Hydrogenotrophic denitrification for treating nitrate contaminated without/with reactive black 5 dye

Abstract

NO3-N and dye colors discharged from textile wastewater pose environmental problems in Thailand. This study aimed to observe the nitrogen removal rate (NRR) with and without RB-5 color contamination via hydrogenotrophic denitrification (HD) processing, which uses H2 gas as electron donor to reduce NO3-N and NO2-N; comparing with bioreactors treatment to evaluate systems that can simultaneously remove NO3-N and dye color. Five reactors under different operation and gas supply conditions were set-up under HRT of 24 h, including an aerobic reactor using air, two anaerobic reactors using argon and H2, and a combined process using intermittent air/argon and air/H2. NRR without dye varied between 45 and 90% for H2 and air/H2 by HD processing, while it was completely removed when adding color. H2 and air/H2 reactors experienced partial decolorization of approximately 20–30%, whereas the other three reactors remained unchanged. Effluent of NO3-N were close to wastewater standards, but the color was still easy to detect, which indicated that the treatment time needs to be sufficient. In conclusion, HD and intermittent air/H2 processing can completely remove NO3-N and NO2-N when contaminated with RB-5 color. Furthermore, RB-5 did not affect the NRR, whereas some particles of dye color can also reduce in these processes. HIGHLIGHTS NRR with and without RB-5 dye contamination was evaluated in HD reactors and compared with bioreactors under various conditions using air, argon and H2 gas supplies.; Simultaneous NO3-N, NO2-N and RB-5 dye removal occurred in H2 and combined air/H2 reactors.; HD processing accelerated when contaminated with RB-5 dye.; RB-5 dye does not affect the NRR removal, while some partial removal can occur with HD processing.; NO3-N, NO2-N was removed faster than RB-5 dye color.;

Keywords

• biodegradation
• dye color removal
• hydrogenotrophic denitrification
• nitrate removal rate
• reactive black 5 dye color