Testing for calcium hypochlorite vs. sodium hypochlorite 3

[GeneratorGrrl]

Dia dhuibh

We currently use sodium hypochlorite to treat water and are considering switching to calcium hypochlorite. Currently we use a Hach DPD Free Chlorine reagent test to test for free chlorine levels. My supplier is unable to answer the question of whether this test will read for calcium hypochlorite; does anybody here know?

Thanks muchly for your time and any answers.
-==- GeneratorGrrl



"Eat well, exercise regularly, die anyways."

 

[LHA]

If the reagent is what its name implies (and I don't know whether or not it is), it is reacting with free chlorine ions. So it is not currently indicating presence of NaOCl, it is not even indicating OCl. It is just reacting with Cl--. It will do that regardless of which compound provides the Cl--.

You might be asking if Ca adds any reactive interferences which Na does not. That might appear on the MSDS, but you will prably have to check Standard Methods.

 

[semo]

Yes, it will work. It checks the free chlorine not where the chlorine comes from.

 

[GeneratorGrrl]

Thank you!

Another question I have, I'm not sure can be answered here, but it never hurts to ask, does it?

We are a commercial farm in a rural area that gets water trucked out. After filtering, the water is dumped into a cistern where it is chlorinated. This cistern gets emptied regularly, as water demand varies depending on what process is being performed that day. With our current set-up, sodium hypochlorite solution is mixed in a vat, then pumped to the cistern in response to changing PPM, so some days we can go through quite a lot of solution. Would calcium hypochlorite work under these variable conditions? If so, would tablet or granular form be more appropriate (I'm thinking tablet, though I would not be able to purchase a tablet-specialized chlorinator system at this time -- the boss, donchaknow )

If any one does have any thoughts or answers, thanks in advance, as its muchly appreciated.

-==- GeneratorGrrl

"Eat well, exercise regularly, die anyways."

 

[LHA]

12.5% Bleach solution would be the cheapest chemical, tablets of CaOCl2 has the cheapest captial outlay for teh erosion-style feeder you have described.

Tablets are the most foolproof and most safe. Since you apparently already have a chlorine concentration monitoring system which doses the solution, you might want to look into long-term cost savings of a tablet feeder, which is pretty much maintenance free (no mixing step).

 

[GeneratorGrrl]

Thanks, LHA. This is what I'd like to look into, but right now I have to convince my boss even to consider calcium hypochlorite (to be frank, he thinks I'm wasting my time even looking into it :sigh: ) So if calcium hypochlorite is appropriate to our variable-dosing needs, then I have to find a way to make the substance work with our current set-up. I suppose it could technically be considered an erosion feeder.... since we currently use liquid bleach, our 'feeder' consists of a vat with a pump =) I suppose a tablet could sit at the bottom of the vat and dissolve...
... although a buddy uses the tablets in his spa, where it floats around in a little duck That'd certainly liven the work environment in the morning =)

Thanks muchly
-==- GeneratorGrrl

"Eat well, exercise regularly, die anyways."

 

[hydrae]

GeneratorGrrl

I give warning on the calcium hypo esp. for variable flow rates

A standard tablet feeder erodes the bottom of the bottom tablet, increasing the flow increases the erosion but discussions I have had with operators is the process is not linear, every time they change flow rates they have to tweak the adjustment, their solution was to set that flow at a fixed rate for that source and use other locations for changes in demand.

There are other feeders on the market that advertise a better erosion rate by using a spray system on an oval bricket instead of a round flat tablet or other such active control systems. These units require power for the spray pump and have moving parts.

As for maintenance free, NO, the tablet feeders get gummed up and need regular cleaning to remove this pasty goop, not pleasant.

The tablet feeder in the spa is using a stabilized chlorine tablet (sodium tri-chloro-S-trititozone sp?) which is not for potable use even for farm animals.

Hydrae

 

[GeneratorGrrl]

Thank you, Hydrae, these are good to know. I may look at the spray system just to see what the options are.

I've never found anything that was truly maintenance-free; everything requires *some* sort of care. Even the "self-cleaning" flow cell on our chlorinator, isn't

And no, I wasn't considering using the spa *tablets* - just the duckie ^___^ I know the spa tablets aren't for potable-water use. And no, I'm not serious about the duckie either; it just made for an amusing thought. Imagine the procedural description: "Check pump for correct function, check and record solution level in vat, check tablet in duckie and replace tablet if necessary..."

All joking aside, thanks very much for your insights, folks. Sounds like I've a case of "six of one, half a dozen of the other", with neither being ideal. Thanks!

-==- GeneratorGrrl


"Eat well, exercise regularly, die anyways."

 

[sbush]

You can use calcium hypochlorite just like you are presently using sodium hypochlorite. Simply buy granulate calcium hypochlorite and dissolve it in a bucket of water and add it to the cistern as a liquid. Since calcium hypochlorite contains 65 percent chlorine, you will be able to calculate the proper mixing ratio to simulate what you are currently adding with bleach. The beauty of using cal-hypo is storage. It degrades very little in dry storage and because it is so concentrated, a little goes a long way when compared to the same volume of liquid bleach.

Your application is too small for a errosion feeder and tablets are really only designed to be used with errosion feeders.

Be sure that you purchase a granular cal-hypo that is NSF listed for drinking water. Cal-hypo will increase the pH slightly and no appreaciable amounts of calcium are added to the water.

S. Bush

http://www.water-eg.com