Research into the treatment of inorganic brines and concentrates (1994)

Two major problems threatening water users in South Africa are:-

• the availability of adequate quantities of water, and
• the deterioration of the quality of water resources due to increasing concentration of total dissolved solids (TDS).

In attempting to deal with these two problems of quantity and quality, increasing use has been made of water conservation and recycling technology. These measures have however, resulted in an increased production of inorganic brines and concentrates. For the purpose of this report, a quantitative definition of a brine has been avoided, and brine has been defined as any stream of high total dissolved solids concentration which cannot be treated adequately by conventional means.

Treatment and/or responsible disposal is however essential for these streams as unless these are adequately treated, they will eventually enter the aquatic environment, threatening the quality of both surface and groundwaters. The basis of this research project was to provide a framework of information which would enable brine producers to assess the best treatment options for their brine and be aware of the latest technology available to them.

The options available for controlling brine disposal into the aqueous environment include:

• engineering out the source of brine,
• converting the brine into a saleable product,
• indirect or diffuse discharge to the environment,
• deactivation or conversion to an inert substance,
• immobilisation or passive storage,
• disposal into designated brine sink impoundments or discharge by pipeline into the sea.

The above options have been listed in terms of increasing environmental impact. Where brine production cannot be prevented it would be advantageous to develop techniques for the on-site disposal of brines. The Water Research Commission contracted with the Pollution Research Group, University of Natal (Project No. 201) to investigate the treatment of inorganic brines and concentrates by physical, chemical, physio-chemical and electrical techniques.

A number of point sources of brine were identified and some specific problematic streams were characterised. Priority sources of brine include:

1. effluent streams generated at some AECI plants,
2. acid mine drainage,
3. cooling tower blow-down water,
4. saline wastes generated at SASOL 2 and 3.
5. bottle washing effluents.

PROJECT AIMS
The aims of this project were to:

• identify point sources of brine and to characterise those with a particulatly problematic chemistry,
• identify options for controlling brine disposal into the aqueous environment,
• develop techniques for on-site