Category Archives: water

I’d like to expand the Jones act so more ships can do US trade.

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If you visit most any European port city, you’ll see a lot more shipping than in the Midwestern US. In Detroit, where I am, your’ll see an occasional ore boat from Wisconsin, and an occasional tourist cruise, but nothing to compare to German, Belgian, or Turkish ports. The reason for the difference is “The Jones act.”

The port of Istanbul with many ships

The Jones act , also known as “The Merchant Marine Act of 1920”, requires that all ships depositing cargo or people between US ports must be US owned, US built, US captained, US flagged, and at least 70% US manned. This raises costs and reduces options. The result is that few ships can move people or cargo between US cities, and these ships are older and less efficient than you’ll see elsewhere. World wide water traffic costs about 1/8 that of rail traffic per ton-mile, but in the US, the prices are more comparable. The original justification was to make sure the US would always have a merchant marine. The Jones act does that, sort of, but mostly, it just makes goods more expensive and travel more restrictive.

The port of Detroit — we rarely see more than one ship at a time.

Because it does some good, I don’t want to get rid of the Jones act entirely, but I’d like to see US shipping options expanded. Almost any expansion would do, e.g. allowing 50% US manned ships delivering along US rivers, or expanding to allow Canadian built ships or flagged, and ships that are more than 50% US owned, or expanding to any NAFTA vessel that meets safety standards. Any expansion of the number of ships available and would help.

The jones act increase the price of oil transport by a factor of five, about.

Currently, the only exceptions to the Jones act are for emergencies (Trump voided the act during several storms) and for ships that visit a foreign port along the route. This exception is how every cruise ship between California and Hawaii works. They’re all foreign, but they stop in Mexico along the way. Similarly, cruises between Florida and Puerto Rico will stop in Bermuda typically, because the ships are foreign owned. Generally, passengers are not allowed to get off in Puerto Rico, but must sleep on board. This is another aspect of the Maritime act that I’d like to see go away.

Because of the Jones act, there is some US freight-ship building, and a supply of sailors and captains. A new, US ore-ship for the Great Lakes was launched last year, so far it’s been used to carry salt. There is also a US built and operated cruise ship in Hawaii, the “Pride of America,” that makes no stop in Mexico. I’d like to see these numbers expanded, and the suggestions above seem like they’d do more good than harm, lowering prices, and allowing modern container ships plus roll-on-roll-off car transports. Our rivers and lakes are super highways; I’d like to see them used more.

The port of Antwerp – far busier than Detroit.

Another way to expand the Jones act while perhaps increasing the number of US-built and operated ship would be through a deal with Canada so that ships from either country could ply trade on either countries rivers. As things stand, Canada has its own version of the Jones act, called the Coastal Trade Act where Canadian vessels must be used for domestic transport (cabotage) unless no such vessel is available. Maybe we can strike a deal with Canada so that the crew can be Canadian or US, and where built ships in either country are chosen on routes in either country, providing they meet the safety and environmental requirements of both.

Robert Buxbaum, June 14, 2023.

Rain barrels aren’t much good. Wood chips are better, And I’d avoid rain gardens, even as a neighbor.

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A lot of cities push rain barrels as a way to save water and reduce flooding. Our water comes from the Detroit and returns to it as sewage, so I’m not sure there is any water saving, but there is a small cash saving (very small) if you buy 30 to 55 gallon barrels from the city and connect them to the end of your drain spout. The rainwater you collect won’t be pure enough to drink, or safe for bathing, but you can use it to water your lawn and garden. This sounds OK, even patriotic, until you do the math, or the plumbing, or until you consider the wood-chip alternative.

The barrels are not cheap, even when subsidized they cost about $100 each. Add to this the cost and difficulty of setting up the collection system and the distribution hose. Water from your rain barrel will not flow through a normal nozzle as there is hardly any pressure. Expect watering to take a lot longer than you are used to.

40 gallon rain barrels. Two of these give about 70 usable gallons every heavy rain fall. That’s about 70¢ worth.

In Michigan you can not leave the water in your barrel over the winter, the water will freeze and the barrel will crack. You have to drain the tank completely every fall, an almost impossible task, and the tank is attached to a rainspout and the last bit of water is hard to get out. Still, you have to do it, or the barrel will crack. And the savings for all this is minimal. During a rainy month, you don’t need this water. During a dry month, there is no water to use. Even at the best, the The marginal cost of water in our town is less than 1¢ per gallon. For all the work and cost to set up, two complete 40 gallon tanks (like those shown) will give you at most about 70 usable gallons. That’s to say, almost 70¢ per full filling.

How much lawn can you water? Assume you like to water your lawn to the equivalent of 1″ of rain per week, your 70 gallons will water about 154 ft2 of lawn or garden, virtually nothing compared to the typical Michigan 2000 ft2 lawn. You’ll still have to get most of your water from the city’s main. All that work, for so little benefit.

Young trees with chip volcanos, 1 ft high x18″. Spread the chips to the diameter of the leaves.You don’t need more than 2″.

A far better option is wood chips. They don’t cover a lawn, but they’re great for shrubs, trees or a garden. Wood chips are easy to spread, and they stop weeds and hold water. The photo at left shows a wood chips around the shrubs, and a particularly poor use of wood chips around the trees. For shrubs, trees, or a garden, I suggest you put down 1 to 2 inches of wood chips. Surround a young tree at that depth to the diameter of the branches. Do not build a “chip volcano,” as this lazy landscaper has done.

Consider that, covering 500 ft2 of area to a depth of 1.5 inches will take about 60 cubic feet of wood chips. That will cost about $35 dollars at the local Home Depot. This is enough to hold about 1.25″ or rainwater, That’s about 100 ft3 or water or 800 gallons. The chips prevent excess evaporation while preventing weeds and slowly releasing the water to your garden. You do no work. The chips take almost no work to spread, and will keep on working for years, with no fear of frost-damage. A as the chips stop working, they biocompost slowly into fertilizer. That’s a win.

There is a worst option too, called a rain garden. This is often pushed by environmental-gooders. You dig a hole near your downspout, perhaps ten feet in diameter, by two feet deep, and plant native grasses (weeds). When it rains, the hole fills with water creating a mini wetland that will soon smell like the swamp that it is. If you are not lucky, the water will find a way to leak into your basement. If that’s your problem look here. If you are luckier, your mini-swamp will become the home of mosquitos, frogs, and snakes. The plants will grow, then die, and rot, and look awful. It is very hard to maintain native grasses. That’s why people drain swamps and grow trees or turf or vegetables. If you want to see a well-maintained rain garden, they have two on the campus of Lawrence Tech. A wetland isn’t bad, but you want drainage, Make a bioswale or muir.

Robert Buxbaum, May 31, 2023. I ran for water commissioner some years back.

Plans to Raise-the-Dead-Sea

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The Dead Sea in Israel is a popular tourist attraction and health resort-area. It is also the lowest point on the planet, with a surface about 430m below sea level. Its water is saturated with an alkaline salt, and quite devoid of life, and it’s shrinking fast, loosing about 1 m in height every year. The Jordan river water that feeds the sea is increasingly drawn off for agriculture, and is now about 10% of what it was in the 1800s. The Dead Sea is disappearing fast, a story that is repeated with other inland seas: the Aral Sea, the Great Salt Lake, etc. In theory, one could reverse the loss using sea water. In theory, you could generate power dong this too: 430m is seven times the drop-height of Niagara Falls. The problem is the route and the price.

Five (or six) semi-attractive routes have been mapped out to bring water to the Dead Sea, as shown on the map at right. The shortest, and least expensive is route “A”. Here, water from the Mediterranean enters a 12 km channel near Haifa; it is pumped up 50m and travels in a pipe for about 52 km over the Galilean foothills, exiting to a power station as shown on the elevation map below. In the original plan the sea water feeds into the Jordan river, a drop of about 300m. The project had been estimated to cost $3 B. Unfortunately, it would make much of the Jordan river salty. It was thus deemed unacceptable. A variation of this would run the seawater along the Jordan in a pipe or an open channel. This would add to the cost, and would likely diminish the power that could be extracted, but you would not contaminate the Jordan.

A more expensive route, “B”, is shorter but it requires extensive tunneling under Jerusalem. Assuming 20 mies of tunnel at $500 MM/mile, this would cost $10B. It also requires the sea water to flow through the Palestinian West Bank on its way to the sea. This is politically sensitive and is unlikely to be acceptable to the West Bank Palestinians.

Vertical demand of the northern route

Two other routes, labeled “C” and “D” are likely even more expensive than route B. They require the water to be pumped over the Judaean hills near Bethlehem, south of Jerusalem. That’s perhaps 600m up. The seawater would flow from Ashkalon or Gaza and would enter the Dead Sea at Sodom, near Masada. Version C is the most politically acceptable, since it’s short and does not go through Palestinian land. Also, water enters the dead sea at its saltiest point so there is no disruption of the environment. Route D is similar to C, somewhat cheaper, but a lot more political. It goes through Gaza.

The longest route, “E” would go through Jordan taking water from the Red Sea. Its price tag is said to be $10 B. It’s a relatively flat route, but still arduous, rising 210m. As a result it’s not clear that any power would be generated. A version of this route could send the water entirely through Israel. It’s not clear that this would be better than Route C. Looking things over, it was decided that only routes that made sense are those that avoided Palestinian land. An agreement was struck with Jordan to go ahead with route D, with construction to begin in 2021. The project has been on hold though because of cost, COVID, and governmental inertia.

In order to make a $5-10B project worthwhile, you’ll have to generate $500MM to $1B/year. Some of this will come from tourism, but the rest must come from electrical power generation. As an estimate of power generation, let’s assume that that the flow is 65 m3/s, just enough to balance the evaporation rate. Assuming a 400 m power drop and an 80% efficient turbine, we should generate 80% of 255 MWe = about 204 MWe on average. Assuming a value of electricity of 10¢/kWh, that translates to $20,000/ hour, or $179 million per year. This is something, but not enough to justify the cost. We might increase the value of the power by including an inland pond for water storage. This would allow power production to be regulated to times of peak load, or it could be used for recreation, fish-farming, or cooling a thermal power station up to 1000 MWe. These options almost make sense, but with the tunnel prices quoted, the project is still too expensive to make sense. It is “on hold” for now.

It’s not like the sea will disappear if nothing is done. With 10% of the original in-flow of water to the Dead Sea, it will shrink to 10% its original size, and then stop shrinking. At that point evaporation will match in-flow. One could add more fresh water by increasing the flow from the sea of Galilee, but that water is needed. When more water is available, more is taken out for farming. This is what’s happened to the Arial Sea — it’s now about 10% the original size, and quite salty.

Elon Musk besides the prototype 12 foot diameter tunnel.

There’s a now a new tunnel option though and perhaps these routes deserve a second look: Elon Musk claims his “Boring company” can bore long tunnels of 12 foot diameter, for $10-20 MM/mile. This should be an OK size for this project. Assuming he’s right about the price, or close to right, the Dead Sea could be raised for $1B or so. At that price-point, it makes financial sense. It would even make sense if one built multiple seapools, perhaps one for swimming and one for energy storage, to be located before the energy-generating drop, and another for fish after. There might even be a pool that would serve as coolant for a thermal power plant. Water in the desert is welcome, even if it’s salt water.

Robert Buxbaum, February 14, 2023.

A new, higher efficiency propeller

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Elytron biplane, perhaps an inspiration.

Sharrow Marine introduced a new ship propeller design two years ago, at the Miami International Boat show. Unlike traditional propellers, there are no ends on the blades. Instead, each blade is a connecting ribbon with the outer edge behaving like a connecting winglet. The blade pairs provide low-speed lift-efficiency gains, as seen on a biplane, while the winglets provide high speed gains. The efficiency gain is 9-30% over a wide range of speeds, as shown below, a tremendous improvement. I suspect that this design will become standard over the next 10-20 years, as winglets have become standard on airplanes today.

A Sharrow propeller, MX-1

The high speed efficiency advantage of the closed ends of the blades, and of the curved up winglets on modern airplanes is based on avoiding losses from air (or water) going around the end from the high pressure bottom to the low-pressure top. Between the biplane advantage and the wingtip advantage, Sharrow propellers provide improved miles per gallon at every speed except the highest, 32+ mph, plus a drastic decrease in vibration and noise, see photo.

The propeller design was developed with paid research at the University of Michigan. It was clearly innovative and granted design patent protection in most of the developed world. To the extent that the patents are respected and protected by law, Sharrow should be able to recoup the cost of their research and development. They should make a profit too. As an inventor myself, I believe they deserve to recoup their costs and make a profit. Not all inventions lead to a great product. Besides, I don’t think they charge too much. The current price is $2000-$5000 per propeller for standard sizes, a price that seems reasonable, based on the price of a boat and the advantage of more speed, more range, plus less fuel use and less vibration. This year Sharrow formed an agreement with Yamaha to manufacture the propellers under license, so supply should not be an issue.

Vastly less turbulence follows the Sharrow propeller.

China tends to copy our best products, and often steals the technology to make them, employing engineers and academics as spys. Obama/Biden have typically allowed China to benefit for the sales of copies and the theft of intellectual property, allowing the import of fakes to the US with little or no interference. Would you like a fake Rolex or Fendi, you can buy on-line from China. Would you like fake Disney, ditto. So far, I have not seen Chinese copies of the Sharrow in the US, but I expect to see them soon. Perhaps Biden’s Justice Department will do something this time, but I doubt it. By our justice department turning a blind eye to copies, they rob our innovators, and rob American workers. His protectionism is one thing I liked about Donald Trump.

The Sharrow Propeller gives improved mpg values at every speed except the very highest.

Robert Buxbaum, September 30, 2022

Exercise helps fight depression, lithium helps too.

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With the sun setting earlier, and the threat of new COVID lockdowns, there is a real threat of a depression, seasonal and isolation. A partial remedy is exercise; it helps fight depression whether you take other measures not. An article published last month in the Journal of Affective Disorders reviewed 22 studies of the efficacy of exercise, particularly as an add-on to drugs and therapy. Almost every study showed that exercise helped, and in some studies it helped a lot. See table below. All of the authors are from the University of British Columbia. You can read the article here.

From “Efficacy of exercise combined with standard treatment for depression compared to standard treatment alone: A systematic review and meta-analysis of randomized controlled trials.” by JacquelineLee1 et al.In virtually every study, exercise helps fight depression.

For those who are willing to exercise, there are benefits aside from mental health. Even a daily walk around the block helps with bone strength, weight control, heart disease, plus the above mentioned improvement in mood. More exercise does more. If you bicycle without a helmet, you’re likely to live longer than if you drive.

For those who can’t stand exercise, or if exercise isn’t quite enough to send away the blues, you can try therapy, medication, and/or diet. There is some evidence that food that are high in lithium help fight depression. These food include nuts, beans, tomatoes, some mineral waters, e.g. from Lithia springs, GA. The does is about 1/100 the dose given as a bipolar treatment, but there is evidence that even such small doses help. Lithium was one of the seven ingredients in seven up — it was the one that was supposed to cheer you up. See some research here.

Robert Buxbaum, October 7, 2021.

Weird thermodynamics near surfaces can prevent condensation and make water more slippery.

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It is a fundamental of science that that the properties of every pure one-phase material is totally fixed properties at any given temperature and pressure. Thus for example, water at 0°C is accepted to always have a density of 0.998 gm/cc, a vapor pressure of 17.5 Torr, a viscosity of 1.002 centipoise (milliPascal seconds) and a speed of sound of 1481 m/s. Set the temperature and pressure of any other material and every other quality is set. But things go screwy near surfaces, and this is particularly true for water where the hydrogen bond — a quantum bond — predominates.

its vapor pressure rises and it becomes less inclined to condense or freeze. I use this odd aspect of thermodynamics to keep my platinum-based hydrogen getter catalysis active at low temperatures where they would normally clog. Normal platinum catalysts are not suitable for hydrogen removal at normal temperatures, eg room temperature, because the water that forms from hydrogen oxidation chokes off the catalytic surface. Hydrophobic additions prevent this, and I’d like to show you why this works, and why other odd things happen, based on an approximation called the  Van der Waals equation of state:

{\displaystyle \left(p+{\frac {a}{V_{m}^{2}}}\right)\left(V_{m}-b\right)=RT} (1)

This equation described the molar volume of a pure material, V_{m}, of any pure material based not the pressure, the absolute temperature (Kelvin) and two, substance-specific constants, a and b. These constants can be understood as an attraction force term, and a molecular volume respectively. It is common to calculate a and b from the critical temperature and pressure as follows, where Tc is absolute temperature:

{\displaystyle a={\frac {27(RT_{c})^{2}}{64p_{c}}}}, {\displaystyle b={\frac {RT_{c}}{8p_{c}}}.} (2 a,b)

For water Tc = 647 K (374°C) and 220.5 bar. Plugging in these numbers, the Van der Waals gives reasonable values for the density of water both as a liquid and a gas, and thus gives a reasonable value for the boiling point.

Now consider the effect that an inert surface would have on the effective values of a and b near that surface. The volume of the molecules will not change, and thus b will not change, but the value of a will change, likely by about half. This is because, the number of molecules surrounding any other molecule is reduced by about half while the inert surface adds nothing to the attraction. Near a surface, surrounding molecules still attract each other the same as before, but there are about half as many molecules at any temperature and pressure.

To get a physical sense of what the surface does, consider using the new values of a and b to determine a new value for Tc and Pc, for materials near the surface. Since b does not change, we see that the presence of a surface does not affect the ratio of Tc and Pc, but it decreases the effective value of Tc — by about half. For water, that is a change from 647 K to 323.5K, 50.5°C, very close to room temperature. Pc changes to 110 bar, about 1600 psi. Since the new value of Tc is close to room temperature, the the density of water will be much lower near the surface, and the viscosity can be expected to drop. The net result is that water flows more readily through a teflon pipe than through an ordinary pipe, a difference that is particularly apparent at small diameters.

This decrease in effective Tc is useful for fire hoses, and for making sailing ships go faster (use teflon paint) and for making my hydrogen removal catalysts more active at low temperatures. Condensed water can block the pores to the catalyst; teflon can forestall this condensation. It’s a general trick of thermodynamics, reasonably useful. Now you know it, and now you know why it works.

Robert Buxbaum August 30, 2021

What I learned by running for office.

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I’m an enemy of unity and a harborer of prejudice. During the election, I was told that all Republicans are, and I’ve come to accept it as true. I’d run for county water commissioner (drain commissioner) as a Republican, see web-site, and the charge is fair. I wasn’t happy to that George Will write to not for any Republicans because, in his opinion, we’re all prejudiced, and thus a Democrat is better for all jobs. When George, or anyone else, talks about getting rid of the prejudiced, it sounds to me like he wants to get rid of me and those who think like me. We’re to be replaced by those who think like him, or (since he has few solid ideas) whose ideas are gleaned as an average of those running the respectable media (It turns out there are only a fairly few people running the respectable media).

Biden seems to have fallen into the presidency. He didn’t campaign, but the press and a lot of people didn’t like Trump, and could not settle on anyone with opinions.

I didn’t like how the Water department was run, or how the costs were distributed, and some of this has to do with prejudice — engineering aesthetics, I call it. After living with these prejudices or aesthetics, I’ve come to think of them as part of me. I worked to form my opinions — opinions of what was fair, and who was likely to do good work, and what was good engineering. My prejudices and opinions were developed over many years. They’re not perfect, but I like them. I don’t want to have to exchange my opinions and prejudices for the government’s. If I felt otherwise, I would not have run for office. I also resent sensitivity training — the person running them rarely shows any sensitivity, IMHO.

One of the things that anti-racists hate, and I support is zionism. It’s a founding principle of Black Lives Matter that black people in the US can’t be free so long as the zionist state (Israel) exists. Why is this? There is an assumption that all black peoples are one, and that zionists are oppressors. Not that you could tell a Palestinian from a zionist by skin color, but it’s a truth that the faculty of Princeton endorses.

Not long ago the faculty of Princeton University voted unanimously for BDS including a ban on any zionist speaker from speaking on campus. The faculty also picked George Will as the graduation speaker in 2020. Most of the professors chose to not vote, but of those who did (1/7 of the total including many Jews) the pro-BDS vote was unanimous. As a result, if Einstein were to rise from the grave, with the unified field equations finally worked out, he’d have to speak off-campus because he was a zionist, and the university is committed to BLM and anti prejudice. (Tell me again, how does anti-zionism help black lives to matter?; how does BLM help you get clean water or good sewage treatment?)

In terms of sewage treatment or bringing clean water, I’ve found that the sort of person willing to do the work is usually someone with an opinion, and that usually it’s a rough opinion. My sense is to let people have their opinions and to say, if you treat the sewage right, I treat you right. Good work isn’t cheap, and people who do it can’t be culled from those with the right views and political opinions.

While campaigning I told leaders of the pipe-fitters union that I could tell that the Pontiac sewage plant was badly run just by smelling the air around the plant — you shouldn’t be able to smell a sewage plant from miles away. They said that was a racist statement. I then told them that the boilers were rusty, and that at the roof of the digester cad caved in, at least a year ago. They said they’d already endorsed the Democrat, and only spoke to me as a courtesy.

Robert Buxbaum June 25, 2021

My two-mode commode.

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Our new, two-mode commode.

We just got a new toilet. Commonly called a commode, and it’s got a cool feature that I’d seen often in Europe but rarely in the US: two levels of flush strength. There is a “small flush” option that delivers, about 3 liters, intended for yellow waste, and a “big flush” option that delivers 6 liters. It’s intended for brown waste, or poop.

The main advantage of two mode flushing, in my opinion, is that the small flush is quieter than the normal. The quality of the flush is quite acceptable, even for brown waste because the elongated shape of the bowl seems better suited to pushing waste to the back, and down the drain. The flush valve is simple too, and I suspect the valve will last longer than the “flapper valve” of my older, one mode commodes. The secondary advantage is from some cost savings on water. That was about 1¢ per small flush in our area of Michigan, but the water department changed how they charge for water in our area and the cost savings have largely disappeared. Even under the old system, the savings in water cost amounted to only about $15 per year. At that rate it would take 15 years or more to pay for the new commode.

There is no real need for water savings in Michigan, and particularly not in our area, metro-Detroit. In other states there often is, but our drinking water comes from the Detroit river, and the cleaned up waste goes back to the river. It’s a cycle with no water lost no matter how much you flush, and no matter how big shower heads. I’d written in favor of allowing big flush toilets and big shower heads in our state, but the Obama administration ruled otherwise. Trump had promised to change that, but was impeached before he could. Even Trump had changed this, Biden has reversed virtually every Trump order related to resource use including those prohibiting China from providing critical technology to our water and power systems. Bottom line, you have to have a low-flush toilet, and you might as well get a two-mode.

Our commode has an elongated front, and I’d recommend that too. It can minimize floor dribbles, and that’s a good thing. The elongated shape also seems to provide a smoother flush path with less splatter. I would not recommend a “power flush” though for several reasons, among them that you get extra splatter and a louder flush noise. We’d bought a power flush some years ago, and in my opinion, it flushed no better than the ordinary toilet. It was very loud, and had a tendency to splatter. There was some slight water savings, but not worth it, IMHO.

Robert Buxbaum, February 8, 2021. I ran for water commissioner with several goals, among them to improve the fairness of billing, to decrease flooding, and to protect our water system from cyber attack.

If nothing sticks to teflon, how do you stick teflon to a pan? PFAS.

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When I was eight or nine year old, I went to the 1963-64 World’s Fair in New York. Among the attractions, in “the kitchen of the future”, I saw the first version of an amazing fry-pan that was coated with plastic. You could cook an egg on that plastic without any oil, and the egg didn’t stick. The plastic was called teflon, a DuPont innovation, whose molecule is shown below.

The molecular structure of Teflon. There is an interior carbon backbone that is completely enclosed with tightly bound fluorine atoms. The net result is a compound that does not bind readily to anything else.

Years later, I came to understand that Teflon’s high-temperature stability and non-stick properties derive from the carbon-fluorine bonds. These bonds are much stronger than the carbon-hydrogen bonds found in food, and most solid, organic things. Because of the strength of the carbon-fluorine bond, Teflon is resistant to oxidation, and to chemical interaction with other molecules, e.g. in food. It does not even interact with water, making it hydrophobic and non-wetting on metals. The carbon-carbon bonds in the middle remained high temperature stable, in part because they were completely shielded by the fluorine atoms.

This is a PFAS. The left side is just like teflon, and very hydrophobic. The right side is hydrophilic and highly bonding to pans, and many other things like water or cotton.

But as remarkable as teflon’s non-stick properties are, perhaps the most amazing thing was that it somehow sticks to the pan. For the first generation pans I saw, it didn’t stick very well. Still, the DuPont engineers had found a way to stick non-stick Teflon to a metal for long enough to cook many meals. If they had not found this trick, teflon would not have the majority of its value, but how did they do it? It turns out they used a thin coating of a di-functional compound called PFAS, a a polyfluoro sulphonyl (or polyfluoroalkyl) substance. The molecular structure of a common PFAS, is shown above.

Each molecule of PFAS has one end that’s teflon-like and another end that’s different. The non-Teflon end, in this case a sulfonyl group, is chosen to be both high temperature stable and sticky to metal oxides. The sulphonyl group above is highly polar, and acidic. Acidic will bind to bases, like metal oxides. The surface of the metal pan is prepared by applying a thin layer of oxide or amidine, making it a polar base. The PFAS is then applied, then Teflon. The Teflon-end of the PFAS is bound to teflon by the hydrophobicity of everything else rejecting it.

There are many other uses for PFAS. For example, PFAS is applied to clothing to make it wrinkle free and stain resistant. It can also be used as a super soap, making uncommonly stable foams and bubbles. It is also used in fire-fighting and plane de-icing. Finally, PFAS is the main component of Nafion, the most common membrane for PEM fuel cells. (I can think of yet other applications..) There is just one small problem with PFAS, though. Like teflon, this molecule is uncommonly stable. It doesn’t readily decompose in nature. That would be a small problem if we were sure that PFAS was safe. As it happens it seems safe, but we’re not totally sure.

The safety of PFAS was studied extensively before PFAS-teflon pans was put on the market, but the methodology has been questioned. Large doses of PFAS were fed to test animals, and their health observed. Since the test animals showed no real signs of ill-health though some showed a slight liver enlargement, PFAS was accepted as safe for humans at a lower exposure dose. PFAS was approved for use on pans and allowed to be dumped under conditions where humans would be exposed to 1/1000 of that used on the animals. The assumption was that there would be little or no health hazard at these low exposure levels.

But low risk is not no risk, and today one can sue for even the hint of an effect though use of a class action suit. That is, lawyers sue on behalf of all the people who might have been damaged. My city was sued successfully this way for complicity in sewage over-flows. Of course, since the citizens being paid by the suit are the same ones who have to pay for the damage, only the lawyers benefit. Still, the law is the law, and at least for some judges, putting anyone at risk is enough evidence of willful disregard to hand down a stinging judgement against the evil doer. Judges have begun awarding large claims for PFAS too. While no individual can get the claim more than a tiny amount of money, the lawyers can do very well.

There is no new evidence that PFAS is dangerous, but none is needed if you can get yourself the right judge. In this regard, an industry of judicial tourism has sprung up, where class-action lawyers travel to districts where the judges are favorable. For Teflon suits, the bust hunting grounds are in New York, New Hampshire, and California, and the worst are blood-red states like Wyoming and Utah. Just as different judges promote different precedents, different states allow vastly different PFAS concentrations in the water. A common standard, one used by Michigan, is 70 ppt, 1 billion times stricter than the amounts tested on animals. This is roughly 500 times stricter than the acceptable concentratios for lead, a known poison. The standard in New York is 7 times stricter than Michigan, 10 ppt. The standard in North Carolina is 140,000 ppt, in in several states there is no legal limit to PFAS dumping. There is no scientific logic to all of this, and skeptical view is that the states that rule more strictly for PFAS than lead do so make money for lawyers. Lead is everyone in the natural environment, so you can’t sue as easily for lead. PFAS is a man-made intruder, though, and a strict standard helps lawyers sue. You can find a summary of state by state regulations here.

Any guideline stricter than about 1000 ppt, presents a challenge to the water commissioner who must measure it and enforce the law. There are tricks, though. You can use the surfactant quality of PFAS to concentrate it by a factor of 100 or more. To do this, you take a sample of river water and create bubbles. Any bubbles that form will be highly concentrated in PFAS. Once PFAS can be identified this way, and the concentrators estimated, the polluters can be held liable. Whether we benefit from the strict rulings is another story. If I were making the law for Michigan, I’d probably choose a limit about 1 ppb, but I’m not making the law. The law, as written, may be an idiot, as Bumble said, but the Law is the Law.

In terms of Michigan fishing, while some rivers have PFAS concentrators above the MI-legal limit, they are generally not far over the line. I would trust the fish in the Huron River, even west of Wixom road but I’d suggest you avoid any foam you find floating there. The PFAS content of foam will be much higher than that of the water in general.

Robert E. Buxbaum, June 30, 2020, edited July 8, 2020. There are seven compounds known as PFAS’s: perfluorooctanesulfonic acid (PFOS), perfluorooctanoic acid (PFOA), perfluorononanoic acid (PFNA), perfluorohexanesulfonic acid (PFHxS), perfluoroheptanoic acid (PFHpA), and perfluorobutanesulfonic acid (PFBS).

Sewage reactor engineering, Stirred tank designs

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Over the past few years, I’ve devoted several of these essays to analysis of first-stage sewage treatment reactors. I described and analyzed the rotating disc reactor found at the plant is Holly here, and described the racetrack,“activated sludge” plug reactor found most everywhere else here. I also described a system without a primary clarifier found near Cincinatti. All of these were effective for primary treatment; soluble organics are removed by bio-catalyzed oxidation:

2 H-C-O-H + O2 –> CO2 + H2O.

A typical plant in Oakland county treats 2,000,000 gallons per day of this stuff, with the bio-reactor receiving liquid waste containing about 200 ppm of soluble and colloidal biomass. That’s 400 dry gallons for those interested, or about 3200 dry lbs./day. About half of this will be oxidized to CO2 and water. The rest (cell bodies) are removed with insoluble components, and applied to farmers fields or buried, or burnt in an incinerator.

There is another type of reactor used in Oakland County. It’s mostly used for secondary treatment, converting consolidated sludge to higher-quality sludge that can be sold or used on farms with less restriction, but it is a type of reactor used at the South Lyon treatment plant, for primary treatment. It is a Continually stirred tank reactor, or CSTR, a design that is shown in schematic below.

As of some years ago, the South Lyon system involved a single largish pond lined with plastic with a volume about 2,000,000 gallons total. About 700,000 gallons per day of sewage liquids went into the lagoon, at 200 ppm soluble organics. Air was bubbled through the liquid providing a necessary reactant, and causing near-perfect mixing of the contents. The aim of the plant managers is to keep the soluble output to the, then-acceptable level of 10 ppm; it’s something they only barely managed, and things got worse as the flow increased. Assume as before, a value V and a flow Q.

We will call the concentration of soluble organics C, and call the initial concentration, the concentration that enters,  Ci. It’s about 200 ppm. We’ll call the output concentration Co, and for this type of reactors, Co = C.  The reaction is first order, approximately, so that, if there were no flow into or out of the reactor, the concentration of organics would decrease at the rate of

dC/dt = -kC.

Here k is a reaction constant, dependent on temperature oxygen and cell content. It’s typically about 0.5/hour. For a given volume of tank the rate of organic removal is VkC. We can now do a mass balance on soluble organics. Since the rate of organic entry is QCi and the rate leaving by flow is QC. The difference must be the amount that is reacted away:

QCi – QC = VkC.

We now use algebra, to find that

Co = Ci/(1 + kV/Q).

V/Q is sometimes called a residence time; for the system. At normal flow, the residence time of the South Lyon system is about 2.8 days or 68.6 hours. Plugging these numbers in, we find that the effluent from the reactor leaves at 1/35 of the input concentration, or 5.7 ppm, on average. This would be fine except that sometimes the temperature drops, or the flow increases, and we start violating the standard. A yet bigger problem was that the population increased by 50% while the EPA standard got more stringent to 2 ppm. This was solved by adding another, smaller reactor, volume = V2. Using the same algebraic analysis, as above you can show that, with two reactors,

Co = Ci/ [(1 + kV/Q)(1+kV2/Q)].

It’s a touchy system, but it meets government targets, just barely, most of the time. I think it is time to switch to a plug-flow reactor system, as used in much of Oakland county. In these, the fluid enters a channel and is reacted as it flows along. Each gallon of fluid, in a sense moves by itself as if it were its own reactor. In each gallon, we can say that dC/dt = -kC. We can thus solve for Co in terms of the total residence time, where t again is V/Q. We can rearrange this equation and integrate: ∫dC/C = – ∫kdt. We then find that, 

      ln(Ci/Co) = kt = kV/Q

To convert 200 ppm sewage to 2 ppm we note that Ci/Co = 100 and that V = Q ln(100)/k = Q (4.605/.5) hours. An inflow of 1000,000 gallons per day = 41,667 gal/ hour, and we find the volume of tank is 41,667 x 9.21 = 383,750 gallons. This is quite a lot smaller than the CSTR tanks at South Lyon. If we converted the South Lyon tanks to a plug-flow, race-track design, it would allow it to serve a massively increased population, discharging far cleaner sewage. 

Robert Buxbaum, November 17, 2019