Putting High-Efficiency Catalytic Ozonation into Practice in Wastewater Purification

With the rapid advance of industrial civilisation and urban construction, water pollution has become ever more pronounced and wastewater purification an urgent environmental task. Conventional treatment methods often suffer from limited efficiency, high cost and fluctuating performance, so more efficient and greener solutions are needed. Against this background, advanced catalytic ozonation has drawn wide attention as a new water treatment approach and is being extensively researched and promoted.

The technology uses ozone and the reactive radicals formed when it decomposes to oxidise and break down organic pollutants. The hydroxyl radicals produced have a redox potential as high as 2.8 V (2.07 V for the ozone molecule), second only to fluorine, and act on impurities in all their forms in water, including dissolved, emulsified, suspended, colloidal and microbial matter, converting complex organics into low-molecular-weight organics, acids and aldehydes while markedly improving turbidity, colour and odour and achieving efficient disinfection.

Early direct ozonation suffered from slow reaction, pronounced selectivity in pollutant removal, low ozone utilisation and high treatment cost. Advanced catalytic ozonation, by contrast, markedly improves ozone utilisation and decomposition efficiency, is almost non-selective towards pollutants, offers outstanding overall purification and causes no secondary pollution, and therefore has broad prospects in wastewater treatment. The process has already been applied successfully in many scenarios, particularly difficult effluents such as landfill leachate, petrochemical wastewater and pharmaceutical wastewater.

Development and application of advanced ozone oxidation:

• O3/H2O2 and other advanced catalytic oxidation

• O3/UV advanced oxidation

• O3/ultrasonic advanced oxidation

• O3/activated carbon advanced oxidation

• O3/metal catalyst advanced oxidation, etc.

Building on existing advanced ozone oxidation technology, SINOKLE has innovatively developed the CDOF process (circulating dissolved-ozone flotation system), which combines advanced catalytic ozonation, cyclonic technology and dissolved-air flotation and, with independently developed supercritical catalytic materials and high-efficiency heterogeneous catalysts, achieves cavitation-driven supercritical catalytic reaction. The system completes efficient catalytic ozonation in a fully enclosed, automatically pressurised reactor and is widely applicable to the efficient integrated purification of various recalcitrant wastewaters.

High-efficiency heterogeneous catalyst

SINOKLE CDOF advanced ozone catalytic oxidation process advantages:

1. First to integrate multiple catalytic ozonation, cyclonic dissolved-air flotation and coagulation in one technology, efficiently removing COD, suspended solids, colloids, bacteria and viruses.

2. Multi-stage, multi-dimensional, multiple catalytic ozonation reactions: pressurised catalytic reaction, homogeneous and heterogeneous catalytic oxidation, hydrodynamic cavitation catalysis, low-pressure catalytic oxidation and cyclonic fluidised reaction, with stable and reliable results.

3. A patented reactor design reacts extremely fast, with a residence time of less than 15 min versus 90 min conventionally; it operates sealed and under pressure with no ozone leakage, safe and environmentally sound.

4. Ozone utilisation above 99.98%, with an ozone dosing ratio of 0.5–1.2 versus 2–4 conventionally, only 1/5–1/2 of the conventional figure, and operating costs of 1/3–1/2 of the conventional process.

5. DCS/PLC automatic control precisely regulates ozone dose, reaction level, pressure and tail-gas concentration and optimises automatically according to water quality, lowering operating costs.

6. A dedicated catalyst with strong activity, high strength, a large specific surface area and strong fouling resistance, effective over a wide pH range and over the long term.

7. A unique catalyst backwash, activation and regeneration process keeps catalyst performance stable over the long term.

CDOF Application cases

CDOF technology application examples:

In a leachate treatment project at a waste-to-energy plant in Shiyan, Hubei, a CDOF advanced ozone catalytic oxidation dissolved-air flotation integrated unit was adopted with a capacity of 300 m³ per day. The influent is upstream MBR effluent with COD of about 1,300 mg/L; after treatment by the CDOF unit, effluent COD falls below 400 mg/L, colour below 30 units and odour is completely eliminated. After further biological treatment, the final effluent reaches COD ≤ 20 mg/L, ammonia nitrogen ≤ 1 mg/L and total phosphorus ≤ 0.2 mg/L, all indices stably meeting the Class III surface water standard for compliant discharge.