Factors Affecting the Simultaneous Removal of Nitrate and Reactive Black 5 Dye via Hydrogen-Based Denitrification

Tippawan Singhopon,Suphatchai Rujakom,Futaba Kazama,Kenta Shinoda

doi:10.3390/w13070922

Tippawan Singhopon, Suphatchai Rujakom + Show 2 more

Open Access

https://doi.org/10.3390/w13070922

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Journal: Water	Publication Date: Mar 27, 2021
Citations: 5	License type: CC BY 4.0

Affiliation: University of Yamanashi, Takeda (Japan)

Abstract

Textile wastewater (TW) contains toxic pollutants that pose both environmental and human health risks. Reportedly, some of these pollutants, including NO3−, NO2− and reactive black 5 (RB-5) dye, can be removed via hydrogen-based denitrification (HD); however, it is still unclear how different factors affect their simultaneous removal. This study aimed to investigate the effect of H2 flow rate, the sparging cycle of air and H2, and initial dye concentration on the TW treatment process. Thus, two reactors, an anaerobic HD reactor and a combined aerobic/anaerobic HD reactor, were used to investigate the treatment performance. The results obtained that increasing the H2 flow rate in the anaerobic HD reactor increased nitrogen removal and decolorization removal rates. Further, increasing the time for anaerobic treatment significantly enhanced the pollutant removal rate in the combined reactor. Furthermore, an increase in initial dye concentration resulted in lower nitrogen removal rates. Additionally, some of the dye was decolorized during the HD process via bacterial degradation, and increasing the initial dye concentration resulted in a decrease in the decolorization rate. Bacterial communities, including Xanthomonadaceae, Rhodocyclaceae, and Thauera spp., are presented as the microbial species that play a key role in the mechanisms related to nitrogen removal and RB-5 decolorization under both HD conditions. However, both reactors showed similar treatment efficiencies; hence, based on these results, the use of a combined aerobic/anaerobic HD system should be used to reduce organic/inorganic pollutant contents in real textile wastewater before discharging is recommended.

Highlights

Textile industry wastewater, which contains high concentrations of organic and inorganic pollutants, is a serious environmental issue, especially in developing countries, such as Thailand, India, and China
An anaerobic reactor (A) and a combined aerobic/anaerobic reactor (B), both with hydrogen-based denitrification (HD) systems, i.e., autotrophic denitrification using H2, were set up to evaluate the treatment process involving the removal of pollutants, especially NO3, NO2, and reactive black 5 (RB-5) dye, from textile industry wastewater
NO3 –N, NO2 –N, and RB-5 dye following the treatment of the textile wastewater in the HD system under both conditions

Summary

Introduction

Textile industry wastewater, which contains high concentrations of organic and inorganic pollutants, is a serious environmental issue, especially in developing countries, such as Thailand, India, and China. Approximately 17–20% of the pollutants in textile wastewater are typically released during the dye manufacturing and textile finishing processes, which involve the use of large amounts of water [1]. Even after treatment using traditional treatment processes, textile industry effluent still contains harmful compounds (predominantly originate from anthropogenic sources) discharged into nature sources. The presence of these contaminants in water decreases dissolved oxygen content, increases insoluble materials, and prevents sunlight penetration [3,4]. The compounds used in the dyeing process, which are the most harmful, are considered to be the major pollutants in textile wastewater [5].

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