Chlorate residuals

Rob,

If chlorate is going to be a problem there is only 3 solutions (other than get small stocks more regularly).

1) Store the tank in a cooler area (maybe even airconditioned.)

2) Go back to chlorine gas.

3) Onsite hypo generation.

I would suggest that going back to gas is not an option that most would contemplate.

On site generation is both good and bad but would need to be considered carefully.

But what would be wrong with putting hypo tanks in cool rooms. I have been in plants in the mid west USA where they put the chem tanks in concrete floor/roof and walled temperature controlled rooms to counteract the effects of blizzard conditions in winter and tornados in summer.

Terry Fagg Treatment Manager WDRC

Does anybody have experience with onsite hypo generation?

Did anyone have a significant Chlorate detection in the recent rounds of SNAP monitoring?

Terry Fagg Treatment Manager WDRC

Terry (and those interested),

With chlorate residual limits being talked about recently, we have taken a couple practical steps with our last gas to hypo swap out to reduce chlorate production post-delivery. These were;

• Install duty/standby tank arrangment to ensure new deliveries are not subject to accelerated degradation by old stock,
• Have storage tanks insulated,

In our smaller rechlorination facilities (100 L storage) we will trial diluting new hypo deliveries to 5% as this concentration is more stable and the degradation rate is much slower than 10-12% solutions.

While these steps won't eliminate the issue, we hope that they will assist us with managing chlorate residuals in the future.

Cameron Ansell SBRC

Townsville Water is doing a Chlorate investigation - registered with the regulator as a research project. We are still in the data gathering phase but have taken the opportunity to fine tune a few chlorine setpoints (we were dosing higher than needed) and in doing so have already had a win on some chlorate levels.

We of course have all of the worst conditions for chlorates - hot, long supply lines, large system connected to 1 major treatment plant which uses hypo. On Magnetic Island we use gas, but the water has previously been dosed with hypo which is fully expended when it gets there, and therefore we still have moderate chlorate levels.

I will post result summaries to this forum as they become available.

Mark

There have been a number of discussions at TRG around this – are you aware of them and have you been getting materials? 

Bundy have been doing a similar study and we were able to obtain some research results for Seqwater.