# US 10,479,715 B2 · Process for the treatment of high sulphate waters

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- Number: US 10,479,715 B2
- Document ID: US10479715B2
- Status: Granted
- Kind: B2
- Application number: 15/303,973
- Filed: 2015-04-20
- Published: 2017-02-09
- Granted: 2019-11-19
- Earliest claimed: 2014-04-22
- Applicants: Richard George Paxton
- Inventors: Richard George Paxton
- Web page: https://patentgrep.com/patent/US10479715B2

## CPC

- C02F 9/00: Multistage treatment of water, waste water or sewage
- C02F 1/5236: {using inorganic agents}
- C02F 1/5245: {using basic salts, e.g. of aluminium and iron}
- C02F 1/529: {Processes or devices for preparing lime water}
- C02F 1/58: by removing specified dissolved compounds (using ion-exchange C02F1/42; softening water C02F5/00)
- C02F 1/66: by neutralisation; pH adjustment (for degassing C02F1/20; using ion-exchange C02F1/42; for flocculation or precipitation of suspended impurities C02F1/52; for removing dissolved compounds C02F1/58)
- C02F 2001/007: {Processes including a sedimentation step}
- C02F 2101/101: {Sulfur compounds}
- C02F 2101/105: {Phosphorus compounds}
- C02F 2101/20: Heavy metals or heavy metal compounds
- C02F 2103/10: from quarries or from mining activities
- C02F 2301/046: Recirculation with an external loop
- C02F 2301/08: Multistage treatments, e.g. repetition of the same process step under different conditions
- C02F: TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE (separation in general B01D; special arrangements on waterborne vessels of installations for treating water, waste water or sewage, e.g. for producing fresh water, B63J; adding materials to water to prevent corrosion C23F; treating radioactively-contaminated liquids G21F9/04; regeneration of reactants for recirculation into processes, see the relevant places for the processes)

## Abstract

The present invention relates to an improved process for treating high sulphate waters. In particular, the present invention relates to an improved process by which ettringite is used to treat high sulphate waste waters by controlled precipitation of sulphate and metal ions.

## Claims

### Claim 1

A process for the treatment of sulphate-containing water, the process including:
a first reaction stage within which ettringite is used to precipitate precipitated solids from the sulphate-containing water, the precipitated solids being selected from the group consisting of metal compounds, phosphate compounds, sulphate compounds and combinations thereof;
a suspended solids removal stage for removal of the precipitated solids produced by the first reaction stage;
a further reaction stage including ettringite production from partially-treated sulphate-containing water from the first reaction stage and the addition of an aluminum containing reagent;
a suspended solids removal stage for removal of precipitated solids produced by the further reaction stage;
a particle separation stage within which some or all of the precipitated solids that are removed within the suspended solids removal stage are separated into an aluminum hydroxide-rich product and a product containing a remainder of the precipitated solids removed by the suspend solids removal stage; and
recovery to the further reaction stage of a portion or all of the aluminum hydroxide-rich product as at least a portion of the aluminum containing reagent; and
recovery of the ettringite produced by the further reaction stage for use in the first reaction stage.

### Claim 2 (depends on 1)

The process of claim 1, wherein the particle separation stage is based on hydrocyclone technology.

### Claim 3 (depends on 1)

The process of claim 1, wherein a portion of the product containing the remainder of the precipitated solids is returned to the first reaction stage.

### Claim 4 (depends on 3)

The process of claim 3, wherein the portion of the product containing the remainder of the precipitated solids is subjected to a washing or leaching process using a portion of the sulphate-containing water.

### Claim 5 (depends on 1)

The process of claim 1, wherein the first reaction stage further comprises a secondary removal stage for removal of the precipitated solids precipitated in the first reaction stage.

### Claim 6 (depends on 1)

The process of claim 1, wherein an additional reaction stage is provided before the further reaction stage and where additional ettringite, lime, or hydroxide containing material is added to raise the pH.