monitoring period. The mass of lead released during this time frame indicates the occurrence of galvanic corrosion and scale destabilization. System-wide, lead concentrations were however lower in households with PLSLRs as compared to those with no replacement, especially for old PLSLRs. Nonetheless, 61% of PLSLR samples still exceeded 10 μg/L, reflecting the importance of implementing full LSL replacement and efficient risk communication. Acute concentrations measured immediately after PLSLRs demonstrate the need for appropriate flushing procedures to prevent lead poisoning.

Crude oil contamination of plastic and copper drinking water pipes

Huang X, Andry S, Yaputri J, Kelly D, Ladner DA, Whelton AJ. Crude oil contamination of plastic and copper drinking water pipes. Journal of hazardous materials. 2017 Jun 17;339:385-394. doi: 10.1016/j.jhazmat.2017.06.015.

This study was conducted to determine the susceptibility of plastic (i.e., PEX, HDPE and CPVC) and copper pipes to short-term contamination by crude oil. Pipes were exposed to highly and slightly contaminated drinking water for the typical duration of Do Not Use drinking water orders. PEX pipes sorbed and desorbed the greatest amount of monoaromatic hydrocarbons (MAHs), whereas copper pipes were less susceptible to contamination. For benzene, toluene, ethylbenzene, and xylenes (BTEX) quantified in water, only benzene exceeded its health based maximum contaminant level (MCL). The MCL was exceeded for copper pipe on day 3, for CPVC pipe through day 9, and PEX and HDPE pipes through day 15. The BTEX compound concentration in water after the pipes were returned to service depended on the initial crude oil concentration, material type, and exposure duration. Total organic carbon (TOC) measurement was not helpful in detecting oil contaminated water. Except BTEX, trimethylbenzene isomers and a couple of polycyclic aromatic hydrocarbons (PAHs) with and without MCLs were also detected desorbing from PEX-A pipe. Oil contaminated water must be thoroughly characterized and pipe type will influence the ability of drinking water levels to return to safe limits.