Abstract

In jar tests, synthetic wastewater was dosed with FeCl₃, Fe₂(SO₄)₃, AlCl₃ or Al₂(SO₄)₃ and flocculated. In each case the concentration of the metal ions in the flocculant was 0.043 M. Samples of the mixture were placed under a light microscope that had been fitted with a camera, so that the flocs could be examined. A further experiment was conducted using the same ratio (1:10) of sample to coagulant solutions with gentle mixing on a microscope slide and was also observed under the microscope. Photographs of the samples from both experiments were captured after 1, 30, 60 and 90 min to compare the area covered by the flocs. The area covered by the flocs in the jar test correlates linearly with the area covered by flocs in the microscope slide experiment. An equivalent means of testing can be carried out using microscope observation, which may be preferable to a jar test on the grounds of simplicity and lower cost.

Key words: Wastewater, flocculant, mixture, mixing, microscope.