Assessing the ecotoxicological impact of hospital wastewater on nile tilapia and the mitigating effects of NiFe₂O₄ nanocomposite

Abstract

The current study evaluated the toxic effects of raw and diluted hospital wastewaters (HWW) on the Nile tilapia, with a focus on antioxidant defense mechanisms, lipid peroxidation (LPO), nitric oxide (NO), and metallothionein (MT) levels. Furthermore, the present study assessed the efficacy and safety of using a NiFe₂O₄ nanocomposite (NiFe₂O₄NC) for treating HWW to reduce its ecotoxic impact on aquatic organisms, particularly fish. The Nile tilapia specimens were exposed to various doses of HWW in its raw form, diluted to 50 %, and 25 %, as well as to raw treated with NiFe₂O₄ nanoparticles at a concentration of 0.1 g/ L for 14 days. The study measured the activity of antioxidant enzymes, including superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione S-transferase (GST), glutathione reductase (GR), and total antioxidant capacity (TAC), as well as biomarkers of oxidative stress such as lipid peroxidation (LPO), nitric oxide (NO), and metallothionein (MT). The results demonstrated that NiFe₂O₄NC effectively removed 85 % of pharmaceuticals (PhACs) from HWW. In contrast, raw HWW exhibited reduced dissolved oxygen (DO) levels and increased turbidity, exceeding the Canadian Council Guidelines for the Protection of Aquatic Life (CCME) guidelines for the protection of aquatic life. A concentration-dependent response was observed, characterized by a reduced activity of SOD, CAT, GPx, and GR, alongside increased levels of LPO, NO, and MT in the liver, brain, and gills of the Nile tilapia exposed to HWW. Fish exposed to HWW treated with NiFe₂O₄NC showed enhanced antioxidant defense responses and lower levels of LPO, NO, and MT across all examined tissues compared to those exposed to untreated HWW. These data suggested that HWW induced an excessive production of various free radicals, including superoxide, hydroxyl, hydrogen peroxide, and nitric oxide, leading to an oxidative damage in hepatic, cerebral, and branchial tissues. In contrast, NiFe₂O₄NC treatment created less stressful conditions for the Nile tilapia compared to raw and diluted HWW. These findings highlight the effectiveness of NiFe₂O₄NC in mitigating the adverse effects of pharmaceutical contaminants in aquatic environments and minimizing the impact on fish.