Global Journal of Human-Social Science, B: Geography, Environmental Science and Disaster Management, Volume 22 Issue 3

Alum had a higher RE for heavy metals compared to FeCl 3 and FeSO 4 . Its values ranged from 72% - 94.28%. Like in other Coagulants, Cr has the highest RE of 94.28%. This was closely followed by Pb (92.8%) and Mn (87.9%) as presented in Figure 9. The maximum COD removal of 41.72% (Figure 10) resulted at 5 g/L coagulant dose. The COD removal increased with alum dosage increase. Zazouli and Yousefi (2008), Bila et.al . (2005) also reported RE of Alum for heavy metals in the range of 71% - 96% and COD in the range of 27% - 40% in their reports. Meanwhile, Trebouet et.al . (2001) reported a much lower maximum RE of 66% for heavy metals. MOS had the best range of RE for heavy metals of all the four coagulants with a minimum of 72.4% and maximum of 95.6% (Figure 11). It removed more of Pb, than Mn and Cr had the least RE. Ravikumar and Sheeja, (2013) reported a 93% RE for Pb and 70% RE for Cr in their work. Both Alum and MOS increased there RE for heavy metals with increase in concentration. Figure 12 showed that MOS treated samples had increased COD concentrations, giving a negative RE. This is similar to the report in previous studies (Arnoldsson and Bergman, 2007). Figure 5: FeCl 3 percentage removal efficiency for Cr, Pb and Mn Figure 6: FeCl 3 percentage removal for COD Volume XXII Issue III Version I 60 ( ) Global Journal of Human Social Science - Year 2022 © 2022 Global Journals B Abatement of Polluting Effects of Waste Dump Leachates using Different Coagulants