RO waste :S

[austinpetemo]

so i bought a RO DI unit so i could have some nice clean water for my nano. well i got it set up and running. however my parents dont like that the waste it puts out is several times the good output water. what can i do to use that water? we are on well water and they dont like wasting so much of it.

 

[gldnegle76]

Collect it as drinking water or put it in washing machine for next wash. Many people collect it and water their plants with it.
Also, you can buy membrane upgrade kits that could possibly get you good/waste ratio to 1:1.
Keep in mind, even the waste water from the ro is cleaner than tap water.

 

[oscar.millan]

Waste water simply has a high mineral content, but will have been through sediment and carbon, which as the previous post suggest is better than tap water.

Plenty of other uses, but I find the application of such uses to be a hassle. I ended up running my line to my garden and it's a done deal.

 

[ludiNano]

What membrane kits can get 1:1 never seen them but I want one

 

[Korrine]

a big long topic about this in Responsible Reefkeeping


http://www.reefcentral.com/forums/showthread.php?t=1931583

 

[Fishbulb2]

Send it down the drain. Yes it's been through a sediment and carbon filter but it is also more concentrated in everything it was originally designed to reject. So it's pretty much 4X concentrated in sodium, calcium, chloride, copper, lead, arsenic, cadmium and other charged molecules. Have you read about Chromium hexavalent in the news recently? This would be also be concentrated in the RO waste water.

RO waste water may have some contaminants removed from it compared to tap water but you should never state that it's purer, or safer than tap water. Anything rejected by the membrane is automatically concentrated in the waste and no longer monitored by any regulatory agencies or industrial standard.

Just dump the water. Don't drink it, don't use it for anything that will eventually end up in your body (like watering a garden).

FB

 

[Acrotrdco]

Waste water simply has a high mineral content, but will have been through sediment and carbon, which as the previous post suggest is better than tap water.

Plenty of other uses, but I find the application of such uses to be a hassle. I ended up running my line to my garden and it's a done deal.

Agreed - it's not exactly "waste water", the term is used incorrectly really, I'd rather call it the "pre-filtered water".

It's ran through pre-filters and trust me, the pre-filters in RO/DI units are 10x better than those "household water filter" you buy from home depot for under $100.

I collect those and use it in my automatic water boiler, good for coffee or tea in the morning.

 

[USC-fan]

What membrane kits can get 1:1 never seen them but I want one

Looking at getting one myself. But its $60. Thats a lot of water. Not sure you would never break even.

http://www.bulkreefsupply.com/store...ssories/150-gpd-water-saving-upgrade-kit.html

 

[Fishbulb2]

Agreed - it's not exactly "waste water", the term is used incorrectly really, I'd rather call it the "pre-filtered water".

It's ran through pre-filters and trust me, the pre-filters in RO/DI units are 10x better than those "household water filter" you buy from home depot for under $100.

I collect those and use it in my automatic water boiler, good for coffee or tea in the morning.

This needs to be thought out. It is really really bad advice.

Yes the sediment filter will remove some sediment. So what? It's probably not harmful to begin with. Yes the carbon filter will remove chlorine and potentially some uncharged organic compounds (like pesticides). That's good. But everything else the membrane rejects, including all heavy metals, are now 400% more concentrated in your coffee, tea, drinking water, ect. It doesn't magically disappear.

FB

 

[Acrotrdco]

This needs to be thought out. It is really really bad advice.

Yes the sediment filter will remove some sediment. So what? It's probably not harmful to begin with. Yes the carbon filter will remove chlorine and potentially some uncharged organic compounds (like pesticides). That's good. But everything else the membrane rejects, including all heavy metals, are now 400% more concentrated in your coffee, tea, drinking water, ect. It doesn't magically disappear.

FB

GAC is known to absorb some heavy metal, so pre-filtered water before going through RO membrane contains less heavy metal concentration than tap water.

Most people I know just use tap water to make coffee/tea - or just use a regular household water filter like Brita, which is nothing more than pre-filters (sediment + GAC).

My measured TDS from tap water is around 62, and my pre-filtered water from RO exhaust is around 70-ish, yes it's slightly higher concentration but it's not 400% higher.

But then again, I don't know your tap water TDS, it might be lethal to drink pre-filtered water in your region perhaps :lmao:

 

[Fishbulb2]

In your case it's fine because clearly your RO membrane isn't working properly and it's not actually filtering out anything (since the waste basically equals the permeate water TDS).

For anyone with a functional unit or who has a unit that doesn't destroy matter, your RO waste water concentration pretty much equals your waste water to permeate ratio (minus the 2 or percent that goes through the membrane). Don't be fooled by smiley faces.


FB

 

[Acrotrdco]

In your case it's fine because clearly your RO membrane isn't working properly and it's not actually filtering out anything (since the waste basically equals the permeate water TDS).

For anyone with a functional unit or who has a unit that doesn't destroy matter, your RO waste water concentration pretty much equals your waste water to permeate ratio (minus the 2 or percent that goes through the membrane). Don't be fooled by smiley faces.

FB

My RO membrane is 3 weeks old. My RO water is 0 TDS and I run it through a DI unit anyway, also 0 TDS.

My RO/DI unit has a pump but it's not the highest quality one producing 1:1 ratio, so it's about 1:4 (1 part RO water 4 part waste), which means about 20% of my input pre-filtered water gets through the RO membrane.

I remembered I talked to the folks at AquaFX during the last MACNA show, and they were producing RO/DI units with 1:1 ratio, one of the guys there were a PhD candidate researching on water purification, I enjoyed the discussion and shared lots of interesting ideas.

Of the remaining 80% pre-filtered water that didn't pass the RO membrane, most of them are water molecules bind with other substance such as heavy metal, it's just that there aren't enough pressure to push them through the RO membrane.

So again after extracting the 20% pure H2O molecule from the pre-filtered water doesn't make your RO exhaust 400% higher concentration in impurities.

I don't know where you get the 2% from, I don't mind having an educated debate but you've gotta get your facts right.

 

[James77]

But everything else the membrane rejects, including all heavy metals, are now 400% more concentrated in your coffee, tea, drinking water, ect. It doesn't magically disappear.
FB

If your RO sysytem is like the typical one that "wastes" 4 gallons for every pure gallon, it is more like 20% higher in the metals and minerals the membrane rejects. The minerals from the gallon that was filtered- one fifth of the water that went in to make that gallon- would now be in the remaining 4 gallons.

 

[bobbychullo]

I would tend to listen to Fishbulb2. for one, he seems to know what he is talking about. two, Cambridge MA is well known as an intellectual center, that alone makes me think he STUDIES this stuff in SCHOOL since 3 out of 5 people in that area are college students and the rest are professors...

My RO membrane is 3 weeks old. My RO water is 0 TDS and I run it through a DI unit anyway, also 0 TDS.

My RO/DI unit has a pump but it's not the highest quality one producing 1:1 ratio, so it's about 1:4 (1 part RO water 4 part waste), which means about 20% of my input pre-filtered water gets through the RO membrane.

I remembered I talked to the folks at AquaFX during the last MACNA show, and they were producing RO/DI units with 1:1 ratio, one of the guys there were a PhD candidate researching on water purification, I enjoyed the discussion and shared lots of interesting ideas.

Of the remaining 80% pre-filtered water that didn't pass the RO membrane, most of them are water molecules bind with other substance such as heavy metal, it's just that there aren't enough pressure to push them through the RO membrane.

So again after extracting the 20% pure H2O molecule from the pre-filtered water doesn't make your RO exhaust 400% higher concentration in impurities.

I don't know where you get the 2% from, I don't mind having an educated debate but you've gotta get your facts right.

 

[Acrotrdco]

If your RO sysytem is like the typical one that "wastes" 4 gallons for every pure gallon, it is more like 20% higher in the metals and minerals the membrane rejects. The minerals from the gallon that was filtered- one fifth of the water that went in to make that gallon- would now be in the remaining 4 gallons.

Exactly. That doesn't increase the concentration by 400% now does it? :lol:

I would tend to listen to Fishbulb2. for one, he seems to know what he is talking about. two, Cambridge MA is well known as an intellectual center, that alone makes me think he STUDIES this stuff in SCHOOL since 3 out of 5 people in that area are college students and the rest are professors...

Interesting statistics!

So if I live in Massachusetts that makes me a MIT graduate, right? Cool, I need to pack my bags.

 

[liquidplumber]

By adding an additional membrane you can cut down on your RO Waste, BRS has an add on kit for sale and they have a nice instructional video as well.

http://www.bulkreefsupply.com/store...ssories/150-gpd-water-saving-upgrade-kit.html

 

[c0mp|ex]

Sorry but Acrotrdco is right about this one. How is waste water 400% more concentrated? A 1:1 ratio of RO water to waste water would only be 50% more concentrated with minerals. A 1:4 ratio of RO to waste water would produce waste water much less concentrated than 1:1 ratio would.

 

[lilmonster]

I ran a line out my window and use it to water my lawn, works great, and the animals like it too.

 

[Fishbulb2]

Sorry, should be 25% more concentrated. If you have 100 TDS in one gallon of water, it will raise each of four waste gallons by 25 TDS. And yes, I would not recommend drinking the waste water of a 1:1 ratio RO unit either as that should technically be double the concentration.

If you have no idea exactly what is passing through the prefilters and concentrating in the waste, you should not be drinking that water. Water municipalities generally test and regulate what can be in your water and we have no idea how close some of these things are to allowed limits. No one should be recommending people to drink their waste water unless you are really looking at the water reports and are sure a 25% boost in anything is even acceptable. Use your RO water to get better drinking water for yourself, not worse.

Another point
People seem to just throw out TDS numbers now as if they are some measure of waters purity for drinking purposes. This is absurd as you have no idea what makes up that number. You can have one local that is supplied from a source high in harmless salts like Na, Ca, or Mg. This will have a high TDS and will pass drinking water standards. Other areas might be fed from a very low TDS region and have industrial seepage giving low TDS and high concentrations of questionable heavy metals (like chromium hexavalent that was in the news this past December). You simply can't through out a TDS number as some magic number to your water's drinking quality. It means nothing. TDS meters are best used to gave a membranes rejection rate and will loosely correlate how much DI resin you will run through before exhausting it (but still completely ignoring any contribution from CO2).

To original poster. Just look for ways to reduce waste if you can. The add-on membrane kit posted above can be a good start. If you use a pressurized storage tank for drinking water, then a permeate pump can save a tremendous amount of water. Lastly just use if for thing that won't end up in your body, like the washing machine. Good luck!

Thanks for the kind words bobbychullo. I'm actually a post doctoral research fellow at Harvard Medical School (in Boston).


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[Porcupinepuffer]

Finally, I'm glad members with some basic math skills have came forward with correcting how much higher the concentration really is. Good lord! It would be about 15-30% more, depending on proper flow restrictor size, water temperature, etc... I would think it's safe to drink... But really, you shouldn't have told your parents about the rejection rates. I'm on a well, and I just let her reject all she wants. I don't pay for the water, but I do pay for the water pump to turn back on and off.