Effects of Contact Time and Flow Configuration on the Acid Mine Drainage Remediation Capabilities of Pervious Concrete

Sandisiwe Khanyisa Thisani,Daramy Vandi Von Kallon,Patrick Byrne

doi:10.3390/su131910847

Sandisiwe Khanyisa Thisani, Daramy Vandi Von Kallon + Show 1 more

Open Access

https://doi.org/10.3390/su131910847

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Abstract

This paper investigates the Acid Mine Drainage (AMD) remediation capabilities of pozzolanic pervious concrete Permeable Reactive Barriers (PRBs) with a specific focus on the effects of flow configuration and contact time on the remediation efficiency. Raw AMD was collected from an abandoned coal mine. Two flow configurations, gravity flow and column flow, were tested at a laboratory scale with gradually increasing contact times. The gravity flow configuration with two orders of magnitude less liquid-concrete contact time achieved AMD treated water quality equivalent to the high retention column flow configuration. Concentrations of iron, aluminium, sulphate, magnesium and sodium were reduced by more than 99%, 80%, 17%, 22% and 20%, respectively, at the tested limits while calcium and potassium concentrations were increased by up to 16% and 300%, respectively. The study findings indicate that the lifecycle costs of pervious concrete PRBs can be significantly reduced when the PRBs are operated under gravity flow.

Highlights

Acid Mine Drainage (AMD) and the pollution associated with it are among the greatest environmental issues faced by mining operations globally [1]
The resulting stream is typically characterised by low pH, high dissolved metals and high dissolved sulphate (SO4 ) concentrations and is referred to as AMD [4,5]
Statistical significance testing was conducted to test the relationship between the treated AMD properties and the change in contact time for the column flow experiments

Summary

Introduction

Acid Mine Drainage (AMD) and the pollution associated with it are among the greatest environmental issues faced by mining operations globally [1]. When oxygenated water accumulates in active or abandoned mines and comes into contact with sulphide-rich minerals from exposed rock faces, the water is converted to a low pH leachate which dissolves heavy metals and other toxic contaminants from the surrounding environment [2,3,4]. The AMD can continue to decant for centuries after commercial mining operations have ceased and poses long-term environmental damage when left untreated [6,7]. The development of a low cost, low maintenance and effective AMD treatment process is one of the most important solutions required for the sustainable future of sulphide-rich mineral mining [1,8]. Permeable Reactive Barriers (PRBs) are porous mediums with reactive material designed to react with passing fluids through chemical or biochemical processes [9,10,11]

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