Study on the Removal of Trace Organic Matter from Water by the Ozone-Activated Carbon (O3/C) Process

Abstract

Owing to the complex structure and low biodegradability of most trace organic compounds found in source water, the removal efficiency of these contaminants by the O₃‑C process declines correspondingly once the adsorption capacity of the activated carbon is exhausted. In the O₃/C process, however, the surface morphology and pore structure of the activated carbon remain largely intact after extended operation. There is only a minor reduction in specific surface area and micropore volume, and its adsorption capacity remains comparable to that of fresh activated carbon; whereas in the O3-C process, the surface pore structure of activated carbon is covered by a dense, uniform layer of pollutants, the adsorption capacity decreases by nearly 75%, and a large number of short rod-shaped bacteria are present on the activated carbon surface, indicating that it has transformed into biological activated carbon, thereby almost losing the adsorption function of activated carbon. This indicates that the O3/C process can prolong the adsorption performance of activated carbon. BET test results showed that continuous ozone oxidation of activated carbon can lead to an increase in the proportion of micropore volume, indicating that ozone contact oxidation has a certain destructive effect on the macropores and mesopores of activated carbon. O₃/C outperforms O₃-C because activated carbon catalyses ozone to generate strongly oxidising •OH and HO₂• radicals; additionally, dissolved O₃ is converted to H₂O₂ on the carbon surface. The decomposition of H2O2 can produce additional HO2•, increasing the production of •OH in the O3/C process and improving the oxidation effect. Ozone–carbon contact produces abundant •OH that oxidises organics and biofilm coating the carbon surface, liberating active sites and accomplishing in-situ carbon regeneration. Through optimized process design, improved equipment efficiency, and strengthened operation management, the O3/C process significantly reduces overall operating costs in three aspects: synchronous regeneration of activated carbon, high ozone utilization rate, and reduced secondary lifting, achieving economically efficient operation goals.