[1] Jimma Univ, Jimma Inst Technol, Fac Mat Sci & Engn, POB 378, Jimma, Ethiopia
[2] Bonga Univ, Coll Nat & Computat Sci, Dept Phys, POB 334, Bonga, Ethiopia
[3] Jimma Univ, Fac Civil & Environm Engn, POB 378, Jimma, Ethiopia
[4] Addis Ababa Univ, Africa Ctr Excellence Water Management, POB 1176, Addis Ababa, Ethiopia
[5] Mahatma Gandhi Univ, Int & Inter Univ Ctr Nanosci & Nanotechnol, Kottayam 686560, India
[6] Univ Rostock, Fac Agr & Environm Sci, Justus Von Liebig Weg 6, D-18059 Rostock, Germany