Recycling DT water with rodi

[Osric]

Why hasn't it been done yet? It's not a necessity to the world to filter salt water for the aquarium hobby, it is though a necessity to filter seawater to drink.

Perhaps you can invent a filter that does what you want, but by definition a reverse osmosis / de-ionization filter is not it.

You solved half the problem by saying “I’ll remove the DI stage so it’s only an RO filter”.

Osmosis is the process of water moving through a membrane that does not permit the passage of a significant number of ions to reach the other side. Under normal circumstances, the side with the higher concentration of salt sucks the water through the membrane to equalize concentrations, essentially dehydrating the other side. By definition a membrane suitable for osmosis does not permit the passage of ions, and especially not the passage of sodium and chloride ions.

Reverse osmosis applies pressure to the salt side of the membrane to force the water through against the osmotic pressure. Since the membrane is an RO membrane, most ions cannot pass through it; and since the pressure is high the water is forced to the wrong side anyway. By definition, a reverse osmosis filter removes virtually every dissolved solid in the water.

So now you can say “Well I’ll use an RO filter without the RO, and without the DI”. And that’ll be the new filter you need to invent that can remove the other elements from your seawater that you don’t want present.

I would have guessed that those elements would be phosphate, nitrite, nitrate, and ammonia. You probably already know that the bacteria in you tanks are supposed to be how you’re dealing with ammonia, producing nitrites, which are consumed by another species of bacteria, producing nitrate, which is consumed by the macro algae in your sump, which you’re removIng. You’re probably running a skimmer and it is supposed to be pulling out the phosphates along with DOCs in your water, or you might run chemi-clean or phosban on top of that.

So I’m not sure what your magic “RO without RO/DI without DI” filter is supposed to remove that you don’t already have a filter for. And the reason we do water changes is that the other filtration doesn’t do a perfect job, and replacing 20% of the water replenishes all trace elements while simultaneously diluting phosphate and nitrate. Since you have perfect dosing for all trace elements already, all you really need to do is step up your skimmer’s game, make sure your macro is growing strong, and maybe remove dead animals before they can overwhelm your system.

Up until this point I have merely stated things that are to the best of my knowledge facts of the true kind, and not of the alternative kind. I’ll restate my opinion that “old tank syndrome” is due to aquarists who aren’t aware of the slow damage lack of water changes causes, and eventually pay the price. That, however, is just my opinion.

 

[K7BMG]

Interesting subject.
I understand with your volume of consumables why you are looking for alternate methods.

I am not a scientist but my thought falls to possibly using a desalination unit. Is there a way to recover the extracted salt and clean it for reuse?

The recovered water can be put through your current RO/DI with less wear and tear on the filters.

But like I said I have no education or background in chemistry so I may be FOS.

 

[Admann]

Oh and 0 TDS water w

Just because both have the word filter in the name, they are in no way the same. RO membranes have many orders of magnitude smaller openings than a pool filter. They're also not running DI.

The RO membrane does remove the salt, at least it did on our units offshore. If you have prefilters, RO with a Smartbuddie and no resin at the end, you have what we had offshore, just much smaller and a lot less pre- membrane pressure

 

[OrionN]

Perhaps you can invent a filter that does what you want, but by definition a reverse osmosis / de-ionization filter is not it.
......

There isn't any use to reason. the OP thinks that the RO membrane have tiny holes in it that water fit through and other molecules and atoms are too big to fit through. He does not have the concept that the membrane reject charged ions. All he need to do is to ask DuPont to adjust the drill or laser to get a little a little larger holes to let the Na+ and Cl- through to have his revolutionized invention.

His next stage of his "...invention that will revolutionize reefing as we know it..." is "..... contacting DOW or Dupont who make industrial membranes and find out if the membrane can be made to allow the salt through..."

 

[fish farmer]

THINK AGAIN

RO and DI filters use different physical reactions to clean water. Reverse Osmosis (RO) is often used to partially clean-up tap water to make it roughly 90% to 99% pure. Deionization (DI) filters exchange positive hydrogen and negative hydroxyl molecules for positive and negative contaminant molecules in water. DI filtering and other processes are sometimes referred to as "water polishing."

To answer the question more specifically, the individual technologies need to be understood.

Reverse Osmosis (RO) is the opposite of a natural process simply called osmosis. Osmosis is the movement of water molecules across a semipermeable membrane. The process naturally moves water from a low ion concentration to a higher ion concentration across a semipermeable membrane to create reverse osmosis water. This natural process is used by our bodies to get water to our individual cells.

By applying pressure to the more concentrated (dirtier) side of a semipermeable membrane, water molecules are pushed back across the membrane to the less concentrated (cleaner) side, resulting in more purified water. This process is called Reverse Osmosis and can typically remove 90-99% of most contaminants. It is not perfect, but is a very cost effective technology; the RO Membrane can last for years if used properly. Reverse Osmosis is often used to partially clean-up tap water before any other purification technology is used to remove the remaining 1-10% of contaminants.

Deionization (DI) filters have many names: Ion Exchange, Strong Acid/Strong Base, Polishing, Nuclear Grade. Nuclear grade DI filters can remove Inorganic chemicals down to very low parts per billon (PPB) levels. This makes them excellent for producing Ultra-Purified (Type I, 18.2 Megohm) water. Water of this quality is used with the most sensitive laboratory analytical instruments, which are designed to detect chemicals at extremely low concentration levels.

Deionization filters function by exchanging positive hydrogen and negative hydroxyl molecules for the positive and negative contaminant molecules in the water. Positive chemicals, like calcium, exchange places with the hydrogen molecules and negative chemicals, like iodine, exchange places with the hydroxyl molecules. Over time, positive and negative contaminants in the water displace all the active hydrogen and hydroxyl molecules on the DI resin and the filter must be replaced. Regeneration of the deionization filter is possible, but only in an industrial environment setting.

Deionization is an on-demand process supplying purified water when needed. This is important because water at this extreme purity level degrades quickly. The nuclear grade deionization resin or polishing mixed bed resin removes almost all the inorganic contaminants in the water increasing the resistivity of the water to a maximum of 18.2 megohm-cm. However, deionization alone does not remove all types of contaminants like dissolved organic chemicals. Deionization filters are not physical filters with a pore size and cannot remove bacteria or particulates.

Here in Vermont....Maple Syrup central, sugar makers use elaborate RO systems to push maple sap through to concentrate the sap prior to boiling. Typical trees will have 1 to 8% sugar content. They are rejecting the clean water and retaining the "dirty" sugar laden water which is now more concentrated and able to be boiled quicker to make syrup.

Do a search for RO for maple syrup production, you may find some ideas.