Recent rule changes and new technology are encouraging recycling and reuse of industrial waste. The Federal EPA’s recently published rule on the handling of coal combustion residuals (“CCRs”) encourages the “beneficial use” of coal ash such as reusing or recycling coal ash to ease use of virgin resources, to lower greenhouse gas emissions, to reduce the cost of coal ash disposal and to improve strength and durability of final product. According to the American Coal Ash Association, nearly half of the coal ash produced in 2014 was used as an ingredient in concrete and wallboard, for road construction or for mine reclamation. Scientists are also exploring the potential extraction of certain materials for use in electronics manufacturing. This is significant as Ohio has 29 coal ash sites.
Likewise, in mining, water is used to process the extracted minerals, for dust suppression and for slurry transportation. The used water contains mineral byproducts known as clay effluent in phosphate mining. For years, that effluent has been pumped into holding ponds, some as large as a mile square and considerably deep. In Florida today, there are more than 150 square miles of such ponds. Those ponds lay stagnant for years and years while the solids slowly fall to the bottom. The process takes so long because the suspended particles are electrically charged. In fact, the particles are “like charged” so that they naturally repel each other. As a result, the settling takes decades – 25 to 50 years.
A University of Florida researcher reduced this process to just two to three hours. The impact on mining operations could be significant.
The new process features a continuous feed of clay effluent into a separation unit where upper and lower electrode plates cause the particles to move to the bottom forming a wet solid cake. Water is thereby forced to the top and can be used repeatedly in further mining operations.
Treating the effluent electrically is certainly not new. In 1807, a process showed that clay particles moved in response to electricity and as late as the 1990’s other devices using electricity were created but deemed uneconomical. The cake may be used for mine reclamation.
Thus, the encouragement to recycle materials and advances in technology provide new methods for dealing with industrial waste. These advances provide an opportunity to reuse materials in a productive manner and offer an opportunity to reduce the impact of industrial processes.