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Making Ocean Water Drinkable

popularmechanics.com

75 pointsprawn55 comments

It's disappointing that desalinization has taken precedent over recycling water. There have been many developments in this area –including the one Bill Gates has been supporting [1] – yet despite being the more cost effective option, people can't get over the idea of drinking water that was poop.

[1] http://www.gatesnotes.com/Development/Omniprocessor-From-Poo...

Singapore has been recycling sewage into potable water for some time now. Although the majority is used in industrial applications requiring very pure water (e.g wafer fabs), some is added to the tap water:

NEWater is mainly used for industrial and air-con cooling purposes at wafer fabrication plants, industrial estates and commercial buildings. The biggest users of NEWater are wafer fabrication plants which require water quality that is even more stringent than water for drinking. NEWater is delivered to industrial customers via a dedicated pipe network.

During dry periods, NEWater is added to our reservoirs to blend with raw water. The raw water from the reservoir then goes through treatment at the waterworks before it is supplied to consumers as tap water. [1]

[1] http://www.pub.gov.sg/water/newater/Pages/default.aspx#newat...

I'm in Northern California. My lawn is dead. I can get over it. Run the purple pipe into the aquifer already like Santa Ana does.

"When you flush in Santa Ana, the waste makes its way to the sewage-treatment plant nearby in Fountain Valley, then sluices not to the ocean but to a plant that superfilters the liquid until it is cleaner than rainwater. The “new” water is then pumped 13 miles north and discharged into a small lake, where it percolates into the earth. Local utilities pump water from this aquifer and deliver it to the sinks and showers of 2.3 million customers. It is now drinking water. If you like the idea, you call it indirect potable reuse. If the idea revolts you, you call it toilet to tap."

http://www.nytimes.com/2008/08/10/magazine/10wastewater-t.ht...

I'm a bit anxious about sewage to drinking water efforts.

While I'm fairly confident that we can eliminate most live pathogenic organisms from sewage with enough work, excreted toxins, hormones, and undigested pharmaceuticals are another matter. Diluting those through a watershed serves a real purpose that sewage treatment facilities are not up to replicating.

Not sure what size these toxins are but nanoporous graphene works for filtering out anything bigger than water molecules -

http://www.ornl.gov/ornl/news/news-releases/2015/ornl-led-te...

it's always an issue of volume flow and membrane effectivenes with these things. many things 'work' that don't work to resupply the population on a daily basis.

Nanoporous graphene is pretty awesome stuff. The numbers are up in the range of 4 litres per square centimetre per hour per megapascal. Or more practically, just a one centimetre by one centimetre "hole" at the bottom of a 100m tall "tank" (it can actually just be a pipe, the key is the water depth not the reservoir capacity) would produce 4 litres per hour powered by nothing but gravity. Of course there's the requisite effort of approximately 100N of work per litre to lift it up that hundred meters, but being otherwise passive is a good illustration of how much more efficient these materials are.

Yes I know I'm ignoring things like biofilm buildup, particulate settling, etc. I'm mainly trying to illustrate the "basic work" required to get drinking water from sea water using the latest technology. Most existing reverse osmosis membranes are only capable of 1 litre per square centimetre per megapascal per DAY. That's not even a remotely practical rate without mechanically applied pressures, and since we're now dealing with hydraulic pressures... a lot more engineering and maintenance.

Thank you, was going to mention the flow rate vs current reverse osmosis tech.

I am still wondering about the efficiency in terms of filtering toxins. Water molecules are smaller than most other molecules but I am not sure if some toxins would still be able to get through the holes in the graphene? Things like heavy metals

What about a grey water system? neither your toilet nor your lawn needs human consumption grade water.

Wouldn't it be an absolutely huge cost to lay down another set of pipes for non-human drinkable water? Especially in cities.

Interestingly, growing up, I thought a second set of pipes for "non-potable" or reclaimed water was standard. Where I grew up in Florida, every lawn was watered with reclaimed water. According to their website[1], Florida is currently reusing 660 million gallons of water per day. Really makes me wonder why states that are in apparent perpetual drought condition haven't adopted similar techniques.

[1] http://www.dep.state.fl.us/water/reuse/

Non-potable is the industry term for "non-human drinkable".

And yes, the cost of that would be huge, not just in cities. In the UK the decision the victorians made to not have separate sewage and rain water drainage systems still has a knock-on today and costs a vast amount in water treatment, but the cost of separating rain runoff and sewage is still seen as prohibitive.

edit:

However, on a small local-scale grey water systems can do a lot of good, both for re-use but also rain water capture and re-use would help with flood prevention. If houses captured rainwater for use for lawn watering and other appropriate uses, this is something that could be done without great expense.

Be careful of the law of unintended consequences. Rainwater capture will be fine so long as only a minority do it (how small I don't know) or only a fraction is captured but if everyone does it then it will change the economics of water supply and give people incentives to use the captured water for other than lawn watering. For instance they might use it for flushing toilets or even bathing. the problem that then happens is that the local water table will fall because it is not getting the water that it used to because that water is now flushed into the sewage system.

I'm not arguing against the idea, especially as it is typically implemented in the UK where a house will generally only have about 500 litres of storage, but scaling it up and making it a requirement could cause some interesting problems.

Some US states have laws preventing rainwater capture. Water rights being a weird and complicated thing.

It's unlikely that a given residential area is drawing water from the area directly beneath it, or that its water supply is fed by residential run-off. That's not going to be clean water that you'd want to drink. Most residential water comes from resovoirs fed by mostly unpopulated catchment areas which are often 10s or 100s of miles away. Also bare in mind that around 50% of rainwater evaporates or ends up in the ocean, so there's plenty to go around.

I thought that the idea of rainwater capture was to prevent the water from going to "waste" as runoff. That is, the water that hits the roof of your house ends up in a torrent in the downspouts, which runs into the streets and the sewer system. Whereas the water that hits your yard has more of a chance to sink into the water table.

I believe most gray-water systems are internal to individual buildings.

For example, a house would fitted with a storage tank for shower water, which is then used for flushing the toilet, or even watering a yard. The toilet water is sent to city sewer system.

Water based toilets and watered lawns aren't used in places with shortage of drinking water. (Except in places with high inequality where an upper class can afford to use water in toilet but lower class can't afford to drink it)

Is there a toilet that isn't water based? Or are you talking about using tree/hole/... as toilet?

Yes, UDDT toilets work so well that environmentally conscious people install them in homes even in places with good access to water. https://en.wikipedia.org/wiki/Urine-diverting_dry_toilet

In arid third word countries people have low tech outdoor arrangements like pit toilets.

Composting or incinerating toilets.

You mean like California? :-)

Afraid I don't know enough about California to get the joke, do you mean tap water is too expensive for the poor there?

I mean that the way California is going that water will be in short supply there.

Thanks for the link, very interesting. Noticed there is an update on this on the blog - http://www.gatesnotes.com/Development/Omni-Processor-Update

Having lived in the Gulf Countries - I feel that they were ahead of the curve for some time when it came to water.

When I lived in Dubai water was really expensive compared to the UK.

You also never drank from the tap but bottled water.

Even the culture adopted to it where people would think you were super posh if you took showers longer than 10 minutes.

Also they has some interesting techniques for desalination. For example I used to live near an aluminium smelter.

Apparently the heat generated due to smelting was recycled to desalinate sea water to produce water and was sold to consumers.

So this process re-introduces the brine back into the ocean, in turn making the ocean water more salty. What type of ecological ramifications does this have on the wildlife in that area?

This is pretty much the most pressing concern in any desalination effort.. Intakes and discharges are expensive in general, but to adequately dilute a brine discharge is on the order of 5x the cost of the intake system. You basically need miles of pipe into the ocean that split off like a fan in order to not significantly disrupt nearby ecosystems.

That caught my attention as well. Why not send some to the east coast to de-ice in the winter?!

The volume of water being drawn from and the volume of evaporation, precipitation and runoff affecting that body of water, dwarf this desalination plant by an exceedingly long way.

It's not the overall volume of slightly saltier water, it's the hot, concentrated brine that's damaging. Most systems are designed today such that the brine is only ~50% more salty than incoming water and only a few degrees warmer, but it's still a significant ecological issue.

Why do they move large amount of salt water when they could move only the sweet water? When the plant is 100 meter down, the water pressure is already the required 10 atmospheres, and when it is offshore at an ocean current the saltifying effect is a not problem. The energy needed is basically the same, but there is much less friction in the pipelines when you move only the non-pressurized end product. In my hand-cranked reverse osmosis plant the difference is 100-fold and you get good 30 minutes exercise for a cup of drinking water. If you live in a submarine, you could just turn the tap and the clean water flows in without any cranking.

Just glancing at the article, it struck me how similar this picture from the article is: http://pop.h-cdn.co/assets/15/35/1440426015-desalinization-2...

To an 1880's Ogden cigarettes card demonstrating how to make an emergency filter inside of a bucket: http://digitalcollections.nypl.org/items/510d47da-d09a-a3d9-...

150 years later, and the method is pretty much identical.

Or we could just stop wasting water on Factory Agriculture of Animals.

http://www.cowspiracy.com/infographic/

The fact that we CAN do this is impressive.

Should we do it is another question. This is one of a host of technologies were going to have to adapt to keep the water flowing not only here in the states but across the globe. Storage, recycling, improved transit (most water systems loose 10%-30% in transport due to aging infrastructure). The reality is this is one part of a systematic change were going to have to make to keep things going.

This scares me to no end. I see a future where all our water comes from bottles and we have to pay for the right to drink.

It is kind of the natural conclusion when you decide to build a metropolis in a desert.

Come to Iowa, our weather isn't as nice, but we've got a shit ton of water.

Really?

http://www.desmoinesregister.com/story/opinion/columnists/io...

Aquifers aren't infinite.

> we have to pay for the right to drink

You already do this if you pay a local municipality for water service.

Except that the price difference is obscene [1]. A future where we are captive to bottled water purveyors control is indeed scary.

[1] http://www.businessinsider.com/bottled-water-costs-2000x-mor...

This is happening now in many third-world countries where it's more profitable for Pepsi and Coca Cola to sell bottled water.

Welcome to the developing world where you don't drink water coming out of the tap, even if it's chlorinated.

Very interesting article ... namely because fresh drinking water is now becoming a valuable resource. I'm sure the time the article has been written, better and more efficient ways would turn up for churning out fresh water for public consumption.

I feel a very American point of view in your comment. Hasn't fresh drinking water been a valuable resource in plenty of places in the world for as long as time can remember?

Two years ago I moved from South Australia to Tasmania. South Australia is known as "driest state in the driest inhabited continent in the world"[1]. Here in Tasmania there's water oozing out of the side of the hills, I'm still amazed by it.

1. http://guides.slsa.sa.gov.au/water

Someone else has usually put it better, this time I'll draw on user adrusi:

___________

https://news.ycombinator.com/item?id=8995524

The problem with freshwater is not that the global supply is limited, rather that supplies in some high-population areas are.

The Amazon river sends 209,000 cubic meters into the Atlantic every second[1]. That's 18,100,000,000 per day. A single human drinks about two liters (0.02 cubic meters) every day. There are 7 billion humans, so the global requirement is 140,000,000 cubic meters of water. The Amazon alone contains 130 times more than the global requirement for drinking water.

This is domestic consumption, which comprises 10% of water usage[2]. That means that 13 times more water flows through the Amazon than all of humanity uses. That's just one river. [1]: https://en.wikipedia.org/wiki/Amazon_River

[2]: http://www.lenntech.com/water-food-agriculture.htm

___________

Clearly. I was just considering the drought in the west of US lately and the statement "is now becoming".

Personally I live in Norway where we wash our garbage and shower in high quality drinking water. I still find it absurd from time to time, considering the lack of fresh water in many places in the world.

Edit: Corrected quote

We've got a similar situation going on in Slovenia. I don't know if we have more fresh water than Norway, or not, but there are towns that get 3meters of rainfall per year.

One such town has an area of 25km^2, that's 25,000,000 square meters. Which means that on an average year, 75,000,000 cubic meters of fresh drinkable water fall from the sky.

Comparing that to stats in the grandparent post: 14 times as much drinking water falls on a tiny town in a tiny European country, as the whole world needs for drinking.

That's crazy.

Somewhere in your calculation there's an error.

75,000,000 cubic meters of fresh drinkable water fall from the sky per year divided by ( 0.002 cubic meters of drinking water needed per person per day x 365 days in a year ) = 103,000,000 people quenched per year.

Your tiny town gets enough fresh water from the sky for 103 million people -- still impressive.

The water is already here - it's just not very evenly distributed.

The sky above the port was the color of television, tuned to a dead channel. Purest of blue, not a cloud in sight.

For those not in the know, this is from William Gibson's Neuromancer (http://www.williamgibsonbooks.com/books/neuromancer.asp).

2 liters = .002 cubic meters The amazon river runs off 1300 times the drinking water of the world into the sea

Sometimes a small scale example helps, my home town of 100K people has a very small semi-navigable river pass through the middle of it, maybe a hundred feet wide and maybe head depth at most, that flows over a hundred cubic meters per second on average per wikipedia or 30K gallons per second.

Some back of the envelope engineering estimates imply 30 kilogallons per second, if somehow shoved thru plumbing, equates to around or over two billion low flow toilet flushes per day.

There's a lot of thirst on the west side of the Mississippi, not so much on the east.

Of course water treatment to drink that river water isn't free, nor sewage treatment to keep it drinkable downstream, but still, that's a lot of water for a river.

There are obvious analogies to income inequality. Humanity has more water than it knows what to do with, but simultaneously there are thirsty individuals.

Not necessarily American; fresh drinking water is becoming scarcer across the world [1] and therefore even more valuable.

[1] http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2727435/

> I'm sure the time the article has been written, better and more efficient ways would turn up for churning out fresh water for public consumption.

Huh? "This story appears in the September 2015 issue of Popular Mechanics."

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