Assessment of aquaculture wastewater impact on Osun river, Ede, Nigeria

Abstract

A study was conducted to determine the impact of aquaculture wastewater discharged from Alhaji Aagberi Fish Farms' fish pond in Ede, Osun State. Samples were collected from four different points around the pond and subjected to physicochemical and metal content analyses to determine the heavy metal levels. The physicochemical tests included pH, temperature, colour, electrical conductivity, chloride, dissolved oxygen, nitrate, phosphate, and turbidity. Biological tests such as fecal coliform, heterotrophic plate count, and adenosine triphosphate tests were also performed. The results showed that the samples had acceptable pH, temperature, and electrical conductivity levels. The colours of the samples ranged from light greenish, greenish, and light brown to no colour. Some samples had a fish-like odour, while others had no odour. The samples had an average chloride content ranging from 99.4 ± 0.2 mg/L to 149.9 ± 0.2 mg/L, dissolved oxygen from 1.94 ± 0.01 mg/L to 2.31 ± 0.02 mg/L, nitrate content from 2.99 ± 0.01 mg/L to 3.12 ± 0.01 mg/L, and turbidity from 2.44 ± 0.01 mg/L to 2.97 ± 0 mg/L. All of these values were within the regulatory limits. The metal content analyses showed that zinc, lead, mercury, and chromium were within acceptable limits. The bacterial counts ranged from 1.5 x 10² CFU/mL to 4.5 x 10² CFU/mL, leading to four genera of gram-negative and gram-positive bacteria, respectively. Aspergillus spp., Mucor, and Penicillum were the fungal isolates obtained from the samples. Therefore, to prevent harmful bacteria from the fish pond, the microbial load should be reduced by regulating and monitoring the water supplied and discharged from the pond ensuring it is free from harmful bacteria.