Biodegradation of Aniline Compounds in Textile Dyeing Wastewater by Enriching Indigenous Bacteria in Wastewater Treatment Processes

透過培植強化菌種提升現有紡織染色廢水處理中苯胺類化合物的生物降解

Student thesis: Master's Thesis

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Award date5 Sep 2019

Abstract

Aniline and its derivatives are notorious environmental pollutants. They are raw materials for manufacturing commercial dyes, herbicides, plastics, and pharmaceuticals. Because of their low biodegradability, these aromatic compounds are challenging to be completely degraded by conventional wastewater biological treatment processes. As a result, these toxic and carcinogenic aniline compounds are often released to soils and water bodies, causing environmental pollution and serious health threats to human. The textile industry that consumes a considerate amount of synthetic dyes in its manufacturing processes faces an urgent need to remove these aniline compounds. In China, a new stringent effluent discharge regulation for bleaching and dyeing of textile industry (GB 4287-2012/XG1-2015) has been implemented since 2015. However, numerous textile dyeing and finishing factories in China have failed to meet the discharge limits.

Composition of microbial communities is one of the critical factors affecting biological treatment performance; however, controlling and enhancing functional bacteria is a major hurdle for many wastewater treatment plants. In this study, aniline-degrading bacteria were identified in five operating textile wastewater treatment plants with aniline problems through 16S rRNA gene sequencing. By enrichment, we developed an enhanced immobilized aniline-degrading microbial consortium from indigenous bacteria with a removal efficiency of aniline compounds up to 98% at a rate of 6.9 ng aniline mg VSS-1 h-1. Biodegradation of aniline compounds was confirmed to be by the commonly known ortho-cleavage pathway. A pilot-scale inverted anoxic/anaerobic/oxic/oxic biofilm (A2/O2-MBBR) system with enriched microbial consortium was set up to treat effluent from a textile factory. The pilot system could effectively remove aniline compounds, chemical oxygen demand, ammonia and total nitrogen in textile dyeing wastewater to below the discharge limits. Bacteria including Ignavibacterium, Planctomyces, Thiothrix, Rhodobacter and Limnobacter with high relative abundance were observed in the biomass samples of the pilot system, suggesting their functional importance in degrading aniline compounds and other wastewater constituents. With a short hydraulic retention time between 8.2 to 13.6 h, an inverted anoxic/anaerobic configuration, the application of recirculation, moving bed biofilm bioreactor and integrated fixed-film activated sludge technologies, and specialized aniline-degrading bacterial consortia, the pilot system was successfully demonstrated to be an effective treatment strategy for use in the textile dyeing industry to meet the stringent discharge limits.

    Research areas

  • Aniline, Bacterial community, Biodegradation, Enrichment, Immobilization, Textile dyes, Wastewater treatment