WEF Discussion Forums
Laboratory Management and Technical Issues
Water Still Questions
We recently moved into our new lab here @ the Town of Newburgh WWTF and have a new addition, a Mega-Pure 6A Water Still. Our goal is to use this to produce our own distilled water to run through our Barnstead EasyPure RF Water Purifier which in turn will provide us with Type I reagent-grade lab water. This will also allow us to cancel our contract w/ the local water company that charges us $2/gal of distilled water!
There are a couple of things I need to know in order to set-up a distillation schedule for the techs:
Any advice you can offer would be greatly appreciated.
Thanks in advance,
You are probably not going to get many responses since this forum is practically dead. I happened to visit to post the Oregon Operator's Short School. Nevertheless, I am here so let me put my two cents worth:
In my opinion, a still is probably not a good idea for producing feed water for several reasons. The primary reason is build up of scale on the heater. Been there done that. It is specially a task if the feed water to the still is plain tap water. This will take it out of service continually since you have to descale. Secondly, is the amount of water produced by a still. It takes an entire day for some of these units to produce appreciable quantities of distilled water for use, much less for using in creating Type I water. You would have been better off with a deionization tank for feed water to either a still or the Barnstead unit. Culligan or Rayne will provide you with DI tanks at low rates. How much Type I water are you using or expect to use? Depending on the analysis, storage of water will determine what type of container and length of time in container.
There's no "holding time" for distilled water. As for storage, most straight DI systems are on demand, delivering purified water via a pump, thus there's no storage involved.
DI with reverse osmosis (RO-DI) is another story, and commercial systems usually have a storage tank of water that's passed through RO and then is pumped through the DI cartridges. I believe the storage tanks we have are made of linear polyethylene (LPE).
The main problem with storage of any water is the potential for bug growth. Our RO tanks have UV sterilization and a circulation pump to prevent this from happening.
We decommissioned our huge Corning still because of enormous energy consumption and the unavoidable formation of silicates in the primary (first) distillation stage. Plus, as victor notes, it was just too slow.
We're also in the process of decommissioning our plumbed-in house DI system because of bug growth that we simply can't control anymore.
With all of that, I'd store your final product in LPE jugs with spigots. Perhaps others visiting the Forum have better ideas. But Victor is correct, WEF has put fixing this forum on the back burner, and there are very few postings anymore.
City of Portland