Drinking water from sewage: less bacteria, more resistance genes

[Darwinsbulldog]

Even the Cleanest Wastewater Contributes to More 'Super Bacteria'

ScienceDaily (Nov. 14, 2011) — A new University of Minnesota study reveals that treated municipal wastewater -- even wastewater treated by the highest-quality treatment technology -- can result in significant quantities of antibiotic-resistant bacteria, often referred to as "superbacteria," in surface waters.
The study also suggests that standard wastewater treatment technologies probably release far greater quantities of antibiotic-resistant genes used by bacteria, but this likely goes unnoticed because background levels of bacteria are normally much higher than in the water studied in this research.
The new study is led by civil engineering associate professor Timothy LaPara in the University of Minnesota, Twin Cities College of Science and Engineering. The study is published in the most recent issue of Environmental Science and Technology, a journal of the American Chemical Society. The research was part of a unique class project in a graduate-level civil engineering class at the University of Minnesota focused on environmental microbiology.
Antibiotics are used to treat numerous bacterial infections, but the ever-increasing presence of antibiotic-resistant bacteria has raised substantial concern about the future effectiveness of antibiotics. In response, there has been increasing focus on environmental reservoirs of antibiotic resistance over the past several years. Antibiotic use in agriculture has been heavily scrutinized, while the role of treated municipal wastewater has received little attention as a reservoir of resistance.
Antibiotic-resistant bacteria develop in the gastrointestinal tracts of people taking antibiotics. These bacteria are then shed during defecation, which is collected by the existing sewer infrastructure and passed through a municipal wastewater treatment facility.
In this study, the Ph.D. students and professor examined the impact of municipal wastewater in Duluth, Minn., on pristine surface waters by gathering water samples from the St. Louis River, Duluth-Superior Harbor, and Lake Superior in northeastern Minnesota. The treatment facility in Duluth is considered one of the best. After solids and biological matter are removed, the Duluth wastewater treatment is one of only a few in the country that filter water a third time through a mixed media filter to remove additional particles of bacteria and nutrients. Standard wastewater treatment treats water twice to remove solids and biological matter.
"This was a unique and ideal location for this study because of the exemplary wastewater treatment mixed with surprisingly pristine surface waters with very low background levels of bacteria that wouldn't mask our results," LaPara said. "Previous studies in which treated municipal wastewater was implicated as a source of antibiotic resistance were more convoluted because multiple sources of antibiotic resistance genes existed, such as agricultural activity and industrial wastewater discharges."
While the levels of overall bacteria were still relatively low in the surface water samples, researchers in the University of Minnesota study found that the quantities of antibiotic-resistant genes and human-specific bacteria were typically 20-fold higher at the site where treated wastewater was released into the Duluth-Superior Harbor compared to nearby surface water samples.
"Current wastewater treatment removes a very large fraction of the antibiotic resistance genes," LaPara said. "But this study shows that wastewater treatment operations need to be carefully considered and more fully studied as an important factor in the global ecology of antibiotic resistance."
In addition to LaPara, researchers involved in the study include civil engineering Ph.D. students Tucker Burch, Patrick McNamara, David Tan; and bioproducts and biosystems engineering Ph.D. student Mi Yan, with help from soil, water and climate Ph.D. student Jessica Eichmiller.
The University of Minnesota research study was funded by the National Science Foundation's broader impacts effort, which combines research and education. The Minnesota Environment and Natural Resources Trust Fund paid for time on the R/V Blue Heron ship to collect water samples.

http://www.sciencedaily.com/releases...cience+News%29

LaPara, T. M., T. R. Burch, et al. (2011). "Tertiary-Treated Municipal Wastewater is a Significant Point Source of Antibiotic Resistance Genes into Duluth-Superior Harbor." Environmental Science & Technology 45(22): 9543-9549.

In this study, the impact of tertiary-treated municipal wastewater on the quantity of several antibiotic resistance determinants in Duluth-Superior Harbor was investigated by collecting surface water and sediment samples from 13 locations in Duluth-Superior Harbor, the St. Louis River, and Lake Superior. Quantitative PCR (qPCR) was used to target three different genes encoding resistance to tetracycline (tet(A), tet(X), and tet(W)), the gene encoding the integrase of class 1 integrons (intI1), and total bacterial abundance (16S rRNA genes) as well as total and human fecal contamination levels (16S rRNA genes specific to the genus Bacteroides). The quantities of tet(A), tet(X), tet(W), intI1, total Bacteroides, and human-specific Bacteroides were typically 20-fold higher in the tertiary-treated wastewater than in nearby surface water samples. In contrast, the quantities of these genes in the St. Louis River and Lake Superior were typically below detection. Analysis of sequences of tet(W) gene fragments from four different samples collected throughout the study site supported the conclusion that tertiary-treated municipal wastewater is a point source of resistance genes into Duluth-Superior Harbor. This study demonstrates that the discharge of exceptionally treated municipal wastewater can have a statistically significant effect on the quantities of antibiotic resistance genes in otherwise pristine surface waters.

http://pubs.acs.org/doi/abs/10.1021/es202775r

[Justtristo]

I guess if we were to use recycled water, we should limit to purposes other than drinking water.

[Darwinsbulldog]

Originally Posted by ziggystardust

I guess if we were to use recycled water, we should limit to purposes other than drinking water.

You would think so, wouldn't you? It seems like a no-brainer. Nevertheless, our water supplies and plumbing are not set up for using/managing water supplies sensibly. Obviously sewage and potable water is separated, but one needs a third line for non-potable water for garden, industry etc. Neither municipal infrastructure, not residential and industrial plumbing is set up this way in most areas.

[Mjt]

So Puppy would this resistant bacteria be able to survive the trip through our system and live to cause us problems?

[Darwinsbulldog]

Originally Posted by Mjt

So Puppy would this resistant bacteria be able to survive the trip through our system and live to cause us problems?

I dunno for sure, but it seems very likely. Bacteria can survive almost anything. They ahve even been found in nuclear power plant cooling systems. But it is a numbers game. Deadly bacteria get into our bodies all the time, but are overwhelmed by our immune systems if their numbers are low. [But it varies with each species and strain. Further, bacteria often communicate by what is called quorum sensing, which means that they often can lay low until their numbers build before they attack.

These little critters have been surviving and thriving for nearly four billions of years, so if there is a "hole" in a waste treatment scheme, these little bugs will probably find it. Bacteria have all sort of tricks that allow them to survive in hostile conditions of all sorts, by forming spores and so on.

The safer and more efficient the water treatment scheme, the more expensive it might be [as a general rule], although new techniques can be cheaper. So it gets down to an economics question-zero risk is probably impossible, so what level of risk is acceptable?

Remember that humans vary enormously, and that includes our immune systems. The very old, the very young or an other immunocompromised individuals are always the "canaries" in the system-they will [statistically] be the first to suffer any ill-health or death.

But that is not the only problem. Water catchments are also used for recreations, like swimming, and of course animal vectors can pick up bugs and possibly transfer them to humans or their domesticated animals.

[Seamus]

so what level of risk is acceptable?

Good question.We actually accept relatively high risks in most food ,fresh and processed. So probably a lot higher than mots people would like to think.

I live in Adelaide. The water is 'hard' and is often the colour of rust in Summer.It's perfectly fine as long as you don't give it to infants and remember to chew.


In such a dry country with a growing population, I think the universal use of recycled sewerage is inevitable.

The government will either just not say anything (that's what I'd do) or do what it did with flouride;make the decision,THEN have the debate.

I think it's easy to overlook that a parliamentary democracy is not government by consensus. Parliamentary debate is pretty much required to give the impression of transparency. Public debate is not required,but used by government to asses the political climate.

A controversial decision on is one which will cost votes.A courageous decision is one which will cost the next election (Sir Humphrey Appleby)