A process for the co-treatment of multiple wastes using an anaerobic system

Abstract

This invention discloses a process for the synergistic treatment of multiple wastes using an anaerobic system. Utilizing one or more anaerobic organic wastewater treatment systems, one or more types of externally generated waste are selectively introduced into the system. Organic pollutants in the water act as electron acceptors, and through microbial metabolism, the waste is rendered harmless and recycled, while also enhancing the system's processing capacity, generating energy, or recovering resources. The method includes five treatment modes: treating organic waste to increase biogas production, treating ferrous sulfide waste to recover ferrous sulfide, treating hexavalent chromium-containing waste liquid to recover chromium, treating nitrogen-containing waste to reduce it to nitrogen gas, and controlling sulfur-containing odors and performing in-situ desulfurization. Waste activated carbon is added in slurry form after grinding and fluidization, and the desulfurization mode uses a sulfate-free ferrous salt solution. This invention expands the anaerobic system into a synergistic treatment center for multiple industrial wastes, achieving waste-to-waste treatment, increased energy production, and resource recovery. The process is flexible and highly adaptable.

Description

Technical Field

[0001] This invention relates to the fields of environmental protection and wastewater treatment technology, specifically to a process method for increasing the treatment function and capacity of an anaerobic system for organic wastewater, and particularly to a method for utilizing an anaerobic system to synergistically treat multiple external wastes and achieve resource recovery. Background Technology

[0002] Anaerobic treatment technologies for organic wastewater (such as UASB, EGSB, and IC reactors) have been widely used to treat high-concentration organic wastewater. Their main principle is to utilize anaerobic microorganisms to convert organic pollutants in the water into biogas (mainly methane), achieving pollutant reduction and energy recovery. However, traditional anaerobic systems have relatively limited functionality, primarily targeting organic matter in wastewater. For other wastes generated during industrial processes, such as waste organic solvents, waste acids, chromium-containing waste liquids, nitrogen-containing waste, iron-containing waste materials, and waste sulfates, separate treatment facilities are typically required, resulting in high costs and complex management. Furthermore, anaerobic systems may face issues such as odor generation and the need for biogas desulfurization. Therefore, developing a process that can utilize existing anaerobic systems to co-treat multiple wastes while simultaneously improving system efficiency and reducing secondary pollution has significant application value. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of the prior art and provide a process method to increase the treatment function and capacity of an anaerobic system for organic wastewater. This method can introduce various external wastes into the anaerobic system for synergistic treatment, realize the harmlessness and resource utilization of waste, and improve the overall efficiency of the anaerobic system.

[0004] To achieve the above objectives, the present invention provides the following technical solution:

[0005] A process for co-treating multiple wastes using an anaerobic system involves selectively introducing one or more externally generated wastes into one or more anaerobic treatment systems for organic wastewater, using organic pollutants in the water as electron acceptors, and achieving the harmlessness and resource utilization of the wastes through microbial metabolism.

[0006] The method includes one or more of the following processing modes:

[0007] (1) Mode of treating organic waste to increase biogas production: introduce waste organic solvents, organic acids and / or waste activated carbon into an anaerobic system, and use methanogenic bacteria to convert them into biogas to increase biogas production;

[0008] (2) Mode of treating ferrous sulfate waste and recovering ferrous sulfide: introduce ferrous sulfate solution containing sulfate or waste sulfuric acid and iron filings into the anaerobic system, control the mass ratio of chemical oxygen demand to sulfate to be less than 10:1, use sulfate-reducing bacteria to generate ferrous sulfide precipitate, and regularly discharge sludge rich in ferrous sulfide for resource utilization.

[0009] (3) Mode of treating hexavalent chromium waste liquid to recover chromium: After adjusting the hexavalent chromium waste liquid to neutral or alkaline, it is introduced into the anaerobic system, so that the hexavalent chromium is reduced to trivalent chromium by microorganisms under neutral anaerobic conditions, and chromium hydroxide precipitate is generated and enters the sludge;

[0010] (4) Mode of treating nitrogen-containing waste to reduce nitrogen gas: After pretreatment of waste liquid or nitrified waste containing nitric acid or nitrate, it is introduced into the anaerobic system, and denitrifying bacteria are used to reduce nitrate nitrogen to nitrogen gas and enter biogas.

[0011] (5) Controlling sulfur-containing odor and in-situ desulfurization mode: Introduce a ferrous salt solution without sulfate into the anaerobic system so that ferrous ions react with sulfur-containing substances generated during the anaerobic process to form ferrous sulfide precipitate.

[0012] Furthermore, in the mode of treating ferrous sulfide waste to recover ferrous sulfide, the mass ratio of chemical oxygen demand to sulfate is controlled below 8:1.

[0013] Furthermore, in the mode of treating organic waste to increase biogas production, the waste activated carbon is ground and fluidized and then mixed into the anaerobic system influent in the form of slurry.

[0014] Furthermore, in the mode of recovering chromium from waste liquid containing hexavalent chromium, the pH of the waste liquid containing hexavalent chromium is adjusted to 8-9.

[0015] Furthermore, in the mode of treating nitrogen-containing waste to reduce it to nitrogen gas, the pretreatment includes a step of removing suspended solids.

[0016] Furthermore, in the mode of controlling sulfur-containing odor and in-situ desulfurization, the sulfate-free ferrous salt solution is a ferrous chloride solution, or is prepared by reacting non-sulfuric acid waste acid with iron filings / iron ore.

[0017] Furthermore, the waste acid used to prepare the iron salt solution is an inorganic or organic acid other than waste sulfuric acid that can be replaced by iron to generate soluble iron salts, and the iron ore is iron ore, iron filings, or iron oxide scale.

[0018] Depending on the treatment requirements and waste type, one or more of the above steps can be independently selected and applied to one or more anaerobic treatment systems. The anaerobic system is one or a combination of the following: upflow anaerobic sludge blanket reactor (UASB), anaerobic granular sludge expanded bed reactor (EGSB), completely mixed anaerobic reactor (CSTR), internal circulation anaerobic reactor (IC), anaerobic baffled reactor (ABR), two-phase anaerobic reactor, upflow anaerobic sludge bed reactor (UBF), anaerobic biological filter (AF), upflow segmented sludge blanket reactor (USSB), upflow anaerobic solid reactor (USR), anaerobic attached membrane expanded bed reactor (AAFEB), plug flow reactor (FPR), anaerobic fluidized bed and expanded bed reactor (AFBR), black film biogas digester, anaerobic pond, and wastewater treatment plant hydrolysis acidification tank.

[0019] Beneficial effects

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] 1. Functional Expansion and Synergistic Effect: The function of the anaerobic system is expanded from a single wastewater treatment to a synergistic treatment center for multiple industrial wastes, realizing waste treatment with waste and reducing waste treatment costs.

[0022] 2. Resource recovery and energy production increase: Waste organic solvents and organic acids are converted into biogas, increasing energy output; at the same time, sulfur-containing waste can be converted into ferrous sulfide precipitate, realizing the recovery of sulfur resources.

[0023] 3. In-situ Harm Reduction and System Stabilization: By introducing sulfate-free ferrous salts, odorous substances are removed in situ, achieving biogas biological desulfurization. This avoids the additional introduction of sulfate, improves the working environment, and reduces the burden on subsequent biogas purification. Simultaneously, the co-treatment of chromium- and nitrogen-containing wastes prevents these toxic substances from causing separate environmental pollution.

[0024] 4. Flexible process and strong adaptability: One or more types of waste can be selectively introduced into one or more anaerobic systems according to different waste generation and treatment needs. The process combination is flexible and the application range is wide. Detailed Implementation

[0025] The technical solution of the present invention will be described in detail below with reference to specific embodiments.

[0026] Example 1: Sulfur Resource Recovery

[0027] A chemical plant generates high-concentration sulfate wastewater and waste sulfuric acid. The proposed method is to utilize this invention for resource recovery. First, the waste sulfuric acid is reacted with iron filings to prepare a ferrous sulfate solution. Then, this ferrous sulfate solution is mixed with high-concentration organic wastewater (high COD concentration), controlling the COD / SO4 ratio of the influent after mixing. 2- The wastewater, with a mass ratio of 8:1 (less than 10:1), enters the EGSB reactor. In the reactor, sulfate-reducing bacteria utilize some organic matter to reduce sulfate ions to sulfides, while simultaneously, organic matter in the wastewater is converted to methane by methanogenic bacteria. The newly generated sulfides immediately react with ferrous ions in the wastewater to form ferrous sulfide precipitate, which accumulates in the granular sludge. When the ferrous sulfide content in the sludge reaches a certain level, a portion of the sludge is periodically discharged, and the ferrous sulfide is recovered through magnetic separation or gravity separation for use as a chemical raw material or soil conditioner.

[0028] Example 2: Co-treatment of waste organic solvents and control of sulfur-containing odor

[0029] A pharmaceutical factory's wastewater treatment plant has a UASB reactor that treats high-concentration organic wastewater. During production, the factory generates small amounts of waste acetone solvent and ferrous chloride-containing waste liquid. The waste acetone solvent is pumped directly into the UASB's influent pipeline in a controlled ratio (ensuring the influent COD load does not exceed the design range) to mix with the main wastewater. Simultaneously, the ferrous chloride-containing waste liquid (without sulfate) is also introduced into the UASB. After operation, it was found that the UASB's biogas production increased by 15% compared to before the introduction of waste acetone, while the foul odor (methanethiol smell) in the air above and around the reactor was significantly reduced. This indicates that the waste acetone is utilized by methanogenic bacteria as an additional carbon source to increase biogas production, and the ferrous ions in the ferrous chloride react with sulfides produced in the anaerobic process to form odorless ferrous sulfide precipitate, achieving in-situ deodorization.

[0030] Example 3: Co-treatment of chromium-containing wastewater

[0031] An electroplating plant generated a small amount of hexavalent chromium wastewater. After collection, the pH of the wastewater was first adjusted to 8-9 with alkaline solution to ensure the relative stability of hexavalent chromium under alkaline conditions. Then, the alkaline chromium-containing wastewater was slowly added to the inlet of the hydrolysis acidification tank at the industrial park's integrated wastewater treatment plant. In the hydrolysis acidification tank and subsequent anaerobic reactor, hexavalent chromium was reduced to trivalent chromium by microorganisms (such as certain reducing bacteria) under anaerobic conditions. The trivalent chromium then reacted with hydroxide ions in the water to form chromium hydroxide precipitate, which entered the remaining sludge. Monitoring showed that the total chromium concentration in the effluent was below the discharge standard, achieving the harmless treatment of the chromium-containing wastewater.

[0032] Example 4: Co-treatment of nitrogen-containing waste

[0033] A fertilizer plant generates wastewater containing nitrates. After pretreatment to remove suspended solids, the wastewater is mixed into the influent of an IC reactor in a specific ratio. The IC reactor contains abundant denitrifying bacteria that utilize the organic matter in the wastewater as a carbon source to reduce nitrate nitrogen to nitrogen gas, which is then collected along with biogas. The treatment results show that the nitrate nitrogen removal rate exceeds 90%, while biogas production increases slightly.

[0034] Example 5: Co-treatment of waste activated carbon

[0035] A fine chemical company generates a small amount of waste powdered activated carbon. This waste activated carbon is ground and fluidized to form a slurry with a mass concentration of approximately 8%, which is then continuously pumped into the inlet pipeline of an IC anaerobic reactor to mix with the main wastewater. Operational results show that the adsorbed organic matter in the waste activated carbon is gradually degraded into biogas by anaerobic microorganisms, increasing biogas production by approximately 10% compared to when no addition was made. Simultaneously, the waste activated carbon is disposed of in reduced volume, eliminating the need for external incineration.

[0036] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A process for co-treating multiple wastes using an anaerobic system, characterized in that, One or more organic wastewater anaerobic treatment systems are used to selectively introduce one or more externally generated wastes into the anaerobic treatment system, using organic pollutants in the water as electron acceptors, and achieving the harmlessness and resource utilization of waste through microbial metabolism; The method includes one or more of the following processing modes: (1) Mode of treating organic waste to increase biogas production: introduce waste organic solvents, organic acids and / or waste activated carbon into an anaerobic system, and use methanogenic bacteria to convert them into biogas to increase biogas production; (2) Mode of treating ferrous sulfate waste and recovering ferrous sulfide: introduce ferrous sulfate solution containing sulfate or waste sulfuric acid and iron filings into the anaerobic system, control the mass ratio of chemical oxygen demand to sulfate to be less than 10:1, use sulfate-reducing bacteria to generate ferrous sulfide precipitate, and regularly discharge sludge rich in ferrous sulfide for resource utilization. (3) Mode of treating hexavalent chromium waste liquid to recover chromium: After adjusting the hexavalent chromium waste liquid to neutral or alkaline, it is introduced into the anaerobic system, so that the hexavalent chromium is reduced to trivalent chromium by microorganisms under neutral anaerobic conditions, and chromium hydroxide precipitate is generated and enters the sludge; (4) Mode of treating nitrogen-containing waste to reduce nitrogen gas: After pretreatment of waste liquid or nitrified waste containing nitric acid or nitrate, it is introduced into the anaerobic system, and denitrifying bacteria are used to reduce nitrate nitrogen to nitrogen gas and enter biogas. (5) Controlling sulfur-containing odor and in-situ desulfurization mode: Introduce a ferrous salt solution without sulfate into the anaerobic system so that ferrous ions react with sulfur-containing substances generated during the anaerobic process to form ferrous sulfide precipitate.

2. The method according to claim 1, characterized in that, In the aforementioned mode for treating ferrous sulfide waste and recovering ferrous sulfide, the mass ratio of chemical oxygen demand (COD) to sulfate ions is controlled below 8:

1.

3. The method according to claim 1, characterized in that, In the aforementioned mode of treating organic waste to increase biogas production, the waste activated carbon is ground and fluidized, and then mixed into the anaerobic system influent in the form of a slurry.

4. The method according to claim 1, characterized in that, In the mode of recovering chromium from waste liquid containing hexavalent chromium, the pH of the waste liquid containing hexavalent chromium is adjusted to 8-9.

5. The method according to claim 1, characterized in that, In the mode of treating nitrogen-containing waste to reduce it to nitrogen, the pretreatment includes a step of removing suspended solids.

6. The method according to claim 1, characterized in that, In the aforementioned mode for controlling sulfur-containing odor and in-situ desulfurization, the sulfate-free ferrous salt solution is a ferrous chloride solution, or is prepared by reacting non-sulfuric acid waste acid with iron filings / iron ore.

7. The method according to claim 6, characterized in that, The waste acid used to prepare the iron salt solution is an inorganic or organic acid other than waste sulfuric acid that can be replaced by iron to generate soluble iron salts, and the iron ore is iron ore, iron filings, or iron oxide scale.

8. A system for treating waste using the method according to any one of claims 1 to 7, characterized in that, The anaerobic system is one or more of the following combinations: upflow anaerobic sludge blanket reactor (UASB), anaerobic granular sludge expanded bed reactor (EGSB), completely mixed anaerobic reactor (CSTR), internal circulation anaerobic reactor (IC), anaerobic baffled reactor (ABR), two-phase anaerobic reactor, upflow anaerobic sludge bed reactor (UBF), anaerobic biological filter (AF), upflow segmented sludge blanket reactor (USSB), upflow anaerobic solid reactor (USR), anaerobic attached membrane expanded bed reactor (AAFEB), plug flow reactor (FPR), anaerobic fluidized bed and expanded bed reactor (AFBR), black film biogas digester, anaerobic pond, and hydrolysis acidification tank of wastewater treatment plant.