Abstract

The indiscriminate land disposal of wastewater sludge in Lesotho poses an environmental and health concern since sludge typically
contains a myriad of hazardous chemicals. This study characterised the physico-chemical properties of the sludge generated at the
Ratjomose Wastewater Treatment Plant in Maseru, the capital city of Lesotho and its chemical safety for application on land as an organic
fertilizer. The sludge was slightly acidic and had considerable amounts of macronutrients The heavy metal concentrations are less than the
maximum limits recommended by the Food and Agricultural Organization and the South African standards for sludge applied to
agricultural land and are slightly higher than those recommended in the national industrial effluent discharge standards in Lesotho.
Principal component analysis did not reveal any major differences between the different cells used in the treatment plant. Since the
nutrients and chemical composition of this sludge match the guidelines for an organic-mineral soil conditioner, it can be concluded that this
sludge is safe for use in agricultural soils with no expected negative effects.

Key words: Waste water sludge, chemical toxicity, nutrient content, bio-fertilizer, soil application, Lesotho