[Combination of Microbubble Catalytic Ozonation and Biological Process for Advanced Treatment of Biotreated Coal Chemical Wastewater].

A combination of microbubble catalytic ozonation and biological process was used for advanced treatment of biotreated coal chemical wastewater (BCCW). The performance of the combination system and the influence of the ratio of ozone dosage to influent COD were investigated. The results indicated that the refractory nitrogen-containing aromatics in the BCCW was degraded efficiently by microbubble catalytic ozonation, which resulted in some COD removal, ammonia nitrogen release, and significant improvement of biodegradability. The ozone utilization efficiency was close to 100% and the off-gas ozone did not need to be treated. Sufficient dissolved oxygen (DO) was provided by the microbubble catalytic ozonation for biological treatment without aeration. COD and ammonia nitrogen were removed further in the biological treatment efficiently. Better performance of the combination system was achieved when the system effluent reflux ratio was 30% and the ratio of ozone dosage to influent COD was 0.44 mg·mg. In this case, for microbubble catalytic ozonation, the COD removal efficiency was 42.5%, the ratio of ozone consumed to COD removed was 1.38 mg·mg, and the ozone utilization efficiency was 98.0%. For biological treatment, the COD removal efficiency was 42.3%. For the combination system, the total COD removal efficiency was 66.7%, the average final effluent COD concentration was 91.5 mg·L, and the estimated total ratio of ozone consumed to COD removed was 0.68 mg·mg, indicating better technical and economic performance.