COM-100 TDS Meter Question

[gdemos]

I run the AquaFX Octopus Model RO/DI Unit with a huge Axeon PVC 4040 Membrane.
I am not certain if the RO/DI Unit's integrated Booster Pump works correctly or not, I Am usually able to maintain 40 on the pressure gauge or slightly less when running.

The RO/DI Unit has an integrated 2 stage TDS Meter.
On the In, it usually settles down to less than 10 ppm.
On the Out, I like to see 0, when i start to see 2ppm I change the Carbon//Sediment//DI Resin, which for me is typicall every 2 months.

So I gather I would benefit a booster pump to feed this huge membrane.

To double check I purchased the COM-100 EC/TDS/Temp handheld meter. The meter is factory calibrated, I have not calibrated it otherwise.

I set the meter to NaCl ppm.
In a beaker of RO/DI water Im testing 3ppm

This is city water.

How will I benefit from a booster pump?
Is my 3ppm something to really worry about? I gather 0 is optimal. if it has an relevance, my Recent Triton test revealed no danger but not certain if their test has any reflection on TDS?

 

[fuzzone99]

For clarity, The 571 is for the RO/DI water and not the "city water". Correct?

If so.....the meter may be giving the erroneous reading in the RO water due to the very low conductivity of the solution. Try using table salt as a standard to check the meter. (1/2g in 1.0 L of RO/DI should be @500ppm on your meter)
This should tell you if the meter is functioning. Alternately, put the meter in the 571ppm solution, and then add a few grains of salt while swirling. You should see the meter respond accordingly. If it is just having trouble picking up the very low conductivity of the RO/DI it should start to read at very low number (5-20ppm?) with the addition of a few crystals of table salt. If the 571ppm is "true" then you will see the addition of more salt (NaCL) simply drive the 571 up from that point.

Very low conductivities are hard to read accurately with consumer grade meters. Not familiar with your meter, but if it is lab grade, you should be able to calibrate it and/or change the cell constant as needed.

Good Luck.

 

[fuzzone99]

For clarity,....when speaking of the calibration and cell constant. This constant cannot be changed as it is a function of the actual geometry of the cell. It can however, be checked by use of the calibration feature on a meter. Some meters may then allow for the factor to be adjusted accordingly based on the calibration. Sorry for any confusion.

 

[Randy Holmes-Farley]

I didn't see the numbers 571 anywhere?

 

[gdemos]

Sorry about that Randy , I had to edit my original post. I had a reading from my RO/DI Kalk top off at 571. I then tested pure RO/DI and got my reading of 3ppm.

So what is it about say kalk top off or tank water that makes the readings for me high like 571 for top off or "over reading" on tank water?

Secondly what will a larger/effective booster pump do to benefit production other than speed on a RODI unit?

 

[Randy Holmes-Farley]

Putting ions such as the calcium hydroxide from kalkwasser or any of the ions in seawater will boost the TDS.

The TDS of seawater is about 35000 ppm TDS, and saturated limewater (kalkwasser) is more than 5,000 ppm TDS. If you have the right meter, this is a perfect way to measure seawater salinity and limewater strength: by conductivity.

 

[Randy Holmes-Farley]

A booster pump may make it more efficient as well as faster, but the DI can make up for the efficiency concern.

 

[gdemos]

Ok I'm back to not understanding the COM-100 tds meter. Testing a beaker of new RODI straight out of my RODI unit showed .09 ppm tds NaCl. This is with fresh sediment, carbon and nuclear grade resin change. Couple hours later and I've got a full 55g batch of RODI. Testing this the meter is 472x10 at 68.2Deg F. I pull d a small cup, added a bit of iodized salt (like less than a pinch) and no change in reading. Help me understand? Thanks, Greg.

 

[gdemos]

A cup of 100deg F tap water tests 94.5. A cup of 65 F tap water reads 78.5

 

[Randy Holmes-Farley]

Measuring TDS outside of the system (not an inline filter) will not usually read 0 ppm TDS. CO2 from the air alone may push it to 1 ppm TDS.

You sure you mean 0.09 ppm TDS? Or is that a conductivity reading (uS/cm)?

 

[gdemos]

Yes .09 ppm on the com100 the set points allow for multiple read outs I chose ppm NaCl and obtained .09 reading with new RODI water collected in a beaker from my float switch. Then testing the barrell of full RODI I get 473x10. Now granted the barrel has some salt mix in it. Hydrometer says 1.003 (I almost emptied my salt mix but maybe a few gallons of 1.025 water remained the rest of the barrel is new RODI I have yet to salt up.

 

[Randy Holmes-Farley]

OK, then the 0.09 ppm TDS is as good as you'll get from RO/DI water measured after collection.

 

[Buckeye Hydro]

You're running a 4x40 membrane at 40 psi???

What most in this hobby would recognize as a "booster pump," for example an Aquatec 8800, is woefully inadequate for a 4x40 membrane. You'll want a motor and pump combo to run this membrane. If you want to contact us we can help you identify what you need.

3 gpm is typical minimum concentrate flow on a 4" membrane.

Russ

 

[Buckeye Hydro]

...what will a larger/effective booster pump do to benefit production other than speed on a RODI unit?

Your rejection will be better (98 to 99%)
Your production will be much faster
You won't foul/scale the membrane due to inadequate concentrate (waste water).

Russ

 

[gdemos]

Buckeye can you please shoot me a text to connect with you on a booster pump. Thanks: 401-578-6874

 

[Randy Holmes-Farley]

Your rejection will be better (98 to 99%)
Your production will be much faster
You won't foul/scale the membrane due to inadequate concentrate (waste water).

Russ

Why would a booster pump lead to less fouling?

If the efficiency is improved, the waste water will be more concentrated, which should lead to more fouling? Or is the overall efficiency reduced?

 

[Buckeye Hydro]

He is way under the minimum prescribed concentrate flow for a 4" element - he doesn't have enough water flowing through the membrane to adequately flush out what doesn't pass through the membrane.

What he needs is a pressure pump, rather than a booster pump - somewhere between 3/4 hp (110v) and 1 1/2 hp (220 v) - I'll have to check.

He's running at about 85% rejection now - should be up around 98.5+ with that membrane - not sure if the membrane is already scaled/fouled, or if that's just the best the membrane can do at 40 psi. I can normalize the data if I had it - and know for sure, but don't have any of the data.

The membrane should be run at 130 psi+, depending upon which 4x40 he has (gdemos do you know? HF1? HF4? HF5? HR1?). With the proper feedwater flow, pressure, and recovery (he's at 50% recovery now - way too high, especially given the feed flow), and at least the minimum concentrate flow, he should be good to go.

 

[gdemos]

Hey Russ here's some info. Appreciate the help!Good speaking with you. -Greg.

 

[Buckeye Hydro]

The spec's in the pics above are for the membrane housing - rather than for the membrane inside. If you don't have any of the original paperwork, you'll have pull the membrane out and look at the membrane label.

Russ

 

[gdemos]

Membra is Dow xle 4040. 2600 gpd