KernOily:
My experience with the WEMCO Depurator dispersed air flotation systems dates to some thirty years ago (1974)in a Caribbean refinery API separator effluent application, specifically at Amerada Hess' St. Croix, USVI refinery (now under a different name?). At the time, my employer, Petrolite Corporation, Tretolite Division in St. Louis, Missouri held the marketing rights for the system to the petroleum industry. As Petrolite and Tretolite don't exist as such due to corporate sell-offs (Petreco and Baker-Hughes I believe were the successors), I have no present knowledge of the owners/marketers of the WEMCO system.
From on-site pilot unit data we accumulated over several weeks on the various API effluent streams, the WEMCO was shown to be a superior oil/solids removal device, to the extent that the unit effluent consistently contained well under 15 ppm O & G, which at the time was acceptable for direct discharge. As I recall the case to be with most air flotation systems, then and now, the WEMCO was in need of selected oil-in-water demulsifiers and or wetting agent to routinely achieve the necessary level of O&G removal.
The upshot of the on-site work was the refinery's purchase of several systems to the tune of more than $100,000, not including the selected chemical aids. While I don't still have the pilot data, nor the actual system performance data after installation of the units (as I left Tretolite and the Caribbean in 1975), my recollection is that the system performed exactly as shown during the pilot runs, and easily met the discharge criteria in place at the time.
I am still of the opinion that the WEMCO is superior to dissolved air flotation technology, particularly in terms of performance. At least at the time of my involvement, WEMCO's CAPEX and OPEX were comfortably competitive with DAF systems.
I'm sorry that I don't have the specifics of the St. Croix applications as that is obviously what you need. Unless things have drastically changed over the intervening years, I believe that you should seriously consider the WEMCO technology as it is (or certainly was) the prince of O&G removal treatment in the oil production and refinery industry.
Orenda