字幕表 動画を再生する 英語字幕をプリント Hey now, won’t you join me in the gutter for another look at waste water. ha. Seriously, with fresh water being so hot an issue today, you would think people should save every drop of the precious liquid. But then you flush your toilet and realize you’ve just spent several gallons of clear water only to get rid of your waste. Why can’t we use saltwater instead, for example? How’s that saving the planet? Well, the short answer is it doesn’t, of course. But the problem is there’s not much we can do about it, at least for now, and even saltwater isn’t a solution. I’ll explain. The modern sewage system works with the help of water that carries waste to the disposal plants. Water is perfect for this kind of activity as it keeps the waste afloat and pushes it through the pipes. When it reaches the cleaning filters, the water simply seeps through, while the hard stuff and particles stay on the kind of a grille, from where they are soon taken and dumped or recycled. Next the water goes for settling. It’s obviously not clean after mixing with all that waste, so it goes into a huge tank where it sits for some time. Heavier particles settle on the bottom of the tank and form a nice and slushy layer of grime. It’s called sludge, and it’s then taken from the tank to use on farms. The sludge gets some special treatment to make it usable as a fertilizer. It’s not all organic in its, um, pure form, but it becomes nice for the soil after being treated correctly. The water above the sludge, in its turn, becomes rather clear to the eye, but don’t let that fool you: it has billions of microscopic dirt particles in it that only wait to infect you if you have a drink. So when the sludge has settled and got removed, the water gets its own treatment. It either fills other tanks or goes through a special filtering system, but the basic principle of both these methods is the same: waste-feeding bacteria. If the almost clear sewage water rushes into tanks, you can be sure they have an atmosphere inside that’s beneficial for bacteria. The air is constantly pumped in to make them grow and multiply, speeding up the water cleaning. If it’s a filtering system, then the water runs over specially treated stone slabs that have overgrown waste-feeders living on them. In any case, the water gets biologically purified and is almost ready to go back where it came from, meaning seas and oceans. Almost, but not quite, since there’s one last stage of cleaning. It differs depending on the country and rules. The most popular method of finishing clean is treating the water with a disinfectant, such as chlorine. It makes the harmful bacteria left in the water vanish, effectively making it clear and ready for use. Instead of chlorine, ultraviolet, peroxide, or ozone can be utilized. Another way to purify the water involves pushing it through a special treatment tank, or a humus tank, where even the tiniest particles and bacteria get stuck in the filtering matter, while the water freely runs onwards. It’s then released back into nature, and the cycle continues, or it can be used as technical water for various purposes: from construction works and irrigation of non-edible crops to cooling nuclear plants. Such water isn’t generally allowed to be used for drinking, recreational or everyday purposes, so you don’t need to look suspiciously at the flow from your tap. It’s okay. But the question remains open: why not use saltwater instead? We have literal oceans of the stuff, and we can barely find any use for it. Well, there’s a huge trouble with salty water in the sewage system. You see, salt is hard. If you’ve ever swum in the sea, you know that if you lick your skin, it’ll be salty to taste. And if you leave it to dry in the sun, you’ll also notice a thin smattering of white on your skin. It washes off pretty well, leaving no trace, but that’s only because you haven’t been in the water for long. Stay for a few days, and the white crust of salt will cover you much more visibly. The same applies to almost any surface saltwater might touch. If you simply send tons of water from the oceans into the plumbing and sewers, several things will happen quite soon. First of all, salt from the water will begin staying behind as a residue — just like that salt on your skin. Now you can wash it away, but still the salt is corrosive. Metal, clay, and concrete all eventually give up to it, and pipes burst. And secondly, the resulting wastewater will not be able to return to the oceans just like that, or be used for other purposes, for that matter. Like I said earlier, fresh sewage water goes through several filters, one of them biological. Bacteria spread in the water and munch on everything harmful they can find around. With saltwater, such a system won’t cut it: the good bacteria can’t survive there because of all the salt. So there’s at least the problem of installing a new system of filtering and cleaning of saline water — and you can guess it’s crazy expensive. Not only that, it’s crazy difficult too. Just imagine having two separate pipe systems underneath your town: one for fresh water we use every day for cooking, washing, and other stuff, and the other for saltwater to flush our toilets. Yep, you’ll still have to have fresh water for your daily activities, because trust me, you don’t want to cook in sea water. But there’s still never going to be a way to use the cleaned saltwater for farming and some other needs — it will have to be desalinated first, and that’s another obstacle. That doesn’t mean we can’t use sea water at all, though. We are, in fact, using it already, and have been for quite some time. There are several desalination plants sprinkled across the globe that work hard to convert sea water into fresh one. They filter and vapor out the salt from the water, leaving behind huge piles of dry stuff, while the liquid goes further and eventually gets to homes and industries. Leftover salt is then used for various purposes too, and you can even be consuming it with your food. The existing desalination method is not perfect, of course, but it’s proven its efficiency. You can even drink the water after it has been devoid of salt! And certainly, it’s used for other everyday activities, including flushing your toilet. Okay, saltwater might be one solution to reduce excess use of water, but there’s another way to do it and you know it pretty well, I guess. I’m speaking about composting toilets. The basic principle is that everything you throw in there goes into the soil and keeps there for some time, until it turns into humus. It isn’t as simple as dumping soil into the ground, of course: there’s a composting unit with three chambers that evaporates the liquid, which makes up for 90% of the human waste, helps bacteria flourish, and eventually makes a safe and non-smelly compost. Sounds awesome, but the trouble with such eco-friendly toilets is that they aren’t practical in big cities, since most people there live in apartments, and you can’t simply install a composting unit in an apartment building. To do so, it will require a separate waste disposal system of its own, and given how composting toilets work, it will most probably cost even more than all the pipes for saltwater. In rural areas and smaller towns, though, where people live in their own homes, composting toilets are the best possible solution. They don’t need any water at all, collecting all you have to throw inside them with quiet dignity and then dumping it into the soil, making it richer. And that’s my latest scoop on poop. 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B2 中上級 トイレを塩水で流したら? (What If You Flushed Toilets with Saltwater) 6 0 林宜悉 に公開 2021 年 01 月 14 日 シェア シェア 保存 報告 動画の中の単語