CDOF in Four Settings: Where an Integrated Ozone Oxidation and Flotation Unit Pays Off

Choosing an advanced treatment process is rarely a question of which technology is best. It is a question of which one fits a particular site, a particular permit and a particular maintenance department. Three variables decide most of the outcome: what the project costs to build, how much land it consumes, and what it costs to run for the next ten years. A process that wins on the first and loses on the third is not a saving; it is a deferred expense with interest.

SINOKLE developed the CDOF advanced catalytic ozonation unit against that set of constraints, and the design choice is visible in the name: oxidation and flotation are one operation, not two. That single decision removes an entire pump, tank and control loop from the conventional arrangement.

What the Unit Actually Contains

CDOF, the Cyclonic Dissolved Ozone Flotation Unit, is a patented SINOKLE product and holds PCT international patents. It integrates multiple catalytic ozonation, hydrodynamic cavitation and swirl dissolved air flotation into a single package, and it comprises five subsystems: oxygen generation, ozone generation, high-efficiency ozone dosing, multiple catalytic reaction, and swirl dissolved air flotation.

The mechanism list is long because the unit has to work on several fronts at once: homogeneous catalysis, heterogeneous catalysis, swirl flow, dissolved air flotation, cavitation, supercritical catalytic oxidation and fully enclosed pressurised oxidation. Between them they remove petroleum substances, suspended solids, colloids, COD, bacteria and the other pollutants that keep an effluent out of specification. In practice, the heterogeneous catalytic path matters most, because it converts ozone into hydroxyl radicals that attack molecules ozone alone will not touch.

Four Design Choices That Show Up on the Quotation

It saves on ozone. The dosing ratio is only 1/2 to that of conventional processes, and since ozone generation is the dominant power load in any ozonation plant, that factor propagates straight into the electricity bill. Fewer chemicals also means lower O&M cost downstream.

It is fast. Multiple catalytic oxidation reacts quickly, with a retention time under 15 minutes. Short residence time is what keeps the vessel small, and a small vessel is what keeps the capital cost down.

It is compact. The skid-mounted design occupies roughly 1/5 of the footprint of conventional processes, is pre-assembled and commissioned in the factory, and starts up quickly. For an existing plant with no spare land, that is often the deciding factor rather than a bonus.

It is stable. Fully automated enclosed pressurised operation means no ozone leakage and no operator exposure; the process tolerates shock loads and significant water quality fluctuation, which is the failure mode that most often takes an advanced oxidation plant offline.

Setting One: Upgrading an Existing Treatment Plant

For a municipal upgrade, the numbers are straightforward. Influent COD of 200mg/L or less and colour of 200 or less go in; effluent COD of 40mg/L or less and colour of 20 or less come out. The COD degradation is substantial and the decolourisation is visible to anyone standing at the outfall. Because the unit is skid-mounted and small, the upgrade does not require a new civil structure, which is what usually makes a retrofit impossible on a built-out site.

Setting Two: Refractory Industrial Wastewater

For complex industrial effluent, SINOKLE pairs CDFU with CDOF. The CDFU stage uses flocculation and flotation to take out colloids first; the CDOF stage then finishes the job by catalytic ozonation. The combination multiplies the ozone oxidation effect by 4 times or more, reduces colour by 90% or more and cuts sludge volume by 90% or more, with effluent meeting the GB 18918-2002 Class 1 B standard — that is, COD of 60mg/L or less, BOD5 of 20mg/L or less and suspended solids of 20mg/L or less.

The comparison that sells this route is against the conventional membrane plus evaporation arrangement. The CDOF route is membrane-free, so it produces no concentrate; it resists scaling and clogging, so it does not need a chemical cleaning cycle; and it carries low O&M cost, a small footprint and a short commissioning period. Over a long operating horizon those four items are the difference between a plant that stays available and one that spends its life being cleaned.

Setting Three: Pharmaceutical Wastewater

Pharmaceutical effluent is complex in composition, hard to biodegrade, saline, toxic and highly variable — a combination that defeats single-mechanism processes. Here CDFU and CDOF work as a pair with genuine synergy rather than as two stages in sequence. Upstream, CDFU generates micron and nano scale ultrafine bubbles and removes suspended solids at a rate of 95% or more, which protects the catalyst bed and extends catalyst life by 30% or more. Downstream, CDOF activates ozone at ambient temperature and pressure to generate hydroxyl radicals with an oxidation potential of 2.8V.

Measured on heterocyclic organics, the degradation rate reaches 85%-99%, and antibiotic removal runs above 99%. The route has been through a successful pilot at a large pharmaceutical group in Inner Mongolia, which is the point at which a chemistry claim becomes an engineering reference.

Setting Four: Fracturing Flowback Fluid

Flowback fluid from oil and gas field fracturing brings its own problems: high viscosity from the gelling agent, stable oil emulsions, and a location that is usually nowhere near a treatment plant. SINOKLE uses a route of CDOF gel breaking and viscosity reduction, followed by CDFU oil and solids removal and then precision filtration. Filtered water meets reuse requirements, and the skid-mounted equipment can be truck-mounted to the well site — which means the water is treated where it is produced instead of being hauled somewhere and back.

Choosing Among the Four

The pattern across these settings is that CDOF earns its place wherever the effluent has to be both oxidised and clarified, and where land or retention time is scarce. Where the duty is purely solids removal, a flotation stage on its own will do the job for less. Where the effluent is going to biological treatment downstream, the value of the unit is in raising biodegradability rather than in achieving a final discharge number.

What the four cases have in common is a specification written around a real permit and a real site. Integration, skid mounting, low energy consumption and stable operation are the four levers SINOKLE pulls, and they are the four that decide whether an advanced treatment plant is still running to specification in year eight.