# US 11,999,642 B2 · Method for removing calcium ions from high concentration organic wastewater

> Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt

- Number: US 11,999,642 B2
- Document ID: US11999642B2
- Status: Granted
- Kind: B2
- Application number: 17/264,304
- Filed: 2019-11-25
- Published: 2022-01-13
- Granted: 2024-06-04
- Earliest claimed: 2019-09-10
- Assignees: Tongji University
- Applicants: Tongji University
- Inventors: Pinjing He; Junjie Qiu; Liming Shao; Fan Lyu; Hua Zhang
- Web page: https://patentgrep.com/patent/US11999642B2

## CPC

- C02F 5/02: Softening water by precipitation of the hardness
- C02F 1/52: by flocculation or precipitation of suspended impurities {(C02F1/463 takes precedence)}
- C02F 1/5209: {Regulation methods for flocculation or precipitation}
- 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 11/04: Anaerobic treatment; Production of methane by such processes
- C02F 2001/5218: {Crystallization}
- C02F 2101/10: Inorganic compounds
- C02F 2103/06: Contaminated groundwater or leachate
- C02F 2103/28: from the paper or cellulose industry
- C02F 2209/05: Conductivity or salinity
- C02F 2209/06: pH
- 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

A method for removing calcium ions from high concentration organic wastewater is provided. The method comprises the steps of: (1) introducing high concentration organic wastewater containing Ca2+, inorganic carbon and a seed crystal into a reactor with a molar ratio of Ca2+ to inorganic carbon of 1:(3.2-6.2); (2) adjusting the hydrogen ion activity α(H+) and ionic strength of the solution in the reactor; (3) sequentially stirring and precipitating in the reactor to convert Ca2+ in the high concentration organic wastewater into calcium carbonate which is then precipitated for calcium removal.

## Claims

### Claim 1

A method for removing calcium ions from high concentration organic wastewater, wherein the method comprises the steps of:
(1) introducing inorganic carbon, a seed crystal and high concentration organic wastewater containing Ca2+ into a reactor,
wherein a molar ratio of Ca2+ to inorganic carbon is 1:(3.2-6.2),
wherein the seed crystal in step (1) is biomass with negative potential on a surface, and a particle size of the seed crystal is 0.2 μm-2 mm;
(2) adjusting a hydrogen ion activity α(H+) and ionic strength of the solution in the reactors,
wherein the α(H+) in step (2) is adjusted to 3.16×10−12-6.31×10−9 mol/L, and
the ionic strength after adjusting in step (2) is in a range of 0.3-2 mol/L;
(3) sequentially stirring and precipitating in the reactor to convert Ca2+ in the high concentration organic wastewater into calcium carbonate which is then precipitated for calcium removal,
wherein the precipitating step is followed after the stirring step is stopped.

### Claim 2 (depends on 1)

The method for removing calcium ions from high concentration organic wastewater according to claim 1, wherein a COD and Ca2+ concentration of the high concentration organic wastewater in step (1) is more than 2000 mg/L and more than 500 mg/L, respectively.

### Claim 3 (depends on 1)

The method for removing calcium ions from high concentration organic wastewater according to claim 1, wherein the inorganic carbon in step (1) is a kind of liquid or soluble solid that can directly release the inorganic carbon by a chemical decomposition or dissociation reaction.

### Claim 4 (depends on 1)

The method for removing calcium ions from high concentration organic wastewater according to claim 1, wherein a reaction temperature of the reactor in step (1) is 10-40° C., and a hydraulic retention time is 6-32 h.

### Claim 5 (depends on 1)

The method for removing calcium ions from high concentration organic wastewater according to claim 1, wherein the stirring in step (3) is at a speed of 100-600 r/min for 10-20 h.

### Claim 6 (depends on 1)

The method for removing calcium ions from high concentration organic wastewater according to claim 1, wherein a precipitating time in step (3) is 6-12 h.