Dear Hans,

Yes, the best solution for you is the use of an activated carbon filter.

With my best regards

Prof. Bachir ACHOUR

Activated carbon is a robust solution. For laboratory scale the type of activated carbon is not very important. If the biofilm in the flow cells is supposed to grow on the NOM in the tap water you need to consider that the activated carbon will also remove some of this.

An alternative method to remove chlorine is to reduce it with hydrogen peroxide. A low residual concentration of this is not harmfull to biofilms.

Another alternative option is to use the sodium ascorbate form of vitamin C to quench residual oxidants in a fast reaction.    

Altough an activated carbon filter is doing the job it is also introducing problems. Especialy fresh activated carbon can increase the pH substancialy and also remove oxigen. This will influence your experiment with biofilms. There are acid-washed activated carbons on the market or you can acid wash yourself. So the pH effect is minimal. But I think the filter will always remove oxigen although the effect is the largest with fresh carbon.

Some interesting  links (home brewing, cooking, health sites, & certain herbs found in some Amsterdam shops!!)  to removing chlorine (Activated carbon filtration is first choice and aeration) below:

http://www.sfwater.org/modules/showdocument.aspx?documentid=4125

http://www.hightimes.com/read/grow-hack-how-remove-chlorine-tap-water

http://homebrew.stackexchange.com/questions/3447/what-are-the-various-ways-to-remove-chlorine-chloramine-from-tap-water

http://www.freedrinkingwater.com/whole-house/water-filter-knowledge-base/why-remove-chlorine-from-whole-house.htm

http://alifeunprocessed.blogspot.com/2012/02/get-chlorine-out.html

http://berkeywaterfilterinfo.com/remove-chlorine-and-chloramine/

http://blog.watertech.com/removing-chlorine-and-chloramine-from-tap-water/

http://thepeopleschemist.com/best-fluoride-filter-how-to-remove-all-fluoride-and-chlorine-compounds-from-tap-water/

Hans there might be a different solution path to consider. Instead of having to monitor and regenerate/replace activated carbon media, why not just deal with the bacterial growth instead? Follow this link,  http://tsinnovations.com.au/, and discuss your process issue at lab level, and I suggest, you can discuss the issue of scale up to commercial/industrial production of the chemistry additionally. Dr. Alex Taube is your point of contact: [email protected]. If you still believe AC is the best route, let me know and I'll link you to a colleague in Hawaii that can direct you to the best outcome.

Regards,

Thomas Cripe

Dear Thomas,

We like to remove the chlorine from the water to enhance the microbial growth in our monitor studies. The water is reverse osmosis produced water which is after remineralisation distributed as drinking water. So the water quality is very high, meaning that regeneration of the carbon filter is limited. The idea is to place two carbon filter in series.

Best regards, Hans

Dear Mohan,

I am not familiar with chlorine removal using aeration. How would this work/do you have some directions to explore this in more detail?

Best regards, Hans  

Dear Bas,

Thanks. The water is quite clean (see the reply to Thomas), so I would not expect beforehand that the water could become anaerobic. We plan to test two carbon filters in series and monitor the feed and outlet water oxygen concentration and pH.

Best regards, Hans   

Dear Florian,

Thanks. Could dosage of such compounds lead to additional bacterial growth?

Best regards, Hans  

Dear Henrik,

Nice consideration to use H2O2. I would expect that even low H2O2 concentrations would impact microbial growth. For now we aim to test carbon filters (as you first suggested) and keep H2O2 in mind.

Best regards, Hans  

Dear Hans,

The removal of chlorine by hydrogen peroxide is sometimes used by laboratories and in ornamental fish keeping (for aquaria, fish ponds, pet shops) that uses tap water for replacing water in their systems. For these it is important to protect the nitrifiers in the system from chlorine exposure.

Hydrogen peroxide disinfection requires 100-1000 mg/L to give a similar effect to 0.1 mg/L Cl2. Compared to this I think you can destruct 0.5 mg/L Cl2 by adding just 2 mg/L H2O2.

If the loss of NOM in the carbon filter is not a problem for your experiment, I think a GAC column is the easiest and most robust solution.

Hi Hans,

While I haven't tried it myself, I know some people use ascorbic acid and sodium ascorbate for dechlorination. Remember, the former will impact your pH and thus microbial growth. So, you could try sodium ascorbate.   

You could try UV if you have access to a flow-through unit that can produce sufficient fluence/dose-I'm guessing but probably in the 500 mJ/cm2 range. There may be small system/POE suppliers that have such products.

Hans - Aeration by cascade, packed column or air diffusion but units may be too large for the lab studies. However, aeration can depend on your tap water pH and also its source - ground water with precursors like H2S, Fe, Mn, or surface water which can have THM precursors. Simple aeration using an air injector and diffuser can work for small volumes closer to a acidic pHeven though research  shows that not all residual chlorine is removed especially if the pH is above 8.3 where the less volatile hypochlorite ion predominates over the hypochlorous acid. See some links below for a wider perspective, one is a recent thesis with a bench scale air stripping unit:

http://hendryutilities.com/plus/docs/Chlorine_Removal_Report_Final_080817.pdf

http://epa.ohio.gov/Portals/28/documents/pws/Aeration_WhitePaper_Final.pdf

http://etd.fcla.edu/CF/CFE0005715/Cassandra_Smith_Thesis_Spring_2015_Final_Draft.pdf

http://www.paxwater.com/science-of-aeration

https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=12&cad=rja&uact=8&ved=0CDwQFjABOApqFQoTCO7L5rGj1sgCFYZsHgod2kQHCA&url=https%3A%2F%2Fetda.libraries.psu.edu%2Fpaper%2F8194%2F3498&usg=AFQjCNF1dCKVvQvy8mhkq-DPvnuNgpFU5g&bvm=bv.105814755,d.dmo

http://www.nativefishlab.net/library/textpdf/17120.pdf

http://extension.uga.edu/publications/detail.cfm?number=B939

http://extension.uga.edu/publications/detail.cfm?number=C858-15

http://www.who.int/household_water/research/HWTS_impacts_on_weakened_immunity.pdf

Hi, Hans:

100L/H  might mean about 28 mls/second ;  I'd like to suggest that you use

three activated carbon filters in series. This would make sure that the chlorine

of 0.5 mg/L is totally removed. You can later remove the first one, pushing

the second one into the first position and the third one into the second position,

and put in a fresh filter in the third position, etc.

Good luck to you!

Eugene Lo Wei

Dear Eugene,

Great, we both had the same idea! Another advantage of having carbon filters in series could be that the final outlet water may be seeded with some bacteria from the last carbon filter. 

Best regards, Hans  

Dear Rasha,

Nice idea to dose ascorbic acid and sodium ascorbate. Just like Florian his response.

Dear William,

Nice idea as well. We have access to UV equipment. Would expect that UV does not increase the feed water biodegradable nutrient concentration to much, since our tap water was made by seawater desalination using reverse osmosis membranes and remineralized before distribution.

I did not think of these options and will keep them in mind when the activated carbon filtration is not effective for our studies. For now carbon filtration is preferred since it is most simple and robust solution.

The idea is to place first 1 cartridge filter (5 or 10 um pore size) followed by 2 or 3 carbon filters in series

Best regards, Hans  

Dear all,

Many thanks for the feedback so far.

Remaining questions are:

- Will carbon particles be washed out of the carbon filter with the passing water (and deposit in the monitors used for biofilm studies? If this happens, it may be of short duration only.  If it is a lot or for a long time than a solution needs to be found to prevent carbon wash out.

- How to know easily when a carbon filter needs to be replaced. The carbon filter housings we just ordered are non-transparent.

The idea for our research is to place first 1 cartridge filter (5 or 10 um pore size) followed by 2 or 3 carbon filters in series. Expect that will be suitable to remove larger sized particles (if present) and free chlorine from the water.feeding the monitors for biofilm studies.

Best regards, Hans

Hi, Hans:

If you are unsure about the filtered water from the activated carbon filtration,

you might try using a reverse osmosis filter following it, rejecting a small amount

of filtered water. Any bacteria or carbon particles would be eliminated this way.

Good luck!

Eugene Lo Wei

Put another cartridge filter after the AC or get a solid block type AC filters or layered ceramic filters. One claims flow rates may cause some units to let some water untreated, so sizing should be looked at too. Was at a trade show  recently and there were a lot of them selling AC and cartridge filter systems -one of them was also selling magnetic demineralizers to attach to your tap pipes - did not see any test data to show its effectiveness. Also a German firm selling activated carbon made from coconut husk from Indonesia. Any some more links and there is a small aeration system too:

http://www.heartspring.net/water_filters_guide.html

http://www.purewateroccasional.net/hwsedimentfilter.html

http://www.purewateroccasional.net/hwaerationtank.html

http://www.extension.org/pages/31567/drinking-water-treatment-activated-carbon-filter#.Viqb78LD85s

http://www.water4life.eu/downloads/Functioning%20ceramic%20filter%20candles.pdf

There's likely no need to replace GAC (or have filters in series) if you are only using it to remove chlorine. Chlorine is not adsorbed like NOM, it is catalyzed to chloride at the surface of the GAC. Maybe I've missed something in this discussion but I thought I'd point this out just in case. It is possible though that you might have to occasionally remove the GAC to deal with excess headloss (unless operating in upflow mode). As for carbon fines, if you initially clean the GAC properly and the hydraulic loading rate isn't terribly high you shouldn't have a problem with fines (at least in downflow mode). The carbon fines are usually only produced with the harsh conditions associated with backwashing which it seems you won't be doing. (For bench or pilot contactors/filters treating turbid waters we just remove the carbon and rinse it out in a bucket and replace it.)

Dear Willliam,

Thanks. The most important is to remove residual chlorine, which is expected to be completely removed after passing 1 or 2 of the GAC filters placed in series, based on the reactions received on this question on Researchgate.

Another objective is to increase the water bacteria cell number. The RO produced water has very low bacterial numbers. The 3rd GAC filter would preferably have some bacterial growth seeding the GAC outlet water, which is feed to the monitors for biofilm studies.

To elevate bacterial cell numbers in the water feeding the monitor, we have a preference not to dose biodegrable nutrients, but consider the extra GAC filter. Maybe a water storage vessel with aeration (bringing in bacteria from the air and increasing the residence time) could be considered between the 3 GAC filter and the monitors. The reason for aeration is not to increase the oxygen concentration of the water (the water already contains oxygen).

Best regards, Hans

Use activated carbon reader can be an alternative but can occur microbial contamination. I think you can test dose hydrogen peroxide for chlorine.

Would dosage of ascorbic acid also be difficult? I think it would introduce less change in bacterial population than GAC filtration and even enhanced aeration. With good dosage there will be almost no change in water composition.

you can add sodium thiosulphate which is regularly used to neutralise oxidising biocides  in microbiological sample bottles without adversely affecting recovery

For the removal of residual chlorine in drinking water, activated carbon/ activated alumina may be a good option. after doing experiment chemical analysis is required,