Response to: A Winning Solution for the City of Oxnard is a Win for Us All
Depending on the level of treatment and thus the cost of delivered water, various contaminants and pathogens can be left in and ignored, or removed and acknowledged. Under some circumstances, the water can be considered as “legal” but that may still beg the issue of its being safe. This, then, bespeaks of a complex issue that bears much more discussion than allotted here.
Removal of pathogens and their genes relates, in part, to the screen and membrane size to control pass through of things like antibiotic resistant genes and on the differences between indicator microbes and some of the contaminants. Some thought and discussion is warranted. Why this? First, the genes are designed small enough to be extruded through the bacterial pilus, the tube connecting to bacteria during coupling, a tube with in internal diameter of about 2 nanometers (2nm). A virus can squeeze through about 30nm. That takes the treatment train down to a fairly sophisticated level. The standard coliform bacteria, as used to test water, is about 2000nm long and about 500nm in diameter. This is why when one looks for antibiotic resistant genes, or that matter, virulence factors, as found in tertiary treated recycled water, it becomes obvious that this level of filtration is insufficient treatment. So, how small do we need to go? Probably down to reverse osmosis, hence high cost. Is the water being delivered going to be RO?
Tests using the now antiquated standard coliform will not do. Tests on one of the most modern wastewater treatment plants in the U.S. showed an abundant output and release of antibiotic resistant genes. They are much more resistant to control than the indicator bacteria. And, tests on indicators fail to appreciate the stealth state of bacteria, known as the viable but non-culturable (VBNC) state. In the VBNC state, these bacteria—-the ones used for standard indicators—don’t show up on the state’s tests. So, the tests results can be false negatives. Further, while passing down the pipe, say toward the crop of leafy greens to be irrigated, these bacteria in the VBNC state can resuscitate and by the time they reach the sprinkler head, their numbers are off the charts——-not good. But, because they entered this stealth state, they could not be seen on the standard test.
Thus, the way to be sure is testing where the water is used, not as it first leaves the treatment works because of VBNC, but at the sprinkler head or spigot. Well, some might say, “so what, these are only genes, not the pathogens”. But testing does show a resuscitation of the stunned bacteria if one bothers to check the end of the pipe. Through gene swapping, bacteria can, in a single gene transfer, become lethal pathogens. Unless the end of the pipe is tested turning your gut bacteria into pathogens can happen with a glass of water, or a leafy green irrigated with recycled water. The scientific literature has an abundance of papers on this.
Are the water agencies and others proposing this willing to test for resistant bacteria and genes, especially at the end of the pipe?
Dr Edo McGowan
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I have taken Cal Poly’s Designer/Manager School of Irrigation program in the past at their San Luis Obispo Campus. Maybe you might bring insight to their program with the concerns you’ve mention regarding recycled water.
Mr. Hicks: Good questions and one might assume that the water industry or the state’s regulatory agencies have answers, or should have answers. My guess is that they don’t, so where does that leave us? The fact that if I use the approved standard test, as conducted at the production facility, generally with those lab tests, I will get a non-detect. So, things look good and the water should be OK, it passed the test didn’t it—-and is legal. But, assuming I really don’t trust those results because I recognize the chance of viable but non-culturable, hence a false negative, and rerun the state’s tests at the sprinkler head and now I get results showing bacterial counts which are now off the charts. But, the water originally checked out OK? So what happened? The bacteria in the original test were in the viable but non-culturable state and the state’s test could not see them. But, traveling down the pipe, they resuscitated. Then, if I run disk diffusion at the same time as I run the original state standard test (coliform), I find drug-resistant microbes hiding in the background (this at the production plant as well as the sprinkler head). These are not picked up by the state’s standard test. And, yes, it’s too late. So, where is the backup system? Harwood and WERF (WERF is the research arm of the water industry) did a year’s study on wastewater treatment plants across the U.S. In their abstract, they note: “The failure of measurements of single indicator organism to correlate with pathogens suggests that public health is not adequately protected by simple monitoring schemes based on detection of a single indicator, particularly at the detection limits routinely employed. Monitoring a suite of indicator organisms in reclaimed effluent is more likely to be predictive of the presence of certain pathogens, and a need for additional pathogen monitoring in reclaimed water in order to protect public health is suggested by this study.” See:https://www.ncbi.nlm.nih.gov/pubmed/15933017. The Harwood paper came out in 2004, so industry and the regulators have been well aware of this for, what, 15 years? Actually, the U.S. EPA did a very comprehensive study along these lines back in the late 1970s, but for political reasons pulled that whole study and all its associated lab notes out of its data base. So, how are the regulators playing with our health versus the profits of industry? If pathogens are known to be hiding in there and the standard test fails to show them, are they gambling that things will continue to slide through unnoticed? Industry knows that biofilms build up in pipes. Once a biofilm is established, it is very hard if not virtually impossible to clear them and they continue to spread and shed bacteria. Thus, there is a need for additional pathogen monitoring in reclaimed water in order to protect public health is suggested by the Harwood and WERF studies.
To give you an appreciation of just how difficult biofilms are to deal with, the Johnson Space Center has problems with biofilms in its space systems dealing with water and biofilms. With all their brains and money, they have yet to effectively correct these issues. See for example: https://link.springer.com/article/10.1023/B:WATE.0000049182.01490.a7
The Trump administration is toying with taking tax dollars to supply grants to industry to improve the nation’s infrastructure. But, unless we have new designs and new standards for sewer plants, the problem will persist, it will just be in newer concrete.
Edo McGowan
IF effluent processed water is sent to spreading grounds to recharge aquifers, would that be an area where it can be “tested at the pipe”?
AND, could exposure to sunlight improve the safety of said water?
Mr Hicks—-Where does it go. It depends on where it is processed. But, basically if it is not fully used as recycled, it is discharged to land, a river, a lake, or the ocean. In the large eastern rivers, one city extracts the water, treats it, then discharges the sewage back into the same river and the next down-stream city pulls it in, and that is cycled over and over down the river. In plants using the ocean outfall, it goes out to sea via a pipe. Some of these pipes discharge miles off shore and some not so far. As an example there are several wastewater plants that have short shallow outfalls, they discharge about 1/4 mile off shore and less that 50 feet below the surface. UCSB did a study on one such sewer plant and used released floating trackers to follow where the current carried the released effluent. About 50% of the time the currents took these trackers back to the beach and surf. It takes about a minute for the warm and less dense or more buoyant effluent to rise to the surface and then start drifting as a plume. Scientists from Scripps have tracked plumes coming north from south of the boarder as fairly concentrated plumes northward. These are supposed to be diluted by diffusion systems, but as seen, these don’t seem all that effective, especially if released near shore. Colleagues mention that perhaps the red tides are related to discharged sewage. Off the Channel Islands there is a gyre, a circulating body of water driven by a northward moving warm current and southward moving cold current. This is one of two unique marine systems on the globe. So, all the discharging sewer plants north of this discharge to the south-moving current and all those south discharge into the north-moving system and this concentrates en-trained toxins in this area of unique marine life. Then, you have all the solids that are separated from the wastewater and these contain pathogens and superbugs as well as contaminants of emerging concern, endocrine disrupters, flame retardants, etc. About 65% of the accumulated solids foes on American farmland or dairy pasture. That means this then is available to incorporation into animal and plants that become our food or the food of livestock or poultry.
Thank you Mr. McGowan
Consumers both on human direct use of water and those using water for crops need to know, in a simpler manner, what it will take to make recycled safe for use.
Measuring safety “at the pipe” would suggest to me that that would be too late if you either were about to drink said water or apply it to crops.
Which brings up another subject….if the water is not used for crops or human ingestion, where does it go and what affect does that water have on the environment where it ends up at?
From Dr. McGowan via email…
In both of these cases (Oxnard and Santa Paula) the water is tested under antiquated criteria relying tests and organisms that would completely miss bacteria harboring antibiotic resistant genes (i.e., superbugs) as well as missing the genes themselves. It does make sense to use recycled water to offset or replace potable supplies ONLY if that alternative does not pose a threat to public health. The way to show that the replacement water does not represent a risk to public health is to test it at the spigot or sprinkler head. As stated elsewhere, tests at the production facility fall prey to significant errors that can and do send out false negative results. One way to look at this water is through a process called disk diffusion, a classical test that will show pathogens that are drug resistant. This may not be what the water industry may want, but if the public wants the truth, using the old standard coliform and most probable number is not the way to go. Finding antibiotic resistant genes can be done with qPCR. The answers can be obtained but is the system willing to run these revealing tests?
Dr. Edo McGowan