Acute toxicity induced by treated sewage to zebrafish (Danio rerio)

Abstract

Objective: Acute toxicity markers in zebrafish caused by exposure to treated sewage from two sewage treatment plants were evaluated in order to obtain accurate and relevant information on the potential environmental health risks associated with these waters.

Design/methodology/approach: The acute toxicity assessment was performed according to the guidelines proposed by the Organization for Economic Cooperation and Development (OECD). Five proportions of each type of water treated with dechlorinated tap water (20, 40, 60, 60, 80 and 100%) were tested to determine the Median Lethal Dilution (LDil₅₀). The dechlorinated tap water was the negative control and as a positive control potassium dichromate at Mean Lethal Concentration (0.065 mg/L). The description of the teratogenic effects was carried out using the spine biomarker, which consists of dividing the fish into three sections to identify the damaged area.

Results: The results revealed that the mixture of treated sewage (mCl) and treated sewage disinfected with sodium hypochlorite (NaClO) caused toxic effects in zebrafish embryos. On the other hand, treated sewage from the Macroplanta de Bahía de Banderas (BBdClO) was not toxic at 96 hours of exposure.

Limitations on study/implications: It would be advisable to characterize the treated sewage from these two sewage treatment plants.

Findings/conclusions: These findings underscore the importance of assessing the toxicity of treated sewage and its short- and long-term effects on aquatic organisms, providing valuable information for water resource management and environmental protection.