Method for enhancing deep degradation of proteins in sludge

Patent metadata

Field	Value
Publication number	US-11548803-B2
Application number	US-202117239699-A
Country	US
Kind code	B2
Filing date	Apr 26, 2021
Priority date	Jun 27, 2020
Publication date	Jan 10, 2023
Grant date	Jan 10, 2023

Abstract

The present invention relates to a method for enhancing deep degradation of proteins in sludge. The method includes the following steps: an anaerobic digestion product of excess sludge as a substrate is treated by Van Soest's washing method to obtain the sludge free of easily degradable organics and containing degradation-resistant proteins; then, with the anaerobic digestion product of excess sludge as an inoculum and the sludge free of easily degradable organics and containing degradation-resistant proteins as a substrate, a first-stage microbial electrolytic cell coupled anaerobic digestion system is started for treatment to obtain a microbial mixture related to targeted degradation of the degradation-resistant proteins; with the microbial mixture related to targeted degradation of the degradation-resistant proteins as an inoculum and the anaerobic digestion product of excess sludge as a substrate, a second-stage microbial electrolytic cell coupled anaerobic digestion system is started to obtain the sludge with deeply degraded proteins.

First claim

What is claimed is:

1. A method for enhancing degradation of proteins in sludge, comprising the following steps:
(S1) using an anaerobic digestion product of excess sludge as a substrate, treating the substrate with a neutral detergent of Van Soest's washing method, removing a resultant supernatant to obtain a residue, and washing the residue with distilled water to be at a neutral pH value to obtain a sludge free of easily degradable organics, wherein the sludge contains degradation-resistant proteins;
(S2) using the anaerobic digestion product of excess sludge as an inoculum, using the sludge free of easily degradable organics obtained in the step (S1) as a substrate, starting a first-stage microbial electrolytic cell coupled anaerobic digestion system by applying an external voltage through a direct current power supply to acclimate and enrich a target microorganism, taking a microbial mixture on a surface of electrodes and in a sludge solution to concentrate by centrifuging to obtain a microbial mixture related to targeted degradation of the degradation-resistant proteins; and
(S3) using the microbial mixture obtained in the step (S2) as an inoculum, using the anaerobic digestion product of excess sludge as a substrate, starting a second-stage microbial electrolytic cell coupled anaerobic digestion system by applying an external voltage through a direct current power supply to degrade proteins in the anaerobic digestion product of the excess sludge.

2. The method for enhancing degradation of proteins in sludge according to claim 1 , wherein in the excess sludge, a proportion by mass of volatile solids to total solids is 40-60%, and the proteins account for 50-60% by mass of total volatile solids; in the anaerobic digestion product of the excess sludge, the proportion by mass of volatile solids to total solids is 30-40%, and the proteins account for 40-50% by mass of total volatile solids; in the sludge free of easily degradable organics in the step (S1), a proportion by mass of volatile solids to total solids is 20-30%, and the proteins account for 20-40% by mass of total volatile solids.

3. The method for enhancing degradation of proteins in sludge according to claim 1 , wherein in the step (S2), a mass ratio of volatile solids between the inoculum and the substrate is 1:2-1:5.

4. The method for enhancing degradation of proteins in sludge according to claim 1 , wherein in the step (S2), the first-stage microbial electrolytic cell coupled anaerobic digestion system is in an anaerobic state, a water content in the first-stage microbial electrolytic cell coupled anaerobic digestion system is 95-98%, an applied external voltage is 0.2-1.0 V, an operating temperature is 20-30° C., and operating time is 2-4 days.

5. The method for enhancing degradation of proteins in sludge according to claim 1 , wherein in the step (S2), when a degradation rate of degradation-resistant proteins in the first-stage microbial electrolytic cell coupled anaerobic digestion system is 40% or more, the acclimation and enrichment of the target microorganism are completed.

6. The method for enhancing degradation of proteins in sludge according to claim 1 , wherein in the step (S2), the concentration by centrifuging is performed under a condition of 800-1500 rpm for 5-10 min.

7. The method for enhancing degradation of proteins in sludge according to claim 1 , wherein in the step (S2), a water content is 90-95% and a proportion by mass of volatile solids to total solids is 30-40% in the microbial mixture.

8. The method for enhancing degradation of proteins in sludge according to claim 1 , wherein in the step (S3), a mass ratio of volatile solids between the inoculum and the substrate is 1:1-4:1.

9. The method for enhancing degradation of proteins in sludge according to claim 1 , wherein in the step (S3), the second-stage microbial electrolytic cell coupled anaerobic digestion system is in an anaerobic state, a water content in the second-stage microbial electrolytic cell coupled anaerobic digestion system is 95-98%, an applied external voltage is 0.2-1.0 V, an operating temperature is 20-30° C., and operating time is 4-8 days.

10. The method for enhancing degradation of proteins in sludge according to claim 1 , wherein in the step (S3), in the sludge discharged from the second-stage microbial electrolytic cell coupled anaerobic digestion system, proteins account for 20-35% by mass of total volatile solids, a degradation rate of proteins is 70-80%, a proportion by mass of volatile solids to total solids in the discharged sludge is 25-35%, and a degradation rate of total volatile solids is 50-70%.

Assignees

• Univ Tongji

Inventors

• Dong Bin
• Chen Sisi
• Gao Jun
• Shen Danni

Classifications

• C02F11/127

  by centrifugation · CPC title

• C02F2201/46105

  Details relating to the electrolytic devices · CPC title

• C02F11/006 Primary

  Electrochemical treatment, e.g. electro-oxidation or electro-osmosis · CPC title

• C02F11/04 Primary

  Anaerobic treatment; Production of methane by such processes · CPC title

• C02F2101/30

  Organic compounds · CPC title