Method and device for treating ammonia-nitrogen wastewater using microbial electrolysis cell assisted SANI system

Patent metadata

Field	Value
Publication number	US-11401185-B2
Application number	US-201817055998-A
Country	US
Kind code	B2
Filing date	Oct 16, 2018
Priority date	Sep 12, 2018
Publication date	Aug 2, 2022
Grant date	Aug 2, 2022

Abstract

Disclosed are a method and a device for treating high ammonia-nitrogen wastewater using a microbial electrolysis cell (MEC) assisted SANI system, including an SANI system, an MEC and a power supply. The cathode chamber and anode chamber of the MEC are separated by a separator and are respectively connected to the cathode and anode of the power supply, and a cathode electrode is enriched with hydrogen autotrophic denitrifying bacteria. The cathode chamber has two main functions. Firstly, a higher denitrification efficiency is achieved due to the enriched hydrogen autotrophic denitrifying bacteria; and secondly, the alkalinity produced in the cathode can adjust the pH of the nitrification chamber. In addition, the cathode chamber can oxidize the residual sulfide in the effluent to meet the discharge standard. This system retains the advantage of less sludge in a SANI process, but also can be applied to the treatment of wastewater with high ammonia-nitrogen.

First claim

What is claimed is:

1. A device for treating ammonia-nitrogen wastewater using a microbial electrolysis cell assisted sulfate reduction, autotrophic denitrification and nitrification integrated (SANI) system, comprising an SANI system, a cathode chamber, a anode chamber and a power supply, wherein the cathode chamber is a cathode chamber of an Microbial Electrolysis Cells (MEC), the anode chamber is an anode chamber of the MEC, and the cathode chamber and the anode chamber are separated by a separator; the cathode chamber and the anode chamber of the MEC are respectively connected to a negative electrode and a positive electrode of the power supply, and a cathode electrode in the cathode chamber is enriched with hydrogen autotrophic denitrifying bacteria,
wherein an outlet of a sulfide autotrophic denitrification chamber of the SANI system is connected to an inlet of the cathode chamber of the MEC; and an outlet of the cathode chamber of the MEC is connected to an inlet of a nitrification chamber of the SANI system.

2. The device for treating ammonia-nitrogen wastewater according to claim 1 , wherein an outlet of the nitrification chamber of the SANI system is connected to the anode chamber of the MEC.

3. The device for treating ammonia-nitrogen wastewater according to claim 1 , wherein the cathode chamber is filled with a graphite filler which is led out by a graphite rod to be connected to the power supply, and the anode chamber uses a Dimensionally Stable Anodes (DSA) electrode.

4. The device for treating ammonia-nitrogen wastewater according to claim 1 , wherein the cathode chamber is in an anoxic condition, with a dissolved oxygen DO<0.5 mg/L; the anode chamber is in an aerobic condition, with a dissolved oxygen DO>0.5 mg/L; and the SANI system, the cathode chamber and the anode chamber are all fully stirred.

5. A method for treating ammonia-nitrogen wastewater by the device according to claim 1 , comprising:
entering a wastewater through a bottom of a sulfate reduction chamber of the SANI system, and reducing sulfate in the wastewater to sulfide by sulfate reducing bacteria under a condition of complete mixing, during which electrons are sourced from organic substrates in the wastewater;
mixing an effluent from the sulfate reduction chamber and a wastewater flowing back from the nitrification chamber at a bottom of the sulfide autotrophic denitrification chamber of the SANI system; converting NH 4 + in the wastewater into NO 3 ″ by nitrifying bacteria in the nitrification chamber so that a large number of NO 3 ″ exist in the sulfide autotrophic denitrification chamber, and converting NO 3 − into N 2 under anaerobic conditions by sulfide autotrophic denitrification microorganisms growing in the sulfide autotrophic denitrification chamber, wherein electrons are sourced from sulfide coming from the sulfate reduction chamber; entering an effluent from the sulfide autotrophic denitrification chamber into the cathode chamber of the MEC, and isolating the anode chamber from the cathode chamber by the separator in order to avoid mutual interference between ion migration in the cathode chamber and that in the anode chamber; in the cathode chamber, performing denitrification for further denitrification by hydrogen autotrophic denitrifying bacteria, and then flowing an effluent from the cathode chamber through an upper outlet to the nitrification chamber to convert NH 4 + in the water into NO 3 − ; effectively neutralizing a large number of protons produced during nitrification in the nitrification chamber by a large number of hydroxyl radicals produced in the cathode chamber along with a hydrogen generating reaction; and finally, directly discharging or pumping an effluent from the nitration chamber into the anode chamber of the MEC for oxidation treatment to remove sulfide in the water to be directly discharged.

6. The method according to claim 5 , wherein a flow ratio of an amount of water discharging from the nitrification chamber to an amount of water flowing back to the sulfide autotrophic denitrification chamber is 1:0.5-1:5.

7. The method according to claim 5 , wherein temperatures of the SANI system, the cathode chamber and the anode chamber are controlled at 25±5° C., and a hydraulic retention time of each chamber is 18-36 h.

8. The method according to claim 5 , wherein a cathode potential ranges from −0.4 V to −1.2 V.

9. The method according to claim 8 , wherein an anode potential ranges from 0.5 V to 2.3 V.

Assignees

• Univ Zhejiang

Inventors

• Li Zhongjian
• Wu Gaoming
• Yang Bin
• Yang Yuxuan
• Lei Lecheng

Classifications

• C02F2201/46115

  Electrolytic cell with membranes or diaphragms · CPC title

• C02F2101/101

  Sulfur compounds · CPC title

• C02F3/345

  for biological oxidation or reduction of sulfur compounds · CPC title

• C02F3/302

  Nitrification and denitrification treatment (C02F3/308 takes precedence) · CPC title

• C02F2101/16

  Nitrogen compounds, e.g. ammonia · CPC title