How to manage and treat acid mine drainage water

Acid mine drainage (AMD) water management and treatment requires urgent action, says SA Water Research Commission mine water research manager Dr Jo Burgess.

Dr. Jo Burgess, Mine Water Research Manager at the SA Water Research Commission

“South Africa has the required water pollution management knowledge. Methods of dealing with AMD do not differ from those used in other parts of the world”, says Dr Burgess in a call to action by the scientific body in September 2012.

GARD Guide list best water practice

The international gold standard for dealing with AMD is the Global Acid Rock Drainage (GARD) Guide. Acid Rock Drainage (ARD) is the common term internationally for mine water.

The GARD Guide includes best practice for treatment of ARD /AMD, neutral mine drainage (NMD) and saline drainage (SD). The guide was created from contributions of many individuals and organisations around the world, including several South African organisations.

“We must allow partnerships to be created. No single stakeholder has all the answers or resources for a complete solution to the problem”, says Dr Burgess.

AMD treatment process options

Dr Burgess notes that there is no one single treatment process for all acid mine drainage water or sites

There are four types of AMD treatment methods, categorised according to result;
• AMD neutralisation
• AMD metals removal
• AMD desalination
• AMD specific target pollutant treatment.

Most water treatment requires a combination of processes. Each process is termed a ‘unit operation’, and several unit operations are put together in a ‘process train’.

If water effluent is acidic and contains heavy metals, then treatment technologies are neutralisation and metals removal.

“Many types of waters exiting mine workings are not acidic. Neutral mine water, with a pH of 6 to 8, is almost harmless, depending on what has dissolved in the water.

“Acidic mine water, with a pH below 6, have been escaping into the environment taking dissolved metals and salts into rivers, lakes and downstream aquifers. These salts and metals can be toxic to plants, animals, and people.”

Saline mine drainage differs from AMD

Dr Burgess confirms that mine water treatment already takes place at several sites in the Johannesburg Witwatersrand reef area. “Every mining and decant site is unique, because the volume of water, characteristics of water, and desired results, all influence what treatment is needed.

“Saline drainage needs a completely different treatment process to acid mine drainage. Mine sites which are still active, require mine water treatment by the mine owners, like water reclamation plants in Mpumalanga, operated by Anglo Coal and Optimum.”

According to Burgess the current hindrances to effective treatment of AMD are not scientific or technical, but relate to institutional arrangements and funding.

There are 20 different methods available for treating all types of mine water pollution, developed and tested worldwide.

South Africa’s acid mine drainage pollution inaction “come from problems identifying who is responsible for paying for or doing the treatment, and deciding what type of water we want to produce by treating AMD”.

Water treatment waste and legal jurisdiction issues

Treated mine water could be used for industry, irrigation of certain crops, release into rivers, or even for drinking.

Another issue is where to take treated water, by-products of treatment, and pollution waste. “We need to align the regulatory functions of the Departments of Water and Environmental Affairs and Mineral Resources relevant to mine water and create a regulatory environment that enables private and public stakeholders to work together in implementing treatment methods.”

Mine water a political and industrial hot potato

Dr Burgess serves on the inter governmental task team on acid mine drainage, where a specialist geological report on safety, health, environmental pollution, economic impacts, costs and possible solutions was tabled a year ago.

“Ownerless mines which have become wards of the state are more vulnerable to releasing untreated water to the environment”, explains Dr Burgess in a call to action. “Nothing has been done yet, while a lot of treatment is required.

“Impacts of uncontrolled decant in groundwater, and into some surface streams, of some types of mine water, are becoming severe.

  • PHOTO; Dr Jo Burgess, Water Research Commission Research Manager for Mine Water Treatment and Management, made an urgent call for AMD action on government, state bodies, municipalities the mining industry in September 2012.
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