Hacker News Reader

Comment by rjmunro | Hacker News Reader

> In fact, the study concluded that for every liter of freshwater a plant produces, 0.4 gallons (1.5 liters) of brine are produced on average.

I hate that they mix the units here. Why not "for every liter of freshwater a plant produces, 1.5 liters of brine are produced" or "for every gallon of freshwater a plant produces, 1.5 gallon of brine are produced" or even "for every unit of freshwater a plant produces, 1.5 units of brine are produced"

Also, producing more brine would make the brine less concentrated and less harmful - it would be better not worse.

View on HN

> Also, producing more brine would make the brine less concentrated and less harmful - it would be better not worse.

Producing more brine, by diluting it, still would require something to dilute it with.

The most obvious, non toxic, choice would probably be water, but the whole exercise is about getting water in the first place.

You could produce a larger volume of more dilute brine by extracting less water per unit of input seawater.

You would need to spend more energy on pumping seawater and brine, but less energy on moving water up a concentration gradient. I have no idea which cost would dominate.

You can just dilute with seawater, as discussed elsewhere in this thread.

Does diluting it with seawater (after which I assume it is returned to the sea?) result in an endlessly increasing salt level in the seawater, over a long period of time, that will reach a dangerous level at some point?

Edit: I realize my naivety now. Other comments mentioned the desalinated water (at least some of it) will end up back in the sea eventually, so that would maybe counterbalance such a concern.

The short term effects are increased salinity and reduced oxygenation for water in the immediate vicinity of the desalination plant, which is enough to drastically alter the biome (aka “kill all the sea life”).

There is also the concentrate it less option - don't wring out all of the water just what is easy and move onto the next batch vs "supersaturated brine".

No water added just less removed from input - which means more but less potent.

I believe at least some desalination plants add copper and or chlorine to the input water to prevent biofouling. In that case running more water through the plant to produce less concentrated brine would require more chemicals

Reply on news.ycombinator.com