What do you do with your waste water?

Curious if anybody's house is on a septic system? Do you still run your waste water down the drain? I would prefer not to add any more water through my septic tank than necessary. Plus, I live in an area that gets snow and freezes in the winter, so plumbing my waste outside could be a problem. Any thoughts?? TIA
 
d0ughb0y said:
1000ml -> [membrane 1] -> 800ml waste -> [membrane 2]->600 waste
_____________________-> 200ml good ________________->200 good
(ignore the underscore, that is just there to position the text in the right place)

so membrane 1 is operating at 1:4 and membrane 2 is operating at 1:3 via the 550ml/min flow restrictor which is what typically comes with a 75GPD RODI systems. The minimum flow ratio for the membrane is 1:3, that is why 75RODI systems come with 550ML restrictors instead of 800ML restrictors.

so in the above illustration, you get 400ml good water to 600ml waste water, hence I said in my earlier post the ratio is 2:3.

The series configuration is not the same as simply having one long 75gpd membrane as you described.

So the original restrictor does not need to be changed.
Click to expand...

placing a second membrane downstream of a flow restrictor ADDS restriction, you you can't figure out the waste to permaete ratio as I think you are here.
 
wouldn't the restriction added on the "waste" side be minimal (or at least a good portion of water pressure will still be present) as it is pretty much free flowing (I have seen the flow when I flush, and it is strong) ? If it was on the good water side, I'd say yes, the pressure there will definitely be lower.

maybe you can explain how placing two 75gpd membrane in series will be equivalent to having a long 150gpd membrane another way, since I did not follow the way you explained it the first time, or rather, it did not make sense to me. As it is physically impossible for the second membrane to get the same input volume as the first membrane which is what is implied by saying it is one single membrane.
 
As water travels through a spiral wound RO element, some of the water makes its way through the semi-permeable RO membrane and ends up inside the center tube. What was once the feedwater continually is loosing some nearly pure h2o, and dissolved solids in the feedwater begin to concentrate (as an aside - that's why "waste water" is more appropriately referred to as "concentrate"). The further the concentrate moves along the element, the more h20 is extracted from it and the more concentrated the dissolved solids become. Regardless if the element is 2 feet long to start with, of if it has a break in the middle where the concentrate temporarily enters some tubing, the concentrate continues to move along the element and pure water is continually extracted.

Russ
 
I thought if you had two 75gpd membranes you used a restrictor sized for a 150 gpd unit?? My understanding is that you don't save any water, you are just making it twice as fast.
 
I have a well, I have always noticed that the waste water is the same ppm as the tap. So all the waste water is deposited directly back to the well.

With wells you sometimes run into the problem of draining the well, depending on how much water needed. In this case you can run the waste to a reservoir then pump it back into your ro. unit while wasting it back to the same res. The res. water will slowly deplete itself. You can do this untill the res water is 1000 ppm or higher.

I've had great success with this method. Using well water that started as 150-300 ppm. producing ro water 10-20 ppm out of a 250g res. with 1000 ppm waste water in it. with an inexpensive 2stage ro. I've experimeented up to 2000 ppm in the res. and the ppm is still15-20 but it takes a toll on your pre and sed. filters.

Anyhow it significantly reduces the waste to water ratio. The last res. recirc. I set up was money, parameters never changed and this is what I came up with.
Tap water, 100ppm never changed
500 gallon res.
Hydropharm 2stage ro. produced 9-12 ppm from tap.
With the 500g res full of 100ppm water we could drain it to 50g with no significant change in ro water ppm. sometimes 0ppm diff. sometimes a rise of 5. The water in the res. oddly enough is around 1000 ppm. If you drain the res to 25g. the ppm will be around 2000. and the ro water will be around 30ppm. But again that takes a toll on your filters. So I would waste the water at 50g. or 10percent of res. Makes 450 gallons, wastes 50 gallons.
 
That depends on the ppm of the water to start with, oddly enough. If your water is 400 or more to start. The ppm of the waste water will be the same. As you aproach 100 ppm to start the waste water is 20% or more dirty. Probably more.

I worked at a warehouse in boulder, where the ppm of the tap was 700-850! It said dont drink tap water on all the mirrors in the bathrooms. The waste water from the ro was regularly cleaner than the tap water. I think it is because the carbon, sed, and prefilters removed some of the ppm.

Also the water restriction valve on the waste line was removed with the res. set up. This makes the unit more like 4/1 I believe. Allowing for cleaner waste water, although it really doesnt matter, restriction valve or not.
 
Let's back up a little here - there seems to be some misunderstanding. Maybe some definitions specific to common systems used in this hobby would help.

1. Feedwater: The water, typically tap water, supplied to and RO or RODI system that includes prefilters.

2. RO water: Also know as "permeate" - this is the purified water that exits an RO membrane.

3. Waste Water: Also known as "concentrate" - this can be thought of at the remnants of the feedwater after the permeate (nearly pure water) has been extracted by the RO membrane. If the RO is configured to produce 4 parts concentrate to every 1 part permeate, we say the system has a 20% recovery - meaning that 20% (1 / 5) of the feedwater exits the RO as permeate.

Because the purpose of an RO membrane is to produce permeate, and assuming the RO membrane is in working order and is in a properly fabricated/configured system, by definition, and regardless of the TDS in the feedwater, the TDS in the concentrate is always higher than the TDS in the feedwater.

Russ
 
I was wondering. Some people said they run the waste water to their koi ponds. Are you sure? Are you having a good healthy pond? Would it be that same as using your waste water for a fresh aquarium or am I not thinking straight?
 
Realize that the quality of the waste water varies all over the board, just like the quality of the feedwater does from place to place in the US.

Russ
 
I use mine to fill my holding tank for koi in basement and then during the summer it runs to the ponds.
 
L8ndeb said:
Curious if anybody's house is on a septic system? Do you still run your waste water down the drain? I would prefer not to add any more water through my septic tank than necessary. Plus, I live in an area that gets snow and freezes in the winter, so plumbing my waste outside could be a problem. Any thoughts?? TIA
Click to expand...

Considering my septic system goes through thousands of gallons I don't consider my waste water a significant addition. Neither is my waste aquarium water at 5 gal/week.
 
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