# US 12,006,271 B2 · Method for sludge dewatering using kitchen waste to synergistically enhance anaerobic biological acidification and low-temperature thermal hydrolysis of excess sludge

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- Number: US 12,006,271 B2
- Document ID: US12006271B2
- Status: Granted
- Kind: B2
- Application number: 17/153,904
- Filed: 2021-01-21
- Published: 2021-10-21
- Granted: 2024-06-11
- Earliest claimed: 2020-04-20
- Assignees: Tongji University
- Applicants: Tongji University
- Inventors: Bin Dong; Sisi Chen; Jun Gao; Renjie Chen; Xiangjuan Sun; Zao Yang; Bing Xue
- Web page: https://patentgrep.com/patent/US12006271B2

## CPC

- C05F 7/00: Fertilisers from waste water, sewage sludge, sea slime, ooze or similar masses
- C02F 9/00: Multistage treatment of water, waste water or sewage
- C05F 11/00: Other organic fertilisers
- C02F 11/04: Anaerobic treatment; Production of methane by such processes
- C02F 11/121: by mechanical de-watering
- C02F 11/127: by centrifugation
- C02F 11/13: by heating
- C02F 11/18: by thermal conditioning (by pyrolysis C02F11/10)
- C02F 2303/06: Sludge reduction, e.g. by lysis
- C02F 2303/10: Energy recovery
- C02F 2305/06: Nutrients for stimulating the growth of microorganisms
- Y02A 40/20: Fertilizers of biological origin, e.g. guano or fertilizers made from animal corpses
- Y02P 20/129: Energy recovery, e.g. by cogeneration, H2recovery or pressure recovery turbines
- Y02W 10/30: Wastewater or sewage treatment systems using renewable energies
- Y02W 30/40: Bio-organic fraction processing; Production of fertilisers from the organic fraction of waste or refuse
- C05F: ORGANIC FERTILISERS NOT COVERED BY SUBCLASSES C05B, C05C, e.g. FERTILISERS FROM WASTE OR REFUSE
- 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)
- Y02A: TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
- Y02P: CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02W: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT

## Abstract

A method for sludge dewatering using kitchen waste to synergistically enhance a coupling of an anaerobic biological acidification and a low-temperature hydrothermal of excess sludge is disclosed. The method includes the following steps: first, uniformly mixing the excess sludge from a sewage treatment plant and the kitchen waste for an anaerobic biological acidification reaction at 36.5-37.5° C. for 2-4 days; then, concentrating the acidified mixture by centrifugation at a speed of 3000-5000 rpm for 5-10 min; performing a low-temperature thermal hydrolysis treatment on a residue obtained after removing a supernatant for 15-30 min at 100-140° C.; and after the thermal hydrolysis treatment is finished, cooling and dewatering to obtain a dewatered sludge cake and a dewatered filtrate. The new method realizes high-efficiency sludge dewatering and innocuous utilization of dewatered filtrate and sludge cake without adding chemical reagents and effectively avoids generating hardly-degradable chemical oxygen demand.

## Claims

### Claim 1

A method for sludge dewatering using kitchen waste to synergistically enhance anaerobic biological acidification and low-temperature thermal hydrolysis of excess sludge includes the following steps:
first, uniformly mixing the excess sludge and the kitchen waste for anaerobic biological acidification at 36.5-37.5° C. for 2-4 days to obtain an acidified mixture, wherein a pH value of the acidified mixture is 4-5;
then centrifuging the acidified mixture at a speed of 3000-5000 rpm for 5-10 min to remove a supernatant and then obtain a centrifuged product, wherein a volatile fatty acid content of the supernatant is 800-1500 mg/L, and a chemical oxygen demand (COD) degradation rate of the supernatant is not less than 95%; the supernatant after centrifugally concentrating is returned to a sewage treatment system of a sewage treatment plant as a carbon source;
performing a low-temperature thermal hydrolysis treatment on the centrifuged product for 15-30 min at 100-140° C. to obtain a treated residue;
and after the low-temperature thermal hydrolysis treatment is finished, cooling and dewatering the treated residue to obtain a dewatered sludge cake and a dewatered filtrate.

### Claim 2 (depends on 1)

The method according to claim 1, wherein a volatile solid mass ratio of the excess sludge and the kitchen waste is 1:1-5:1.

### Claim 3 (depends on 1)

The method according to claim 1, wherein an initial moisture content of the excess sludge is 90-98%; the kitchen waste is food waste collected and transported in a centralized manner, and an initial moisture content of the kitchen waste is 85-90%; before use, the kitchen waste is ground to have a particle size of 0.1-5 mm.

### Claim 4 (depends on 1)

The method according to claim 1, wherein waste heat of the low-temperature thermal hydrolysis treatment is used for maintaining a required temperature for the anaerobic biological acidification, and an energy recovery rate of the low-temperature thermal hydrolysis treatment is 80-85%.

### Claim 5 (depends on 1)

The method according to claim 1, wherein a solid content of the dewatered sludge cake is 35-40%.

### Claim 6 (depends on 1)

The method according to claim 1, wherein the dewatered sludge cake is used as an organic fertilizer after being subjected to a drying-free incineration or an aerobic fermentation.

### Claim 7 (depends on 1)

The method according to claim 1, wherein a COD content of the dewatered filtrate is 8000-10000 mg/L, a COD degradation rate of the dewatered filtrate is not less than 90%; the dewatered filtrate is returned to the sewage treatment system of the sewage treatment plant as a carbon source.

### Claim 8 (depends on 2)

The method according to claim 2, wherein an initial moisture content of the excess sludge is 90-98%; the kitchen waste is food waste collected and transported in a centralized manner, and an initial moisture content of the kitchen waste is 85-90%; before use, the kitchen waste is ground to have a particle size of 0.1-5 mm.

### Claim 9 (depends on 5)

The method according to claim 5, wherein the dewatered sludge cake is used as an organic fertilizer after being subjected to a drying-free incineration or an aerobic fermentation.