Soma WAKABAYASHI

Removal of Heavy Metals in Road Runoff Using Porous Concrete

Toshiya Komatsu

The proportion of nonpoint pollution whose source is unclear is increasing nowadays. The main source of non-point pollution in urban area is pollution by heavy metals contained in road runoff. In this study, we examined the reduction of pollution by porous concrete. Since heavy metals have the property of being easily fixed to the hardened cement material, which is the material of concrete, we focused on porous concrete, which has many voids among concrete and is considered to be suitable for water permeability. 
Test pieces with porosities of 20%, 25%, and 30% and ordinary concrete were prepared. A literature review was conducted on heavy metal concentrations in road runoff. As a result, Cu(0.2mg/?), Pb(0.1mg/?), and Zn(1.0mg/?) were chosen for this research. In the heavy metal removal experiment, a solution of Cu, Pb, and Zn was prepared, and test piece (about 150g) was submerged in water (1.5 ?). Heavy metal solutions were collected every day until the 7th day. And on the 10th day, and concentration was measured. 
As a result, there was no significant difference in the amount of adsorption of porous concrete having different porosities. But It was confirmed that porous concrete has better adsorption capacity than ordinary concrete. The adsorption rate was in the order of Zn (75~88%)> Pb (62~85%)> Cu (42~59%), and the removal rate of porous concrete in 10 days was higher than that of ordinary concrete. For Cu, phenomena of elution from cement was found.
It is important to carry out column experiments and to measure the infiltration capacity in the next step. And it should also be considered to carry out heavy metal elution experiments from concrete.