Nobody likes a smart .... (carbon filtration for home use)

[Nat N]

Hi all,
I need help! I have been involved in a discussion/argument about carbon filtration... I need to confirm that I am right (or wrong) in this discussion. I am not a chemist, unfortunately...
I really hope that Clive will see this post and will put things right as I am curious as well.
I bought a filter on Ebay – just activated carbon filter for home use - not that much for my aquariums but just for boiling the kettle for a cup of tea. Being what I am, I decided to use my TDS meter to see if the filtered water is any different from the tap water... And here it goes: tap water – TDS 173, filtered water – TDS 190. In my naivety, I thought that filters are there for, ermmm, filtering – so, the TDS would be lower in the filtered water. So, I sent a message to the seller on Ebay saying that I am not quite seeing the advantage of using the filter. They came back with a long-winded explanation that the filter is still working... My reaction was : ?????? I presume that pure H2O is just H2O, and anything dissolved in water increases TDS... So, I said this to that Ebay seller. However, they insist that the filter is still “filtering” (e.g. removing contaminants) even when the TDS meter cannot register this. Is this correct? (I omitted posting exact conversations with the Ebay seller – just to save time and space).
Am I right in thinking that this particular filter is useless in removing Chlorine and organic compounds or is the Ebay supplier right and I am totally wrong?

 

[Ian Holdich]

Carbon will increase tds from a filter like a brita etc etc, as they don't contain a micron filter, and you're actually adding a bit of carbon to the water. The carbon will remove chlorine and metals like copper, mercury, lead etc etc. the guys from eBay is correct I'm affraid. The best way of lowering tds is by using ro water. But tbh, with a tds of 173 I wouldn't be to bothered.

 

[Nat N]

Thanks Ian, My main "goal" is just to understand the way carbon filters work. I suspected myself that the increase of TDS in carbon filtered water is due to suspended particles of carbon media... Yes, our tap water is not too bad, really - but to be honest, I hoped that the filter would remove Chlorine and heavy metals AND organics and the result would be in slightly lower TDS than the original tap water... For my aquariums, I have a DI filter which shows zero TDS after filtering - I use it for topping up avaporation and sometimes for partial water changes. I only hope that filtered through carbon water will make a nicer cup of tea! By the way - is there a way of removing organics from the tap water by filtering whilst maintaining inorganic content (e.g. GH and KH)? Just curious, really...

 

[kirk]

you will be drinking high quality h20.!! When ever I hear h20 it reminds me of the water boy)

 

[ceg4048]

Nat,
Carbon is a selective ion/selective compound filter. If the ions it selects are not in the water of interest then there will be little to no effect of using the carbon. Also, people need to realize what carbon is. It's just coal dug out from the ground. The same stuff folks used to (or still do) burn in their fireplaces. Originally, the coal was a tree. Because the carbon in coal was once a living thing it is organic, and so when you put the coal in water there will be organic material that will leach from the coal. It is not the carbon that is dissolving, but the proteins and other material like potassium that is being washed back into solution. Furthermore, if the coal being used has not been "activated", then it is much less effective at removing those selected compounds. Activation is the technology of using high pressure gas or steam to sinter the coal, thereby creating a high surface area within the coal's physical structure. Therefore using a TDS measurement to determine the effectiveness of a carbon filter is a completely irrelevant exercise.

Please review JamesC's comments on the adsorption potential of specific compounds in the thread Does carbon remove trace elements? | UK Aquatic Plant Society

Cheers,

 

[niru]

Why would you want to boil tea in a tds reduced water? It will ayway increase the tanins!! The secret to a great tasting tea is using the real tap water with all its impurities.

Boiling water will anyway remove most dissolved gases, and the water company wouldnt let you drink tap water if its too much contaminated. Moreover, tea powder itself will have loads of other stuff that might contain these "toxic" substaces themselves.

Jokes aside, i guess most carbon filters work on basis of adsorption, i.e. they adsorb and hold on-to the contaminents till the filter material is saturated with these. Then you either replace the filter material (or find a way to clean them). Not sure if simple washing under the tap suffices since adsorption differs from a simple mesh filter. Moreover, once saturated, it will start leaching out these substances back in water. Plus carbon is a selective adsorber; guess there is a link somewhere from JamesC talking about activated carbo filteration.. Not sure if TDS is a good/appropriate measure for this. Hope Clive will chip in..

cheers

 

[niru]

Ok,

Clive has already posted....