The Pure Water Occasional for January 20, 2013
In this issue you’ll learn how many tons of water the sun evaporates each day, the percentage of the human brain that consists of water, the number of openings in each and every inch of a 40 mesh screen, and the micron size of a white blood cell. You’ll find a book about water treatment written specifically for dummies and hear how the need for electricity is threatening Europe’s few remaining wild rivers. Learn about the excellent progress in the cleanup of the Pantex plant in Texas, the dastardly deeds of the Drummond Corporation, the alarming number of trace chemicals being found in drinking water, and what happened to a Texas school that failed to pay its water bill. And, as always, there is much, much more.
To read this issue on our website, please go here.
Numerical water facts from B. Sharper, the Pure Water Gazette’s numerical wizard.
Percentage of the human brain that is water: 75%.
Percentage of the human blood that is water: 83%.
Percentage of human bones that are water: 25%.
Tons of water that are evaporated each day by the sun: 1,000,000, 000,000 (one trillion).
In a one hundred year period, the amount of time spent in the ocean by the average water molecule: 98 years.
In a one hundred year period, the amount of time spent as ice by the average water molecule: 20 months.
In a one hundred year period, the amount of time spent in lakes and rivers by the average water molecule: 2 weeks.
In a one hundred year period, the amount of time spent in the atmosphere by the average water molecule: 1 week.
Amount of time that groundwater, once polluted, can remain polluted: several thousand years.
Number of the Earth’s people that must walk at least three hours to obtain drinking water: 1,000,000,000 (one billion).
Meshes and Microns: The Measurements of Water Treatment
by Gene Franks
So much attention is given to the materials of water filter media (coconut shell vs. standard bituminous filter carbon, for example) that the size measurements of filter media are often ignored. Size, however, is very important in water filters.
Filter media are usually manufactured substances that are ground to a specific size. The “grind,” usually expressed as a mesh size, greatly affects the performance of the filter.
In large tank-style filters, the general rule is that the smaller the granules of filter media, the more effective the filter will be at reducing contaminants, but the greater the restriction it will offer to the flow of water. Performance must be weighed against flow rate. A filter is of no value if water won’t go through it, nor is it of value if it’s so porous that it won’t remove the targeted contaminant.
The size of the particles in granular filter media is usually expressed as mesh size. Mesh refers to the number of holes or openings per inch in a testing sieve. A 12 mesh screen has 12 holes per inch. A 40 mesh screen has 40 much smaller openings per inch.
Filter media is usually described with a two number designation. Twelve by 40 mesh filter carbon is a common size. If filter carbon is said to be 12 X 40 mesh, it means that the granules of carbon will fall through a screen with 12 holes per inch but be caught by a screen with 40 holes per inch. (Since nothing is perfect, some allowance is made for a small percentage of granules to be outside the size range. The undersized particles that wash out of the filter when water first goes through it are called “fines.” Over-sized chunks are called “overs.”) Eight by 30 mesh carbon is a courser blend than 12 X 40 carbon. It will fall through an 8-mesh screen but be retained by a 30-mesh screen. Water goes through 8 X 30 carbon faster, but for many jobs it is less effective.
In general, the larger the mesh number, the smaller the granules.
The familiar term “granular activated carbon,” or GAC, is used to describe most granular carbon. The technical definition of GAC is carbon of which 90% is retained by an 80 mesh screen. Finer-ground carbon, often compressed into carbon block filters, is called powdered activated carbon. Powdered activated carbon is in the 80 X 325 mesh neighborhood. Powdered carbon is more effective than GAC, but it is much more restrictive.
As things get tinier, filter makers usually switch to another measurement, the micron.
Here’s the Wikipedia definition: A micrometer or micron , the symbol for which is µm, is one millionth of a meter. It can be written in scientific notation as 1×10−6 m, meaning 1⁄1000000 m. In other words, a micron is a measurement of length, like an inch or a mile.
To put this in context, an inch is 25,400 microns long, or a micron is 0.000039 inches long.
Here are measurements of some common items:
Red blood cell — 8 microns.
White blood cell–25 microns.
An average human hair (cross section) –70 microns.
Cryptosporidium Cyst — 3 microns.
Bacteria — 2 microns.
Tobacco smoke–0.5 microns.
The naked human eye can normally see objects down to about 40 microns in size.
In water treatment, the relative “tightness” of filters is usually expressed in microns. A five-micron sediment filter is a common choice for prefiltration for a reverse osmosis unit or an ultraviolet lamp. A 5-micron filter is one that prevents the passage of most of the particles of five microns or larger. A one-micron filter is much tighter than a five-micron.
Two qualifying words are used to describe the effectiveness of the filter: absolute and nominal. An absolute filter catches virtually all the particles of the specified size, while a nominal filter catches a good portion of them. There is, unfortunately, within the industry a lot of wiggle room in defining what exactly constitutes a nominal or an absolute filter rating.
The nominal pore size rating describes the ability of the filter media to retain the majority of particles at the rated pore size. Depending on the standard used, a “nominal” filter can be anywhere from 60% or 98% efficient.
Absolute is a higher standard, but again the term is slippery and its meaning depends on whose definition you accept. The standard water treatment industry’s trade associations, to accommodate marketers, in some cases lower its definition of “absolute” to as little as 85% efficiency. Other standards exist, such as industrial/commercial filtration (98%-99%), US EPA “purifier grade” (99.9%), and very high purity industry standards, e. g. pharmaceutical, (99.99%).
To clarify: a “0.5 micron absolute” carbon block filter sold by an aggressive commercial marketer isn’t necessarily as tight a filter as a 0.9 micron absolute ceramic filter that is designed to purify water by removing bacteria. Marketing standards allow some leeway because the carbon block filter isn’t being sold as a purifier (i.e., bacteria remover).
Here is some common size information regarding water filtration that may be helpful.
Granular tank-style filters are generally assumed to have about a 20 micron particle rating. Some are tighter. A multi-media filter (containing filter sand, anthracite, garnet, etc.) is considered to be about a 10 micron filter. Some of the newer natural zeolite media (ChemSorb, Micro Z, for example) are considered 5 micron filters.
Good carbon block drinking water filters, which are manufactured by binding very small carbon particles together, are frequently in the 0.5 and smaller range. Doulton ceramic filters, which are very effective bacteria reducers, are in the 0.9 micron absolute area. As you would guess, flow rates are slow and pressure drop is significant. Newer technologies known as ultrafiltration operate in the 0.1 micron range, and nano filtration (often called “loose reverse osmosis”) goes down to the 0.01 micron area. Reverse osmosis membranes have a micron rating of around 0.0005 to 0.001 microns–so tight that they reduce the “dissolved solids” (minerals) in water which pass easily through carbon and ceramic filters.
Comparing and converting mesh sizes to microns is most easily done by visiting one of the many web sites that offer conversion charts. Some common equivalents, to give you the idea:
10 mesh equals about 2,000 microns.
100 mesh equals about 149 microns.
400 mesh equals 37 microns.
If you’d like to figure it out for yourself, an engineer has worked it all down to this neat formula: microns = 14,992 X mesh(-1.0046). This can be rounded off to mesh = 15,000/microns. That’s certainly a lot easier than looking it up on a chart.
World Water News for the Week
Is your city water department hiding something in your neighborhood? If there’s a home on your block with no sidewalk and no driveway, it may not be a residence but a . . . . Watch the video.
The Water Quality Association has issued an interesting e-book, Water Treatment for Dummies, that can be read free online in a convenient digital flipbook format. Click here to open.
Chlorine gas detected north of Alaska. An international Canadian-led research project on ozone and mercury in the Arctic has detected surprisingly high levels of chlorine gas over the ice sheet north of Barrow, Alaska.
llinois village leads charge for tougher oil train rules. Barrington, Ill., a suburb of about 10,000 people 30 miles northwest of Chicago, has been leading a push for tougher U.S. safety regulations on the nation’s sharply-increasing oil train traffic. Pipelines aren’t the only way that oil gets into water.
Hydropower struggle: Dams threaten Europe’s last wild rivers. Europe’s last remaining wild rivers flow through the Balkans, providing stunning scenery and habitat to myriad plants and animals. But hundreds of dam projects threaten to do irreparable harm to the region’s unique biospheres – to provide much-needed electricity to the people who live there.
Colombia aims to improve its embattled coal mining industry. Alabama-based Drummond Co. has been fined $3.6 million in Colombia for polluting beaches and dumping coal into the ocean. Drummond reflects a wider dilemma facing the Colombian government.
Gas storage tanks leak as fund intended to help flows elsewhere. Contamination from more than 9,000 leaking underground petroleum storage tanks in Michigan has awaited cleanup for years, as a gasoline regulatory fee intended to fund such work was diverted by state lawmakers to plug general fund budget holes over the past decade.
Advocates say canal project improving Florida Bay. A major Everglades restoration project is exceeding expectations after its first year of operations, according to environmental activists.
LUBBOCK, Texas (AP) — The effort to clean up soil and groundwater contamination at the nation’s only plant for assembling and disassembling nuclear weapons has been effective so far and will continue for years, according to the first five-year review of the site.
Pantex in the Texas Panhandle was added to the national Superfund cleanup list in 1994 because of past site practices that included burning chemicals in unlined pits, burying waste in unlined landfills and discharging waste into on-site surface waters known as playa lakes.
The review says the long-term project is focusing on removing contamination from soil and a shallow aquifer beneath the plant, located 17 miles northeast of Amarillo.
“We are already seeing significant reduction in contaminant concentration in parts of the perched aquifer,” said Camille Hueni, who’s overseeing the project for the Environmental Protection Agency.
One of the top goals of the cleanup is to keep contamination from reaching the Ogallala Aquifer, which underlies eight Plains states and is the Panhandle’s major source of water for municipal, industrial and agricultural use. The shallow aquifer, or groundwater, is perched as much as 200 feet above the Ogallala.
The methane article below is from the Pure Water Products collections of water treatment issues from our main website. The article was prepared by James Washington.
Methane (CH4) is the simplest of the alkanes, a family of compounds consisting only of carbon and hydrogen atoms. It’s colorless and odorless—odor is added to make it detectable—and most often in the form of gas. It makes up 75% or more of natural gas used for heating, etc. It naturally dissolves in some groundwaters, especially near petroleum deposits or coal seams.
Wells that contain methane are often located in areas where gas and oil wells are common. Methane is common in nature, resulting from anaerobic digestion of plant and animal matter. It’s also known as “swamp gas,” “biogas,” or, in coal mines, “fire-damp” or “coal-gas.”
Effects of Methane
- Non-toxic, but can produce suffocation by replacing oxygen in confined air space. Can be absorbed into the body by inhalation.
- Flammable and potentially explosive when mixed with air.
- Can cause “water hammer” in plumbing systems or “fizzing” of water drawn from taps.
- When dissolved in water, it can give water a milky look, or “swampy” odor and taste
Methane in the form we’re most familiar with.
Water Treatment for Methane
Atmospheric aeration is essentially the only treatment for methane in well water. Atmospheric aeration involves allowing the methane gas to escape to the atmosphere. Pressurized aeration tanks, though vented, will not work well for methane. Exposing the water in an atmospheric tank means that water pressure will be lost and a repressurization system consisting of a pump and usually a pressurized pump tank will be needed.
Methane is not filterable or removable chemically.
Recommendations for aeration:
- Prefilter to avoid particle or precipitate blockage of spray nozzles.
- Disinfection (typically chlorination) of aeration-system feedwater is recommended to avoid biofouling/contamination, especially in warmer climates.
- Aeration-released methane must be ventilated from tank to the outdoors with spark-free air blower fan, preferably operating 24/7.
Sources: International Occupational Safety and Health Centre; University of Wisconsin — Madison; Wes McGowan, Water Processing, Third Edition, published by Water Quality Association. Water Technology Volume 32, Issue 3 – March 2009. Photo: WikiMedia, author: Rickjpelleg
School’s Out Because of Water Bill Dispute in La Villa, Texas
Schools are closed in a one-stoplight South Texas town after the city shut off their water amid a dispute over the bill.
The city of La Villa shut off water and sewer service to the La Villa Independent School District in December, shortly after students started their holiday break. The city had increased a water surcharge and the school district has refused to pay the higher rate.
The district’s approximately 625 students were supposed to return to classes Monday, but instead found this message on the school district’s website: “All La Villa I.S.D. schools will be closed until further notice.”
Students raising pigs at the district farm just behind the baseball field had to find new homes for their projects. The boys and girls basketball teams have had their home games converted to away games until the dispute is resolved. They beg court time for practices from other area districts. Seniors fret _ perhaps prematurely _ over whether they might be forced to finish out their final year in another district.
Read the rest at PostBulletin.com.
What should we do about the trace chemicals found in drinking water?
by Mark Brush
Editor’s Note: This Michigan Public Radio report is also available in a radio version.
Before I talk about the small bits of chemicals often found in drinking water, I want to direct some attention to the national water contamination story going on now because I think it reveals something.
The water is bad in West Virginia
The nation has its eyes on a nine-county area in West Virginia that’s under a state of emergency. A coal-processing chemical leaked into a river and poisoned the drinking water there. Cleanup is ongoing. As they attempt to flush the chemical out of their drinking water systems, officials are trying to determine what level of the chemical is safe.
Ken Ward Jr. of the West Virgina Gazette reports that local and federal officials are saying that “1 part per million” of crude 4-methylcyclohexanemethanol (the coal processing chemical) is safe for people to drink.
But Ward is having a tough time finding out what they based that number on:
When asked for more information about where the number came from, Department of Health and Human Resources Secretary Karen Bowling pointed to the “material safety data sheet,” or MSDS, from Eastman, the maker of the chemical that leaked.
Bowling, though, downplayed the fact that there is precious little toxicological data and few – if any –public and peer-reviewed studies of what the chemical would do to humans if ingested.
There it is. The research on how these chemicals affect our health can be pretty thin.
Trace amounts of chemicals in drinking water
Around much of the nation, the fact that chemicals get into our drinking water has been known for some time. We’re talking tiny amounts. Scientists use terms like “parts per billion” or “nanograms.”
The kinds of chemicals found depends on what gets into the water.
Larry Sanford is the assistant manager of the Ann Arbor Water Treatment plant. On a recent tour of the plant, he read from a list of chemicals researchers found going into the drinking water supply. These were trace amounts of chemicals found after the treatment process.
“Ibuprofen… Carbamazepine – I’ve never said that word before. Seventeen b estradiol … 17 a ethinyl estradiol, and estrone, and estriol, and cholesterol, and coprostanol.”
The researchers were looking for trace amounts of pharmaceuticals and personal-care products in the water. Our bodies don’t take up all of the medicine in birth control pills, or antidepressants, or even coffee.
You go to the bathroom, and the extra stuff gets flushed down the drain. Small amounts end up in the drinking water.
The water samples in Ann Arbor showed that 19 different types of drugs were going into the treatment plant. And the treatment process took out eight of them.
Sanford called that “serendipity.”
“None of these plants were built with the intention of removing any of this stuff,” said Sanford. “You just get the removal based on what’s there already. Now when you decide what it is you want to remove, then you’ll have to build a treatment facility that will take that out. It may take other things out at the same time, it may not.”
So what should we do with this information?
That’s what researchers are trying to figure out right now. What’s worth worrying about, and what’s not?
They found more than a third of these plants had trace amounts of 18 unregulated contaminants. In addition to leftover drugs, they found traces of many industrial chemicals, and traces of pesticides too.
Linda Birnbaum is the Director of the National Institute of Environmental Health Sciences. She’s one of the nation’s leading experts on how exposure to these contaminants might affect our health.
I had her look at the list of chemicals found in drinking water. She told me that several of the chemicals found were of some concern, such as the perfluorinated compounds and some of the pesticides.
But she said, “Again the levels are very low.”
So should we not be concerned at all?
“Well, the answer is we’re beginning to find out that continuous low level exposure, may in fact be problematic,” said Birnbaum.
She says studies are beginning to show that continuous low-level exposure to some chemicals might harm the endocrine system. The endocrine system regulates how your body grows and how you behave.
That’s why researchers are focusing on how this stuff impacts pregnant mothers, developing babies, and kids.
More science needed
The EPA is still gathering more information. They’ve called for more testing at water treatment plants, and they have a list of chemicals they’re watching for. Federal regulators call these “emerging contaminants.”
The Ann Arbor Water Treatment Plant just started a year-long monitoring program.
The treatment plant’s Larry Sanford says we might find that these things really don’t have a big impact on us, but they might have an effect on other things.
“The things that live in the water are much smaller, and there may be an impact on them,” said Sanford. “And it may be something that would be worth doing something about.”
Researchers are looking at what these low-level contaminants are doing to fish.
We’ll take a look at that in our next report.
What you can do
Michigan Radio’s Rebecca Williams gathered much of the tape for this story, and in doing so she spoke with Professor Nancy Love of the University of Michigan. Love teaches in the Department of Civil and Environmental Engineering and focuses her work on how environmental biotechnology and engineered water quality treatment systems can clean up these trace chemicals.
The two discussed reverse osmosis treatment systems, and Love agreed that such a system does a good job of removing many contaminants. She said it’s often difficult to know what might be in bottled water, but if the label says “treated by reverse osmosis,” it’s a sign that the water has been treated well.
There’s not much we can do about the drugs we excrete (drugmakers could work to make sure we use more of the available medicine, rather than excrete it), but if we have left over medicine in the house, we should NOT flush it down the toilet.
Here’s what the FDA recommends.
If you have susceptible people living in your house (kids, or people struggling with substance abuse), you might want to go through the process of disposing the drugs in the trash, rather than storing them in your home while you wait to take them to a drug take-back program.
Source: Michigan Radio.
The lesson to be taken from this is that “final barrier” treatment in the home is very important. A good carbon filtration system for the whole home and, especially, a reverse osmosis drinking water system offer the best protection against extraneous chemicals.–Editor.
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