Improvement of the Biggest Catalytic Ozonation Wastewater Treatment Plant in China : From Pollution Control to Carbons Reduction

Catalytic ozonation is an effective technology widely used in advanced treatment to remove refractory organics from wastewater. Meanwhile, it is also a highly energy-consuming technology, usually accounting for 30%~40% of the total electricity consumption of a wastewater treatment plant (WWTP). The O3 consumption per unit COD removal (g-O3/g-COD) is usually higher than 1.5 g-O3/g-COD, and the total carbon emission of catalytic ozonation is usually higher than 393.12 kgCO2e/m3 wastewater. In this study, the energy reduction strategy of the biggest catalytic ozonation WWTP was investigated from experiment to corresponding engineering application. The laboratory-scale experiment showed that the mass transfer rate of dissolved O3 to the catalyst surface is decisive for COD removal efficiency. To improve the efficiency of catalytic ozonation, adding the effluent backflow is a simple method, as it could enhance the removal of extracellular polymeric substances (EPS) from the catalyst surface and promote surface exposure. In the pilot-scale experiment (48 m3/d), when the backflow ratio increased from 0% to 100% (the optimal value), the proteins in EPS on the catalyst surface significantly decreased by 66.7%. The corresponding O3 consumption per unit COD removal was reduced from 2.0 to 1.0 g-O3/g-COD. Furthermore, in the engineering application (52,000 m3/d) with the backflow ratio of 100%, the effluent COD reduced from 52.0 to 43.3 mg/L, and the O3 consumption per unit COD removal reduced from 0.98 to 0.69 g-O3/g-COD. From the perspective of carbon reduction, the indirect carbon emission reduction was about 3.0×103 t CO2 e/a. The study demonstrates the advantages of the catalytic ozonation improvement and provides an engineering model of energy saving and carbon emission reduction for more than 35 similar WWTPs in China