Sulfate and Sodium Levels

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Cuzco_Brew

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Is it possible to estimate the sulfate and sodium levels in water?

I got a water report from the water authority however it doesn't have the levels of sulfate and sodium. It does have the level of salinity.

By knowing the salinity of the water can I make an assumption regarding the level of sulfates and sodium?

These are the numbers I got from my report.

Total Alkalinity - 141.82 mg/lt CaCO3
Total Hardness - 400 mg/lt CaCO3

Calcium - 157.11 mg/lt Ca++
Magnesium - 1.94 mg/lt Mg++
Chlorides - 124.96 mg/lt
Conductivity - 914 uS/cm
Total Dissolved Solids - 429 mg/lt
Salinity - 0.2%

I realize there are quite a few post already on understanding water reports, however I couldn't seem to find what I was looking for. If this has already been asked and answered, please point me in the right direction.

Thanks
Zac
 
No, I'm afraid not and, unfortunately, there are no simple (read involving inexpensive equipment) tests to measure either. So your best bet is to send $25 to an outfit that has the expensive equipment (Ward Labs or another lab) and let them do the measurement for you. OTOH the water authority very likely measures both of those. Perhaps a little persistence with them on the phone might get the answer.

One might be tempted to estimate the sodium from the salinity but I suspect that this number is derived, as is the TDS, from a conductivity measurement. This also might be something to ask the supplier about.
 
Thanks. Will try my luck with the Water Authority first. As I live in Peru sending a sample up to Ward Labs isn't really an option.

Based on the above report I am looking at getting an RO filter as the hardness is way up there.

Zac
 
OK, there is some conflicting data in the OP's post. Fortunately, there is some coordinated data too.

The likely water profile is:

Ca: 157 ppm
Mg: 2 ppm
Na: 0 ppm
HCO3: 172 ppm
SO4: 80 ppm
Cl: 125 ppm

The salinity refers to all ionic salts in the solution, not sodium. I'm pretty sure that AJ knows that and was just dozing. The total dissolved solids (TDS) from the profile above is 536 ppm, which differs markedly from the 429 ppm quoted. The conductivity equates to a TDS of about 585 ppm, so I'm pretty sure that the quoted TDS is wrong.

The sodium value is an estimate since there is not enough data on which to base an accurate assessment. If the TDS based on the conductivity (585) is to be believed, then the sodium is about 20 ppm and the sulfate jumps to 120 ppm.

Not really a great brewing water under most situations.

AJ: I believe you didn't notice that Zac was from Peru because his original location information header did not say Peru, it only said Cusco if I remember correctly. Yet another reason why members on this forum should be a little more forthcoming with information.
 
Thanks Martin. I will post a scan of the orignal report on Monday, I have it in the office. However it is in Spanish.

I realize with the water isn't great for brewing and am looking at RO filter to fix that. With hard water like this, would it be worth running it through a water softener before the RO filter?

AJ: Sorry about the confusion with my location. I have updated this to avoid this in the future. I appreciate all the help. Thanks!
 
Look at your water authority website and try to find a phone number for their (bio)chemist. If that's not on there, call the operator and try to get a hold of the chemist that way. Ask him/her if they record "secondary standards" and they can email the report to you.

The chemist at my water authority was super nice and I had the report within 5 minutes of me calling him. He even called back to make sure I got it and to tell me they do testing about every six months.
 
Pretreatment with an ion-exchange water softener will greatly extend the life of a RO system. I do that now. It does mean that the sodium concentration in the product water will be very slightly elevated, but not enough to be concerned with. The RO water profile shown in Bru'n Water represents a typical profile after water softener pretreatment (8 ppm Na).
 
The salinity refers to all ionic salts in the solution, not sodium.
Actually it refers to all the dissolved matter with the organics oxidized, the carbonate and bicarbonate converted to oxide the bromide and iodide replaced by equivalent amounts of chloride. IOW it's pretty complicated and difficult to measure directly and that's why it is almost universally measured (estimated) through conductivity. Wherein lies the rub.

I'm pretty sure that AJ knows that and was just dozing.

No, not dozing this time. As I said in the earlier post, I suspect that the TDS and salinity numbers were derived from the given conductivity measurement as salinity is almost never measured any other way and it is common practice to "measure" TDS with a conductivity meter. I have one in my RO unit. It measures conductivity and displays it as the mg/L sodium chloride which has that same conductivity.

The OP has a conductivity of 914 uS/cm. The art here is in determining how to process that number. If you are an oceanographer you want salinity and so divide the conductivity reading by the conductivity of a standard potassium chloride solution and insert the ratio into a fairly elaborate polynomial. That process is only valid down to S =2 but there is a correction which lets you go lower - another polynomial.

If you aren't an oceanographer you have lots of options, one of which is to use the extended polynomial or to do what most do and that is take half the conductivity and call it the TDS ; here 457. Whether this is an accurate measurement of the TDS depends on the water ion profile. Conductivity is proportional to the amount of ions dissolved but also to their mobilities.
Note OP's posted value of 429 which is pretty close but not equal to half his posted conductivity. Thus suggests that the lab may use a sligthly different factor based on familiarity with their water.

Another approach is to convert the conductivity reading to the amount of sodium chloride that has the same conductivity as is done in the meter on my RO unit. A 1000 uS/cm NaCl solution contains 491 mg/L NaCl so that a 914 uS/cm solution would contain about 448 mg/L NaCl. Again pretty close to the reported TDS with the disparity possibly explained by the fact that the three ways of processing the conductivity reading are by no means the only ways. Most conductivity meters give the user the option of inserting his own calibration constants and have programmed within them one or more of these methods in which the user can change the coefficients dependent on his particular application.

Now what apparently does not compute here is the salinity listed as 0.2%. But though OP wrote 0.2 % (percent) he meant to write 0.2 permil. The permil sign looks like a percent sign except that there are 2 0's to the right of the slash (0/00 not 0/0) (Per mil - Wikipedia, the free encyclopedia). If I stick my conductivity probe in 1000 uS/cm standard and put it in salinity mode it reads 0.5 per mil consistent with the common practice of calling TDS 0.5 times the conductivity - unless I change the meter's factor. If I stick the 914 uS/cm number into the practical salinity formula (the one that compares conductivity to a standard KCl solution) I can only get down to 0.2 permil if I use a temperature close to 0 °C. At 20 C I get 0.41 per mil - close to the value assumed by taking one half.

It is because of all this variability that I suggested that a conversation with the lab might be of some help.

The sodium value is an estimate since there is not enough data on which to base an accurate assessment.

As the TDS and salinity numbers (which latter is inconsistent with the conductivity) depend only on the conductivity and some unknown model connecting conductivity to TDS I don't see how any conclusion, other than a crude bound, could be drawn concerning the sodium level.

AJ: I believe you didn't notice that Zac was from Peru ..

True, I was dozing there.
 
Ok here is the water report I got from my water authority here in Cusco (Peru).
Water Report

AJ, the Salinity reading still looks like a "%" to me not permil symbol. I will try and contact the water authority to get the sulfate and sodium levels today, but I am not holding my breath. Either way I think I am going to have to look into water treatment options.

Thanks
Zac
 
Yes, looks like a percent sign to me too but that leaves a major disconnect. Salinity is reported permil. I note that they clearly state that their procedures are taken from Standard Methods for the Analysis of Water and Waste Water - the bible in North, and apparently South America as well. Standard Methods description of salinity is the usual one in which the water's conductivity is compared to that of a potassium chloride solution of particular strength which is defined as having salinity of 35 per mil (which is approximately that of the ocean). Results are expressed in per mil. If the salinity were really 0,2% (2 per mil) it would have a conductivity of about 4500 and probably be unpleasant to drink let alone brew with. There must be some simple error. Perhaps they meant "0,02%" or the printer couldn't set the per mil symbol properly.
 
Follow up question.

AJ you mentioned in another thread that a water softener used before a RO filter can help avoid overloading the RO membrane. As well Martin mentioned in this thread, that a water softener can also help to extend the life of the RO membrane.

With water like I have here (see report in first post), how likely is it that I would overload the membrane if I didn't use a water softener? Or how soon would I need to replace the RO membrane?

I ask as water softeners down here are all imported from the US or elsewhere and go for about double what they do up in the US. I do intend to get a water softener at some stage. However the price is a bit out of reach for the moment, so if I can get by with out one for the time being then great. If not, I will need to find the cash.

Any advice is appreciated.
Thanks
Zac
 
Unfortunately, the consumer grade membrane units that you are likely to use in home use do not have design software associated with them. I have RO design aids from several of the commercial RO vendors that I deal with on a professional basis, but they don't deal with the type of low-pressure and high cross-flow that the consumer products use. I would not worry too much about the fouling potential. The rule of thumb life of these units is about a year. Then the membrane cartridge is replaced along with the inlet side carbon filter.
 
The question is one of deposition of the "limiting salt" on the membrane which would tend to clog it. In your case the limiting salt will be calcium carbonate. The softeners remove the calcium so no carbonate forms - the limiting salt will be something else.

FWIW I had 2 GE units - very inexpensive here in the US one of which I had in service for 7 years and the other for about 3. They were used exclusively for brewing so perhaps that is why. My water has calcium hardness of about 80 ppm and alkalinity of about 80 ppm both as CaCO3 - both much lower than yours . That amounts hardness of about 4.7 grains per gallon and as I recall, these units were specified for up to 20 or a bit over. IOW you (at 22 gpg) are at or close to the limits. Specifications or no, the more hardness and alkalinity (temporary hardness) in the water the faster the limestone will build up.

Now the commercial membranes can be cleaned with acid and I don't see any reason why the smaller cartridges used in home units couldn't be cleaned this way as well. Perhaps Martin can comment on that. If your experience matches mine it should be a couple of years before you notice output dropping off (I never did) and at that point you can either throw away the membrane and replace it or try to clean it with acid. If I'm dead wrong and that ruins the membrane you are not any worse off (except for the cost of a little acid) than if you didn't try and you might get a good bit more life out of the thing.

Martin alluded to the reason these small units are so tollerant: the low recovery rate typically 25% percent meaning that for every liter processed 3 go down the drain (as opposed to the fancier units where recoveries can be 50% or higher). I mention this because dependent on the nature and cost of your water supply this could be at issue.
 
Thanks Martin and AJ.

This the RO unit I am looking at, it is a Made in China job. However I don't have a lot of other options in my price range.

I can't find a lot of information on that unit online and the supplier has even less. I have no idea of the recovery rate, but water is pretty cheap down here.

I was also thinking I could maybe rig up a collection tank for the waste water, so I could re use this for running through my immersion chiller, try and cut down on water use that way.
 
Well, it does have a nice shelf and pressure gauge....

Collecting the concentrate for other use is a good idea but keep in mind that it will be even richer in minerals than the feed - by about 33% if the recovery is 25%.
 
:D Yeah the nice shelf is a definite selling point...

Thanks! When I get it and have it installed, I'll try and get a sample of the water tested to see how it's doing.
 
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