If I am using biocide and chlorine is this necessary? 2

[mattatequity]

We operate a 22 story office building. It has two chillers and a looling tower. we have recently installed a new chemical feed system and controller (high tech might i add) and our water quality company has instructed us to use chlorine, molybdate, and a biocide. Is the chlorine necessary? We have been keeping it at about .5 ppm to 1.0 ppm and still have algae growing on the cooling fins and in the resevoir. Also what is a good way of controlling ORP (oxidation reduction potential)?

 

[cammax]

who is your water treatment contractor?

In a nutshell if you have any visable biological growth your sytem needs adjustments

 

[kbparham]

Maybe this will help:
Chlorine - oxidizing biocide
molybdate - corrosion inhibitor
Biocide - can be non-oxidizing (quat's iso's, glut's and others) or oxidizing (chlorine, bromine, ozone).

It's fairly traditional to recommend an alternating biocide program - one that alternates from oxidizing to non-oxidizing biocides would be acceptable. The purpose of this is to prevent biologicals in your system from building up resistance to any one biocide program.

ORP - an indicator of how much strength your system water has to oxidize contaminants.

Some oxidizing biocide programs use ORP setpoints to determine when to feed chemical rather than feeing it strictly on a timer basis. This approach prevents excessive spiking in ORP when oxidizers are fed in bulk, instead feeding chemical only when ORP falls below a specific setpoint -- and/or shutting off chemical feed when ORP reaches a specific setpoint.

Controlling ORP - would indicate a concern about oxidation - dissolved oxygen in the system water. The molybdate is there to protect the metals in the system from excess oxidation that might be caused by the chemicals fed to prevent biological growth. By using ORP setpoints to govern the feed of an oxidizing biocide program -- thus reducing ORP spikes, you are also enhancing corrosion protection provided by your molybdate.

The key to water treatment is TIGHT CONTROL. Set your operating parameters, use that high tech controller's datalogging feature to review water quality trends and discover if your operating parameters need adjustment.

You may find that due to the high temps of the summer and the tendency to grow algae that you need to run higher ORP in the summer months than in the winter, just to stay ahead of the algae. You can also choose a non-oxidizing biocide based on a particular problem - for example, poly-quats are known for being good with algae problems. If you notice an accumulation of sludge or bio-slime periodic addition of a bio-dispersant may be of assistance.

The alkalinity of your system should also govern your choice of biocide. The more alkaline your system, the more natural corrosion protection it has, but some biocides don't operate as well in alkaline conditions. Chlorine for example isn't very effective in alkaline systems with a pH over 8.0 - where Bromine works well in those conditions. Of course alkaline conditions while providing natural protection against corrosion, can lead to the formation of mineral scale - again the key is TIGHT CONTROL.

Hope this info helps,
KBParham

 

[coolingtowersrus]

A lot of great info KB - higher cooling tower pH circa 8.5 eliminates chlorine as a successful algae treatment.

We have had a lot of success using BCMDH tablets - these bromochloro hydantoin tablets dissolve slowly and offer good stability at higher pH. It can be fed in to the system as simply as using a floater in the tower basin or through the use of a properly fitted and sized brominator with an ORP controller feed set at 550 mv with upper limit 600mv.

Use a shock treatment to rid tower of current algae growth (about a gallon of 10% quat - quaternary ammonium chloride and be sure to have plenty silicone based antifoam on hand) One can use pressure hose to remove algae off the fins. The shock treatment and proper on-going treatment should keep it off.

I would share this info with your water treatment provider and suggest that this is really his job and that you want your cooling tower algae free by the end of the week.

 

[EdStainless]

May systems require periodic shocking (a high dose of biocide). Often you don't want to continiously expose your system of Cl levels needed to suppress all growth. So you run a level (like you do) that takes care of most growth and slows it down a lot. Then periodicly you hit it with higher dosage to kill everything. In the long run this uses less chemicals.

Your water treatment provider should help you sort this out.

= = = = = = = = = = = = = = = = = = = =
Rust never sleeps
Neither should your protection

http://www.trent-tube.com/contact/Tech_Assist.cfm

 

[kbparham]

EDSTAINLESS makes a good point. I agree that you don't want long-term exposure to high levels of the chloride ion.

I also agree with COOLINGTOWERSRUS that BCDMH is a ,ore versitle product with good results. I'm in the southeast -natural pH levels here run too high for effective cooling water treatment using chlorine without the use of acid. With BCDMH Bromine is the primary component, Chlorine is a very small component - only used to oxidize the Bromine. DMH is a stabilizer. Ozone can also be used to oxidize the Bromine sidestream, but a stabilizer is still needed to prevent the formation of bromates.

A Poly Quat would be a great product to shock the system with since Algae is stated to be a problem. The Poly Quat would need to be feed in dose to achieve the recommended 2-12 PPM active ingredient.

The makeup water in many cities in my part of the country has an ORP of over 600mv - simply due to pretreatment in order to meet drinking water standards. Thus, running an ORP with an upper limit of 600 wouldn't be terribly unreasonable for an oxidizing biocide feed program.

Your location, makeup water quality, the amount of sunlight your tower recieves, schedules, flow rates, low flow areas, the type of windborne debris you're exposed to, and any existing metalurgy/corrosion problems, will dictate what a successful water treatment program is for you. For example if you're using free cooling or have SWUD units - you'll need to set a schedule so that those systems periodically receive flow with treated water so that you don't end up with a MIC (Microbiologically Induced Corrosion)problem coming from units that were supposed to save money by improving energy efficiency. Interview several water treaters in your area, ask other facility managers who thay use and how they like them. A good water treater can design a program to work with whatever circumstances you present. A cookie cutter approach just isn't prudent considering the cost of the capital equipment involved.

 

[mattatequity]

My issue now is that my Conductivity is way too high and i have been bleeding for about 3 days. The city conductivity is hovering around 750 and i was pushing about 2800. My ORP is around 450-500mv and it is being controlled by the chlorine feed. I understand the chlorine in this set up isnt effective with my current ph (8.8-9.0) but the bacticide worked wonders with a 3 hour 50% feed last week. Can Chlorine affect my Cond? I havent fed any chlorine for about a week. Any advice. I have a ChemAqua rep coming out tomorrow but it just for the new controller set-up. The first rep didnt know squat about it. I also havent fed any inhibitor for about a week also. getting stumped on this!

 

[mbeychok]

mattatequity:

I think you would find it useful to read about preventing and controlling the growth of Legionella (the bacterium that causes Legionnaire's disease) in cooling tower systems at

http://en.wikipedia.org/wiki/Cooling_tower#Cooling_towers_and_Legionnaires.27_disease

.

In particular, read some of listed guidance documents in that article on that subject from governmental and non-governmental agencies and organizations, as well as from the Marley Company (one of the leading cooling tower manufacturers).

Milton Beychok
(Visit me at www.air-dispersion.com)
.

 

[cjw81]

A lot of concerns about this subject and for good reason.
Some of the information in the above posts are not exactly correct and in this aspect you must be exacting in your knowledge, develop a comprehensive plan and be meticulous in execution. First, get as much knowledge about the subject as possible, these forums are great for help, but they do not constitute an authorative, code or rulemaking body.I do not know what state you are in, but in New York, the DEC (Department of Enviornmental Conservation) requires a license (pesticide applicators) for you to even open the can. There are both corporate and PERSONAL fines involved
in violations. Don't take on responseability if you do not have respond-ability. Legionella is one small but important aspect of the dangers involved in the operation of microaerosolation of water. There are about twenty different varients of legionella (pneumophelia being only one). Go and get your licensed, they are critical in protecting both you and your Facility, and those that depend on your knowledge as the Engineer or operator of the equipment. Legionella is ubiquitous (everywhere!) It is in the air , ground and water in varying amounts. In teh tower you are biomisting the water droplets and it is then that it is believed to be more dangerous to humans. It is also the same condition you produce in the showerhead, and yes, there is great concern lately over that issue also. It is mainly when related to an immune compromised patient ( a sick patient with a weak immune system) that sickness or even death may be a result of these conditions. Go to the CDC (Center for Disease Control) website and your state's application protocols fo rteh the right info.