Introduction

A specific feature of sulfide containing waste is the risk for acid/neutral drainage generation (A/NRD). Acid drainage occurs if the acid generation from sulfide oxidation exceeds the acid buffering from minerals in the waste while, in this context, neutral drainage occurs when neutralisation generation exceeds the acid generation.

Test methods for the determination of acid generation behaviour can be divided into static and kinetic tests. A static test is used for screening purposes. It is usually relatively fast to perform, but gives only indicative information based on total content of sulfur (or sulfides) and of readily available buffering minerals in the waste material. Kinetic tests give more detailed information on behaviour based on the determination of mineral reaction rates under specified conditions. A European Standard, EN 15875, has been established for the static testing, while this Technical Report gives guidance on how the kinetic testing may be performed and interpreted.

Kinetic testing has been required as part of permit processes for many new and operating mine sites. Many different test methods have been used over the last 20 to 30 years. These tests are commonly designed to avoid that the oxidation rate is limited due to the lack of oxygen or build-up of secondary minerals. Kinetic tests based on current standards and laboratory-scale standard practise (ASTM D5744 ‑ 96:2001 and ASTM D5744 ‑ 07:2007; Morin and Hutt, 1997; Lapakko, 2003) are not designed to evaluate short- and longterm drainage water quality. However, adjustments to the standard protocols can be done to produce indicative information about short-term drainage water quality. Together with modelling, this information can be used to predict/estimate long-term drainage water quality.

This Technical Report is a guidance document that discusses the main kinetic test methods that are used within the mining sector internationally, the applicability of the different tests and how to evaluate the results. Kinetic test results may provide valuable information, but it is important to understand their limitations. Sulfide oxidation in the field is controlled by many different factors that may be difficult to simulate within the laboratory. Some of these factors may in fact be unknown at the time of testing. The complexity of applying test results to field conditions may to some extent be balanced by long experience in evaluating such data.

The objective of this Technical Report is to support the management of waste from extractive industries by giving guidance on how to characterize the kinetically controlled process of acid drainage generation.

The target audience of the document includes all stakeholders concerned with the management of extractive waste including the extractive industry, authorities, regulators, consultants, and testing laboratories.

PD CEN/TR 16363:2012

Characterization of waste. Kinetic testing for assessing acid generation potential of sulfidic waste from extractive industries

Current

Published:

31 Jan 2013