Bioremedial Capacity of Indigenous Hydrophytes and Microalgae of Bangladesh: A Comparative Study on their Potential in Tannery Effluent Treatment

Abstract

Aims: This study aimed to identify the bio-remedial potential of indigenous hydrophytes (Salvinia cucullata and Lemna minor) and microalgae (Spirulina platensis) of Bangladesh for treatment of tannery wastewater disposed in the open environment. Study Design:  The capacity of improving the water quality of the tannery effluent by bioremediation was assessed. The quantitative determination included the comparison of physical characters (pH, TDS, EC, DO, COD) and heavy metal profile (Pb, Cr, Cu, Zn) of the tannery effluent before and after treatment. Effluent treatment was carried out by individual species separately and in combination with all for a total of 25 days. Place and Duration of Study: Major experiments were carried out at the Applied Botany Laboratory, Dhaka Laboratory, BCSIR, Dhaka, Bangladesh from January 2022 to February 2024. Quantitative estimations were carried out at Soil & Water Laboratory, Dhaka Laboratory, BCSIR, Dhaka, Bangladesh. Methodology: The tannery effluent was characterized by means of physiochemical parameters and heavy metal concentration prior to the experimental procedure. Four treatment plans were designed, three treatments (TSC, TLM, TSP) using individual species separately and one treatment (TC) using all three species in combination. The treatment continued for 25.0 days. The physiochemical parameters of the treated effluent were measured at 5.0-day intervals and heavy metal conc. Were measured on the 0th, 10th, and 25th days of the experiment. Comparative analysis of the data was utilized to determine useful species for further applied studies in future. Results: After treatments, a reduction at TDS level down to 3230 from 5150 mg/L, and an EC dropdown to 3290 from 10340 μS/cm was observed. Heavy metals removal capacity of the tested species was found as follows, S. cucullata: Zn > Cr >Pb> Cu, L. minor: Pb> Cr > Cu > Zn, S. platensis: Cu > Zn >Pb> Cr, and the combination treatment: Pb> Cu > Zn > Cr. The observation showed high efficiency of S. platensis in TDS reduction and Zn absorption, L. minor in COD reduction and Pb absorption, and S.cucullata in Zn absorption. Conclusion: The comparative data suggested the overall improvement of the effluent quality can be achieved by a combined treatment of L. minor and S. platensis, quickly and cost-efficiently. Further investigation is required for an in-depth understanding of their combined potential. Additionally, investigation will be carried out on their potential in Arsenic (As) removal and nano-particle production from post-treatment biomass.