Optimization of Abandoned Mine Drainage Treatent by Commercially Available Nanofiltration Membranes

Abandoned or acid mine drainage (AMD) is characterized with high sulfate and metal ion concentrations and acidic pH and has been a pervasive environmental concern for over five decades. Problems of sludge disposal and inability to achieve EPA sulfate limits with conventional treatment strategy of lime neutralization and cost ineffectiveness of the new suggested treatment techniques encourages the use of nanofiltration (NF) membranes for the recovery of AMD. NF allows the use of recovered AMD in two ways: treated water (NF permeate) to be used as a substitute for fresh water and the concentrate (NF reject, which has high sulfate concentration) to be used for treatment of produced water from unconventional gas extraction. This study provides a protocol for testing nanofiltration membranes at laboratoryscale based on rejection and permeability optimization for AMD recovery. Eight commercially available NF nanofiltration membranes covering the entire spectrum of NF (i.e., MWCO’s between 200 to 800) and with three different active layer chemistries (polyamide, poly(piperazineamide) and cellulose acetate) were screened to optimize AMD recovery. Tests were conducted with both dead-end and cross-flow laboratory scale-modules with synthetic and real AMD. This study suggested that amongst the tested NF membranes, NF90 would be best suited for the recovery of AMD and is suggested for use in the pilot/full scale recovery of AMD.

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