Impact of hydraulic loading on the removal of separate and mixed heavy metals in porous concrete

Porous concrete roads have a strong potential to immobilize different heavy metals from urban runoff. The immobilization potential is highly dependent on the characteristics of the cementitious binder and hydraulic loads. In this study, the effect of hydraulic loading on the removal of separate and mixed heavy metal ions from simulated industrial wastewater was investigated in a fixed bed based on porous concrete. Cadmium, copper, zinc, and lead were mixed into the wastewater and passed through porous concrete samples operated with full and empty water heads throughout the experiment. The removal of these ions reached a level of more than 93% when they were passed separately, but such removal was found to be greatly affected when the hydraulic load was maintained to a maximum in the concrete samples. The pH of wastewater percolated through concrete samples has become alkaline as a result of the leaching of calcium ions from the cement components. This calcium leaching was found to occur more in the case of concrete samples operated with zero hydraulic load. These findings highlight the importance of heavy metal-ion contact time when designing porous concrete water filters to treat wastewater disposed of by the electroplating and pigment manufacturing industries.