Method and system for treating wastewater
Methods and systems for treating brine to produce distilled water and dried NaCl are disclosed. The brine enters a crystallization plant and is heated. Once heated, the brine is circulated to an evaporator. The evaporator increases the concentration of NaCl in the brine to a point about the super saturation level. Once above the super saturation level, NaCl crystals are formed. The larger crystals are circulated to a centrifuge for drying and the smaller crystals are recirculated through the evaporator for continued growth. The NaCl crystals are dried in the centrifuge.
1. A system for treating wastewater comprising:
a wastewater input line for receiving wastewater;
a storage tank for receiving and storing the wastewater from the input line to allow the wastewater to be screened for a total dissolved solids (“TDS”) concentration and a methanol concentration;
a methanol treatment system for removing methanol from the wastewater;
a pretreatment system configured to pretreat the wastewater to produce a pretreated wastewater suitable for crystallization/evaporation;
a routing system in communication with the storage tank, the methanol treatment system and the pretreatment system, the routing system adapted to:
route the wastewater through the methanol treatment system when the methanol concentration is greater than 500 mg/L; and
route the wastewater through the pretreatment system only when the TDS concentration is at least 150,000 mg/L;
an evaporation/crystallization unit configured to produce, from the pretreated wastewater, a distilled water, a concentrated brine comprising CaCl 2 ), and a salt slurry comprising NaCl;
a purification system configured to receive a first portion of the distilled water from the evaporation/crystallization unit and remove contaminants therefrom to produce a purified water; and
a post-treatment system comprising at least one of an ion exchange system and a reverse osmosis system, the post-treatment system configured to convert the purified water from the purification system into a de-wasted water.
2. A system according to claim 1 , further comprising a centrifuge configured to:
receive the salt slurry produced by the evaporation/crystallization unit; and
dewater the salt slurry to produce a centrate/filtrate and a sodium chloride product comprising NaCl crystals.
3. A system according to claim 2 , further comprising a circulation line connected to the centrifuge and the evaporation/crystallization unit, the circulation line configured to route back to the evaporation/crystallization unit the centrate/filtrate produced by the centrifuge.
4. A system according to claim 3 , wherein the centrate/filtrate from the circulation line is mixed with the pretreated wastewater as the pretreated wastewater is fed to the evaporation/crystallization unit.
5. A system according to claim 2 , wherein the sodium chloride product comprises greater than 98% w/w NaCl.
6. A system according to claim 1 , further comprising a washer system configured to:
receive a second portion of the distilled water from the evaporation/crystallization unit; and
wash the salt slurry with the second portion of the distilled water.
7. A system according to claim 1 , wherein the evaporation/crystallization unit is further configured to produce a vapor comprising liquid droplets.
8. A system according to claim 7 , further comprising a demister configured to remove the liquid droplets from the vapor to produce a demisted vapor.
9. A system according to claim 8 , further comprising a compression unit configured to compress the demisted vapor to produce a compressed vapor.
10. A system according to claim 9 , further comprising a heating chest configured to receive the compressed vapor from the compression unit.
11. A system according to claim 10 , further comprising a circulation line configured to:
receive a second portion of the distilled water from the crystallizer/evaporator unit; and
circulate the second portion of the distilled water from the crystallizer/evaporator unit, through the heating chest, and back into the crystallizer/evaporator unit.
12. A system according to claim 1 , further comprising a second stage thermal mechanical evaporation/crystallization unit configured to:
receive the concentrated brine produced by the evaporation/crystallization unit; and
produce a high-purity calcium chloride product from the concentrated brine.
13. A system according to claim 12 , wherein the high-purity calcium chloride product comprises approximately 35% w/w CaCl 2 ).
14. A system according to claim 13 , wherein the concentrated brine comprises approximately 18% to 20% w/w CaCl 2 ).
15. A system according to claim 12 , wherein the second stage thermal mechanical evaporation/crystallization unit is further configured to generate solid crystals from the concentrated brine, the solid crystals comprising one or more of: barium, strontium and sodium.
16. A system according to claim 12 , further comprising a lithium removal system configured to remove lithium from the concentrated brine before the concentrated brine is received by the second stage thermal mechanical evaporation/crystallization unit.
17. A system according to claim 1 , wherein the evaporation/crystallization unit is a mechanical vapor recompression (“MVR”) crystallizer.
18. A system according to claim 1 , wherein the pretreatment system comprises one or more of: a pH adjustment/chemical addition tank, a flocculation tank, a clarifier, and an equalization tank.
19. A system according to claim 1 , wherein the purification system comprises:
an anoxic treatment system configured to denitrify nitrogen compounds in the first portion of the distilled water under anaerobic conditions to produce a denitrified distilled water therefrom;
an aerobic treatment system configured to nitrify additional nitrogen compounds in the denitrified distilled water under aerobic conditions to produce a nitrified distilled water therefrom; and
a membrane separation system comprising a membrane, the membrane separation system configured to remove the contaminants from the nitrified distilled water to produce the purified water.
20. A system according to claim 1 , wherein the de-wasted water comprises a chemical oxygen demand (“COD”) of less than or equal to 15 mg/L, a methanol concentration of less than or equal to 3.5 mg/L, a nitrite-nitrate nitrogen concentration of less than or equal to 2 mg/L, a sodium concentration of less than or equal to 25 mg/L, a TDS concentration of less than or equal to 500 mg/L, and a total suspended solids (“TSS”) concentration of less than or equal to 45 mg/L.