Passive systems for the
treatment of acid mine drainage (AMD) are typically more economic in the long
term than active systems. Various flow charts for treatment selection have been
prepared by scientists in the USA, however,
they have typically not included a variable important at New Zealand AMD sites
on the West Coast: topography and available land area. Very steep topography,
dense and often protected vegetation (and animals such as snails), and a
high-rainfall climate result in AMD with very high flow rates in locations with
very limited space for remediation. Flow charts specific to New Zealand have
been prepared which accommodate topography and available land area. Parameters
necessary to use the flow charts are iron and aluminium concentrations, pH,
ferrous to ferric iron ratio, dissolved oxygen concentration, topography and
available land area. Prior to full scale construction, is it recommended that
flow rates be quantified, small-scale trials be conducted, and cost,
effectiveness, limitations, and risk of failure be reviewed for various options.
One full-scale remediation system has been installed in New Zealand
based on this methodology and another is planned. The performance of these
systems, as well as future systems to be installed, will be used to validate
these treatment system flow charts.