Randy - question about your source water

[patsfan1130]

I am 99% sure we get our tap from the same place and simply wanted to ask if you knew chloramines were added to our water? I have been able to get a hold of the 2008 MWRA report but nothing more recent. I have always used RO/DI but I do not have a unit the removes chloramines. My tanks seem fine. But now I am curious and thought I would ask the expert.

Thanks

[HighlandReefer]

You need to add a carbon block filter before the rodi unit to remove the chloramines and chlorine in city tap water. They all may use chloramines occationally & may switch back & forth between chlorine and it.

[HighlandReefer]

Randy goes into more details in this article:

Reverse Osmosis/Deionization Systems to Purify Tap Water for Reef Aquaria
http://reefkeeping.com/issues/2005-05/rhf/index.htm

From it:

"Carbon Filters

The next filter in line typically contains activated carbon. The primary purpose of this activated carbon is to break down the chlorine and chloramine in the tap water (Figure 2). If not removed, these compounds may damage the RO membrane. They will also pass through the remaining filters (RO and DI) fairly readily, and so can end up in the final filtered water.

Figure 2. A schematic representation of an activated carbon granule. Both chlorine
(as hypochlorite) and chloramine are catalytically broken down on the carbon surface.
The reactions within the activated carbon that break down these compounds rely on having enough active surface area for these catalytic reactions to take place. If the sediment filter is faulty, sediment may clog the activated carbon and reduce its ability to break the compounds down. Chlorine and its hydration product in water, hypochlorite ion (ClO-), are broken down into chloride ion (Cl-) and oxygen as shown in reactions 1 and 2 below. Equation 1 occurs at the water supply site where the water is chlorinated, and equation 2 takes place on the activated carbon in the RO/DI filter (where C* stands for the activated carbon and CO* stands for the activated carbon with an attached oxygen atom).

(1) Cl2 + H2O � OCl- + 2H+ + Cl-

(2) ClO- + C* � Cl- + CO*

Some of the oxidized activated carbon remains, and some breaks down to produce oxygen (O2):

(3) 2CO* � 2C* + O2

None of the products of reactions 2 or 3 is of concern to reef aquarists.

The reaction of chloramine (NH2Cl) on activated carbon is a bit more complicated, and produces ammonia (NH3), chloride (Cl-), and nitrogen gas (N2). Equations 4 and 5 show the processes.

(4) NH2Cl + H2O + C* � NH3 + Cl- + H+ + CO*

(5) 2NH2Cl + CO* � N2 + H2O+ 2H+ + 2Cl- + C*

Unlike the breakdown of chlorine, one of the byproducts of chloramine breakdown, specifically ammonia, is of significant concern to reef aquarists. Ammonia will pass fairly readily through an RO membrane (discussed later in this article), but if there is a DI system, it should effectively remove ammonia.

The carbon filters used in an RO/DI system will also remove certain organic chemicals from the water. Most of these are large enough not to pass through the RO membrane, but a few may be small enough to get through, yet still be reasonably well bound by the carbon. An example of something bound by the carbon that might otherwise get through the RO membrane is trichloromethane (CHCl3). In general, however, I do not believe that this binding is important for reef aquarium applications using normal potable water as the source.

Often the carbon filter also acts as a secondary sediment filter, and can therefore become clogged over time. A pressure drop at the RO membrane that is not solved by replacing the sediment filter may be due to a clogged carbon filter. In some cases, clogged filters may be cleared somewhat by backwashing, if the system permits reverse flow. Both carbon and sediment filters can become clogged with bacteria as well. In such a situation, some aquarists dry the filters out, thereby opening the pores, and then reusing them. I have never backwashed or dried any of my filters."

[patsfan1130]

Hmm..If I am reading that correctly my unit is removing chloramines. I am running 2 carbon blocks as well as sediment in front of the DI. I thought special cartidges were used specifically for chloramines. I guess you never really do know it all.

Thanks Cliff

[HighlandReefer]

Your welcome.

Good to hear you have the carbon block filters already installed.