Technical method for relieving ammonia inhibition in high-temperature aerobic digestion process of organic solid waste

Abstract

This invention discloses a technical method for alleviating ammonia inhibition during the high-temperature aerobic digestion process of organic solid waste. The method involves reacting fulvic acid with a mixture mainly containing Cu... 2+ Mn 2+ Fe 2+ The enzyme-catalyzed solutions of ions were mixed to prepare a conditioning mother liquor, which was then added to the high-temperature aerobic digestion system for organic solid waste in a specific ratio. The total ammonia nitrogen concentration in the digestate was monitored, and when it rose to 800 mg / L... ‑1 In this process, soluble magnesium salts and phosphogypsum slurry are sequentially added to the treatment system of wet organic solid waste. Heavy magnesium oxide is intermittently added to adjust the pH of the digestion system to 8.0-9.0, and high-temperature aerobic digestion is continued. Then, a silicate nitrogen-fixing agent is added to the digestion system. This invention combines the principles of enhancing oxidase activity with ammonia nitrogen precipitation, adsorption, and ion exchange to alleviate ammonia inhibition during the high-temperature aerobic digestion of wet organic solid waste through multiple pathways. After stabilization treatment, the solid residue obtained from solid-liquid separation has a high degree of humification and nitrogen content, making it suitable for subsequent substrate utilization.

Description

Technical Field

[0001] This invention belongs to the field of organic solid waste treatment, disposal and resource utilization technology, specifically relating to a technical method for alleviating ammonia inhibition during the high-temperature aerobic digestion process of organic solid waste. Background Technology

[0002] Organic solid waste originates widely from industrial and agricultural production activities, municipal engineering projects, and daily life, and mainly includes typical categories such as animal manure, crop straw, sewage sludge, food production waste, industrial organic waste, wood processing waste, and kitchen waste. With rapid socio-economic development and the continuous improvement of people's living standards, the generation of organic solid waste has increased rapidly. According to statistics from 2021, my country's sludge production reached 72.88 million tons, of which municipal sludge production was 55.52 million tons; kitchen waste generation was approximately 301,800 tons / day, while as of the end of 2020, the kitchen waste treatment capacity of 46 key cities nationwide was only about 62,800 tons / day, which could only handle about 20% of the total kitchen waste generated.

[0003] Currently, the main technologies for treating and disposing of organic solid waste include: land application after pyrolysis or carbonization, high-temperature incineration, sanitary landfill, aerobic composting or anaerobic fermentation, and hydrothermal oxidation of wet waste. Incineration has the most significant volume reduction effect, but its energy consumption is relatively high, and the purification of harmful gases such as dioxins in the exhaust gas is quite difficult. Due to the complex composition and significant differences in moisture content of solid waste, the pyrolysis and hydrothermal treatment processes for organic solid waste are not entirely the same, and the requirements for waste sorting are very strict. Solid wastes such as animal manure, sewage sludge, food production waste, and kitchen waste usually have high moisture and organic matter content. The three main routes for treating and disposing of or utilizing this type of wet organic solid waste are anaerobic digestion, aerobic fermentation for fertilizer production, and bioconversion. Compared with anaerobic digestion and bioconversion technologies, the aerobic treatment process for wet organic solid waste is accompanied by heat release and maintains the self-heating and high-temperature state of the compost pile, resulting in more thorough degradation of organic substrates. It also has significant advantages such as fast stabilization and good pathogen inactivation. In recent years, high-temperature aerobic digestion technology has shown broad application prospects in the treatment and disposal of organic solid waste such as urban wet waste, kitchen waste, sewage sludge, and livestock and poultry manure. More than 80 engineering facilities for the stabilization treatment of sewage sludge have been built in countries and regions such as Germany and North America.

[0004] When treating organic solid materials using high-temperature aerobic digestion technology, nitrogen-containing organic matter or extracellular polymers are hydrolyzed into amino acids by proteases and phthalimides, and then converted into ammonia through deammoniation. However, the temperature of the aerobic system is usually as high as 45℃ or even higher. Under these conditions, the nitrification and denitrification processes of nitrogen are completely inhibited, leading to a large accumulation of ammonia nitrogen, which in turn inhibits the aerobic process and its treatment efficiency. Studies have shown that when the ammonia nitrogen concentration exceeds 1000 mg / L, the VS removal rate increase of volatile solids in the high-temperature aerobic digestion system of sludge is only 1.28%. There is no consensus on the extent to which free ammonia or ionic ammonium inhibits the biochemical reaction process in the high-temperature aerobic digestion system of organic solid waste. How to effectively alleviate ammonia inhibition and improve biochemical treatment efficiency is a technical problem that urgently needs to be solved in the stabilization treatment and resource utilization of organic solid waste with high water content. Summary of the Invention

[0005] This invention provides a technical method for mitigating ammonia inhibition during the high-temperature aerobic digestion process of organic solid waste. The method involves adding fulvic acid and an enzymatic solution to the reactor to enhance the activity of thermophilic microorganisms and slow down the excessive oxidation of intracellular substances by reactive oxygen species. When the total ammonia nitrogen concentration in the digestion system is high, soluble magnesium salts and phosphogypsum slurry are added promptly. High-temperature aerobic digestion continues under weakly alkaline conditions, generating magnesium-containing ammonia-phosphorus precipitates and reducing the ammonia concentration. Furthermore, a nitrogen-fixing agent is added to the digestion system, and through adsorption and ion exchange, some ammonia nitrogen is transferred to the silicate-based nitrogen-fixing agent, thereby appropriately reducing the ammonia concentration in the digestion system. After stabilization treatment of the organic solid waste, the solid residue obtained from solid-liquid separation has a high degree of humification and nitrogen content, making it suitable for subsequent substrate utilization.

[0006] The specific implementation steps of this invention are as follows:

[0007] (1) Fulvic acid and Cu 2+ Mn 2+ Fe 2+ The enzyme-catalyzed solutions of the components are mixed and a conditioning mother liquor is prepared. It is added to the high-temperature aerobic digestion system of organic solid waste at a ratio of 0.6‰ of the total volume of the material to be treated. The reaction time of the conditioning stage is not less than 1 hour.

[0008] (2) When the total ammonia nitrogen concentration in the digestive system rises to 800 mg / L -1 At that time, soluble magnesium salts and phosphogypsum slurry with a solid content of 30% were added in sequence, mixed evenly, and heavy magnesium oxide was added intermittently. The pH value of the high-temperature aerobic digestion system was controlled at 8.0-9.0, and the digestion treatment was continued for 12-15 hours.

[0009] (3) Add silicate nitrogen-fixing agent with a particle size of 3-5 mm to the high-temperature aerobic digestion system of organic solid waste and continue to stabilize it for more than 5 hours to achieve rapid stabilization treatment of organic solid waste under high ammonia nitrogen conditions.

[0010] Preferably, in step (1), the amount of fulvic acid is determined according to a ratio of 1.0-2.0‰ of the dry weight of organic solid waste.

[0011] Preferably, in step (1), Cu in the enzyme-catalyzing solution 2+ Mn 2+ Fe 2+ The molar ratio is (0.8-1.2):(0.6-1.0):1. The pH of the enzyme catalytic solution is adjusted to 4.0-5.5 using dilute sulfuric acid. The Fe content in the enzyme catalytic solution... 2+ Concentration of 0.5-0.8 mol L -1 .

[0012] Preferably, in step (1), the ratio of fulvic acid (kg) to enzyme solution (L) is 1:(4-12).

[0013] Preferably, the soluble magnesium salt in step (2) is magnesium sulfate, and the amount of magnesium sulfate added per cubic meter of digestion system is 0.25-0.40 kg.

[0014] Preferably, in step (2), the phosphogypsum slurry is ultrasonically activated for 15-25 minutes, and then 2.8-4.5 kg of phosphogypsum slurry is added per cubic meter of digestion system. The phosphogypsum slurry is a phosphogypsum slurry with a solid content of 30%.

[0015] Preferably, after adding magnesium salt and phosphogypsum slurry in step (2), heavy magnesium oxide is added intermittently to adjust the pH of the digestion system to 8.0-9.0.

[0016] Preferably, when zeolite is selected as the nitrogen fixative in step (3), 0.4-0.8 kg is added per cubic meter of digestion system; when a mixture of zeolite and expanded perlite is selected as the nitrogen fixative, the mass ratio of the two is 1:(0.3-0.6), and the amount of mixture is determined by adding 0.3-0.6 kg of nitrogen fixative per cubic meter of digestion system.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] This invention utilizes fulvic acid and enzymatic solution to condition the high-temperature aerobic digestion process of wet organic matter, thereby enhancing oxidase activity and alleviating the oxidative stress on microorganisms under high ammonia nitrogen conditions. In addition, by combining the ammonia nitrogen precipitation reaction under weakly alkaline conditions with the adsorption and ion exchange effects of zeolite silicate nitrogen-fixing agents, ammonia inhibition in the high-temperature aerobic digestion process of organic solid waste is alleviated through multiple pathways. After rapid stabilization treatment of organic solid waste, the solid residue obtained from solid-liquid separation has a high degree of humification and nitrogen content, making it suitable for subsequent substrate utilization. Detailed Implementation

[0019] The following specific implementation examples further illustrate the present invention, providing detailed implementation methods and operating procedures, but the scope of protection of the present invention is not limited to the content described.

[0020] Example 1

[0021] The process employs high-temperature aerobic technology to stabilize food waste. The cylindrical liquid high-temperature fermentation device has a diameter of 3.0 m, a height of 4.5 m, and an effective volume of 22 m³. 3 Food waste with a solids content of 5.5% is crushed and pulped before being sent to the digester, where compressed air is pumped at 32 m³ / h. 3 h −1 The slurry is blown into the reactor from the bottom-mounted microporous aeration discs, and the slurry is drawn from the bottom and returned to the reactor from the top via a return pump with a flow rate set to 20 m³ / s. 3 h -1 A stirring device is installed at the center of the top of the reactor.

[0022] A control group and an experimental group were set up to conduct a batch operation test of liquid high-temperature fermentation of kitchen waste. The thermophilic microorganisms that had been acclimated were inoculated into the kitchen waste. When starting the experimental group, the amount of fulvic acid was determined according to a ratio of 1.0‰ of the dry weight of organic solid waste, and 1.2 kg of fulvic acid was added to a 13.2 L volume of enzymatic solution, in which Cu... 2+ Mn 2+ Fe 2+ The concentrations were 0.50, 0.40, and 0.50 mol L, respectively. -1 The prepared conditioning mother liquor, with a pH of 5.0, was added to the food waste digestion system. After 60 hours, the reactor temperature rose to 54.6 °C, the pH reached 5.9, and the total ammonia nitrogen (TAN) concentration increased to 812 mg / L. -1Under these conditions, 5.5 kg of magnesium sulfate and 62.0 kg of phosphogypsum slurry (30% solids content, activated for 15 min in an ultrasonic generator at 45 kHz and 2 kW) were sequentially added to the sludge digestion system. The pH of the digestion system was measured every 10 min. 1.2 kg of heavy magnesium oxide was added each time to adjust the pH to 8.0-8.3. After 15 h of continuous digestion, 9.0 kg of a mixture of zeolite and expanded perlite (1:0.4 ratio) with a particle size of approximately 4-5 mm was added to the reactor for further stabilization. After 15 days of batch operation, the volatile solids (VS) removal rate from the food waste was 75.1%, and the chemical oxygen demand (COD) in the digestate was 4780 mg / L. -1 The ammonia nitrogen content was 760 mg / L. -1 Compared to the experimental group, in the blank control group (which did not implement ammonia inhibition and mitigation measures), the VS removal rate of volatile solids in food waste was 62.7%, and the chemical oxygen demand (COD) in the digestate was 6590 mg / L. -1 The ammonia nitrogen content was 873 mg / L. -1 .

[0023] Example 2

[0024] Dewatered sludge from a municipal wastewater treatment plant with a solids content of 6.5% was added to an area with a diameter of 2.3 m, a height of 3 m, and an effective volume of 10 m³. 3 In a cylindrical high-temperature aerobic digestion reactor, compressed air is pumped at 12 m... 3 h −1 The flow rate is introduced into the reactor through a microporous aeration disc installed at the bottom. The digested sludge is drawn out from the bottom and sent back to the cylindrical digester from the top via a 7.5 kW sludge return pump. A stirring device is installed on the side of the reactor.

[0025] For the experimental apparatus used to alleviate ammonia inhibition during digestion, 1.5 kg of fulvic acid was added to a 6 L volume of enzyme solution at startup, wherein Cu 2+ Mn 2+ Fe 2+ The concentrations were 0.72, 0.50, and 0.60 mol L, respectively. -1 The prepared conditioning mother liquor, with a pH of 5.5, was added to the high-temperature sludge digestion reaction system. After 72 hours, the reactor temperature rose to 51.8 °C, the pH reached 6.8, and the total ammonia nitrogen (TAN) concentration increased to 896 mg / L. -1Under these conditions, 3 kg of magnesium sulfate and 40 kg of phosphogypsum slurry (30% solids content, activated for 12 min in an ultrasonic generator at 45 kHz and 2 kW) were sequentially added to the sludge digestion system. The pH of the digestion system was measured every 10 min. 0.5 kg of heavy magnesium oxide was added each time to adjust the pH to 8.4-8.6. After 15 h of continuous digestion, 6.0 kg of zeolite with a particle size of approximately 4 mm was added to the reactor for further stabilization. After 12 days of batch operation, the volatile solids (VS) removal rate in the sludge was 43.2%, and the chemical oxygen demand (COD) in the digestate was 8830 mg / L. -1 The ammonia nitrogen content was 830 mg / L. -1 Compared to the experimental group, in the blank control group without ammonia inhibition and mitigation measures, the VS removal rate of volatile solids in the sludge was 36.5%, and the COD in the digestate was 9910 mg / L. -1 The ammonia nitrogen content was 930 mg / L. -1 .

[0026] Example 3

[0027] A control experiment was conducted under continuous operation conditions, referring to Example 2. The experimental setup, feed sludge concentration, aeration rate, sludge return, and other conditions were all the same as in Example 2. During continuous operation, 1.2 m³ of sludge was discharged daily. 3 Digest the sludge, then replenish with 1.2 m³ of water. 3 Fresh sludge with a solids concentration of 6.5%. 0.7 kg of fulvic acid was added to a 6 L volume of enzymatic solution, containing Cu. 2+ Mn 2+ Fe 2+ The concentrations were 0.60, 0.70, and 0.70 mol L, respectively. -1 The pH value was 4.5. The prepared conditioning mother liquor was added to the high-temperature digestion reaction system of sludge. After 2 hours of conditioning, 2.4 kg of magnesium sulfate and 30 kg of phosphogypsum slurry (activated for 20 minutes) were added to the sludge digestion system sequentially. The pH value of the digestion system was measured every 10 minutes. 0.3 kg of heavy magnesium oxide was added each time to adjust the pH value of the digestion system to 8.6-9.0. After 12 hours of continuous digestion, 4.0 kg of zeolite with a particle size of about 4 mm was added to the reactor for further stabilization treatment until the next day when the sludge was discharged. During continuous operation, the volatile solids (VS) removal rate in the experimental group sludge was 43.9%, and the chemical oxygen demand (COD) in the digestate was 10750 mg / L. -1 The ammonia nitrogen content was 1050 mg / L. -1Compared to the experimental group, in the blank control group without ammonia inhibition and mitigation measures, the VS removal rate of volatile solids in the sludge was 38.2%, and the COD in the digestate was 12460 mg / L. -1 The ammonia nitrogen content was 1240 mg / L. -1 .

Claims

1. A method for mitigating ammonia inhibition in the high temperature aerobic digestion process of organic solid waste, characterized by The method comprises the following steps: (1) mix humic acid with enzymatic liquid to prepare conditioning mother liquor, add the conditioning mother liquor to the organic solid waste high-temperature aerobic digestion system according to 0.6 ‰ proportion of the total volume of the material to be treated, the reaction time of the conditioning stage is not less than 1 h; the dosage of humic acid in the conditioning stage is determined according to 1.0-2.0 ‰ proportion of the dry basis mass of the organic solid waste; the enzymatic liquid contains Cu 2+ , Mn 2+ , Fe 2+ ions, the molar ratio of which is (0.8-1.2):(0.6-1.0):1, the pH value of the enzymatic liquid is adjusted to 4.0-5.5 with dilute sulfuric acid, the concentration of Fe 2+ in the enzymatic liquid is 0.5-0.8 mol / L -1 ; the solid-liquid ratio when mixing humic acid with the enzymatic liquid is 1:(4-12); (2) when the total ammonia nitrogen concentration of the digestion system rises to 800 mg / L -1 When the total ammonia nitrogen concentration of the digestion system rises to 800 mg / L, soluble magnesium salt is added to the wet organic matter solid waste treatment system, then phosphogypsum slurry is added and mixed uniformly, the digestion system is adjusted to be weakly alkaline, and the digestion treatment is continued for 12-15 h; the soluble magnesium salt is magnesium sulfate, and the magnesium sulfate dosage per cubic digestion system is 0.25-0.40 kg; the phosphogypsum slurry is subjected to ultrasonic activation treatment for 15-25 min, then 2.8-4.5 kg of phosphogypsum slurry is added per cubic digestion system, and the phosphogypsum slurry is a 30% solid content phosphogypsum slurry. (3) adding a silicate solid nitrogen agent with a particle size of 3-5 mm to the digestion system, and continuing the digestion treatment for more than 5 h to realize the rapid stabilization treatment of the organic solid waste under the high ammonia nitrogen condition.

2. The method of claim 1, wherein After the magnesium salt and the phosphogypsum slurry are added in step (2), the heavy magnesium oxide is intermittently added to control the pH value of the digestion system to be 8.0-9.

0.

3. The method of claim 1, wherein The solid nitrogen agent in step (3) is composed of zeolite or zeolite and expanded perlite, and when the zeolite and the expanded perlite are selected as the solid nitrogen agent, the mass ratio of the zeolite to the expanded perlite is 1:(0.3-0.6).

4. The method of claim 3, wherein When the zeolite is selected as the solid nitrogen agent, 0.4-0.8 kg is added per cubic digestion system; and when the zeolite and the expanded perlite are selected as the solid nitrogen agent, 0.3-0.6 kg of the solid nitrogen agent is added per cubic digestion system.