RO - Putting RO waste water to good use

[sinder255248]

I was wondering, I have an RO unit for my Reef, but there's alot of waste water. I have a fresh water tank and wanted to know if I could use the waste water for that, since it has to be better than treated tap water. I know you can't use just RO water in freshwater without adding the minerals back in. Do any other people use the rejected water in their fresh water tanks, or is it not a good idea?

Thanks

 

[wesleydnunder]

The wastewater or concentrate is higher in dissolved solids than your tap water. I don't think it would benefit you to use it in your FW aquarium.

Mark

 

[Z Man]

The so called "waste" water should be only slightly higher than your tap water. My tap water is 175ppm and my "waste" water is 186ppm. WHY? All the things removed are actually trapped in the filters and only a small amount will slip through. I use use it in all my other tanks.

 

[wesleydnunder]

I guess I don't know enough chemistry, Z Man. I thought the water that came off the concentrate side of the membrane had a much higher TDS than that. If its only harder by 11ppm then it should be fine to use.

Mark

 

[rrkss]

An RO water filter usually uses 6 gallons of water to make 1 gallon of purified water. That leaves 5 gallons of waste water with 1/6 more minerals than the purified water (if we have 100% rejection which most don't). That leaves a TDS increase of 16.67% maximum on your average filter. To me that is not much. For 200 ppm source water, it would now be around 233 ppm. I would consider its use acceptable.