By Richard Young, Aquatic Commercial

Many indoor pools, even with excellent water chemistry, suffer from persistent “chloramine odor”. chloramines (“combined chlorine”) develop from poor or incomplete oxidation levels in pools with moderate to high organic loading (sweat, saliva, urine, etc.). Oxidation is the process of chemically breaking down organics with “free chlorine” (hypo-chlorous acid, HOCl). In an ideal situation, this active chlorine compounds oxidize the organics and many of the by-products are carried away (easy in an outdoor pool) via air circulation.

Air handling systems often fall short of providing ample air turnovers with fresh air to remove the by-products developed during the oxidation process. As result, partially oxidized compounds return to the pool water forming new chloramines with many literally “hanging” in the air. Eye burn, skin irritation and the chloramine odor often prevail. In short, swimming in the pool, soaking in the spa, or just being in the natatorium becomes unpleasant and uninviting.

In addition, very heavily used outdoor pools (such as public spas) also develop chronic chloramine problems, as the amount of organics introduced exceeds the oxidation potential of the chlorine residual – even 3+ PPM!.

So, what can be done?

First of all, prevention is the key. That is, we want to insure that ample oxidation is maintained (a combination of ample free chlorine, proper pH values, and minimal stabilizer) by properly monitoring and dosing the pool or spa. That almost always means employing automation, controlling properly sized feeders). Most pools can preclude the formation of chloramine residuals through diligent chlorination with wisely-chosen, contantly maintained break point.

Once chloramines form, however, there are basically five means of removing them.

1. Super-chlorination –raising the active chlorine residual to 10 times the
amount of chloramine present. (This only works well if there is ample air circulation.
2. Drain and refill the pool or spa
3. Frequently add expensive non-chlorine shock
4. Install a large, full-stream corona-discharge ozone system
5. Install a medium pressure UV. System

Let’s look at the various options…

1. Super-chlorination: This is the traditional process used to eliminate
chloramines. It involves testing for free chlorine and total chlorine, then calculating the combine chlorine (chloramine residual by subtracting the two. That residual is then multiplied by 10, resulting in the target PPM increase needed in chlorine residual in order to oxidize the chloramines. Air circulation and exchange remains critical.

NOTES: 1. The pool must be closed during this procedure.
2. Ample chlorine and pH-adjusting chemicals must be added quickly
3. De-chlorination might be needed
4. Operating personnel need to schedule 2 to 3 hours
For the job, usually with a day’s closure.

2. Drain and re-fill: This is costly and time prohibited. Heated, chlorinated,
pH adjusted, total-alkalinity adjusted, calcium-hardness adjusted, filtered water is expensive! Many facilities even pay for waste-water discharges. And the costs and timeto drain and refill are unrealistic.

3The use of non-chlorine shock: Potassium mono-per sulfate has long been used as an alternate to super-chlorination. The actual chemical is rather Expensive, and any residual in the pool water is displayed as “combined chlorine” on test kits. Operating personnel must purchase, store and handle yet another chemical. Finally,only a partial chloramine
reduction is realized.

4Large corona discharge ozone systems have proven to be very useful in
decreasing chloramines. These systems require a rather large equipment footprint with an ozone generator, boost pump, venture and substantial contact chamber. Ozone is classified as a very hazardous gas and special ventilation requirements, gas detectors, warning signs, emergency shut- down switches and permits are required. Annual, costly maintenance procedures are also required.

5. Medium pressure UV. Developed for municipal water treatment, “medium pressure” ultra-violet light, not to be confused with common low- pressure UV systems, has proven to be excellent not only as a sanitizer
but it readily destroys organic chlorine compounds (chloramines) on the fly, in circulation water returning to the
indoor pools and spas, thereby eliminating almost all chloramine odor.

Simply put, the high-intensity, controlled spectrum UV light uses photolysis and photo-oxidative reactions to destroy virtually all residuals of Mono-, Di- and Tri-chloramines and most other pathogens, including cryptosporidium
and Giardia. There is little to no maintenance, with lamps often operating
up to 8,000 hours before replacement is required (about once a year).

While some promote conventional low-pressure UV, the spectrum of UV light only affects mono-chloramine so the more offensive chloramine residuals remain.

OUTPUT COMPARISON OF LOW VS MEDIUM PRESSURE UV.

Low Pressure UV provides two frequencies: 185 & 254 nm only
Medium Pressure UV covers two ranges: 175-182 & 187 through 280 nm Conclusion: Medium Pressure UV covers extensively more of both the oxidation and disinfection regions.

Of all the processes, medium pressure UV has emerged as the most complete and most effective way to eliminate chloramine and chloramine odor. NSF listing is strongly recommended. The actual power required is minimal, however, most systems operate on 3-phase power to gain the intensity required. Bulb replacement is usually completed annually. Facilities report dramatic improvements in both water and air quality.