Parameter Value Operating time (min.) of 90% removal for each metal Pb2+ Cd2+ Cu2+ As3+ Bed height 2.5 cm 30 17 27 15 5 cm 38 22 36 19 7.5 cm 44 37 41 33 Superficial velocity 1.1Umf=2.5 mm/s 38 22 36 19 1.5Umf=3.5 mm/s 22 14 19 10 Particle diameter 0.4-0.6 mm 38 22 36 19 0.6-1 mm 35 19 33 17

Table 3: Breakpoint time for each metal at different operating conditions.