Chlorine, Chlorine dioxide, Bromine, Bleach or Ozone 3

[Brian2903]

We are in the stage of deciding what biocide to use for our new cooling tower in the power plant. The rate of water is around 60,000GPM, and we are using groundwater and discharge directly to the river close by.

Also, does any of you know this kind of device/treatment method?

http://www.clearwater-dolphin.com/current_business.htm

Please give me some pros and cons in the options that you have experience on.

Thank you very much!!

 

[bimr]

The dolphin device is one of those quack quack type of quackity quack devices. Don't waste your money. No point in discussing it any further. See the other posts.

http://www.eng-tips.com/viewthread.cfm?qid=146946&page=1

You are going to have to permit the CT discharge. Most places have limits on the type of disinfectant that can be discharged. Since you have not said where you are located, nothing futher can be added. Check the permit requiremnts.

You options are to use chorine (hypochlorite) and bromine. You will find that chlorine dioxide is so expensive that you can not afford to use it.

Chlorine will be the least expensive. If you want to go to the trouble of making a risk managment plan, than you can use chlorine.

Most power plants are now using hypochlorite. Some power plants are using bromine because it is thought that the combination of chlorine/bromine is more effective than just chlorine.

Ozone does not work because you get no residual disinfection in the CT.

 

[Brian2903]

Thanks bimr!! I'm located in Iowa, and I'll going to check the permit requirments tomorrow to make sure what chemicals I am allow to discharge.

Could you give me more advise on using hypochlorite? Why it is more commonly use in power plant now? what are the pros and cons of that? IS that just because it's the cheapest?

And how much better is using combination of chlorine/bromine?

One last thing is, I dont quit understand why we need residual for our system? and how much more expensive is ozone system in market comparing to chlorine system now?

Thank you very much for your help.

 

[bimr]

If you use chlorine, you will be required to develop and maintain a risk management plan. The RMP is going to cost anywhere from $50K to $100K to develop and then will be an ongoing expense to maintain. If you are close to urban developed areas, the RMP will have to address those areas.

For that reason, many chlorine users are moving to hypochlorite. Hypochlorite is a little more expensive and harder to handle, but less bother from a regulatory standpoint.

You can not use just bromine alone. Bromine is activated by chlorine. Some users claim that bromine works better. Not sure about that myself. It may be that some organisms develop a resistance to sustained application of a chemical. For that reason, many cooling towers vary the applications of chemicals.

The cooling tower is an ideal breeding ground for organism. Ozone will not provide a long lasting residual like you can get with chlorine. I do not know of a single power plant that uses ozone.

 

[Brian2903]

Thanks bimr, after I read the paper from DOE, our water temperature is around the edge of the recommended range, and the half life of ozone would be around 10-12mins. Since our water is directly discharge to the river next by. 10-12 mins half life should be enough for the water to travel from the tower to the river.

Moreover, since we still haven't start building chemical storage tanks and the related mechines for chlorine. I think the inital cost for ozone and chlorine would be around the same.

Please advise.

 

[Brian2903]

Does any one know what would be the disadvantages of using chlorine gas as cooling tower water treatment? Many Thanks !!

 

[stanier]

Suggest you read Comparison of UV Irradiation to Chlorination: Guidance for Achieving Optimal UV Performance DIsinfection WERF

Geoffrey D Stone FIMechE C.Eng;FIEust CP Eng

http://www.waterhammer.bigblog.com.au

 

[bimr]

Brian2903,,
Are you working on that Council Bluffs Power Plant? If so, I am somewhat surprised as the issue of chlorination should already have been addresses.

Further, I would expect that your process would be similiar to the existing power plant although the water quality from the wells is much worse than from the river.

 

[Brian2903]

Thanks stanier; however, is "Comparison of UV Irradiation to Chlorination: Guidance for Achieving Optimal UV Performance DIsinfection WERF" a book or one of the topic in this forum? It is because I couldn't have a topic related to the topic above in this forum. I am greatly appreciate that if you could send me the link if that's on the web.

Thanks bimr, I'm not working in Council Bluffs Power Plant. And I'm actually working in other end of Iowa--Clinton. Anyways, would you please give me some more details on the issue of chlorination.

 

[bimr]

Don't bother to waste your time looking up UV. It is not a technology that is appropriate for cooling towers.

You need to talk to a chemical supplier such as Betz, Dearborn or other who will be managing your cooling tower chemical treatment program. The chemical treatment program must take into account all aspects of your cooling tower, design and construction, water quality, etc. to properly manage the cooling tower system. Disinfection is just one component of it.

You can also get information from EPRI, the cooling tower institute, and the chlorine institue.

http://www.chlorineinstitute.org/

 

[oxilume]

Brian,

Contrary to BIMR's comment about UV lights, a well designed UV light system can control microorganism growth in cooling towers.

However, at a recirc rate of 60,000 gpm, capital expense may be prohibitive for using low pressure high output or medium pressure mercury vapor lamps.

If you are interested in watching the world's most powerful EMR system, fly to Houston.

The cost of the system is about what you would pay for one year's chlorine dioxide generation costs. I treated the cooling tower at Henry Hub (55,000 gpm recirc rate) with chlorine dioxide. Henry Hub is the Gas facility in Henry, Louisiana that sets the price for NG.




Todd

http://www.oxilume.com

 

[oxilume]

Brian,

You can see pictures of the PlasmaWhirl and ArcWhirl at:

http://www.plasmawhirl.com

The city of Houston is looking at the system for treating storm water runoff. (200 million gallons per day).

Todd

Todd

http://www.oxilume.com

 

[kbparham]

Mike, there are other important facts to consider when choosing a biocide. The choice may need to be dictated by your operating pH. When a cooling tower cycles water and CO2 flashes off -- alkalinity increases. Mineral Hardness increases as well. So it is important to know what pH range the cooling tower will operate. If the operating pH is expected to be over 8.0, Bromine -- or a Bromo-Chloro-DMH product would be a better choice than Chlorine products which lose effectiveness at higher pH.

For example; if your raw water pH is over 7.4, mineral hardness is over 90, and total alkalinity is 70+, and you expect to run 4.0+ cycles of concentration. You can bet your operating pH is going to be 8.4-8.6. Chlorine isn't the most effective choice for a biocide in this range -- it would take a lot more product to work as effectively at this pH than it would at a pH of 7.5.

I believe someone told you that ozone is no good because there would be no residual in the tower. That comment is only partially correct. With the kind of total flow you are talking about, you could circulate enough water through a sidestream ozone application to keep your system sparkling clean. The key is proper flow rate - venturi size, static mixers, etc... If you can flow enough water to circulate the entire system volume through the ozone application at least twice per day, you don't need or want residual ozone in your sump.

Residual biocide is important with slug dosing or periodic feed. You need to keep enough residual to make it to the next feed. If ORP is used to govern an ozone or traditional oxidizing biocide application, you apply only as much ozone/biocide as is required to keep the system clean and limit the system from keeping a residual in your sump, which like any oxidizing biocide - can cause corrosion. Using ORP setpoints to govern biocide feed allows your system to vary application of the biocide to match the biological load present in the system at a given time.

Ozone is an excellent choice for river/stream discharge - as it leaves NO RESIDUAL. Ozone can operate in a wide range of pH. Temperature is more an enemy for ozone than pH. In process systems with extremely high temp loads (much more than typical HVAC), ozone may not be the best choice.

Whatever you choose - the key to success is TIGHT CONTROL. Use a good controller, let it log data, pay attention to trends, and adjust the setpoints as necessary based on seasonal variances.

KBParham

 

[kbparham]

Brian -- you mentioned the LSI -- don't use it for a cycled tower - The LSI is great for raw water - but for CT cycled water use the PSI. Paul Puckorius is well respected in water treatment. He developed the PSI which is refined from the Ryznar, which is refined from the LSI. The PSI (Practical Scaling Index) comes much closer to actual scaling tendencies than LSI. With LSI - you actually tend to run a little corrosive and don't realize it.

Here's a reference:

http://www.awt.org/members/publications/analyst/2004/spring/the_ph_values.htm

Oh, and one other note -- Betz bought Osmonics (ozone) a couple of years back -- so even the big guys may think there is something to that ozone thing.

 

[podbelsek]

Finding some info about water disinfection and chlorine systems on:

http://www.cm-abw.si/WATER_DISINFECTION_consideration.htm

http://www.cm-abw.si/Scheme.htm

 

[gkielman]

Sorry I'm kind of late to this thread. As the other poster mentioned chlorine dioxide is more expensive than hypochlorite but it is also a more specific biocide than chlorine and ozone. Chlorine dioxide tends to react with carbon bonds so it reacts with the microbiology you are trying to control instead of everything else. It also provides a disinfection residual.

To counter the cost issues, chlorine dioxide is often used on cooling towers on a slug basis for only a couple of hours per day which lowers the cost to under competitive products. The same discharge rules to waterways apply to chlorine dioxide as chlorine so some neutralization on once through water would be required the same as it would to chlorine or hypochlorite.

Like ozone chlorine dioxide is an unstable gas and must me generated on site. The generation process is very simple and a basic generator can be purchased for under $10,000 from most vendors. There are two processes for its generation. One method is the chlorine chlorite reaction that requires sodium chlorite solution and gaseous chlorine, the other is sodium chlorite and HCl and sodium hypochlorite. In the latter method HCl and sodium hypochlorite are premixed in the chlorine dioxide generator to form chlorine which then reacts with the sodium chlorite. Both methods are chlorine / chlorite chemistry. The generator, precursor chemicals and storage tanks all add to the cost and complexity that must be considered.

Chlorine dioxide is a very strong disinfectant and very effective on cooling towers where it is used extensively. In the central California Valley, in the food processing industry, it is used with much success considering the high organic loading of the food products. On a continuum chlorine dioxide would be much closer to ozone than chlorine but its generation cost would be much less. But when you consider the cost of the precursor chemicals, tankage, containment, and the chlorine dioxide generator, there are lot of costs to be considered. Chlorine dioxide can be very effective and shouldn’t be ruled out. Many places have done the economics and are using it. But the cost of using it, its efficacy, and that of all the alternatives need to be considered which will keep you busy for a couple of days.

Gary Kielman
gkielmn@sabretechnologies.com