Impact of untreated and microbially treated equalization tank effluent of textile industry on freshwater fish Channa punctata using haematological, biochemical, histopathological and ultrastructural analysis

The unregulated expulsion of untreated or partially treated industrial effluents poses serious threat to the aquatic ecosystem. Therefore, in the present study fish Channa punctata were exposed to untreated and microbially treated equalization tank effluent of textile industry and toxicity studies were carried out for 45 days. The study was planned to analyze the toxicity proffered by textile effluents through haematological, biochemical, histopathological and ultrastructural analysis in blood, liver and gill tissues of fish. While comparing untreated and microbially treated effluent exposed groups haematological parameters were significantly (P <= 0.05) less in the untreated effluent exposed group whereas White blood cell count was highly escalated. However, in the microbially treated groups, the alterations were less severe. Increased malondialdehyde content indicating oxidative stress, reduced Catalase (CAT) and Superoxide dismutase (SOD) activity showing a weakened antioxidant defence system and increased glutathione activity was also perceived in untreated effluent exposed groups in comparison to microbially treated groups. Histopathological alterations in gill (telangiectasia, lamellae fusion, breakage, vacuolization and bending of lamellae) and liver (sinusoid dilations, fusion, necrosis and congestion) were more pronounced and severe in the untreated effluent exposed group as compared to microbially treated group. The results observed in histopathology were further reaffirmed by scanning electron microscopy. The study clearly highlights less alterations and deformities in microbially treated effluent groups in comparison to untreated effluent groups. These findings, therefore, necessitate the search for more effective microbial inocula for the better treatment of effluents in order to protect the aquatic life as well as human beings. Graphical Abstract

Automated summary

The unregulated discharge of untreated or partially treated industrial wastewater poses a serious threat to aquatic ecosystems. This study exposed Channa punctata fish to untreated and microbially treated textile industry effluent to analyze their toxicity effects. The results showed that the untreated effluent group had more severe hematological, biochemical, histopathological, and ultrastructural alterations compared to the microbially treated group. This highlights the importance of finding more effective microbial treatments to protect aquatic life and human health.