[Arrath]

Most desalination methods are unfortunately quite energy intensive, and produce a concentrated brine that has environmental/disposal concerns such that it can't just be pumped back into the ocean, really.

It presents a difficult problem for entrepreneurs to tackle. Definitely the potential to change people's lives for the better, though.

[nradov]

Most desalination plants do just pump the brine back into the ocean. That isn't ideal from a marine conservation standpoint but if the outflow pipe runs out deep enough then it's not too bad.

[Arrath]

If it's not ideal right now, how well does it scale if more and more desalination plants come online to meet freshwater demands, and dispose of their brine in the same manner?

[akiselev]

The global water cycle is the embodiment of scale and even though engineers would learn a lot of interesting new things and make mistakes in the process of implementing desalination at scale, the brine problem is trivially solvable with existing technology like longer pipes and flow control (changing the exhaust concentration based on ocean currents and seasonal factors).

The problem is the criminal mispricing of water in most of the world. Anything that interacts with saltwater - especially brine - is in a completely different class of infrastructure that requires constant maintenance, something that most political systems are especially bad at. It's compounded by the artificially low price of water and accompanying lack of funds.

Humans have built over three million kilometers of natural gas and oil pipelines globally. The longest undersea pipeline is over 1,200 km long, which is at least twenty times longer than the longest pipelines we'd need to build for ideal brine dispersion in the worst case geographies. For better or worse, the problems with desalination are economic and political, not technological. We just need to spread out our impact so that it's within the margin of error of ocean currents and evaporation.

[_rpd]

The “brine” at the outlet pipe is just 2-3% saltier than the ocean water at the intake pipe. The impact is not zero, but it is very low if done right.

[rektide]

This statement could mean just about anything. My understanding is that desalination plants often have a fairly-sizable fairly-dead-zone around them, taht the salinity is a pretty pronounced local issue.

Sea-water is about 3.5% salt by weight. Are you saying that the brine water coming out is 3.5 * 1.025% salt, or that it's 5.5% salt? Do you have anything you can cite? What % of the water that goes in the inlet makes it to the "brine" outlet?

[tinco]

It's not ideal if the brine is dumped in one location. If it is dumped deep enough it gets a chance to be diluted before it hurts the environment.

In the end, all fresh water goes back to the ocean so it's not like we would be creating an imbalance, there's just a risk of causing local damage.

[Arrath]

Yeah the local imbalance is what worries me. I have a mental image of a big long 'soaker hose' style brine dumping pipe rather than a single outlet, that way the brine is further diluted. Wonder how much that helps.

[raidicy]

Stupid question. Can't we just let the brine evaporate and then compress the minerals left over?

[_rpd]

This is a common method of salt production ...

https://en.wikipedia.org/wiki/Sea_salt

[nradov]

In theory sure, but that would consume huge areas of valuable coastal real estate. And we don't really need more salt.

[Izikiel43]

Is brine useful for something?

[lovemenot]

Lithium, magnesium and other minerals can be extracted from sea-water / brine. Currently it's not economic, but this is a technology to watch.

For instance, according to a recent research paper[0] from Saudi Arabia, sea-water yields hydrogen, chlorine and lithium all from a single multi-stage process. These are all useful materials for industry. I imagine the process is both energy and capital intensive, but SA would be a good place to begin something like that.

[0] https://phys.org/news/2021-06-electrochemical-cell-harvests-...

[djxfade]

For pickles?