Organo-metallic pollutants of distillery effluent and their toxicity on freshwater fish and germinating Zea mays seeds

Anaerobically treated molasses-based distilleries spent wash is a major source of terrestrial and aquatic pollution due to the mixture of the various unknown organometallic compounds in discharged waste. The nature of pollutants present in effluent has to be characterized prior to the evaluation of their fate in the environment at various tropic levels. The absorption maxima (lambda(max)) were obtained at 295 nm of pollutants present in spent wash which indicated that melanoidins are a major colorant along with other organic compounds. Abundantly identified compounds with GC-MS in effluent were found: 1,2,4,5-tetrahydro-2-methyl-3H-2-benzazepine-3-one, 6-(trifluoromethyl)-1H-imidazole [4,5-c] pyridine, 4,6-di-t-butyl-1H, 3H-thieno[3,4-c] thiophene, butanoic acid, trimethylsilyl ester, silane, (dodecyloxy)trimethylsilyl ester, 4-styryl [2,2] paracyclophane, 4-(p-cumylphenoxy) phthalonitrile, hexadecanoic acid, trimethylsilyl ester, butyl ester, and squalene. Some of these compounds are known with mutagenic and androgenic properties. The toxicity test of post-methanated distillery effluent (PMDE) showed direct toxic effects on catfish (Heteropneustes fossilis) even at 1% (v/v) concentration and caused degeneration of primary and secondary lamellae of the gill and the epithelial layer. Further, higher concentrations between 5 and 10% of PMDE showed loss of primary and secondary lamellae of gills, and liver catalase activity was also increased dramatically in H. fossilis, indicating the generation of oxidative free radicals. Similarly, inhibition of alpha-amylase activities in germinating Zea mays L. (Maize) seeds was also noted at 10% PMDE. This study confirmed the environmental toxicity of effluent with freshwater fish and Zea mays seeds.

Automated summary

This study reveals the presence of various unknown organometallic compounds in anaerobically treated molasses-based distilleries spent wash, with some of them known to have mutagenic and androgenic properties. Toxicity tests on catfish and maize seeds showed that higher concentrations of the effluent can cause direct toxic effects on catfish, leading to damage in their gills and liver, as well as inhibition of alpha-amylase activities in germinating maize seeds.