# US 5,346,620 A · Process for waste water treatment by removal of sodium sulfate

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- Number: US 5,346,620 A
- Document ID: US5346620A
- Status: Granted
- Kind: A
- Application number: 08/114,701
- Filed: 1993-08-31
- Granted: 1994-09-13
- Earliest claimed: 1993-08-31
- Assignees: BASF SE
- Inventors: David C. Hendrix; Andrew J. McNabb; Nguyen L. Kim; Michael Loden; Jaime R. Morales
- Web page: https://patentgrep.com/patent/US5346620A

## CPC

- C02F 3/302: {Nitrification and denitrification treatment (C02F3/308 takes precedence)}
- C02F 1/5272: {using specific organic precipitants}
- C02F 3/12: Activated sludge processes
- C02F 9/00: Multistage treatment of water, waste water or sewage
- C02F 2101/327: {Polyaromatic Hydrocarbons [PAH's]}
- C02F 2101/345: {Phenols}
- Y02W 10/10: Biological treatment of water, waste water, or sewage
- Y10S 210/903: Nitrogenous
- 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)
- Y02W: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
- Y10S: TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS

## Abstract

The present invention is a process for treatment of waste water streams having a sodium sulfate content of above 20 percent. The process is useful for treating waste water generated in the production of polyethyleneimine and cyclohexanone. The process includes the steps of removing sodium sulfate from waste water by the addition of organic solvent. The waste water having reduced sodium sulfate content is then subjected to biological treatment with activated sludge. First the waste water is subjected to pre-treatment. Pre-treated waste water is combined other waste water and treated by denitrification and nitrification.

## Claims

### Claim 1

A process for treatment of waste water streams having a concentration of above 20% sodium sulfate, including the steps of
a) removing sodium sulfate from waste water in the form of crystals, by the addition of organic solvent, wherein said solvent is miscible in aqueous solution at temperatures between 20.degree. C. and 110.degree. C.,
b) biological pre-treatment with activated sludge
c) denitrification with activated sludge and
d) nitrification with activated sludge.

### Claim 2 (depends on 1)

The process of claim 1, wherein the organic solvent is selected from the group consisting of methanol, ethanol isopropyl alcohol, acetone and monoethanolamine.

### Claim 3 (depends on 1)

The process of claim 1, wherein the solvent is utilized in an amount between 20 and 70 weight percent, based on the total weight of waste water and solvent.

### Claim 4 (depends on 1)

The process of claim 1, wherein the crystallization of sodium sulfate from the waste water is conducted at temperatures ranging from 40.degree. C. to 80.degree. C.

### Claim 5 (depends on 1)

The process of claim 1, wherein the pre-treatment time is between 21 and 24 hours.

### Claim 6 (depends on 1)

The process of claim 1, wherein denitrification residence time is 24 hours.

### Claim 7 (depends on 1)

The process of claim 1, wherein denitrification is conducted at a temperature of between 25.degree. C. and 30.degree. C.

### Claim 8 (depends on 1)

The process of claim 1, wherein denitrification is conducted at a pH of between 7.5 and 8.0.

### Claim 9 (depends on 1)

The process of claim 1, wherein nitrification residence time is 24 hours.

### Claim 10 (depends on 1)

The process of claim 1, wherein nitrification includes bacterial treatment with nitrosomonas and nitrobacter organisms.

### Claim 11 (depends on 1)

The process of claim 1, wherein nitrification is conducted at a temperature of between 25.degree. C. and 30.degree. C.

### Claim 12 (depends on 1)

The process of claim 1, wherein nitrification is conducted at a pH of between 7.2 and 7.7.

### Claim 13 (depends on 1)

The process of claim 1, wherein the waste water stream contains compounds selected from the group consisting of polyethyleneimime and cyclohexanone, by products from production of polyethyleneimime and cyclohexanone and mixtures thereof.

### Claim 14 (depends on 13)

The process of claim 13, wherein the waste water stream contains cyclohexanone, by products from production of cyclohexanone and mixtures thereof, wherein the process further comprises the step of acidifying the waste water to a pH of 2, prior to removal of sodium sulfate.

### Claim 15 (depends on 14)

The process of claim 14, wherein the waste water is acidified with concentrated sulfuric acid.

### Claim 16 (depends on 14)

The process of claim 14, further comprising the step of extracting an aqueous sodium sulfate phase by the addition of triisooctylamine, prior to removal of sodium sulfate.