The tannery industries (TIs) have greatly improved their treatment system, treated effluents still need to be properly delineated for contaminants and toxicity. In this study, the analysis of both raw and treated tannery effluent (TE) revealed the maximum reduction of chromium (91%) followed by chemical oxygen demand (COD) (76.7%), total dissolved solids (TDS) (43.3%), oil and grease (37.2%), and biological oxygen demand (BOD) (33.3%) after common effluent treatment plant (CETP) treatment. Further, the concentration of TDS (13317±2.7 mg/l), BOD (280±4.47 mg/l), COD (409±2.4 mg/l), sulphate (3773±7.3 mg/l), nitrate (734.86±0.4 mg/l) and chloride (8053.59±18.7 mg/l) and chromium (7.153±0.02 mg/l) in treated TE were 6.3, 9.3, 1.6, 3.8, 73.4, 13.4 and 3.6-fold higher than the permissible limit fixed by central pollution control board (CPCB). Gas chromatography-mass spectrometry (GC-MS) analysis revealed the presence of recalcitrant organic pollutants such as furan, phthalate, and fatty acid in CETP treated TE. Phytotoxicity investigation of TE on fenugreek (Trigonella foenum-graecum L.) and mung bean (Vigna radiata L.) seeds germination show that both raw and CETP treated TE were inhibitory for seed germination and plant growth. Further, treated TE inhibited seed germination (30%) root length (97.3%), and shoot length (88.7%) in Trigonella foenum-graecum and at 50% concentration, respectively. However, CETP treated TE was less toxic than the raw TE. Further, fenugreek seeds were more sensitive to TE, as they could not be germinated in both undiluted raw and treated TE. The finding of the present study reveals that CETP treated effluents contain a complex mixture of toxic contaminants indicating it is not safe to discharge these effluents into the environment.
Key words: Tannery effluent, CETP, Recalcitrant organic pollutants, GC-MS, Phytotoxicity
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