Sequential approach of photoelectrochemical oxidation and biodegradation of reverse osmosis reject water from the tannery industry

• Published in: Journal of environmental chemical engineering 2025-02, Vol.13 (1), p.115078, Article 115078
• Main Authors: Duraimurugan, Ramanathan, Dhandapani, Perumal, Velu, Premalakshmi, Parthipan, Punniyakotti, Devanesan, Sandhanasamy, AlSalhi, Mohamad S., Rajasekar, Aruliah, Babujanarthanam, Ranganathan
• Format: Article
• Language: English
• Subjects: Electrochemical oxidation; Mixed salts; Reverse osmosis rejects; Total organic carbon; Vreelandella piezotolerans
• ISSN: 2213-3437
• DOI: 10.1016/j.jece.2024.115078

The common effluent treatment plant (CETP) of tannery industries, discharges tons of wastewater as effluent along with reverse osmosis reject water (ROR) in the environment. This study focuses on recovering mixed salts from the ROR. Before the electrochemical oxidation process, the hardness of ROR was reduced by chemical softening from 2900 ± 11.4 mg/L to 399 ± 9.5 mg/L. The removal percentage of total organic carbon (TOC) reveals that PEO was 76 %, compared to EO (67 %). It was due to the higher production of the electrochemical generation of hypochlorite (34.45 mmol L−1 60 min−1), which acted as a strong oxidizing agent for the degradation of organic pollutants. Besides, the presence of hypochlorite in the treated EO and PEO was reduced (86 %) by the exposure (72 hrs) of sunlight-induced photolytic process. PEO-treated ROR was subjected to biodegradation (PEO-BIO) using the bacterial strain Vreelandella piezotolerans DM1. The treatment by Vreelandella piezotolerans DM1 effectively eliminated the TOC content (90 %) than the BD (56 %). Gas chromatography-mass spectrometry (GC-MS) confirms the PEO-BIO has the higher effective removal of the organic compounds in the ROR and the degradation efficiency was 87 % achieved than the BD (57 %) respectively. CHNS analysis confirms that lesser concentration of carbon (3.911 %) and nitrogen (1.812 %) content in the recovered salt from the treated PEO-BIO. Overall, this study has proven that the systematic sequential approach of PEO-BIO has feasible solution for the removal of toxic contents in ROR. Treated salt was potential to reuse in the industrial applications effectively for tanning process. [Display omitted] •The study sequential approach of chemical pre-treatment further photo electrochemical oxidation and biodegradation of ROR.•XRD result was concluded to remove the Ca and Mg in ROR.•The PEO was effectively removed TOC (76 %) compared to EO (67 %).•The hypochlorite gradual decrease of sunlight-induced photolysis process.•Biodegradative strain Vreelandella piezotolerans DM1 achieved complete mineralization.