METHOD FOR BARIUM AND NORM REMOVAL FROM PRODUCED WATER
A method of removing barium and naturally occurring radioactive material from produced water. The method includes pretreating the produced water having a pH in a range of from about 4.0 to about 10.0 with a sulfate source to form a suspension of barium sulfate, radium sulfate, or a combination thereof, treating the pretreated produced water with an anionic flocculant and gravitational])′ separating the treated produced water from the barium sulfate, radium sulfate, or a combination thereof.
1 . A method of removing barium and naturally occurring radioactive material from produced water, the method comprising:
pretreating the produced water having a pH in a range of from about 4.0 to about 10.0 by adding a sulfate source to form a suspension of barium sulfate, radium sulfate, or a combination thereof;
treating the pretreated produced water with an anionic flocculant; and
gravitationally separating the treated produced water from the barium sulfate, radium sulfate, or a combination thereof.
2 . The method of claim 1 , wherein the sulfate source comprises at least one of sodium sulfate, potassium sulfate, magnesium sulfate, calcium sulfate, and strontium sulfate.
3 . The method of claim 1 , wherein an amount of the sulfate source utilized in pretreating the produced water is based on a molar ratio of sulfate to barium dissolved in the produced water, from about 0.90 to about 1.20.
4 . The method of claim 1 , wherein the produced water comprises greater than 70,000 mg/L total suspended solids.
5 . The method of claim 1 , wherein treating the pretreated produced water includes adding a coagulant when the anionic flocculant has a molecular weight below 15 million Daltons.
6 . The method of claim 1 , wherein treating the produced water includes adding a coagulant when treating the sulfate source and the anionic flocculant alone results in a cloudy clarate greater than 100 mg/L TSS.
7 . The method of claim 1 , wherein the anionic flocculant includes anionic acrylamide copolymers.
8 . The method of claim 1 , wherein the anionic flocculant includes copolymers of acrylamide and acrylic acid.
9 . The method of claim 1 , wherein the anionic flocculant has a molecular weight in a range of about 1 million to about 50 million Daltons.
10 . The method of claim 9 , wherein the anionic flocculant has a molecular weight in a range of about 15 million to about 50 million Daltons.
11 . The method of claim 8 , wherein the anionic acrylamide copolymer flocculant has a mole percent in a range of about 50% to about 95%.
12 . The method of claim 1 , wherein a concentration of the anionic flocculant is in a range of about 1.0 mg/L to about 150 mg/L.
13 . The method of claim 1 , wherein the anionic flocculant has an anionicity of about 5% to about 30%.
14 . The method of claim 1 , further comprising adjusting the pH of the produced water, the pretreated water, or the treated water to a range of about 9.0 to about 10.0.
15 . The method of claim 14 , further comprising adjusting the pH of the produced water to a range of about 9.0 to about 10.0 prior to adding the sulfate source.
16 . The method of claim 14 , further comprising aerating the pH adjusted water to produce a sludge comprising metal-hydroxides from the produced water.
17 . A method of producing a recovered salt product with a low concentration of barium and naturally occurring radioactive materials from produced water, the method comprising:
removing barium and naturally occurring radioactive materials from produced water, comprising:
pretreating the produced water having a pH in a range of from about 4.0 to about 10.0 with a sulfate source to form a suspension of barium sulfate, radium sulfate, or a combination thereof;
treating the pretreated produced water with an anionic flocculant; and
gravitationally separating the treated produced water from the barium sulfate, radium sulfate, or a combination thereof;
evaporating the gravitationally separated water to form distilled water and a concentrated brine;
crystallizing salt crystals from the concentrated brine; and
washing the salt crystals to produce recovered salt product.
18 . The method of claim 17 , further comprising adjusting the pH of the gravitationally separated water to a neutral pH prior to evaporating the separated water.
19 . The method of claim 17 , wherein evaporating the separated water is controlled such that the mass concentration factor is maintained between y 1 and y 2 , where:
y 1 =−0.00001446 x+ 2.046; and
y 2 =−2.3591 n ( x )+25.846,
where x is a feed barium concentration (mg/L).
20 . A system for producing a recovered salt product with a low concentration of barium and NORM from produced water, the system comprising:
a barium and NORM treatment apparatus configured to:
pretreat the produced water having a pH in a range of from about 4.0 to about 10.0 with a sulfate source to form a suspension of barium sulfate, radium sulfate, or a combination thereof; and
treat the pretreated produced water with an anionic flocculant;
a gravitational separation unit configured to separate the treated water from the barium sulfate, radium sulfate, or a combination thereof;
an evaporation unit that produces distilled water and a concentrated brine from the separated water;
a crystallization unit configured to produce salt crystals from the concentrated brine; and
a crystal treatment unit configured to wash the salt crystals to produce the recovered salt product.