Effects of activated carbon and bacteriostatic filters on microbiological quality of drinking water

Applied and Environmental Microbiology (Impact Factor: 3.67). 04/1981; 41(3):646-51.
Source: PubMed


Three activated carbon filters for point-of-use water treatment were tested in laboratory and field studies for chemical removal and microbiological effects on water. All removed free available chlorine in municipally treated water to below the limit of detection, but removed only about 50 to 70% of the total available chlorine and 4 to 33% of the total organic carbon. Standard plate count bacteria in the effluent increased steadily with time for 3 weeks and remained elevated over the 8-week period of the study. Total coliform bacteria were found to persist and proliferate on the filters for several days after transient contamination of the influent water. Silver-containing activated carbon filters suppressed total coliform but not total bacterial growth. Pseudomonas aeruginosa was recovered from the effluents of all filters at some time during the tests.

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    • "AC, activated charcoal; Ag-AC, silver-activated charcoal nanocomposite. formation,[51] [52] [53] and the use of silver nanoparticles alone leads to leaching of the material into the filtrate during water treatment. "
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    ABSTRACT: We report for the first time the green synthesis of silver nanoparticles using West Indian cherry (Malpighia emarginata) extract known for its high vitamin C content. UV–visible spectroscopy, powder X ray diffraction (PXRD), dynamic light scattering (DLS), scanning electron microscopy (SEM) and energy dispersive X ray spectroscopy (EDX) analysis were used to characterise silver nanoparticles. Silver nanoparticles thus synthesised exhibit antimicrobial activity against gram-negative bacteria such as Pseudomonas aeruginosa, Escherichia coli, and gram-positive bacteria such as Bacillus subtilis and Staphylococcus aureus. The antimicrobial property of nanoparticles thus synthesised was applied in the production of silver-activated charcoal nanocomposite towards fabrication of antimicrobial water filtration columns. The microbial filtration efficiency of the nanocomposite was found to be higher compared to virgin activated charcoal even with reusage.
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    • "Another accelerated pilot study (Deshommes et al, 2010a) conducted on under-the-sink POU devices up to 120% of their prescribed capacity revealed that total Pb levels were reduced adequately and that particulate Pb was removed more efficiently than dissolved Pb. One concern about POU devices is the bacterial colonization of their media because culturable bacteria could proliferate on activated carbon filters and therefore potentially aggravate the quality of POU effluent water (Tobin et al, 1981). Su et al (2009) showed indevice and post-device colonization by heterotrophic plate counts (HPCs) during an accelerated laboratory study on carbon block POU devices, with accumulation of biofilm in dead-end spaces. "

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    • "Point-of-use (POU) filters have been suggested for use as home water treatment devices. Activated carbon is commonly used in POU filters to remove unpleasant tastes and odors and organic compounds from water, but they will also remove chlorine and chloramine from water, and can be heavily colonized by heterotrophic micro-organisms (Weber et al. 1978; Brewer and Carmichael 1979; Tobin et al. 1981; Stewart et al. 1990; Snyder et al. 1995), even when silver is added to the filter as a bacteriostatic agent (Tobin et al. 1981). The growth of heterotrophic micro-organisms in biofilms, particularly in hot water systems, may provide an environment conducive to colonization by pathogenic micro-organisms such as Legionella spp. "
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    ABSTRACT: To evaluate throughput of seeded Legionella pneumophila bacteria in domestic point-of-use filters. The filters were challenged with tap water seeded with Leg. pneumophila. After multiple challenge events (4.25 x 10(11) CFU per filter), the levels of Legionella were lower in the effluent from the filter containing both copper and silver (mean 4.48 x 10(3) CFU ml(-1)) than in the effluent from the filter containing copper only (1.26 x 10(4) CFU ml(-1); P < 0.001). After a single challenge event of approx. 5 x 10(9) CFU L. pneumophila per filter, there was no significant difference between the levels of Legionella in the effluents from a carbon filter containing copper and a carbon filter with no metals (mean 6.87 x 10(2) and 6.89 x 10(2) CFU ml(-1), respectively; P = 0.985). Legionella was detected in filter effluent up to 6 weeks after being challenged, indicating that while filters may reduce the levels during an initial contamination event, the exposure is extended as the accumulated bacteria slough off over time. This study has provided an understanding of the response of Legionella to the use of silver and copper in domestic point-of-use carbon filters.
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