RO Pilot Necessity

[TurtleboyTom]

Is it common practice to run a pilot study when considering Membrane Filtration?

 

[ashtree]

Yes, absolutely if this is a high priority and or expensive project with large consequences if you get it wrong.

I have been involved in about 10 RO projects on green field sites and have had to operate and support many of those plants long term afterwards. The one that we have had the most problem with had the least amount of pilot studies. Eventually i had to get the pilot plant back in to assist with the determination of what was going wrong.

Ideally you would pilot test for 6 months at least which would, if everything was going really well, be about 2 intervals between CIP. This would be long enough to be confident that your pretreatment train was working correctly and the flux rate and recovery were correct.

If things are going bad and you obviously have inadequate pre treatment or excessive recovery you will probably need to trial some modifications or different configurations. In this case in the ideal world you should try to get six months at least after modification of good clear running.

Longer is better, and any pilot work will be better than none. Sometimes pilot trials are better at finding out what does not work rather than what does. Even then the investment is worth it.

Regards
Ashtree
"Any water can be made potable if you filter it through enough money"

 

[TurtleboyTom]

Thanks for the thoughtful response. I'm glad to hear it. We are considering a 900 gpm RO unit and I've been telling management that we need a pilot study before we commit to it. The other day we had an RO expert come on site and tell everyone that it isn't necessary and that it's rare for anyone to do pilot studies. Lab numbers & and SDI test tell them all they need to know. Of course, this didn't sit right with me.

High recovery is the ultimate goal and this project would be a disaster if we didn't meet our desired outcome.

 

[ashtree]

Lab numbers and SDIs are important no doubt and will set the basis of design. But in nearly every case unless you are going to be super conservative there are risks , unknowns or degrees of uncertainty. A pilot project can help to reduce those uncertainties, eliminate some or all of the unknowns and reduce risk. In nearly every case i have been involved in the pilot plant has either shown that xyz was not the problem that the numbers suggestted or that something else that you might not have even considered is a problem.

For example , in one project the numbers suggestted that iron would be an issue and that certain measures needed to be in place to deal with it The pilot plant owever operated satisfactorily without any particular treatment because the iron could be kept in solution provided there was no oxidation occurring. 14 years on this plant is still going strong with no hint of trouble, however biofouling has been a seasonal issue some years. The original bacto numbers suggestted that it would not be. After some minor modifications the plant has few biofouling issues.

The other thing that needs to be considered in this, how good are the numbers? I have seen a plant designed on one grab sample that was not representative of the range of quality that could be encountered. Given that you are aiming at high recovery this is a particular risk.

Regards
Ashtree
"Any water can be made potable if you filter it through enough money"