Assessment of heavy metal contamination in faeces of cattle grazing in wastewater treatment plants in Limpopo Province, South Africa
Résumé
In Limpopo Province, South Africa, livestock commonly graze freely around wastewater treatment plants (WWTPs), raising contamination concerns and prompting the assessment of heavy metal levels in palatable grasses, sludge liquors, and cow faeces. Twenty-one cow faecal samples were collected from two WWTPs and a control farm, while 12 palatable grass samples and 16 sludge liquor samples were collected from two WWTPs. Samples were collected from February to March 2024 and analysed for heavy metals using inductively coupled plasma-mass spectrometry. Heavy metal concentrations in the grass samples were within the maximum tolerable limits for cattle feed and in the order aluminium > zinc > copper > chromium > strontium > nickel > arsenic > selenium > cadmium. In the sludge liquor, metals such as aluminium, copper, mercury, and lead exceeded permissible limits for livestock drinking water, posing a health risk for both the animals and the consumers of the animal products. The mean concentrations in the faecal samples were in the order aluminium > zinc > strontium > copper > chromium > nickel > lead > arsenic > selenium > cadmium; in most cases, the control farm faecal samples contained significantly higher concentrations than the WWTP faecal samples. The strong correlations found between the heavy metal concentrations in the faeces, grass, and sludge liquor samples suggest that the grass and sludge liquor are contaminating the animal tissue. These findings indicate that livestock should be prevented from grazing near WWTPs and that heavy metal concentrations in animal products from the study area need regular monitoring. (Submitted 20 February 2025; Accepted 27 June 2025; Published 22 August 2025)
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