CN1270985C - Anaerobic treating process for high concentration organic waste water - Google Patents

Abstract

The invention relates to an anaerobic treatment process for high-concentration organic wastewater. The process is composed of a mixture of iron filings and granular activated carbon (or carbon particles) inserted between the hydrolytic acidification stage and the methanogenic stage in the two-stage anaerobic treatment. The micro-electrolysis stage forms a three-stage anaerobic treatment process for high-concentration organic wastewater. The three-stage anaerobic treatment process for treating high-concentration organic wastewater can improve the biochemical properties of anaerobic methanogenesis, increase the rate of methanogenesis, thereby increasing the volume load of the anaerobic reactor, greatly reducing the concentration of residual COD in the effluent, and the total COD The removal rate is greater than 91%. It can be widely used in the anaerobic treatment of a large amount of high-concentration organic wastewater produced in the production process of light industry, food, pharmaceutical and chemical industries.

Description

An anaerobic treatment process for high-concentration organic wastewater

Technical field

The invention relates to anaerobic treatment technology for a large amount of high-concentration organic wastewater produced in the production process of light industry, food, pharmacy and chemical industry. The COD in wastewater and the treatment cost of wastewater are reduced. It belongs to the technical field of water pollution control.

Background technique

At present, a large amount of high-concentration organic wastewater produced in the production process of light industry, food, pharmaceutical and chemical industry is generally treated by single-stage anaerobic reactor, and the most common anaerobic reactor is an upflow anaerobic reactor. Oxygen Sludge Bed Reactor (UASB). For organic wastewater that is difficult to degrade or has a high concentration, the treatment efficiency and stability of the single-stage anaerobic reactor are poor. In 1971, some scholars proposed the concept of two-stage anaerobic process (also known as two-phase anaerobic process) based on the four-stage theory of anaerobic treatment of wastewater, that is, fermentation, acidifying bacteria and methanogenic bacteria were divided into two reactors ( hydrolytic acidification stage and methanogenic stage) to provide individual suitable growth conditions for cultivation. Since then, scholars from various countries have begun to conduct research and industrial experiments on the two-stage anaerobic process. The treatment efficiency of wastewater with a large amount of refractory substances is limited to a certain extent. The reason is that the growth conditions of methanogenic bacteria are relatively strict, especially for the oxidation-reduction potential, content of toxic substances and trace elements in wastewater. It is difficult to fully satisfy the growth conditions of methanogenic bacteria, that is, it is difficult to achieve the dominant growth and optimal efficiency of dominant methanogenic bacteria. Therefore, these two anaerobic processes have the disadvantages of low treatment volume load, long hydraulic retention time, large reactor volume, low treatment efficiency, and large one-time investment in treatment facilities.

Contents of the invention

The purpose of the present invention is to adopt a new process of anaerobic treatment for high-concentration organic wastewater produced in the production process of light industry, food, pharmacy and chemical industry, so as to improve the anaerobic treatment efficiency, reduce the COD concentration of anaerobic effluent, and reduce the subsequent Aerobic treatment of organic loads in order to reduce the treatment and operating costs of the entire treatment process.

The technical scheme of the present invention is: a micro-electrolysis (or acidification stage for short) and a methanogenic stage are inserted between the hydrolytic acidification stage (or acidification stage for short) and the methanogenic stage in the two-stage anaerobic process. Internal electrolysis) physical and chemical treatment unit, forming a three-stage anaerobic treatment process of hydrolytic acidification stage + micro-electrolysis stage + methane production stage.

High-concentration or relatively high-concentration organic wastewater passes through the hydrolytic acidification reactor, micro-electrolyzer, water collection tank and methanogenic reactor in sequence according to different hydraulic retention times, and each stage exerts its best treatment effect according to its own treatment mechanism.

The hydrolytic acidification reactor can use a common hydrolytic acidifier, and the effluent is clarified by a common radial flow sedimentation tank to enter the subsequent stage, part of the sludge is returned to the acidifier, and the remaining sludge is discharged; in addition, the hydrolytic acidifier can also be clarified by continuous acidification reactor or upflow anaerobic sludge bed reactor (UASB).

The micro-electrolyzer is a commonly used micro-electrolyzer or internal electrolyzer. The middle part of the tank is filled with a mixture bed of iron filings and carbon particles. The slightly acidic hydrolysis and acidification effluent is clarified again from the bottom of the micro-electrolyzer and then flows upwards, passing through the iron filings and carbon particles. The mixture bed overflows from the upper part into the integrated semi-closed sump, and a small amount of lye can be added to the upper part of the sump to adjust the pH value to 6.0-7.0.

The methanogenic reactor can be a common upflow anaerobic sludge bed reactor (UASB) or an internal circulation anaerobic reactor (IC), and an ordinary intermittent anaerobic digester can also be used.

The specific principles are as follows:

After neutralization, the high-concentration organic wastewater with a neutral pH value enters the hydrolysis and acidification stage. The reactor is in contact with the fermentation and acidification bacteria (active hydrolysis and acidification sludge) in it, and the organic substances in the wastewater undergo biochemical reactions such as hydrolysis and acid production. , to degrade hydrocarbons and carbohydrates into volatile fatty acids VFA, CO ₂ , H ₂ O, such as: acetic acid, propionic acid, lactic acid and butyric acid, etc.; decompose protein into amino acids, VFA, CO ₂ , H ₂ O and _NH3, etc., the content of volatile fatty acids (hereinafter referred to as VFA) in the wastewater entering the reactor gradually increases with the residence time, and its pH value gradually decreases. At the same time, the harmful substances to the methanogenic bacteria in the wastewater are also degraded, and the oxidation-reduction potential (hereinafter referred to as eh) drops to about -100mV. To achieve the growth potential of methanogens below -330mV, it is too slow to rely on the action of facultative bacteria.

The concentration of VFA in the effluent treated by hydrolysis and acidification is relatively high, and the pH value is between 3.5 and 6.0. After entering the micro-electrolyzer, the redox reaction can be carried out, and the refractory substances and substances harmful to methanogens can be further hydrogenated or oxidized, so that the biodegradability of anaerobic methane production can be further improved.

In addition, the growth conditions of methanogens are very strict, and they are strictly anaerobic bacteria. This is because there are many enzyme systems with low redox potential in the cells of methanogens. When the standard potential of oxidized substances in the wastewater system is high or the concentration is high, these enzyme systems will be destroyed by irreversible oxidation at high potential, resulting in The growth of methanogens is inhibited, so that the biochemical reaction rate of anaerobic enzymes is lowered. After micro-electrolysis treatment, the oxidation-reduction potential eh of the influent water in the methanogenic stage is reduced to about -300mV, which is close to or reaches the growth potential of methanogenic bacteria. In addition, there are still some facultative bacteria in the methanogenic stage, and it will soon be The optimum growth potential for methanogens below -330mV is reached. Therefore, under this condition, the enzymes in the anaerobic methanogens have high activity, and the rate of the enzyme-catalyzed reaction is high, that is, the rate of anaerobic methanogenic bacteria is high.

During the oxidation-reduction reaction process in the micro-electrolysis, a small amount of iron filings dissolves and enters the wastewater. At the same time, trace amounts of the same transition elements Co and Ni in the iron filings also enter the wastewater in the form of ions, which is very important for the subsequent methanogenic stage. beneficial.

Description of drawings

Fig. 1 is a process flow block diagram of the present invention.

Detailed ways

Example 1

The rinsing acid wastewater containing SO ₄ ^2- produced during the production of saponin hydrolyzate by the sulfuric acid hydrolysis process of turmeric has a pH value of 1.6 to 1.8, and is neutralized by 20% lime milk until the pH value is within the range of 6.8 to 8.0. After clarifying for 1-5 hours, the supernatant overflows to the water collection well, and its COD is 16500-18000mg/L. From the submersible sewage pump at the bottom of the water collection well, the neutral waste water is heated up to 37±2°C through a heat exchanger at a flow rate of 1m ³ /h and sent to an effective volume of 16m ³ for ordinary hydrolysis and acidification containing domesticated acidified sludge The reactor is used for hydrolytic acidification reaction, the hydraulic retention time is 16 hours, after the sedimentation treatment, the COD of the hydrolytic acidification effluent is reduced to 12700~14100mg/L, and the eh is reduced to -90~140mV, and the removal rate of COD in the hydrolysis acidification stage is 25%. about.

The effluent in the hydrolysis and acidification stage enters from the bottom of the micro-electrolyzer with an effective volume of 3.5m ³ filled with a mixture of iron filings and activated carbon particles. The hydraulic retention time is 3 hours. After micro-electrolysis treatment, the COD of the effluent is reduced to 11300-12600mg/L, eh Reduced to -280 ~ 340mV.

The effluent from the micro-electrolysis stage enters the UASB anaerobic reactor with an effective volume of 20m ³ after adjusting the pH value to 6.5-7.0. The anaerobic sludge in the UASB is the excess sludge produced by an anaerobic reactor for food production wastewater . The residual COD concentration in the effluent is 1080-1170mg/L. The hydraulic retention time of this stage is 20 hours, and the COD removal rate is greater than 90%.

The total removal rate of the three stages is greater than 93%.

Example 2

The comprehensive acid wastewater containing SO ₄ ^2- produced during the production of saponin hydrolyzate by sulfuric acid hydrolysis process of turmeric has a pH value of 0.6 to 0.8, and is neutralized by 20% lime milk until the pH value is within the range of 6.8 to 8.0. After clarification for 3-5 hours, the supernatant overflows to the water collection well, and its COD is 36400-43000mg/L. From the submersible sewage pump at the bottom of the water collection well, the neutral waste water is heated up to 37±2°C through a heat exchanger at a flow rate of 0.7m ³ /h and sent to the continuous hydrolysis and acidification with an effective volume of 18m ³ containing domesticated acidified sludge Clarify the reactor and carry out the hydrolysis and acidification reaction. The hydraulic retention time is 24 hours. After the treatment, the COD of the hydrolysis and acidification effluent drops to 29500-34100mg/L, and the eh drops to -110--140mV. The removal rate of COD in the hydrolysis and acidification stage is 20%. about.

The effluent in the stage of hydrolysis and acidification enters from the bottom of the micro-electrolyzer with an effective volume of 3.5m ³ filled with a mixture of iron filings and activated carbon particles, and the hydraulic retention time is 4 hours. Reduced to -310 ~ -330mV, the COD removal rate is about 11%.

The effluent from the micro-electrolysis stage enters the improved UASB anaerobic reactor with an effective volume of 20m ³ after adjusting the pH value to 6.0-7.0. The anaerobic sludge in the UASB is produced by an anaerobic reactor for food production wastewater residual sludge. The residual COD concentration in the effluent is 1680-1830mg/L. The hydraulic retention time of this stage is 28.5 hours, and the COD removal rate is greater than 92%.

The total removal rate of the three stages is greater than 95%.

Example 3

The high-concentration organic wastewater produced during the production of edible yeast with molasses as raw material has a pH value in the range of 6.8 to 8.0, and its COD is 26500 to 28000 mg/L after adjustment of water quantity and quality. From the submersible sewage pump at the bottom of the water collection well, the neutral waste water is heated up to 37±2°C through a heat exchanger at a flow rate of 0.5m ³ /h and sent to the UASB with an effective volume of 8m ³ containing domesticated acidified sludge for hydrolysis Acidification reactor, for hydrolytic acidification reaction, the hydraulic retention time is 16 hours, after treatment, the effluent COD of hydrolytic acidification is reduced to 21700~22800mg/L, eh is reduced to -110~-150mV, and the removal rate of COD in the hydrolytic acidification stage is 20% about.

The effluent in the hydrolysis and acidification stage enters from the bottom of the micro-electrolyzer with an effective volume of 2.0m ³ filled with a mixture of iron filings and activated carbon particles, and the hydraulic retention time is 3.5 hours. Reduced to -300 ~ -330mV, the COD removal rate is about 9%.

The effluent from the micro-electrolysis stage enters the UASB anaerobic reactor with an effective volume of 12m ³ after adjusting the pH value to 6.0-7.0. The anaerobic sludge in the UASB is the remaining sludge produced by an anaerobic reactor for food production wastewater. . The effluent residual COD concentration is 2080-2260mg/L. The hydraulic retention time of this stage is 24 hours, and the COD removal rate is greater than 88%.

The total removal rate of the three stages is greater than 91.5%.

Example 4

The high-concentration organic wastewater produced in the process of producing industrial alcohol with molasses as raw material has a pH value of 4.0-5.0. After adjusting the water volume and quality and neutralizing and clarifying, the pH value is 6.8-7.8 and the COD is 27500-32000mg /L. From the submersible sewage pump at the bottom of the water collection well, the neutral waste water is heated up to 37±2°C through the heat exchanger at a flow rate of 0.5m ³ /h and sent to the UASB with an effective volume of 8m ³ containing domesticated acidified sludge for hydrolysis Acidification reactor, for hydrolytic acidification reaction, the hydraulic retention time is 16 hours, after treatment, the effluent COD of hydrolytic acidification is reduced to 23200~25400mg/L, eh is reduced to -90~-130mV, and the removal rate of COD in the hydrolytic acidification stage is 20% about.

The effluent in the hydrolysis and acidification stage enters from the bottom of the micro-electrolyzer with an effective volume of 2.0m ³ filled with a mixture of iron filings and activated carbon particles, and the hydraulic retention time is 3.5 hours. Reduced to -300 ~ -330mV, the COD removal rate is about 12%.

The effluent from the micro-electrolysis stage enters the UASB anaerobic reactor with an effective volume of 12m ³ after adjusting the pH value to 6.0-7.0. The anaerobic sludge in the UASB is the remaining sludge produced by an anaerobic reactor for food production wastewater. . The residual COD concentration in the effluent is 2040-2250mg/L. The hydraulic retention time of this stage is 24 hours, and the COD removal rate is greater than 90%.

The three-stage total removal rate is greater than 92%.

Claims (5)

1. the anaerobic treatment process of a high concentrated organic wastewater, it is characterized in that: insert little electrolysis stage of forming by the mixture of iron filings and granular carbon or carbon granules between acidication stage in two stage anaerobic treatment process and the product methane phase, the organic waste water of high density passes through reactor for hydrolysis and acidification, little electrolyzer and methane-producing reactor successively according to different hydraulic detention times, forms three stage anaerobic treatment process of high concentrated organic wastewater.

2. the anaerobic treatment process of a kind of high concentrated organic wastewater according to claim 1, it is characterized in that: reactor for hydrolysis and acidification is common acidication device, continuously acidizing settler or upflow anaerobic sludge blanket reactor.

3. the anaerobic treatment process of a kind of high concentrated organic wastewater according to claim 1 is characterized in that: the water outlet pH value that control is handled through acidication is 3.5～6.0.

4. the anaerobic treatment process of a kind of high concentrated organic wastewater according to claim 1; it is characterized in that: in little electrolysis stage; the water outlet of slant acidity acidication is clarified the upper reaches, back once more from little bottom of electrolytic tank; through iron filings and the carbon granules bed of mixture in the groove; overflow from top and to enter semiclosed water leg, add a spot of alkali lye on water leg top and regulate pH value to 6.0～7.0.

5. the anaerobic treatment process of a kind of high concentrated organic wastewater according to claim 1, it is characterized in that: methane-producing reactor is upflow anaerobic sludge blanket reactor, internal-circulation type anaerobic reactor or common anaerobic digester at intermittence.

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