The mystic DAF
Expensive to build, bypassed for months, irreplaceable on the worst day.
I have a friend we call the mystic. He’s been part of the group for years, yet somehow we still know very little about him.
He shows up, he’s clearly one of us, and then he disappears into a fog of half-answered questions.
If I had to assign that adjective to a single step in a desalination plant, it would be the DAF.
A quick caveat before we go further: here we’re talking only about seawater desalination plants. Dissolved Air Flotation has a much clearer, more settled role in specific industrial water treatment applications. In desal, it lives in a grey zone in my opinion sometimes.
The range of opinions you collect from water professionals about this system is so wide that it’s genuinely hard to write about cleanly.
So I’ll do my best to give you the context around the unit that causes so many headaches.
As always in our world, understanding the root cause behind each piece of feedback is a case-by-case exercise — same region, same intake water, and yet two clients (or the consultants who wrote their specifications) will reach opposite conclusions.
Here’s the tension in one paragraph. The Capex is significant. The Opex is “minimal”. So are we sometimes pouring millions into a system that returns very little?
And if you don’t install a DAF — what are the risks, and how badly do they hit the business model when things go wrong?
Last week at Euromed in Marrakech, I really enjoyed moderating the session with Alexander Baekelandt from SeQual, winner of the Innovation Award.
We talked about “predicting tomorrow to act today”. A great example is forecasting an algae bloom so operators can switch on the DAF system before it is too late.
As you can read later, it is not simply a matter of turning it on or off.
This predictive capability provides added value by giving operators the time they need to respond, making it the kind of insurance every desalination plant should have.
Listen to some feedback I got and you’ll hear two camps:
“It doesn’t really work once you’re in operation. It’s bypassed most of the time, and when you finally need it, it hasn’t been maintained — or you discover it can’t go from 0 to 100 in one second, it needs time to stabilise.”
“It should be running permanently, because it protects the RO downstream and saves you when conditions turn.”
Both camps are right, depending on the plant. That’s exactly why the DAF is the mystic.