The effect of ph and contact time on the concentration of As(III) and As(V) in coal ash systems

The concentrations of As(III) and As(V) were determined as a function of pH and contact time for water/coal ash systems. Laboratory studies showed that adsorption was the major controller of concentration at all pH values studied. Field studies in a coal ash disposal basin/stream system showed elevated As concentrations in the basin waters, but no increase of As(III) or As(V) in a stream receiving ash basin outflow. As(III) was preferentially removed from solution relative to As(V) in laboratory studies of acidic systems and in field studies at near neutral pH values.