Chlorination 2

[vsmech]

Is anybody aware of breakdown of Sod Hypochlorite under high ambient temperatures. The site where we want to use sod hypo for chlorination is between 35 to 60 °C. Is there a max temp. upto which sod hypo cold be used?

 

[quark]

Free chlorine is very volatile and even if kept at atmospheric temperature it evaporates. If you can mix the sodium hypochlorite solution below the water surface or directly into the pipeline (plenty of venturis are available) then you won't have much problem.

 

[vsmech]

Dosing the chemical is not an issue. Actually, the issue is the hypo brekdown under high ambient temperatures while in storage,say for a week.
We plan to buy commercial hypo, store it in tanks (1 week capacity), and dose it in pipelines or water storage tanks with dosing pumps.
With temp being 35-60 C, is hypo a good choice? Or, alternatives like bromine solutions or ozone should be looked at?

 

[kclim]

One text you might want to have a look at it

"Power Plant Water Chemistry: A Practical Guide"
by Brad Buecker
ISBN 0-87814-619-9

Figures on page 200 quote half lives of

800 days at 59F (15C)
220 days at 77F (25C)
3 days at 140F (60C)

So I'd say your looking at storage lifetimes of anywhere between 200 and 3 days.

This was just a general figure quoted from the book, depends on a number of other conditions including pH and contamination. I imagine if you can keep your storage tanks cool, it should be OK.

As far as alternative water treatments,

Chlorine has been the traditional choice, but there are safety issues involved. Bromine has proven to be more effective than chlorine, but the environmental/safety issues still persist.

Ozone will have to be generated on site and is too short lived to store. It tends to be consumed by organics in the water too, which places high dosage demands.

Chlorine dioxide is a relatively new alternative, but also has to be generated on site. It is more potent than chlorine, but still has safety issues.

Good luck

 

[equestrian]

We use 12- 15% sodium hypochlorite here in Florida. A rule of thumb here is to never store more than 14 days of solution. If you are storing below 6% solution, degradation is minimal. We do advise covering the tanks from the sunlight. A/C is even better.

 

[tomatge]

This being the "Power Generating" forum, I assume you're using Sodium Hypochlorite as a biocide in an open cooling water system. If this is the case, I would offer some more thoughts :

There are basically two types of industrial biocides, oxidising and non-oxidising. Halogens (chlorine, bromine compounds) are oxidising. Whilst they can be effective at killinf free bacteria, the halogen levels tend to fall fairly quickly in the cooling water, particularly where the system is exposed to sunlight. Virtually continuous dosing may be required to maintain halogen concentration at a level that kills bacteria.

Non-oxidising compounds are more like "industrial poisons", and vary from manufacturer to manufacturer. Their effectiveness at maintaining bacteria levels depends upon their constitution.

In Britain, the Health and Safety Executive issue guidelines for cooling water systems, in respect of legionella. The document is known as "L8" and can be obtained from the HSE website (at a cost). This recommends alternate dosing of two types of biocide, since bacteria has been known to develop immunity over time to a single biocide.