Research on advanced treatment of phenolic chemical wastewater and carbon replacement by the multi-layer biological activated carbon filter

Abstract

After a series of biochemical processes, the wastewater engendered by the production of phenolic resin is ultimately left with a majority of difficult degradation organic matter. Most of these organic compounds are harmful to the water environment and require further advanced treatment before discharge. In this study, the original simple biological activated carbon (BAC) filter column device was improved. The new multi-layer BAC filter does not require backwash after improvement. The treatment efficiency of the multi-layer BAC filter was studied through long-term operation, and the variation of pollutants in the wastewater was analyzed. The results indicated that the multi-layer BAC filter could effectively remove hardly biodegradable organic matter, ammonium‑nitrogen (NH4+-N), and total nitrogen (TN), and its mechanism was mainly that hardly biodegradable organic matter and TN were removed by adsorption and biodegradation, while NH4+-N was only removed by microbial degradation. The pore-size distribution characteristics on the BAC surface were analyzed, and it was found that the adsorption and biodegradation reactions mainly occurred in the microporous region. The experiment on carbon replacement indicated that the service time of the BAC system could be prolonged by choosing the correct time of carbon replacement and adding the appropriate amount of microorganisms. Based on high-throughput sequencing, it was found that the microbial communities on BAC at the same height were significantly different before and after carbon replacement. The results of this paper are of some relevance for the upgrading of advanced treatment processes for chemical wastewater in practical engineering.