Efficient treatment of recalcitrant textile wastewater using two-phase mesophilic anaerobic process: bio-hythane production and decolorization improvements

The industrial effluents recently have become more complex and a constant health hazard polluting and contaminating water, soil and air. In this study, it is important to obtain high performance for the treatment of recalcitrant and toxic azo dyes being caused by textile industries and deal with inhibitory factors. For this aim, a continuous two-stage mesophilic anaerobic system has been employed to treat synthetic textile wastewater contained C. I. Acid Red 88 dye. A laboratory-scale of acidogenic continuous stirred tank reactor followed by methanogenic upflow anaerobic sludge bed reactor was operated at hydraulic retention time (HRT) of 48, 24 and 12 h. The acidogenic reactor was able to remove 50.3% of the total COD added and 90.3% of the color at HRT of 12 h. However, the maximum bio-hydrogen conversion as COD was 30.7% with acetate and butyrate as main by-products at HRT of 24 h. The second stage showed a total of 94.8% COD removal and 97.2% decolorization at HRT of 12 h with maximum methane production of 1.01 l/l/day. The experimental results showed that the changing in the soluble by-product could explain the effect of HRT and the maximum total hythane energy produced was 121.5 MJ/m³.