Safety assessment on microbial and heavy metal concentration in Clarias gariepinus (African catfish) cultured in treated wastewater pond in Kumasi, Ghana

Abstract

This study assesses the microbial and heavy metal distribution in African catfish (Clarias gariepinus) cultured in waste stabilization pond, and their subsequent suitability for human consumption. Treated wastewater-fed pond (WFP) was used in the culture of the fish with a non-wastewater fed pond (NWFP), fed with ground and rain water as control. Pond water, sediments and fish tissue (gill, liver, gut and skin) samples from both sources were analyzed for pathogens and heavy metal levels. Escherichia coli populations in the sediments and water from the WFP exceeded the maximum permissible limit by 2-3 log units as expected. Significantly higher levels of pathogen contamination were detected in the gut and skin of fish from the WFP than the NWFP. Heavy metal concentrations in all samples fell within the Food and Agricultural Organization (FAO)/World Health Organization (WHO) and National Oceanic and Atmospheric Administration (NOAA) permissible limits except for iron and cadmium. There were significantly higher heavy metal concentrations in gill and liver than the muscle. Even though iron recorded the highest concentrations in fish tissue, the concentrations (0.1-2.0 mg kg) were below the expected daily nutritional requirement (1-2 mg) for humans and pose no toxicological risk. However, catfish from WFP would require precautionary measures such as cooking/grilling prior to consumption to avoid pathogen infection.

A Review of Environmental Contamination and Health Risk Assessment of Wastewater Use for Crop Irrigation with a Focus on Low and High-Income Countries

“…Besides these benefits, a number of drawbacks are associated with the use of wastewater for crop irrigation [ 4 , 10 , 12 ]. Wastewater contains potentially toxic elements (PTEs) such as zinc, chromium, copper, cadmium, nickel, lead, mercury, and parasitic worms, which can induce severe risks to the human health and the environment [ 13 , 14 , 15 ]. The use of untreated wastewater for crop irrigation can also cause soil hardening and shallow groundwater contamination [ 16 , 17 ].…”

Treated municipal wastewater as a water source for sustainable aquaculture: A review

“…However, in most of the reported cases, the levels of pathogenic bacteria on the skin were within the acceptable or marginally acceptable limits, except for two studies, as reported by Harnisz and Tucholski and Mark et al 68,69 The microbial flora of fish tissues naturally originates from the water since fish passively accumulate microbial pathogens mostly on their skin and in their gut. 20,70 25,71 The results of this study also indicated that when the concentrations of faecal coliforms in the water were about 10 3 per 100 ml, they were not detected in the muscle or in most of the tested organs.…”

Can Reclaimed Water Be Used for Sustainable Food Production in Aquaponics?

“…A study by Mark et al (2019), found that fish of the species Clarias gariepinus cultivated in ponds with domestic reclaimed water can have Fe and Cd levels within the maximum levels allowed by the FAO, WHO, and NOAA. The tissues that presented a higher bioaccumulation of toxic metals were the gills and liver with concentrations of 0.1 -2.0 mg kg −1 , which were still below the safety threshold for human consumption (1 -2 mg kg −1 ).…”