Degradation of dye containing in textile wastewater by sequential process: photocatalytic and biological treatment

Our plain-English summary of Degradation of dye containing in textile wastewater by sequential process: photocatalytic and biological treatment, by J.C. Mendoza Hernández, G. Pérez Osorio, J.E.M. Gutiérrez Arias, et al (Turkish Journal of Chemistry, 2022).

The study

• Authors: J.C. Mendoza Hernández, G. Pérez Osorio, J.E.M. Gutiérrez Arias, J. Castañeda Camacho
• Journal: Turkish Journal of Chemistry
• Published: 2022;46(6):2046-2056
• Cited by: 2 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

In this research, a combined photocatalytic and biological treatment is proposed for the elimination of pollutants present in textile wastewater using a natural erionite zeolite (PE) and aluminum oxide (PA) synthesized by the sol-gel method as photocatalysts, and solar radiation. Both catalysts were characterized by XRD, SEM, and EDS. For biological treatment two bacterial consortium were used: BC1 (Escherichia coli N16, Serratia k120, Pseudomonas putida B03 and Enterobacter hormaechei), and consortium BC2 (Escherichia coli N16, Serratia Mc107, Enterobacter N9, Enterobacter hormaechei Mc9). The photocatalytic and microbiological treatments were carried out initially separately and subsequently in a sequential manner, first the photocatalytic followed by the microbiological to determine if a synergistic effect was achieved. Comparing the photocatalytic performance, erionite showed higher performance of dyes degradation (54.75%) than alumina (28.62%). While in the biological process, BC1 decreased the dye concentration to 56.93% and BC2 to 53.56%. Finally, the best combined process was PA+BC1 reaching pollutants degradation 64.62%, showing that the application of both processes promotes a decolorization in textile wastewater. The water resulting from the combined photocatalysis-microbiological degradation processes was tested for toxicity using Daphnia magna, obtaining that none of the effluents shows toxicity.

© TÜBİTAK.

In plain English

This laboratory study from Puebla, Mexico, tested dye removal from real textile wastewater. It did not study asbestos, human exposure or disease. The team used two catalysts under sunlight for 6 hours: natural erionite zeolite from Agua Prieta, Sonora, and synthetic aluminum oxide (alumina). X-ray analysis showed the zeolite's main peaks matched erionite and chabazite-Mg. The water then went to one of two bacterial mixtures (BC1 or BC2) for 6 days. Used alone, erionite degraded 54.75% of the dye and alumina 28.62%. BC1 alone degraded 56.93% and BC2 alone 53.56%. The best combined result, alumina then BC1, was printed as 64.16% in the results and 64.62% in the abstract. Alumina then BC2 cut chemical oxygen demand by 92% and color by 91.2%. Daphnia magna tests found no toxicity in the treated water; the authors gave no figures. The authors concluded that alumina followed by bacteria worked best and that treated water met Mexican discharge limits. However, suspended solids after erionite treatments (165.48 and 135.89 mg/L) exceeded river limits for public use (125 mg/L) and aquatic life (60 mg/L).

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Laboratory experiment on treating wastewater: sunlight-driven photocatalysis followed by treatment with bacteria, plus an acute toxicity test with Daphnia magna
• Who was studied: Real textile wastewater (the article does not say where it came from), treated in experiments at Puebla, Mexico. No people were studied. The natural erionite zeolite came from Agua Prieta, Sonora, Mexico.
• Exposure: Not a human exposure study. Two catalysts (natural erionite zeolite and sol-gel synthetic aluminum oxide) were added at 45 mg per 450 mL of wastewater and exposed to sunlight for 6 hours. Two bacterial consortia (BC1 and BC2) were then applied for 6 days.
• Main results:
  • Photocatalysis alone: erionite degraded 54.75% of the dye and alumina 28.62%
  • Bacteria alone: BC2 degraded 53.56% and BC1 56.93%
  • Combined treatments: alumina then BC1 (PA+BC1) 64.16% degradation; PE+BC1 57.65%; PA+BC2 60.44%; PE+BC2 56.20% (Table 3). The abstract gives 64.62% for PA+BC1.
  • Reduction in chemical oxygen demand (COD): PA+BC1 85%, PE+BC1 65.1%, PA+BC2 92%, PE+BC2 68.6%. Untreated wastewater was 1872 mg/L and PA+BC2 reached 150 mg/L (Table 2).
  • Decolorization: PA+BC1 86.4%, PE+BC1 68.2%, PA+BC2 91.2%
  • Total suspended solids fell from 525.64 mg/L to 35.45 (PA+BC1), 165.48 (PE+BC1), 19.45 (PA+BC2) and 135.89 mg/L (PE+BC2) (Table 2). The listed river limits are 200 mg/L for agricultural irrigation, 125 mg/L for public use and 60 mg/L for protection of aquatic life. The erionite-treated water met only the irrigation limit; the alumina-treated water was below the aquatic-life limit.
  • X-ray diffraction of the natural zeolite showed main peaks matching erionite and chabazite-Mg
  • Acute toxicity testing with Daphnia magna found no toxicity in any of the treated effluents. No numerical results were given.
• The authors' conclusion: The authors concluded that photocatalysis with alumina followed by bacterial treatment gave the best results, reducing COD and color by more than 90%. They stated that the treated water met Mexican discharge limits, showed no toxicity, and could possibly be reused for services without direct contact with people. Their own Table 2, however, shows suspended solids after the erionite treatments above the public-use and aquatic-life river limits. Mexican regulations list no limits for COD, conductivity, turbidity or color (marked 'not specified').

Topics

Medical terms in this study, explained in our Lexicon: erionite, Zeolite, Synergistic Effect.

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