The Improvement of Water Quality in an Acidic River Environment Using Waste Concrete Aggregates

Abstract

This study was carried out to develop a technique for treatments of acidified river water using waste concrete aggregates for sustainable protection of the water environment. In this study, the water quality in the Matsukawa River, Japan, which receives acidic mine drainage, were investigated as a model field of an acidic water environment. Additionally, chemical component analyses of the waste concrete aggregates and neutralization testing in batch mode were carried out to use of waste concrete aggregates to neutralize acidified rivers. The results of the field investigation suggested that dissolved Al acts as a buffer substance, inhibiting rises in pH in acidified water environments. The results of the neutralization tests confirmed that it was possible to neutralize acidified river water by using concrete aggregates; dissolved Al in the acidified river water was settling removed effectively by these neutralization treatments. Additionally, increases in pH could be accelerated by adding aeration to the neutralization process. Aeration decreased the requirement for neutralization aggregates by approximately 30%. These results suggested that use of waste concrete aggregates effectively neutralizes water that has been acidified by high concentrations of Al acting as a buffer inhibiting pH rise.