COMPARATIVE EFFECTS OF CONVENTIONAL AND NON-CONVENTIONAL FLOCCULANTS AND DISINFECTANTS ON MICROBIAL CONTAMINANTS IN WATER PURIFICATION

Abstract

Flocculating and antibacterial activities of bioflocculant purified from Bacillus sp and Moringa oleifera seed powder were tested on well, stream and abattoir waste water samples. Soil and water samples were collected from Onyearugbulem market abattoir, Akure, Ondo State. Bacteria were isolated from the sediments of stream, its bank and abattoir soil at Onyearugbulem market by dilution and pour plate methods. Screening for best bioflocculating bacterium was also performed. The bioflocculant was compared with alum. Effects of metal ions (such as Mg2+, Ca2+ and Al2+), temperature and pH were also determined on flocculating activities of bioflocculant. The purified bioflocculant was tested in the treatment of well, stream and abattoir waste water samples. Three bacterial isolates producing flocculating substances were isolated and the bacterium with the best flocculating property was selected. The identified bioflocculant producing bacteria include Bacillus subtilis, Bacillus cereus, Bacillus anthracis, Bacillus thurigiensis, Streptomyces griseus, and Streptomyces somaliensis. The best bioflocculant was produced from Bacillus subtilis. The flocculating activity of the bioflocculant was stimulated in the presence of Mg2+, Ca2+and Al3+. The bioflocculant was thermostable and retained more than 80% of its flocculating activity after being heated at 100oC for 25 minutes. It had a wide pH range of 3-10 with the highest flocculating activity of 85% at pH 6. Optimum bioflocculant dosage was recorded at 90.06% at 0.8ml of the bioflocculant dosage when added to 1 liter of water. This bioflocculant was effective in the treatment of well, stream and abattoir waste waters with optimum flocculating activity at 88.72%, 96.95% and 62.51% respectively. This bioflocculant inhibited the growth of coliform for well, stream and abattoir waste water samples. On the other hand, alum sulfate when compared with bioflocculant at a dosage level of 200mg for well and stream waters and 800mg for abattoir waste water yielded flocculating activities of 87.33%, 78.42% and 24.60%. This indicates that purified bioflocculant was more effective than alum sulphate. Bioflocculant produced from Bacillus subtilis should be exploited in water treatment. Moringa Oleifera seed powder exhibited both flocculating and disinfecting potentials in water treatment but not effective in the treatment of abattoir waste water.