Integrated Environmental Impact Assessment of Tannery Effluent: Community Perception, Microalgal Bioremediation, And Phytotoxicity Evaluation

Abstract

Introduction: Industrial activities such as leather processing generate large volumes of wastewater that pose serious environmental and public health concerns. Tannery effluents are particularly problematic due to their high concentrations of organic matter, suspended solids, and toxic heavy metals, especially chromium. In many industrial regions, untreated or partially treated effluents are discharged into nearby environments, negatively affecting soil quality, water resources, agricultural productivity, and surrounding communities. Phycoremediation, which utilizes microalgae to remove pollutants from wastewater, has emerged as a promising biological approach. Microalgae possess the ability to assimilate nutrients, absorb heavy metals, and reduce organic pollutants while simultaneously producing valuable biomass.

Objectives: The present study aimed to evaluate the environmental impact of tannery effluents in the industrial regions of Pammal and Nagalkeni, Tamil Nadu. It also sought to investigate the effectiveness of phycoremediation using mixed microalgal cultures in tannery wastewater. Additionally, the study aimed to assess the influence of treated and untreated effluents on the growth and biomass of selected vegetable crops.

Methods: An Environmental Impact Assessment (EIA) was conducted through field observations, community surveys, and evaluation of physical, ecological, and socioeconomic parameters to determine the overall environmental impact of tannery activities. Effluent samples were collected from tannery discharge points and analysed for key physico-chemical parameters including pH, Biological Oxygen Demand (BOD), Chemical Oxygen Demand (COD), Total Suspended Solids (TSS), and heavy metals such as chromium. A mixed culture of microalgae was cultivated and applied for the treatment of tannery effluent under controlled conditions for 15 days. To evaluate phytotoxicity, growth experiments were conducted using two vegetable crops, Solanum melongena and Capsicum annuum under different irrigation conditions including untreated effluent, treated effluent, and diluted treated effluent.

Results: The Environmental Impact Assessment revealed a net Environmental Impact Value (EIV) of –19, indicating an overall negative environmental effect of tannery operations in the study area. Initial physico-chemical analysis showed that parameters such as BOD, COD, TSS, and chromium concentrations exceeded permissible environmental limits, confirming severe contamination. Following 15 days of treatment with mixed microalgae cultures, significant reductions in pollutant indicators were observed, accompanied by plant growth experiments using untreated and treated effluent in both crop species.

Conclusions: The findings of this study demonstrate that tannery effluents in the Pammal and Nagalkeni industrial zones exert a significant negative environmental impact. However, the application of mixed microalgae cultures for phycoremediation effectively reduced the pollutant load.