Pure Water Occasional, December 12, 2019 |
Dark Waters: Water Contaminants in the Movies
A highly promoted movie called Dark Waters came out in late November 2019. It stars Mark Ruffalo and tells the story of Cincinnati lawyer Rob Bilott and his dozen-year battle against the centuries-old American chemical company, DuPont. From an effort to gain justice for a single client whose livestock were poisoned by Dupont’s chemical PFOA, Bilott’s efforts resulted in large class-action settlements for hundreds of injured parties. Ruffalo, who is known as an environmental activist as well as an actor, produced the film as well as starring in it. Other top actors featured are Anne Hathaway and Tim Robbins.
Dark Waters joins other important movies that brought significant water contaminants to public attention. The stories of all are similar. They feature an individual who takes on a powerful company that seems to be above the law. The best known of these is Erin Brockovich, starring Julia Roberts, which tells the story of the hexavalent chromium (aka chromium-6) poisoning of the water in Hinkley, CA by Pacific Gas and Electric. A lesser known but equally compelling story is that of the TCE poisoning of the wells that supplied Woburn, MA by the W.R. Grace company. The incident inspired an outstanding book by Jonathan Harr that in turn inspired the 1998 movie A Civil Action, starring John Travolta and Robert Duvall. (The book was better than the movie, but both deserve your attention.)
As if climate change science weren't confusing enough already, according to a new study published in Environmental Science Technology, hundreds of active hydro-power plants are making a worse impact on the climate than fossil fuels. The study shows that hydro-power, popularly seen as a source of green, clean energy, can under some conditions release more greenhouse gases than coal- or oil-burning power plants. Grist.
Central Arkansas Water has a new tool to detect leaks in its distribution system. It is Vessel, the nation’s first water leak detection dog. The black Labrador mix was trained to sniff out treated water that has leaked from the system’s pipes and bark when she finds the location. Leak detection technology is expensive, so Vessel is expected to be a cost-effective and efficient option.
The mercury content of Great Lakes fish has not declined as expected in spite of great reductions in mercury emissions because invasive species, mainly zebra mussels and quagga, have disrupted the the natural feeding patterns of fish. All five lakes still have fish consumption advisories. Details.
FYI: An estimated 141 billion liters of water are used every day to flush toilets. Researchers at Penn State University have developed "a robust bio-inspired, liquid, sludge- and bacteria-repellent coating that can essentially make a toilet self-cleaning.” Use of the coating, they say, can cut the amount of water needed to flush toilets in half. Details.
Acknowledging that past efforts have failed to curb the phosphorous runoff that fuels algal blooms in Lake Erie, Ohio Gov. Mike DeWine unveiled his plan to address the green scourge: pay farmers to reduce runoff. More information.
Researchers at the University of Texas announced that the Nile River is several million years older than was previously believed. Fox News.
A Detroit property contaminated with uranium and other dangerous chemicals partially collapsed into the Detroit River on Nov. 26.
Shortly after the Regional Council of Veneto, in Italy, voted against climate-change legislation, its chambers were flooded. Harpers Weekly Review.
A whale found dead on a Scottish beach had a 220-pound ball of mostly plastic garbage in its stomach.
A California company announced a new technology called Sea-Thru which allows great underwater recording clarity by "removing the water from underwater images." Details.
A report from a consulting firm hired by the the city of Newark concludes that of 198 filters tested for lead removal, all but five reduced lead to acceptable Environmental Protection Agency levels. That’s a 97% effectiveness rating. The report also found that when residents let the tap run for five minutes, the filters worked 99% of the time.The filters are the tiny end-of-faucet models provided to residents by the city.
Spillage of 4 million gallons of raw sewage into the ocean caused the closure of several beaches in Orange County, CA.
Out of control fires in the rain forest are affecting the water supply of Andean communities that depend on water from glaciers for their water supply.
President Trump revealed plans on water conservation relief for small businesses and the origins of ocean trash on US shores. See article below.
Rise of the Jellyfish
As oceans warm and oxygen levels are depleted, the lowly jellyfish is coming into its own. Unlike other sea life, jellyfish thrive in higher temperatures and can breed in polluted water that’s largely lacking oxygen. Over the last century, the average surface temperature of the world’s seas has risen by almost 1°C while oxygen levels in the sea have fallen by around 2 percent over the last 50 years. As the oceans get warmer, jellyfish are also spreading into areas that had historically been too cold.
The most promising suggestion for combatting the takeover by jellyfish is for humans to learn to like eating them. More from WaterOnline. See our article below, which appeared in a 2015 Occasional.
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Jellyfish: Ancient, Gelatinous, Diverse
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Jellyfish in a group are called a smack. The ignorant, however, just call them a bunch of jellyfish.
Some things you may not know about one of earth’s most ancient creatures.
They have been around longer than the oldest of dinosaurs, approximately three times as long. They go back at least 500,000,000 years.
Although they are called fish, they actually aren’t. They are zooplankton.
They are heartless and brainless and made almost entirely (up to 98%) of water. When exposed to air, they can actually evaporate.
Some, but not all, have eyes. One variety has 24 eyes, in fact, and has a full 360-degree view of the world.
One species, Turritopsis nutricula, has the ability to renew its cells and is, therefore, theoretically immortal.
They conveniently eat and defecate through the same orifice which serves as both mouth and anus.
Jellyfish are aquarium favorites.
Just to be different, they have a unique group name. A group of fish is called a school, but multiple jellyfish are referred to as a bloom, a swarm, or a smack.
They are deadly and they don’t mind to sting. One species can kill a human in a matter of minutes with a single sting. And jellyfish stings are very painful.
They come in all sizes. They range in size from a few millimeters in diameter to 440 lbs. The longest jellyfish has tentacles that can extend 120 feet.
Some are edible. They are a popular delicacy in places like Japan and Korea, but haven’t caught on in most parts of the world. In Japan they make jellyfish candy.
Jellyfish have been used in space experiments because of their similarity to humans as regards adaptation to zero-gravity environments.
Jellyfish live in every ocean and can be found from the surface to the deep sea.
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What Kind of Carbon Is Best?
or, How Is Filter Carbon Like a Parking Lot?
by Emily McBroom and Gene Franks
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The “carbon” (often called “charcoal”) that is used for water treatment is made from a variety of raw materials. Someone has said that filter carbon can be made from anything that contains carbon, even peanut butter. Most filter carbon is made from coal–bituminous, sub-bituminous, lignite–and from nut shells, especially coconut shells.
Some of the characteristics that are considered by filter makers when choosing raw materials for the carbon products are:
- Surface area – square meters of surface per gram of carbon. The surface area determines how much adsorption can take place and what types of contaminants the carbon can take onto its surface.
- Iodine Number – indicates the ability of the carbon to adsorb small, low molecular weight organic molecules, like volatile organic chemicals.
- Molasses Number – indicates the ability of the carbon to adsorb large, high molecular weight organic molecules, like colors.
- Bulk Density – indicates the density as pounds per square foot in a column. In general, the higher the density, the more surface area available for adsorption.
Water Quality Association training materials provide such a good explanation of how these four parameters apply to carbon suitability that we can’t resist borrowing it.
The inside surface of the activated carbon particle can be viewed as a large parking lot for organic molecules. Further, one can view the large molecules as semitrucks, and the small organic molecules as compact cars. Using this viewpoint, it is easy to illustrate a number of things. First, if most of the pores in the activated carbon are micropores (small parking spaces), the semitrucks are going to have a difficult time moving inside the parking lot, and they will have difficulty finding a parking site which fits. But, the compact cars will have an easy time. (This corresponds to a high iodine number.) Second, it the pores are mostly macropores (large parking spaces), the semitrucks will be able to get around fine, but it will be an extremely inefficient way to park compact cars. (This corresponds to a high molasses number.) Third, if there are only a few roads connecting the various areas inside the parking lot, the cars will all pile up, and the roads will act as a bottleneck. Ultimately, a large number of small cars can be parked, but the parking lot will fill slowly. This is what happens if there is not a suitable mix of micropores (small spaces) and macropores (big spaces).
So, activated carbons made from lignite coal tend to have large pores (macropores) and make good parking spaces for big trucks, like tannins.
Carbons made from coconut shells have very small pores (micropores) and are especially good parking spaces for very small molecules like VOCs, which are the compact cars of the organic chemical world.
But over the years, the most widely used carbon material of all is bituminous coal, because bituminous carbon has big pores and little pores and a lot of mid-sized pores (mesopores) that are just right for parking the great many average-sized family sedans, SUVs, and pickups. In other words, bituminous carbon is widely used because it works pretty well for just about anything. Bituminous coal based activated carbons are frequently a good first choice for general dechlorination and reducing the concentration of a large range of organics.
All carbons, by the way, work well for removing chlorine and even chloramine, although contact time with the carbon needs to be about twice as long for chloramine as for chlorine. (Specially processed carbon called “catalytic carbon,” which is available in coal- or coconut-based, is much better at chloramine removal than standard carbon.) All carbons work well for taste/odor improvement, and we find no scientific basis to support the common belief that coconut shell carbons make water taste better than other carbons.
There are other considerations, of course, that are left out of the parking lot method for choosing carbon. An important one for residential users is a test called Ball-Pan Hardness. It puts a numerical value on the hardness of the carbon–how much banging around it will take before it breaks down. In this test coconut shell carbon always comes out way ahead of bituminous. This is significant for tank-style residential filters because when carbon breaks down because of the rolling and tumbling of repeated backwashing it gets into service lines. Think of it as the coconut shell parking lot having tougher walls and posts to withstand the banging it gets from those wild compact car drivers.
Carbon made from peanut butter, by the way, fares poorly on the Ball-Pan Hardness test but has an excellent Molasses number and great Surface Area.
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Pressure, Flow Rate, and Delta P
A 2″ pipe is considerably larger than two 1″ pipes when it comes to flow and pressure drop performance. Water does not flow through pipes uniformly. It flows faster in the middle than on the sides.
Pushing high flows of water through a small pipe wastes both energy and money. It can also cause corrosion and shorten the life of the pipe.
Water flowing through a pipe does not flow uniformly from edge to edge. Water in a pipe flows like water in a river, with water in the middle flowing much faster than water at the edges. Flow is fast at mid stream, and the water against the wall of the pipe is scarcely moving.
As water pressure pushing the flow increases, flow within the pipe becomes more turbulent and “thinner.” By thinner we mean that there is rapid flow at the center of the pipe but the areas of relatively low flow extend further out from the walls of the pipe.
Flow with high turbulence requires far more energy than smooth flow. Thus, to double the flow rate in a pipe by increasing pressure, it takes four times as much energy.Therefore, it is important to limit linear flow when designing a piping system.
There is a general rule that says flow through a pipe should be no more than 8 to 10 linear feet per second.
There is a measurement used in pipe and water filter design called “Delta P.” In general terms, Delta pressure, or delta P, most commonly refers to the difference in pressure before and after a fluid filter (oil, hydraulic, or fuel) which indicates when the filter is clogged.
Most aircraft have “Delta P” indicators to show this condition. With water filters a pressure gauge is sometimes mounted in front of a filter and another after. The difference between the readings of the two gauges indicates the delta P. If the filter is clean, the gauges should read nearly the same, but as the filter takes on contaminants, the difference between the inlet and the outlet gauges, the delta P, increases.
There is a common misconception that pipe capacities increase in direct proportion to the stated size, i.e. that a 2” pipe has twice the carrying capacity of a 1” pipe, and that, therefore, two 1” pipes side by side would have the same fluid carrying capacity as a single 2” pipe. This is not so. A 2″ pipe actually has the carrying capacity of four 1″ pipes. The rule of thumb is twice the diameter equals four times the flow. See How Many 1″ Pipes Will Fit Into a 2″ Pipe?
Without getting too technical, consider these examples of how delta P works:
If you put 10 gallons of water per minute through 100 feet of 1” irrigation pipe, the pressure at the end of the pipe will be 15 psi less than the pressure at the input end. That’s a delta P of 15 psi per 100 feet of pipe.
If you put 10 gallons of water per minute through 100 feet of ¾” irrigation pipe, the pressure at the end of the pipe will be 20 psi less than the pressure at the input end. That’s a delta P of 20 psi per 100 feet of pipe.
If you put the same 10 gallons of water per minute through 100 feet of 1/2” irrigation pipe, the pressure at the end of the pipe will be 35 psi less than the pressure at the input end. That’s a delta P of 35 psi per 100 feet of pipe.
Another example:
Water flowing through a 10 foot section of 4” pipe at the rate of 10 feet per second will put out 400 gallons per minute.
Water flowing through a 10 foot section of 2” pipe at the rate of 10 feet per second will put out 100 gallons per minute.
Water flowing through a ten foot section of 1” pipe at the rate of 10 feet per second will put out 25 gallons per minute.
Therefore, a 2″ pipe is much larger than double the size of a 1″ pipe when it comes to flow and pressure performance.
Indebted to a Water Conditioning and Purification article, February 2013, paper issue, by Chubb Michaud, and to Ryan Lessing and Pure Water Annie, via the article cited above.
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Gazette’s Introductory Note: The piece below is adapted from an information sheet provided by the non-profit Water Systems Council. It addresses one of the more confusing topics in water treatment, the “sulfur” or rotten egg smell in well water. Bad smelling water is variously attributed to sulfur, sulfate, or hydrogen sulfide. This document seeks to shed some light on the origin and treatment of bad smelling water.
What is Sulfur?
Two forms of sulfur are commonly found in drinking water: hydrogen sulfide and sulfate-reducing bacteria. Both forms are nuisances that usually do not pose a health risk at the concentrations found in domestic wells.
Hydrogen sulfide gas occurs naturally in some ground water that contains decaying organic matter, such as wetlands, marshes, swamps, river beds. It may be found in deep or shallow wells. Hydrogen sulfide is often present in wells drilled in shale or sandstone, or near coal or peat deposits or oil fields.
Sulfate is a combination of sulfur and oxygen, and is part of naturally occurring minerals in some soil and rock. The mineral dissolves over time and is released into ground water. Sulfur odor is produced when a non-harmful sulfur-reducing bacteria digests a small amount of the sulfate mineral.
What are the health effects of Sulfur?
The EPA considers sulfur a secondary water contaminant, with no direct threat to human health. Sulfate gives water a bitter taste and can have a laxative effect that may lead to dehydration. Hydrogen sulfide gives water a “rotten egg” odor and taste, and can cause nausea.
Hydrogen sulfide is corrosive to metals such as iron, steel, copper and brass. It can tarnish silverware and discolor copper and brass utensils. Hydrogen sulfide can also cause yellow or black stains on kitchen and bathroom fixtures. Coffee, tea and other beverages made with water containing hydrogen sulfide may be discolored and the appearance and taste of cooked foods can be affected. High concentrations of dissolved hydrogen sulfide also can foul the resin bed of an ion exchange water softener.
How do I test for Sulfur?
Testing for hydrogen sulfide can be difficult because the gas escapes into the atmosphere so quickly. Onsite testing is the most accurate method for determining hydrogen sulfide concentration, especially if the odor is excessive. Hydrogen sulfide concentrations greater than 5 mg/L are more difficult to treat and could require special testing methods to assure accuracy.
Sulfate-reducing bacteria is rarely tested, however testing for sulfate ion (mineral) concentration is. The premise is: if a rotten egg odor is present and the sulfate ion concentration is excessive – greater than 150 mg/L – the odor is created by sulfate-reducing bacteria.
The EPA sets standards for secondary water contaminants based on taste, odor, color, corrosiveness, foaming and staining properties. Hydrogen sulfide is not regulated because any concentration high enough to pose a health hazard will also make the water too unpalatable to drink. The EPA’s secondary limit for sulfate in drinking water is 250 parts per million (ppm).
What are the treatments for Sulfur in drinking water?
Treatment options depend on the form (whether hydrogen sulfide or sulfate-reducing bacteria) and quantities of the “rotten egg odor-producing” contaminants. Hydrogen sulfide treatment is with chlorination or aeration followed by filtration. Often, treatment for hydrogen sulfide is the same as for iron and manganese, allowing the removal of all three contaminants in one process.
Most water heater anode rods contain some sulfate so, in the presence of sulfate-reducing bacteria, a rotten egg odor is created in the hot water only. If this occurs, the first course of action is to replace the anode rod with an aluminum-based rod which limits the sulfate and therefore stops the odor.
Sulfate-reducing bacteria is treated with continuous chlorination. Removing sulfate mineral is difficult and usually not feasible, so chlorination kills the bacteria instead. The chlorination process involves a chemical feed pump system that injects a chlorine solution into the inlet of a retention tank that must be installed in the house piping. The retention tank must hold enough water to provide a 20-minute time period for the chlorine to react with the bacteria. The capacity needed for the retention tank can be calculated by multiplying the well pump output times 20. A continuous chlorine residual of 1.0 mg/L is required at the outlet of the retention tank to assure the bacteria were destroyed. Since chlorine can be combined with natural organic matter, it’s always recommended that an activated carbon filter be installed after the retention tank to remove the chlorine.
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At a December 16, 2019 meeting of small business leaders at the White House, President Donald Trump talked at length about water and energy conservation, saying the Environmental Protection Agency is looking into restrictions in part because people are flushing their toilets 10 to 15 times instead of once and are therefore using more water.
“We have a situation where we’re looking very strongly at sinks and showers and other elements of bathrooms, where you turn the faucet on in areas where there’s tremendous amounts of water, where it all flows out to sea because you could never handle it all, and you don’t get any water,” he said.
“They take a shower and water comes dripping out, very quietly dripping out. People are flushing toilets 10 times, 15 times, as opposed to once; they end up using more water. So EPA is looking very strongly at that, at my suggestion.
“You go into a new building, new house, a new home, and they have standards where [you] don’t get water, and you can’t wash your hands practically; there’s so little water,” he added. “And the end result is that you leave the faucet on, and it takes you much longer to wash your hands, and you end up using the same amount of water. So we’re looking very seriously at opening up the standard, and there may be some areas where we go the other route, desert areas, but for the most part, you have states where they have so much water where it comes down — it’s called rain — that they don’t know what to do with it.”
In his comments, the president appeared to be referring to the standards set by the National Energy Policy Act of 1995, federal regulations that stipulated that all newly manufactured toilets had to use a maximum of 1.6 gallons of water per flush, a significant decrease from previous standards.
Just a couple of days earlier, at a NATO conference in Europe, the president blamed ocean trash in US waters on the bad habits of other countries: “I also see what’s happening with our oceans, where certain countries are dumping unlimited loads of things in it. They float — they tend to float toward the United States. I see that happening, and nobody has ever seen anything like it, and it’s gotten worse.”
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How to Pick the Best Filter Cartridge
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The “best” water filter cartridge is not necessarily the one that removes most contaminants or the one that treats the most gallons of water or the one that has the least pressure drop. The best for you is the one that does what is needed in your application.
This article makes some generalizations about water filter cartridges to help clarify what performance information provided by manufacturers means to the filter customer. We’re using “whole house” carbon filter cartridges, 4.5″ X 20″, treating chlorine and chloramine, to illustrate, but the principles apply as well to other filters, like sediment filters and “media” cartridges that are intended for problems like iron, turbidity, lead, and nitrate reduction.
In general terms, the more tightly the filter media is packed together, the more effective the filter is at removing contaminants, but the more it restricts the flow of water through it and the more likely it is to become clogged by particles. The looser the media is packed, the less effective the filter is at contaminant removal, but the less it restricts the flow of water and the less likely it is to be clogged. Tighter means more effective performance but greater pressure loss.
Another generalization that’s true of most cartridges is the slower the water goes through the filter, the more effectively it treats contaminants, the longer it lasts, and the less water pressure is lost. Conversely, the faster the flow, the poorer the performance, the greater the pressure loss, and the shorter the lifespan of the filter.
The art of selecting a filter, then, is to choose one that’s tight enough to be effective but not so tight that it restricts service flow or stops up easily. It must also be large enough to accommodate the needed service flow rate. Sometimes with cartridge filters to get a larger filter the most practical approach is to install 2 or more filters in parallel. (See the picture below.)
To see how pressure drop, capacity, and micron size are related, here is a comparison of chlorine treatment figures for two 4.5″ X 20″ MatriKX carbon blocks, identical except in tightness. (Micron size is the way filter makers state tightness: the lower the micron number, the tighter the filter.)
Two Identical Carbon Block Filters of Different Micron Ratings: Chlorine Reduction
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MatriKX CTO |
MatriKX CTO+ |
| Filter Type |
Coconut Shell Carbon Block |
Coconut Shell Carbon Block |
| Micron Rating |
Nominal 5 microns |
Nominal 1 micron |
| Chlorine Removal Capacity |
34,000 gallons @ 7 gpm |
160,000 gallons @ 7 gpm |
| Pressure Drop |
8 psi @ 7 gpm |
16 psi @ 7 gpm |
| Current Retail Price |
$68.00 |
$89.00 |
Considerations
The very tight CTO+ would seem like the better value in terms of gallons treated per cost, but it is very unlikely that in residential use such a tight filter would treat 160,000 before it stops up. Also, the excessive pressure drop gets even worse as the filter picks up particulate. Its performance is remarkable, but it probably is not the better choice for whole house residential treatment of chlorine.
The looser CTO has half the pressure drop. Most residential water use is at a rate below 7 gpm, so you can expect the 34K capacity of the CTO to go up. We’ve found the CTO to be an excellent residential filter for water treated with chlorine.
The pair of filters compared below are identical “radial flow” granular filters. Though both are rated at 25 microns, the chloramine filter evidently uses a finer carbon and is therefore a bit more restrictive. These are very high grade radial flow cartridges, not to be confused with the standard axial flow cartridges that normally use regular-grind (not powdered) carbon and have much lower performance numbers. (Axial vs. radial explained.)
Similar Radial Flow Granular Carbon Filters: One for Chlorine, the other for Chloramine
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Pentek RFC20BB—Chlorine Grade |
Pentek CRFC20BB –Chloramine Grade |
| Filter Type |
Radial Flow GAC (powdered) |
Radial Flow Catalytic GAC (powdered) |
| Micron Rating |
25 Microns |
25 Microns |
| Chlorine Removal Capacity |
70,000 gallons @ 4 gpm |
Unknown |
| Chloramine Removal Capacity |
Unknown |
10,000 gallons @ 5 gpm
25,000 gallons @ 2.5 gpm
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| Pressure Drop |
0.9 psi @ 4 gpm
2 psi@ 7 gpm
4 psi @ 11 gpm
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1 psi @ 2.5 gpm
2.5 psi @ 5 gpm
5 psi @ 7 gpm
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| Current Retail Price |
$95.00 |
$168.00 |
Considerations
Reducing the flow rate more than doubles the lifespan of the chloramine cartridge. While this ratio doesn’t apply everywhere, as a general rule cutting the flow rate through the filter significantly adds to its life expectancy, adds to its efficiency, and reduces pressure drop. Therefore, running two filters in parallel more than doubles the valve of a single filter. In many cases using multiple filters actually costs less than using one, plus you get lower pressure drop.
Split installation: each filter gets half the flow rate. Efficiency goes up, pressure drop goes down, and cost goes down.
With a flow rate of 5 gpm, one filter treats 10,000 gallons with a pressure drop of 2.5 psi, but two filters treat 50,000 gallons with a pressure drop of 1 psi. What’s more, operation cost is 1.6 cents per gallon for one filter and 0.66 cents for two.
Flow rate matters!
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Places to visit for additional information:
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Thanks for reading and be sure to check out the next Occasional!
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