We have been dealing with high chlorine in our carbon tanks at one of our hospitals first thing in the morning. We have put in multiple tanks (replaced both at the same time). The city water hasn't changed chlorine levels. We thought we might be getting bacteria in the tanks and reading amonia coming off the bacteria, but we bleached our tanks really good and soaked the carbon and it was still high the next morning. These tanks do not have backflush heads and at this time we can't put them in. Still... we've had this system in place for years without this problem. We've tried everything except obviously the correct solution, so I'm needing some expert advice. Thanks, I'll be watching closely for your help.
Oh, this is a direct feed system, shut off at night.

Sounds like your getting a rebound of chlorine from the bleaching. I would switchout the carbons with fresh ones from your vendor or rebed the existing ones.

chiefa,

Are you getting a positive chlorine level from your second tank also or just the first?

We had a similar problem at one of our facilities and found that the staff were not letting the water system run long enough before drawing their sample. When the water sits stagnant at night, some of the chlorine that had been absorbed by the carbon is released back in to the water and is subsequently removed by the second tank.

If you are also getting a positive reading from the second tank I would agree with orc that you are getting a rebound from bleaching the tanks and not rinsing the bleach out completely.

Chuck

If I don't quite understand your situation. You say you were "reading ammonia". I am not familiar with such a reading. You then bleached your carbon tanks, because you surmised you had bacteria there. Is this a regular procedure at your unit? Subsequently, you had chlorine post carbon tanks? Did the bleach you used to clean the carbon tanks contribute to your chlorine readings post carbon tanks?

The first thing that comes to mind ( well, at least my mind) is your testing methodology. Have you tried either a different bottle of strips, or a different sealed packet of powder, or any other possible variation?

No on the rebound. Tanks are rinsed thoroughly and carbons are flushed for fines. FYI, chlorimines are chlorine and ammonia. Ammonia is released from bacteria, I learned that from Mark H. who is a top notch tech out in California, "Hi Mark". Anyway, I've never heard of the tanks releasing chlorine, but... I'll research that. Yes, both tanks are high. As far as testing, we don't use strips, we use a Colorimeter so the testing isn't an issue because we check the Colorimeter with standards every morning.

I would maybe try a different testing compound or brand. You might be getting false positives. It never hurts to rule out possibilities one by one in this type of situation.

ARE YOU GETTING YOUR WATER FROM A SURFACE SOURCE?? THE REASON I ASK IS SOMETIME'S THERE IS A BLOOM IN SURFACE WATER WHICH WHEN RELEASED THE CHLORINE CAN ATTACH IT SELF TO THE ORGANIC MATERIAL, WHEN THIS TAKES PLACE IT WILL GIVE YOU A FALSE CHLORINE READING. HAVE YOU CHECKED THE CHLOINE READING AFTER THE R.O.?? IS IT BELOW ACTION LEVEL??

Just how high are the readings? < or > 1.0? In some of our facilities, after many carbon tank re-beds we were still getting some residual chlorine out of both or all (4) tanks. We noticed that in most cases that when we got a 0.06-0.08 after the last corbon tank that the RO product water read 0.0 or < 0.02. Seeing how RO membranes reject chlorine compounds very poorly, what were we "straining" out of the water? It has been suggested, by folks a lot smarter than I am, that organics could be the problem. We have tried a single tank of lignite carbon upstream of all other carbon tanks and have had great results. We are still evaluating but are encouraged. The readings out of the 'regular' carbon tanks is negligible. We use the lignite in addition to our AAMI grade carbon so we are still "code".

Our "city" water comes in around 1.2 to 1.3 mg/l of total chlorine and we're getting readings around .13 out of both tanks. Our water comes from an aquafor to a facility about 35 miles away. Our free chlorine is 0.0 all the time by the time it gets to us. We have units in other parts of town from the same source (different pumping stations)and aren't seeing this. The realtime chlorine monitoring by the city is very steady. Our problem is in our tanks and I'm pretty sure we're going to have to start backwashing to rid ourselves of the problem. Our problem is we're sitting in a very small water room and I won't have the 10 gpm's I'll need to backwash. The booster is hooked up to the RO so that will need to be changed to a pressure switched pump in order to use auto heads. If it is organic, wouldn't this resolve our problem? Aren't you talking about another tank Mark? I already had to put these tanks in front of the RO in order to get my EBCT up to snuff. I just don't have the room for another tank. I could tell the staff to come in an hour earlier and flush them out everyday before using. I'm sure they'd be happy to.

Does your softener before the carbon tanks and regenerate every night?

Chlorine removal can be affected by many things. The following things have been known to reduce chlorine removal: high feed water pH, organics in the water, the city injecting orthophosphates or polyphosphates into the water, low feed water temperature, etc. Your profile does not say where you are from but I doubt if temperature is an issue right now unless your water room is very cold in the morning.

My first throught is old reagent for your colorimeter. As reagents get old, they will turn the water more pink. You might want to borrow some reagent from the other clinics in town. Old reagent would impact the chlorine reading from the Primary and Secondary Carbon Tank.

My second thought is there is something else in the water turning the solution pink. Bromine, iodine, ozone, manganese, and chromium can also react with the DPD chemicals to turn the solution pink. This would also affect the chlorine reading from the Primary and Secondary Carbon tanks. There are procedures on how to get rid of these interferences, but they are involved. The RO can take many of these other impurities out of the water, so your RO permeate sample should show low chlorine (which is the most important thing). The waste water from your RO should show higher chlorine. You may need to contact your city water supplier to see if the pumping stations feeding your clinic have these impurities.

Keep in mind that the colorimeter is looking for the amount of light the sample blocks. If the sample turns cloudy after adding the powder, this cloudiness will block light just like the pink color. Is the sample really pink as compared to the blank or is it just cloudy?

If these don't work, try a different carbon vendor. Or, you may need to use a different chlorine kit.

City water systems in the Northern Ohio area have been adding extra manganese lately in an attempt to clear up the cloudy water that resulted from recent flooding. When manganese oxidizes it turns pink.

Chiefa,
It's my understanding that the reason the carbon tanks are backwashed every night is to "wash" the activated charcoal granules and displace chlorine which has been captured by the charcoal all day long. I understand you don't backwash the tanks, and wouldn't this suggest a chlorine buid up in the tanks. On top of this normal accumulation of chlorine you treated the tanks to a bleaching, which only intensified the chlorine in the tanks. BTW, thanks for refreshing my mind about the ammonia. Good luck,
John

I understand that when you backwash the carbon tanks yhe carbon do not regenerates. The purpose of backwasing is to utilize better the carbon surface and to avoid channeling.
Am I right?