Turning desalination waste into a useful resource | Hacker News Reader

Turning desalination waste into a useful resource

news.mit.edu

I would also point out that there is an endless stream of oil-field brines and related contaminated waters available for processing should anyone want to have a continuous source of raw material.

The industry, in its never-ending quest to monetize waste products or to place the cleanup burdens on someone else (the public usually) is currently trying to get Texas to agree to allow pumping of these highly contaminated wastes into aquifers.

Any time you produce oil or gas you always produce some waste water with it. Volumes will vary from well to well depending on a lot of variables unique to a field or a well. This water, or most of it, is not all water from production if I read the article correctly, a lot of it is flow-back water from the fracking process. That means it is not water that would normally be reinjected to help maintain formation pressures to allow continued production. It is water pulled from public and private potable water supplies including, lakes, aquifers, etc. This water should have been reserved for human consumption or for use in farm or ranch maintenance.

T Boone Pickens set in motion the whole idea of gathering rights to large volumes of water and selling it to users far from the source. This really set the stage for the massive over-use of public water in fraacking in the Permian Basin and other related areas that saw a large fracking boom.

The potable water is gone now, polluted by the O&G industry, and now they want to be able to just put it back where they found it and let God sort out the contaminants. Disgusting really.

But, it sounds like a great opportunity for someone operating in the water treatment space to test and validate options for wastewater treatment and for recovering chemical and mineral contaminants from non-potable water.

> The team also continues to look at the possibility of extracting other, lower-concentration materials from the brine stream, he says, including various metals and other chemicals

Lithium from desalination brines seems to be one potential (and promising) such [0], environmentally better in more than one way than the current methods of lithium mining [1].

[0] https://www.researchgate.net/publication/313372304_Towards_l...

[1] https://www.wired.co.uk/article/lithium-batteries-environmen...

You can also extract uranium from seawater, and use it to fuel nuclear reactors, and use the nuclear reactors to power your desalination.

Do you get enough volume for this to work? My intuition would be the levels of Uranium would be low enough that it would not be energy positive. Do you have more information about this process?

I remember some projects going on at MIT on this topic.

https://dspace.mit.edu/handle/1721.1/111821

Energy consumption of reverse osmosis is about 4kWh/t. The byproduct is a ton of brine. Sea water contains about 3ppb Uranium, so our brine contains 6mg of U per ton of fresh water produced.

A 1GW nuclear power station consumes about 1t of U per year and produces about 8000GWh of electricity in that time. So we need about 1mg/8kWh. We got 12 times that much.

So, it sort of works out. Of course, this assumes a breeder reactor and I pretended that brine is purified uranium. If breeders are commercialized, it might be worth looking into this. Right now, it isn't.

Awesome, thanks!

Nice analysis. But the premise of the discussion here is that people do the desalination for its own sake, not in order to harvest Uranium.

This [1] article from 2012. It presents a Uranium extraction method from seawater that would put the extraction cost at $300/kg. Nowadays the market price is about $70/kg. However, if method were to be applied to brine instead of regular seawater, maybe the cost would go down. Hard to see it going down by a factor of 5 though.

[1] http://large.stanford.edu/courses/2012/ph241/ferguson2/

I think you overestimate the energy in uranium. 8000GWh per tonne and year would be 28.8 TJ/kg, while the numbers I have seen is more like 0.7 TJ/kg (http://www.plux.co.uk/energy-density-of-uranium/).

What part of "this assumes a breeder reactor" did you not understand?

Oh I missed that!

So 4kWh/t is used to desalinate 2 tons of seawater that turn into 1 ton of freshwater and 1 ton of brine?

Googling a bit: it takes about 13 MJ to desalinate 1 m^3 of water by reverse osmosis. Seawater contains 3mg uranium per m^3, which gives 2 MJ, So it's not energy positive.

2/3rds power rebate on your desalination ain’t bad!

For a long time, bromine was an important product made from brine. But that market has fallen away, since the lions share used to be made into lead scavengers for leaded petrol. The bromine works at Amlwch on Anglesey closed in 2004: https://www.octelamlwch.co.uk/

The other obvious product would be magnesium, but they didn't isolate magnesium chloride at the bromine plant. The Wylfa nuclear power station was nearby, and Rio Tinto had an aluminium smelter nearby to provide a base load. Since magnesium is oftentimes produced through electrolysis a magnesium plant would have made sense, but somehow they didn't build one, likely for economic reasons.

HN community seems to really like desalination. Various innovations seem to hit the FP occasionally.

I'll say this to the general sentiment. My 9th grade chemistry teacher say 'your generation will face two major problems: xxxxxx and water'[1]. He's been a sage in my life, retired for about 1.5 decades.

I say all this to attempt to say that 'this is refreshing' that this community understands that we are in an impending crisis of water. Onward! :)

[1] - I'm a millennium and I won't reveal 'xxxx' because I'm not trying to incite anger but he was correct about 'xxx'.

My thesis in grade school thesis from ~17 years ago was that the two most important problems to by solved in my lifetime were going to be low cost, low emission and low land use energy production and efficient information processing and communication.

I think desal is much less of a problem if we had a cheap, clean, and reliable source of energy to power it such as nuclear.

Quality of life is strongly correlated with energy intensity.

I'm not entirely sure how but in the past two years, I've become a believer in the capitalism structure for the markets and that it's able to solve any given problem (including what you're saying). Capitalism just needs to get nudged into a direction and the solutions will be a product of markets.

To elaborate my point, through government subsidies: - American has seen massive production of food (so much that we waste an insane amount every year) - Massive creation with minimal resources (via petrol innovation; even if y'all don't like it, it was an easy win for society and we're living with the second order effects) - Vehicle fuel efficient rise - Green revolution is almost profitable without government subsidies.

I'm not an economist but the game theory does seem to playout in such a way, for the past century, to confirm 'we'll find a way, given a nudge in the right direction'.

You should check out the Decouple podcast :)

https://podcasts.apple.com/us/podcast/decouple/id1516526694

Also another thing I hear a lot of hype about is Atmospheric Water Extraction, but as of now remains longway from being practical at scale.

xxx = misinformation

We don't have a water crisis. We have a clean energy one. With abundant energy we could simply boil sea water to get drinkable water. The biggest problem of the various desalination methods are their energy cost, and this method to reprocess the brine is meant to offset it by extracting commercial value from the desalination residue. While it's great to make desalination commercially viable, we also need to remember our energy needs will not drop.

I have the nagging feeling that the "commercial" part is what we'll need to solve if our species is to survive long term. In some matters, whether its commercially viable should not be a concern.

> With abundant energy we could simply boil sea water to get drinkable water.

That still leaves you with either solid salt that needs to be disposed of (preferably, somewhere where it can't eventually leach out into groundwater) or highly concentrated brine which will kill anything near it.

How much waste salt would we have compared to the amount of salt that we are going out of our way to extract or mine already? I mean, I literally pay money for sea salt at the grocery store.

How much salt do you use in a month? How much water do you drink?

That's not really a fair comparison. There's easily 25x as much water vs salt in the ocean, and a 10x higher fraction of water usage is residential than salt usage. The break-even point you're pointing to is closer to 250:1, not 1:1.

That's fair enough, but I still doubt you use 1/250 of water in salt, even when you're cooking. If you add things like showering, washing clothes, and lawn care, it's not even close

The numbers I gave did include factors like showering.

Edit: I do think that you use more than 1/250 salt vs water in cooking though (whether by mass or volume). By mass that's around 1tsp of salt per 6.3 cups of water, and soup recipes for example will often call for that much extra salt on top of whatever is already in the other ingredients you're using.

Edit: Individual recipes are probably the wrong way to look at that. It's recommended to eat under 1tsp of salt (actual usage is higher in the USA) and drink over 10 cups of water each day, so whatever combination of food/beverages you're taking in you still wouldn't quite hit that crude 1/250 threshold.

Salt is also useful for things other than eating it, and more of those uses may be cost-effective if salt were more plentiful.

Sea salt contains microplastics. You should seek out mined salt.

Or we could find a way to remove them from, say, the brine.

Just put it back from whence it came. The extracted water doesn't exactly leave the environment, it will find its way back into the oceans anyway.

If the excess brine is diffused over a wide enough area or as is often the case, the outlet of an estuary, local disruption is minimal and global disruption is exactly zero.

"highly concentrated brine which will kill anything near it."

That sounds a bit dramatic, for salt in water, don't you think?

Sure, it is not a enviroment, live can prosper and it kills most living things, that would have to live in it, but it is also not deadly toxic, "killing anything near it" like your comment implies.

xxx = pollution? energy?

edit: or a certain political guy?

xxx = Mass migration?

Depends on where you live, it is already happening. And it is sometimes caused by long droughts, actually.

Why do the x's keep getting fewer? Is the crisis a lack of x's?

> Why do the x's keep getting fewer? Is the crisis a lack of x's?

Yeah. I ran out of ink.

I've got karma to burn, so I'll come out and address the controversy straight on. xxxx is the rarity of Charizard in Pokemon Go.

Tangentially related: there are millions of abandoned oil wells emitting greenhouse gases like methane across the US. Vice had a great video about this last month, but it didn't get much attention here on HN. [1] [2]

[1] https://news.ycombinator.com/item?id=25516076

[2] https://welldonefoundation.com/

Is it possible to capture the natural gas leaking from oil wells like we already capture flue gas? Would that be economical?

I'm guessing it's not economical or they would be doing it, but I don't know.

Maybe 3d-printed containment vessels and Seuss-like pumping toolery?

Could geodesic domes solve this problem given market economics and current penalties and incentives?

> The researchers have discussed the concept with companies that may be interested in the next step of building a prototype plant to help work out the real-world economics of the process. “One big challenge is cost — both electricity cost and equipment cost,” at this stage, Kumar says.

Huh, I thought their big breakthrough would be figuring out how to make this economically viable. It's not a big surprise you can make useful chemicals out of brine, right?

Use it to maintain salinity levels in deep ocean currents, to sustain current circulation patterns and reduce the impact of arctic runoff, impacting weather systems. Or something.

https://www.nature.com/articles/s41467-020-14474-y

There was some research into using it in concrete.

I thought perhaps it can be shipped to northern territories that spray brine onto streets in winter to melt snow.

Reply on news.ycombinator.com