Zero-Waste Water Purification

[Ray]

As you know, I sell a lot of RO systems. Folks sometimes don't like RO, as there is a flush-water stream that some view as "waste" unless a reasonable use can be found for it - watering non-orchids, humidification, or in my case, filling an artificial pond that caters to local wildlife.

Because of that, and/or a small demand, many buy RO or distilled water at their local grocery store for as much as a$1/gallon, so I have come up with cost-effective alternatives: small deionization (DI) systems.

Rated at about 1/2 gallon per minute flow and roughly 3000 gallons capacity before needing cartridge replacement, one is a 2-stage unit (sediment removal and DI column) for plants (cost = about $0.02/gallon), and the other is a 3-stage (just under $0.03/gal) unit that has a pH stabilization column that adds Ca if you want drinking/cooking water or grow a lot of calcium-hungry plants like some paphs.

These are pretty compact - the larger, 3-stage unit occupies a volume of about 20" x 8" x 3".

[LinhT]

Hi Ray,

Just needed some clarification on the way this system attaches...

I have an RO system right now that I bought at an aquarium store. It has 3 filters plus the RO membrane thing. My RO water comes out of the blue tubing and the RO waste comes out of the black tubing.

So, would I attach this zero waste system to the black tubing on my RO system? Is that how it works?

Also, does this zero waste system still have a small amount of "waste" water that comes out? I always thought it was not possible to have completely ZERO waste with any system.

[Ray]

This is an alternative to RO, not an "add-on".

An RO system uses a membrane to "filter" dissolved ions from the water, so needs a flushing system to carry them away, or the membrane would get clogged in no time. The so-called "zero-waste" RO systems have a pump that injects the flush stream into your household hot water system, so it can be used. It is not truly a zero-waste RO system, just an alternative way to use it.

This alternative uses a cartridge (the big one in the middle) containing deionization resins. They capture the ions from the water, only letting the pure water pass. Those ions are permanently trapped, rather than being flushed away in another stream. As you approach 3000 gallons, their absorption capacity is done, and the TDS increases to that of the incoming water supply, so you replace the cartridge. There is no waste stream - a single inlet line connects to the sediment filter, and a single line delivers the pure water.

[tropterrarium]

Hi Ray,

I'm right now looking into adding a DI column, so perfect timing.
- The 3000 gal rating, at what incoming TDS count? The amount of DI water is inverse proportional to the TDS count.
- Is it a single bed, mixed bed, or dual bed DI column?
- What do you do with the spent cartridge? Toss (is it legal for household waste? Got very cagey answer from another supplier, whom I do no longer consider). Repack by me? Repack by you?
- Fittings look like 1/4" RO tubing, correct?
- What is the pressure it can handle?
- What's the price? If my calculations are correct, about US$100.

[isurus79]

Yes, I'm also curious about the price.

[zxyqu]

Per Ray's website, the 2 stage is $65.00 and the 3 stage is $85.00.

[Eyebabe]

What is the entry and exit water pressure for the system?

[Ray]

They are disposable, mixed-bed cartridges.

Yes, 1/4" tubing.

They are rated at up to 100psi, flow rate about 1/2 gpm.

I have no idea what the pressure drop across the system is.

I have sold several and have gotten two pieces of feedback data: In 275 ppm/out 20 and another in 325/out 10. (Probably more of a meter variation than cleansing - they were new, so as was stated, the life of the second will likely be shorter.)

[Rivka]

Can you give a summary of the differences between RO and DI filtered water? Is one purer? In anyway that really matters to orchids? Why would someone use one over the other?

[Ray]

Reverse osmosis pushes water through a membrane in which the pores are engineered to exclude almost everything but the pure water. The flush water takes most of them away, extending the life of the membrane.

Deionization passes the water over a bed of resins that capture and hold the dissolved solids. There is no flushing, so they eventually will stop working, and have to be replaced.

Used individually, at similar purchase prices, the end result is about the same. More often than not, DI is added after RO for the ultimate in purification - but not as pure as distilled.

For orchids, it doesn't matter.

Let me add something about the DI system I mentioned above: The manufacturer had a typo in their specifications literature, and they do not have near the capacity claimed. They refunded my money on the components purchased, and I did likewise for the folks who bought the systems from me, when I discontinued making them.