In a recent study in South Arizona, a group of scientists from the University of Arizona developed a method of monitoring the quality of tap water using filters from commercial vending machines. They think this system could also help in understanding the patterns of all stages of bacterial outbreaks.
The scientists took the filters from the vending machines and passed water with a known level of contamination through them. Then they collected the organisms form them to figure out how well the filters caught the bacteria. A total of 48 filters were sampled from 41 different shopping malls and convenient store parking lots. They tested three types of filters: new, artificially aged and naturally aged. The artificially aged filters were new filters that had 16000L of treated water passed through them over six days in a laboratory. “Out of 48 SBC [solid block carbon] filters 54.2% were positive for at least one organism. The number of filters positive for total coliforms, E. coli, enterococci, and enterovirus was 13, 5, 19, and 3, respectively, corresponding to 27.1%, 10.4%, 39.6%, and 6.3% of the total filters. No filters were positive for noroviruses or Cryptosporidium.” (Miles, 2009)
The results of these experiments were that the efficiency of catching the microbes in the filters was higher in the aged filters than the new ones. This is probably because the aged filters had more matter and particles that it had accumulated over time, which helped catch the bacteria and hold on to it. In the study they mention why they might not be able to recover one hundred percent of the bacteria from the filters: the organisms might not be retained in the filters, they could get caught permanently in the filters, or they may be injured and therefore not be measurable. These factors make it falsely seem that the water is cleaner than it really is.
Post-treated water can be contaminated due to treatment deficiencies, contamination of main pipes due to construction, water and sewer pipes inadequately separated, broken or leaking pipes, cross-connection or backflow events, intrusion events (i.e., bio terrorism), or bacterial re growth. All these reasons seem inevitable and while this monitoring system is still under development, it seems like it might be an economical way of monitoring our tap water.
References:
Miles, Syreeta L., Gerba, Charles P., Pepper, Ian L. and Reynolds, Kelly A. (2009). Point-of-Use Drinking Water Devices for Assessing Microbial Contamination in Finished Water and Distribution Systems. Environ. Sci. Technol 2009. 10.1021/es801482p. January 29, 2009
Great article!! I am now going to think twice when I drink out of the tap. I could follow your article perfectly. It was flowing, captivating and quite interesting to say the least. To think that I could be drinking E. coli and I would not even know!
ReplyDeleteAs well as I really like that you included the numbers and the procedures followed by the scientists but at the same time any one from the general public could follow along and get the full message.
I thought it was really good of you to include a simplified version of the procedures followed in the experiment. From a reader's perspective it adds credibility to the article. I think it may have been more effective if you summarized the results of the experiment in more general terms rather than including a quote. Some people might not be familiar with noroviruses or cryptosporidium, so it may be a little confusing. But it was good that you explained these results.
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