Eliminating turbidity in drinking water using the mucilage of a common cactus

Diced Nopal cladodes (pads) have been used for the treatment of turbid natural spring waters in Latin America. To investigate this phenomenon, the mucilage derived from the species Opuntia ficus-indica was investigated. Comparison against the commonly used synthetic flocculant, aluminium sulfate (Al₂(SO₄)₃) demonstrated the high efficiency of the cactus to eliminate turbidity. The mucilage extract increased particulate settling rates 330% compared with aluminium sulfate, at dosage concentrations of 3 mg L⁻¹, while its performance was equivalent at doses 0.3% of the required Al₂(SO₄)₃ concentration. The cactus mucilage, which consists of complex carbohydrates and sugars, has unique surface activity characteristics that make it an ideal candidate for enhancing dispersion properties, creating emulsifications, and for reducing the surface tension of high polarity liquids. These results indicated that the Nopal cactus mucilage has the potential to be the basis for a new ‘green’ technology, which is environmentally benign and cost-effective.