Process for treatment of mine contact water

A process for treating Mine Contact Water (MCW) including selenium and nitrate, the process comprising:

• providing the MCW to a feed stream;
• adding acid to the feed stream to provide a reduced pH and alkalinity feed stream having a pH of from about 6 to about 8.5 and alkalinity as CaCO3 of from about 50 to about 450 mg/L;
• subjecting the reduced pH and alkalinity feed stream to filtration and adding antiscalant followed by a membrane treatment to separate the reduced pH and alkalinity feed stream into permeate and brine, producing a brine with a Langelier Saturation Index (LSI) less than 2 and a gypsum supersaturation (Gs) less than 6;
• subjecting the brine to a high density sludge (HDS) process to produce a processed brine and residues;
• recycling a majority of volume of the processed brine to the feed stream;
• separating a remainder of the volume of the processed brine to provide a bleed off of the processed brine prior to the recycling;
• subjecting the bleed off of the processed brine to a subsequent treatment to remove at least some contaminants including at least some selenium and nitrate.