Methods and systems for treating phosphogypsum-containing water
Methods for treating phosphogypsum-containing water are disclosed. The water may be treated so as to promote precipitation of one or more target constituents and to facilitate downstream membrane treatment. A coagulant may be added to promote phosphate recovery. Related systems are also disclosed.
1 . A method of treating phosphogypsum-containing water, comprising:
promoting precipitation of at least one target constituent from the phosphogypsum-containing water to produce a supernatant water;
introducing aluminum to the supernatant water using electrolytic addition from the electrolysis of an anode consisting of aluminum to provide a pretreated supernatant water;
recovering phosphate from the pretreated supernatant water;
subjecting the pretreated supernatant water to membrane separation subsequent to phosphate recovery to produce treated water having at least one predetermined discharge requirement; and
discharging the treated water.
2 . The method of claim 1 , wherein precipitation is promoted in a multi-stage process.
3 . The method of claim 2 , wherein calcium and/or magnesium is precipitated in a first precipitation step.
4 . The method of claim 3 , wherein phosphate is precipitated in a second precipitation step.
5 . The method of claim 2 , further comprising adjusting a pH level of the phosphogypsum-containing water to a first pH level in the first precipitation step.
6 . The method of claim 5 , further comprising adjusting the first pH level to a second pH level in the second precipitation step.
7 . The method of claim 4 , further comprising a third precipitation step.
8 . The method of claim 3 , further comprising recovering calcium fluoride from a precipitation slurry associated with the first precipitation step.
9 . The method of claim 4 , further comprising recovering phosphate from a precipitation slurry associated with the second precipitation step.
10 . The method of claim 1 , wherein the membrane separation involves one or more of nanofiltration, ultrafiltration, and reverse osmosis.
11 . The method of claim 10 , wherein the membrane separation involves reverse osmosis and one of nanofiltration and ultrafiltration.
12 . The method of claim 1 , wherein the predetermined discharge requirement pertains to a phosphorous or silica level.
13 . The method of claim 1 , further comprising recycling at least one reject stream back to a source of the phosphogypsum-containing water.