Activated carbon enhanced traditional activated sludge process for chemical explosion accident wastewater treatment

With the development of industries, explosion accidents occur frequently during production, transportation, usage and storage of hazard chemicals. It remained challenging to efficiently treat the resultant wastewater. As an enhancement of traditional process, the activated carbon-activated sludge (AC-AS) process has a promising potential in treating wastewater with high concentrations of toxic compounds, chemical oxygen demand (COD) and ammonia nitrogen (NH₄⁺-N), etc. In this paper, activated carbon (AC), activated sludge (AS) and AC-AS were used to treat the wastewater produced from an explosion accident in the Xiangshui Chemical Industrial Park. The removal efficiency was assessed by the removal performances of COD, dissolved organic carbon (DOC), NH₄⁺-N, aniline and nitrobenzene. Increased removal efficiency and shortened treatment time were achieved in the AC-AS system. To achieve the same COD, DOC and aniline removal (90%), the AC-AS system saved 30, 38 and 58 h compared with the AS system, respectively. The enhancement mechanism of AC on the AS was explored by metagenomic analysis and three-dimensional excitation-emission-matrix spectra (3DEEMs). More organics, especially aromatic substances were removed in the AC-AS system. These results showed that the addition of AC promoted the microbial activity in pollutant degradation. Bacteria, such as Pyrinomonas, Acidobacteria and Nitrospira and genes, such as hao, pmoA-amoA, pmoB-amoB and pmoC-amoC, were found in the AC-AS reactor, which might have played important roles in the degradation of pollutants. To sum up, AC might have enhanced the growth of aerobic bacteria which further improved the removal efficiency via the combined effects of adsorption and biodegradation. The successful treatment of Xiangshui accident wastewater using the AC-AS demonstrated the potential universal characteristics of the process for the treatment of wastewater with high concentration of organic matter and toxicity. This study is expected to provide reference and guidance for the treatment of similar accident wastewaters.