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Water Science & Technology—WST Vol 59 No 8 pp 1551–1558 © IWA Publishing 2009 doi:10.2166/wst.2009.155

The effect of turbidity levels and Moringa oleifera concentration on the effectiveness of coagulation in water treatment

T. Nkurunziza, J. B. Nduwayezu, E. N. Banadda and I. Nhapi

WREM Project, National University of Rwanda, P.O. Box 117, Huye Southern Province, Rwanda E-mail: nkurtheo@yahoo.fr
Institute of Scientific and Technological Research (IRST), P.O. Box 227, Huye Southern Province, Rwanda
Department of Food Science and Technology, Makerere University, P.O. Box 7062, Kampala, Uganda


ABSTRACT

Laboratory experiments were carried out to assess the water purification and antimicrobial properties of Moringa oleifera (MO). Hence different concentrations (25 to 300 mg/L) were prepared from a salt (1 M NaCl) extract of MO fine powder and applied to natural surface water whose turbidity levels ranged from 50 to 450 NTU. The parameters determined before and after coagulation were turbidity, pH, colour, hardness, iron, manganese and Escherichia coli. The experiments showed that turbidity removal is influenced by the initial turbidity since the lowest turbidity removal of 83.2% was observed at 50 NTU, whilst the highest of 99.8% was obtained at 450 NTU. Colour removal followed the same trend as the turbidity. The pH exhibited slight variations through the coagulation. The hardness removal was very low (0 to 15%). However, high removals were achieved for iron (90.4% to 100%) and manganese (93.1% to 100%). The highest E. coli removal achieved was 96.0%. Its removal was associated with the turbidity removal. The optimum MO dosages were 150 mg/L (50 NTU and 150 NTU) and 125 mg/L for the rest of the initial turbidity values. Furthermore all the parameters determined satisfied the WHO guidelines for drinking water except for E. coli.

Keywords: E. coli removal; flocculation; iron removal; manganese removal; Moringa oleifera; turbidity


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