Consider for the scenario described below the potential contamination by lead of a raw drinking water drawn from one of the rivers in the lake system presented schematically in Figure 2.1.
A large underground clay-lined waste pit at a former industrial site is located alongside River A, near its confluence with LAKE I. The existence of this pit has been known for some time, but no seepage has ever been found. After a recent Richter-Scale three earth tremor> however 1 a waste plume from the pit has been discovered, the major contaminant in the stream being lead (Pb2+). Following the onset of the relatively steady new seepage from the pit1 dissolved Pb2+ concentrations averaging 100 µmol/1 are found in River A immediately above its discharge to LAKE I.
A community located along River F just down stream from LAKE II draws its public water supply from that river. The community has a relatively simple water treatment plant that has no provision for removal of dissolved Pb2+. The drinking water standard for lead is 15 µg/1. Determine whether the water supply to the community will exceed this standard if there is no remediation of the pit seepage. The Pb2+ undergoes a precipitation reaction of the form
Pb2+ + 20H- {::} Pb(OH)2(s) L
at a rate given by r = k[Pb2+][oH-]2, where k = 5.0 x 107 (1/mol)2(min-1). The lakes are well buffered at pH== 8.3.
A large underground clay-lined waste pit at a former industrial site is located alongside River A, near its confluence with LAKE I. The existence of this pit has been known for some time, but no seepage has ever been found. After a recent Richter-Scale three earth tremor> however 1 a waste plume from the pit has been discovered, the major contaminant in the stream being lead (Pb2+). Following the onset of the relatively steady new seepage from the pit1 dissolved Pb2+ concentrations averaging 100 µmol/1 are found in River A immediately above its discharge to LAKE I.
A community located along River F just down stream from LAKE II draws its public water supply from that river. The community has a relatively simple water treatment plant that has no provision for removal of dissolved Pb2+. The drinking water standard for lead is 15 µg/1. Determine whether the water supply to the community will exceed this standard if there is no remediation of the pit seepage. The Pb2+ undergoes a precipitation reaction of the form
Pb2+ + 20H- {::} Pb(OH)2(s) L
at a rate given by r = k[Pb2+][oH-]2, where k = 5.0 x 107 (1/mol)2(min-1). The lakes are well buffered at pH== 8.3.
