Effects of untreated hospital effluents on the accumulation of toxic metals in sediments of receiving system under tropical conditions: Case of South India and Democratic Republic of Congo

Physicochemical and ecotoxicological analyses have been performed to assess the quality of sediments receiving untreated hospital effluents from Indian and Democratic Republic of Congo (DRC) hospitals. The sediments were collected monthly and characterized for grain size, organic matter, total organic carbon, total carbon, nitrogen, phosphorus, toxic metals and ecotoxicity. The results highlight the high concentration of toxic metals from the Indian hospital effluent receiving systems, especially for Cr, Cu, As, Zn and Hg. On the other hand, the metal concentrations in the sediment receiving system from DRC are low (e.g. maximum Hg and Zn concentration were 0.46 and 48.84 mg kg⁻¹ respectively). Ostracods exposed to sediment samples H2 (September month sample) and H3 (June and September month samples) were found dead after 6 d of exposure whereas the higher mortality rate for Congo sediments was 23% but was accompanied with 33 ± 7% of growth inhibition. The results of this study show the variation of sediment composition on toxic metal levels as well as toxicity related to both, the type of hospitals and the sampling period. Additionally, hospital effluent disposal practices at the study sites can lead to the pollution of water resources and may generate risks for aquatic organisms and human health.