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November 26

Why isn't hydrogen peroxide used for wastewater treatment?

The U.S. primarily uses chlorine gas, U.K. primarily uses ozone, for water sewage disinfection. My environmental chem textbook talks about the 2, as well as chlorine dioxide. Basically, using chlorine gas causes all kinds of small chemicals like chloroform and trihalomethanes as byproducts. But nobody talks about hydrogen peroxide as sewage disinfectant. It kills viruses and bacteria, and it eventually decomposes to water and oxygen. My gut reaction is... it must be really expensive? Also, is anyone from a country or municipality that uses disinfection other than chlorine or ozone? 67.165.185.178 (talk) 02:39, 26 November 2021 (UTC).[reply]

Apparently membrane filters and UV light can be used too, but our article tells me that sewage water usually isn't disinfected at all, which matches my experience from visiting the local wastewater processing facility some years ago. PiusImpavidus (talk) 09:13, 26 November 2021 (UTC)[reply]

Right, in my area sewage discharges not suitable for drinking water, but discharging it to rivers that eventually reach the Gulf of Mexico. And we get out water from Lake Michigan which is not discharged from our sewage. So, I am also curious if any jurisdiction in the world, treats sewage water all the way back to drinkable water? 67.165.185.178 (talk) 13:24, 26 November 2021 (UTC).[reply]

See reclaimed water. Mikenorton (talk) 15:31, 26 November 2021 (UTC)[reply]

Hydrogen peroxide is one of several chemicals used in advanced oxidation processes, a step in wastewater reclamation. Some issues are mentioned in the section Advanced oxidation process § Current shortcomings. See also Hydrogen peroxide § Disinfectant, which states that hydrogen peroxide is used in certain wastewater treatment processes to remove organic impurities, and that it is seen as an environmentally safe alternative to chlorine-based bleaches, as it degrades to form oxygen and water and it is generally recognized as safe as an antimicrobial agent by the U.S. Food and Drug Administration. The cost difference with chlorine-based treatment does not have to be large for a water management authority, often hard-pressed for money, to engage in penny-pinching and opt for the cheaper solution. --Lambiam 10:03, 26 November 2021 (UTC)[reply]

But I also feel like the process to make mass hydrogen peroxide is a overwhelm compared to making chlorine. 67.165.185.178 (talk) 13:25, 26 November 2021 (UTC).[reply]

Poisonous plants examples.

Q1. It is possible to be poisoned to death, from drinking the milk of cows, that ate poisonous plants. Such is the example of the plant white snakeroot because it contains tremetol. This is how Abraham Lincoln's mother died. Are there any other examples? Basically, these plants must not be poisonous to cows.

I don't know of other examples involving cow milk, but for a related item see mad honey. AFAIK, the bees are not affected by the grayanotoxins, though we obviously are. For some reason, I thought locoweed poisoning could be passed through to us via livestock, but that doesn't seem t be the case. Matt Deres (talk) 18:24, 26 November 2021 (UTC)[reply]

Q2. Same question, but cases where the cow'w body digested the plant to no longer be poisonous in their cow milk.

Q3. It is possible to have a skin irritation just by standing under a poisonous tree when it rains. The only example I have is the manchineel tree, probably the most poisonous tree species in the world. But eating its fruit is a lot more toxic. Any other examples?

Q4. Most of the poisons are biological compounds, such as alkaloids, cardiac glycosides, neurotoxins, ribosome-inactivating proteins, and saponins. The infamous ricin falls under ribosome-inactivating proteins and the poison that killed Socrates, coniine, is an alkaloid. What are inorganic chemical examples, besides calcium oxalate? And coumarins. 67.165.185.178 (talk) 02:46, 26 November 2021 (UTC).[reply]

Reason drawings of cubes tend to slant left

After drawing File:Snake_cube_solution.svg, I found with a cursory search on Commons and Google that simple diagrams of cubes made by drawing two squares and joining corresponding vertices tend to slant left, as in above images.

Is there a psychological reason for this preference? (I can understand the preference for the viewpoint from above as gravity causes most things to be viewed from above.)

Thanks,
cmɢʟee⎆τaʟκ 10:02, 26 November 2021 (UTC)[reply]

Maybe because we write from left to right? Also, the second item in your "more common" illustration looks like an Escher drawing. ←Baseball Bugs ^{What's up, Doc?} carrots→ 14:09, 26 November 2021 (UTC)[reply]

Yes, that's an Impossible object. Sorry I mean it's a drawing of an Impossible object. I wonder how do people who write right to left draw cubes? Martinevans123 (talk) 14:12, 26 November 2021 (UTC)[reply]

Top-left lighting discusses part of this. Bazza (talk) 14:42, 26 November 2021 (UTC)[reply]

Also if the majority of people see the right and top of the cube in front before the opposite (?) then the right, top, front, north, east and up come before their opposites in Western culture (e.g. right hand of God). And a right-handed person can draw diagonal northeast arcs just by swinging the wrist in a normal writing position which is closer to drawing a northeast line than northwest. Sagittarian Milky Way (talk) 15:18, 26 November 2021 (UTC)[reply]

You're saying it's (partly) a product of handedness? Is there any empirical evidence? Thanks. Martinevans123 (talk) 15:23, 26 November 2021 (UTC)[reply]

Two guesses of things that might at least subtly increase the percentage of northeast chirality in the cubes OP has seen. Right, up, front, north and east also have some sort of priority in coordinates cause they got to be the positive sides, if an intelligent species was 90% left-handed and somehow underground 90% of the time for gamma ray reasons or something like that then left and down may have priority instead and their analog of church Latin wouldn't have a negative word (sinister) that also means left. Sagittarian Milky Way (talk) 17:35, 26 November 2021 (UTC)[reply]

That's not really the sort of "empirical evidence" I was thinking of. But thanks anyway. Martinevans123 (talk) 19:04, 26 November 2021 (UTC)[reply]

Most of the pictures in the article 3D projection also show the right and top sides if possible. Technical drawing surely has also settled on a convention of which sides to show if taking the shortcut of only drawing the orthographic projection from one side of a Cartesian axis instead of both. Sagittarian Milky Way (talk) 19:55, 27 November 2021 (UTC)[reply]

I'm interested in why the original poster calls that slanting left because I would describe them as pointing right.--Khajidha (talk) 18:14, 26 November 2021 (UTC)[reply]

The front face slants left w.r.t. the back face. The back face slants right w.r.t. the front face. --Lambiam 01:20, 27 November 2021 (UTC)[reply]

Thank you very much, everyone who replied. Handedness and writing direction are both good explanations. It was also eye-opening to realise my own bias in calling it slanting left and right. Cheers, cmɢʟee⎆τaʟκ 22:02, 27 November 2021 (UTC)[reply]

Resolved

Proton decay with naked senses

If the easiest to notice proton in the human body decayed while a human with good [sense] was paying attention to [sense] what would they notice? Is this proton in the eyes or nervous system? Maybe in a rhodopsin molecule in a dark-adapted eye? What would be the detection mechanism? (Cherenkov radiation? A shower of descendant xyz particles similar to a cosmic ray in air? Direct nervous system stimulation somehow?) Sagittarian Milky Way (talk) 18:00, 26 November 2021 (UTC)[reply]

Did you really mean to use the proton as an example, Sagittarian Milky Way? According to the article, proton decay is hypothetical and the minimum half-life is a factor of about 10²⁴ longer than the age of the universe! So a bit difficult to speculate what would happen if one did decay.... Mike Turnbull (talk) 18:32, 26 November 2021 (UTC)[reply]

Yes but there has been a cumulative ~10³⁰ times age of the universe years worth of chances for a proton to decay in a man since the 18th century.

I cannot assign a meaning to this sentence. How much is "one year worth of chances" worth, in terms of probability? Where does the number 10³⁰ come from? --Lambiam 01:04, 27 November 2021 (UTC)[reply]

If you're confused by something I didn't say clear enough it doesn't mean I'm an imbecile. If the proton half-life is 10²⁴ times the age of the universe then about 6.93x10^-25*100% of your protons decay in 13.8 billion years or ~6.93x10^-33 in 138 years or ~1.612x10^-32 in 321 years (since 1701.0 AD) but multiply by 7x10²⁷ atoms in a 70kg human body then multiply by the average number of protons per atom (~0.24*8+0.12*6+0.62*1+0.011*7+0.0022*20+0.0022*15+0.00033*19+0.00038*16+0.00037*11+0.00024*17+0.00007*12+0.0000067*26+0.000012*9+0.0000031*30+0.000058*14+0.000007*31+0.00000033*37+0.00000033*38+0.0000003*35+0.000000045*82+0.000000104*29+0.00000015*13+0.000000045*48≈3.44) then multiply by some sort of representative population of the world for that time period let's say 1 billion (too low but 70kg is too high) and you get 388,000 proton decays in the human species after 1700. If it'd take ~10²⁴ times the age of the universe to see one proton decay then that much proton decay would take about 10^29.6 times the current age of the universe (but you'd have to pick a new proton to watch 388,000 times, as the proton has only one life to give, not 388,000. Of course it could be anything from over 100,000 to exactly zero. And maybe not something that'd cause one to suspect proton decay if it was sensed, if a spot of skin itches I don't suspect proton decay. Sagittarian Milky Way (talk) 03:56, 27 November 2021 (UTC)[reply]

I know it's only a hypothesis and has never been detected by anything (or if it has then non-proton decay reasons must be more likely as a single event over 50% likely to be proton decay would surely be physicist-interesting enough to be in the article). Sagittarian Milky Way (talk) 20:01, 26 November 2021 (UTC)[reply]

And some physicists predict gamma rays will come out, a particle who's interactions with flesh are surely not unknown speculation. Sagittarian Milky Way (talk) 20:07, 26 November 2021 (UTC)[reply]

We are hit all the time by gamma rays arising from cosmic radiation. A couple of gamma photons once every so many lifetimes of the universe won’t make much of a noticeable difference. --Lambiam 01:17, 27 November 2021 (UTC)[reply]

Yeah but you have 2*10**28 protons, you'd only have to wait a few thousandths of the current age of the universe. Or maybe up to infinity. How bright would it be if it was in the eyeball? Could you hear it if it was on a cochlea hair or eardrum? Sagittarian Milky Way (talk) 03:56, 27 November 2021 (UTC)[reply]

I estimate the energy of the photons to be about 75 p J or about 470 M eV, which is very high for a single photon but not a whole lot on a macroscopic scale. While their wavelength is not in the range of visible light, they might excite the neurons of one or two rods of the retina, but not of the cochlear hair cells. --Lambiam 00:54, 28 November 2021 (UTC)[reply]

Curbing SARS-CoV-2 mutations

Are there any official plans on how to curb the ongoing mutations of SARS-CoV-2? Particularly, does the emergence of a variant of concern entail some preventive measures or is it just another blah-blah term? 212.180.235.46 (talk) 20:24, 26 November 2021 (UTC)[reply]

I don't know about officials, but vaccine manufacturers have plans. Novavax is working on adapting its vaccine "in weeks", Moderna says it will develop one, BioNTech says it could ship one in 100 days if its old vaccine isn't good enough, AstraZeneca is collecting data on how well its existing vaccine performs against the new variant. Card Zero (talk) 00:04, 27 November 2021 (UTC)[reply]

COVID variants

And, speaking of COVID variants, has the WHO said anything about how they intend to give them short names after they run out of Greek letters? --184.144.99.241 (talk) 20:54, 26 November 2021 (UTC)[reply]

Maybe they could name them after COVID deniers. ←Baseball Bugs ^{What's up, Doc?} carrots→ 23:19, 26 November 2021 (UTC)[reply]

They could name them after numbers. You know, like

e

,

\pi

,

{\sqrt {2}}

and so forth. There are lots of those, even more than there are integers. 2601:648:8202:350:0:0:0:69F6 (talk) 00:01, 28 November 2021 (UTC)[reply]

Too late -

\pi

will come next, after

\mathrm {o}

(omicron).--Verbarson (talk) 15:49, 29 November 2021 (UTC)[reply]

That's pi, the letter. After that we could have pi, the number, followed by pie, the dessert, whose symptoms can be be improved by scooping ice cream on top of the patient. DMacks (talk) 02:24, 30 November 2021 (UTC)[reply]

Variants of SARS-CoV-2 says "In the event the WHO used the entirety of the Greek alphabet, the agency considered naming future variants after constellations", according to Maria Van Kerkhove. Card Zero (talk) 11:40, 1 December 2021 (UTC)[reply]

Are they really going to go straight from omega strain (the name of a bioterror supervirus in multiple unrelated cheesy fiction universes) to Andromeda Strain? Sagittarian Milky Way (talk) 23:44, 1 December 2021 (UTC)[reply]

One hopes that the WHO spends its time discussing more urgent matters. Alansplodge (talk) 11:13, 2 December 2021 (UTC)[reply]