Abstract
The concentration of total nitrogen (TN) (between 40 and 60 mg/L, mainly nitrate) in the biological and catalytic ozonation treated dyeing and finishing wastewater needs to be reduced before discharge. The present study investigated the feasibility of using waste iron shavings as electron donor for nitrogen removal by biological denitrification. Two anoxic sequencing batch reactors (AnSBR) were continuously operated for more than 100 days. The results showed that the TN removal efficiency increased from 12% in the control reactor (AnSBR-C) to 20% in the reactor with waste iron shavings (AnSBR-Fe). The TN removal was mainly achieved by the reduction of nitrate by heterotrophic denitrification and autotrophic denitrification for AnSBR-Fe. The residual COD (38.4 mg/L) in the effluent of AnSBR-Fe was higher than that (22 mg/L) in the effluent of AnSBR-C, which could be due to that the bacteria preferred to use iron instead of the recalcitrant organics that present in the wastewater. Furthermore, 3DEEM, UHPLC-QTOF and GC–MS analysis were used to characterize the organics in the wastewater, and the results showed that the addition of waste iron shavings affected the degradation of organics during the biological denitrification process.
Highlights
The wastewater from dyeing and finishing process in the textile industry is characterized by a high content of organic pollutants, which poses a serious environmental pollution if it is not properly treated (Lu et al 2010; Wu et al 2016)
Based on the above considerations, the present study aimed to investigate the feasibility of using waste iron shavings for nitrogen removal from the biological and catalytic ozonation treated dying and finishing wastewater (DFW) by biological denitrification
The results from the present study showed that the addition of waste iron shavings increased the nitrogen removal efficiency from the biological and catalytic ozonation treated dyeing and finishing wastewater
Summary
The wastewater from dyeing and finishing process in the textile industry is characterized by a high content of organic pollutants, which poses a serious environmental pollution if it is not properly treated (Lu et al 2010; Wu et al 2016). The use of organic compounds for biological denitrification by heterotrophic bacteria can produce excessive biomass and soluble microbial products, which requires further treatment (Mansell and Schroeder 2002), while the use of inorganic compounds can avoid this problem (Schnobrich et al 2007). Both H2 and nano zero-valent iron (NZVI) have been studied as electron donor for denitrification (Chen et al 2014; Shin and Cha 2008; Xia et al 2010), they are generally limited by the relatively high cost and technical difficulties
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