Water treatment: "Papa, I wonder what the astronauts drink?"

Felix, a curios stakeholder of Donau Chemie, wants to know exactly how wastewater and seawater can be turned into pure drinking water. His father has the answers ready ...

"Papa?"
"Yes, my dear?"

"I can't sleep tonight, the moon is shining so bright."
"Just try to close your eyes. It's full moon today, so the man in the moon is taking extra good care of you!"

"OK, eyes are already closed."
"Sweet dreams, Felix!"

"Papa? Does the man in the moon actually have a sewage treatment plant?"
"No. There's no water on the moon, at least not in liquid form."

"But where do the astronauts get their water from?"
"For them, it's a matter of saving water and recycling the rest. For example, the water used for washing or excreted through sweat and breathing. But also the urine of the space travelers as well as the animals that are sometimes on board."

"Wuhh, ugh! I'll never become a spaceman, I'd rather stay on Earth."
"Well, on Earth this will possibly also happen in the future in regions with low drinking water supplies - and it already exists in some cases. On the ISS, the international space station, for example, the water is collected from urine and distilled, the debris such as hair etc. is filtered out and pathogens are destroyed by a special heat treatment. It is then purer than our drinking water. The technology already exists and is being applied - even on Earth."

"Where?
"In Singapore, for example - there is the so-called 'New Water'. In this process, the wastewater that has left the sewage treatment plant is first cleaned by microfiltration. Small particles, including bacteria and larger viruses, get retained here. The resulting filtrate must then flow through a membrane in a reverse osmosis process. This membrane has such fine pores that only water and other very small molecules can pass through. Bacteria, viruses and various toxins remain behind."

"Ah yes, membrane - I know that already, it's like the one at the electrolysis plant in Brückl."
"Yes, similar, although the product is different. The water is additionally disinfected with UV light for safety. In the end, minerals have to be added to make it usable and consumable."

"Does this water come out of the tap in Singapore?"
“Not directly. Most of it is used for industrial purposes and cooling systems - probably for psychological reasons. In the dry season, however, part of it is fed into the drinking water reservoirs and goes through conventional drinking water treatment with the other water - even if it would not be necessary from a hygienic point of view. In this way, Singapore covers 30 per cent of the country's total water consumption. By 2060, this figure is expected to rise to 55 per cent.”

"Will there be something like this in Austria in the future?"
"We are one of the few countries on earth with sufficient water reserves of drinkable quality and hopefully it will stay that way for a long time despite climate change. But in other regions on earth there is too little or at least too little clean water. 160 million people, mainly from poor countries, have only polluted water from rivers, water holes or lakes available, which is not suitable for consumption. As a result, up to 10,000 people - mostly children, the elderly and refugees - die every day around the world from diseases spread by dirty water."

"Well, that's sad!"
"Yes, I suppose it is. Climate change, the rapidly growing global population and wars don't necessarily make it any easier. In many world regions we are seeing decreasing rainfall and long periods of drought.  Even rich countries like California are affected. There, as early as 1976 in Orange County, south of Los Angeles and not far from Disneyland, the Water Factory 21 has been treating wastewater from the sewage treatment plant using a process similar to that in Singapore and pumping it back into the ground."

"Great, can we visit this place sometime? Then I can see Mickey Mouse! But what's the purpose of the water pumping?"
"It's to prevent groundwater from mixing with seawater. The drinking water is then taken out of the ground again. This means that treated wastewater eventually bubbles out of the pipes around Disneyland, but of a drinkable quality. Water Factory 21 now produces over 300 million litres per day. That could supply more than 2 million people in our country."

"But what about the sea? There's an incredible amount of water there."
"That's right. The oceans contain 97 per cent of all the water on earth. But it can't be used as drinking water as it is."

"Why not?"
"When you were swimming in the sea, you must have caught a mouthful. How did it taste?"

"Ugh, salty!"
"Well, you see! If you drink too much salt water, your body dries out - you quasi die of thirst."

"Really? That's not cool at all."
"No. But there are ways to turn the salt water into drinking water."

"Maybe we should take away the salt shaker from King Triton?!"
"You mean the King of the Seas from Ariel? You don't have to. There are different ways to desalinate seawater. In the past, such processes always required a lot of energy. Modern techniques work on the principle of reverse osmosis and are therefore cheaper."

"Exactly: reverse mimosa - that's what they have in Singapore and at Disneyland."
"Good thinking, reverse osmosis, right. People probably prefer to drink desalinated seawater than the purified wastewater - from a chemical-hygienic point of view there is no difference between them. Treated seawater will become the most important source of water for many countries.

The recycling of our wastewater will become more important in the future as well. This will also bring new challenges for us at Donau Chemie, perhaps we will need even more effective precipitants and flocculants, disinfectants such as chlorine gas, and in any case activated carbon for the further purification of wastewater or completely different, new products - in any case, the future has already begun."

"Wow. What's coming up?"
"Later, my dear. Now it's time to sleep. Good night!"

"Papa, maybe I will become a spaceman after all - then I could take a glass of water to the man in the moon. He must be extreeeemely thirsty by now!"
 

References