CN115893784A - A method for reducing hydrogen sulfide production during sludge treatment - Google Patents

Abstract

The invention relates to a method for reducing hydrogen sulfide generation in a sludge treatment process by intermittent and pulse feeding of calcium peroxide. The specific method comprises the following steps: (1) Naturally settling primary sludge and excess sludge generated by an urban sewage treatment plant, removing supernatant, and concentrating to obtain a fermentation raw material; (2) Adding calcium peroxide into the obtained fermentation raw material, and performing anaerobic fermentation treatment to inhibit the generation of hydrogen sulfide. The sludge is fed in an intermittent and pulse mode, after the calcium peroxide is added, sulfate reducing bacteria are obviously influenced, and the activity of microbial enzymes is greatly inhibited, so that the generation of hydrogen sulfide in the anaerobic fermentation process of the sludge can be greatly inhibited. Through the rapid, efficient, low-investment and effective operation, the generation of toxic and harmful hydrogen sulfide gas in the anaerobic fermentation treatment of the sludge is reduced, and the method has important significance for the treatment and disposal of the sludge.

Description

A method for reducing hydrogen sulfide production during sludge treatment

technical field

The invention belongs to the technical field of environmental protection and sludge treatment and resource utilization, and in particular relates to a method for reducing the generation of hydrogen sulfide in the process of sludge treatment by adding calcium peroxide intermittently and in pulses.

technical background

With the continuous acceleration of urbanization, the sewage treatment capacity of sewage treatment plants is also increasing, and the output of surplus sludge is also increasing. Because the sources of sewage vary from good to bad, it may contain various pollutants. These substances pass through the municipal pipe network and finally enter the sewage treatment plant. Therefore, the remaining sludge contains a large number of pathogenic microorganisms, heavy metals and organic pollutants, which cannot be properly treated. Easy to cause secondary pollution to the environment.

The cost of excess sludge treatment is high, but the organic matter and nutrients rich in excess sludge can be recycled through the production of energy substances. Anaerobic fermentation is an effective disposal method to achieve harmlessness and resource utilization. It can degrade biodegradable organic matter, stabilize and reduce excess sludge, kill pathogens, and recover a large amount of short-chain fatty acids from sludge. Products with high added value, such as hydrogen, methane, etc., have achieved the effect of turning waste into wealth, which has a great effect on alleviating the current energy crisis.

Anaerobic fermentation of sludge produces hydrogen sulfide gas while degrading organic matter to produce high value-added products. The stench of hydrogen sulfide not only pollutes the environment, but also causes certain harm to the human body. Hydrogen sulfide is a highly toxic gas that is soluble in water, colorless, and smells like rotten eggs. It is a strong irritant and asphyxiating neurotoxin. Smell can also be smelled at very low concentrations. Above 10ppm will produce some symptoms, such as tearing, coughing, nausea, vomiting and other symptoms. Above 300ppm, human life will be threatened. Due to the serious health hazards of hydrogen sulfide gas, the research on the control of hydrogen sulfide has become one of the important hot issues concerned by research institutions. Therefore, it is necessary to find a simple, safe, cheap and efficient method to inhibit the production of hydrogen sulfide from sludge anaerobic fermentation.

Calcium peroxide, as an oxidizing and slow-release peroxide, has been widely used in aquaculture, agriculture, medicine, water treatment and other fields. It has the advantages of low price, strong oxidizing ability, safe and convenient operation and use. . Slow release means that when calcium peroxide is dissolved in an aqueous medium, it slowly decomposes into hydrogen peroxide, oxygen and calcium hydroxide. Based on this special physical and chemical characteristics, calcium peroxide has been used as an additive for sludge pretreatment. It can effectively promote the breakdown of sludge cells and increase the release of organic matter. Therefore, calcium peroxide has been widely used in the removal of pollutants in sewage, dehydration of sludge, and anaerobic fermentation to produce volatile fatty acids and hydrogen. So far, the use of calcium peroxide to reduce hydrogen sulfide production during sludge treatment has not been reported.

Contents of the invention

The object of the present invention is to provide a method for inhibiting the generation of hydrogen sulfide by anaerobic fermentation of sludge, that is, to reduce the generation of hydrogen sulfide in the process of sludge treatment by intermittent and pulse dosing of calcium peroxide. It can effectively reduce the frequency of drug dosing, save drug costs and operating costs, and thus provide a fast, efficient, low-input, and no potential risk to the environment control method for controlling the production of hydrogen sulfide by anaerobic fermentation of sludge.

In order to achieve the above object, the technical method adopted in the present invention comprises the following steps:

(1) Natural settlement of primary sludge and excess sludge from urban sewage treatment plants. The settling time was 24 hours and the temperature was 4°C.

(2) removing the supernatant and concentrating it into excess sludge with a volatile solid content of 20-35g/L to obtain fermentation raw materials.

(3) Calcium peroxide is added to the above sludge for mixed treatment, and fermentation is carried out under anaerobic environment.

In the above step (3), 3 times of equal-volume pulse dosing are adopted, and the dosing interval is 10-30 minutes. This method can significantly suppress the generation of hydrogen sulfide by changing the dosing method without increasing the actual dosage. resulting in better control.

(4) Use calcium peroxide to treat fermented sludge intermittently, add calcium peroxide to the reactor in a short period of time, and after 5-10 days, use calcium peroxide to treat sludge again in a short period of time. In fact, the inventors believe that the optimal period for treating sludge will depend on the specific operating parameters of that particular environment. Optimum periods of treatment and resting can be readily determined by those skilled in the art by performing fairly straightforward experiments.

In the above-mentioned step (3), the total amount of calcium peroxide added is 0.05～0.25g/gVSS, preferably 0.1～0.15g/gVSS. The fermentation environment is an anaerobic environment, that is, after adding calcium peroxide to the sludge, nitrogen gas (nitrogen purity is 90.00%-99.99%) is introduced for 5 minutes to remove the presence of oxygen in the reactor. After sealing, the reactor is put into 35 °C in a shaker with a shaking speed of 125 rpm/min.

In the above step (3), the time for sludge anaerobic fermentation is 12-25 days.

In a preferred implementation case, the dosage of calcium peroxide is 0.1-0.15g/g VSS. Although the amount of calcium peroxide can inhibit the production of hydrogen sulfide by anaerobic fermentation of sludge within a certain range, and within a certain range, with the increase of the amount of calcium peroxide, the inhibitory effect on the production of hydrogen sulfide by anaerobic fermentation of sludge is more effective. obvious. But consider the relation of raw material cost and hydrogen sulfide output, the consumption scope of the ideal calcium peroxide that the present invention adopts is at 0.1～0.15g/g VSS.

When calcium peroxide is dosed in a step-by-step pulse manner in the above step (3), the preferred dosing interval is 10-20 minutes.

When adopting intermittent mode to add calcium peroxide in the above-mentioned step (4), preferably adding interval time is 6-8 days.

Owing to adopting above technical scheme, the present invention has following achievement:

1. The present invention utilizes calcium peroxide to react with water to produce hydrogen peroxide, calcium hydroxide and oxygen, and then produce active oxygen free radicals such as hydroxyl radicals to suppress sludge anaerobic fermentation and produce hydrogen sulfide. It can significantly inhibit the abundance of sulfate-reducing bacteria in excess sludge and reduce the activity of related microbial enzymes, which is of great significance for the large-scale application of sludge anaerobic fermentation and has a positive impact on environmental protection.

2. Compared with the prior art, the present invention can significantly reduce the generation of internal hydrogen sulfide in the process of sludge treatment within a very short action time, and adopts intermittent and pulse dosing methods to effectively reduce the dosing of calcium peroxide frequency, saving drug costs and running costs.

3. The present invention suppresses the production of toxic and harmful substances such as hydrogen sulfide in sludge anaerobic fermentation, which not only reduces the harm to the environment and even the human body, but also promotes the safe and effective promotion of sludge anaerobic fermentation technology. The reduction and resource utilization of mud is of great significance. The strategy of adding calcium peroxide pretreatment has the advantages of environmental friendliness and environmental economy for practical application, and further expands the application field of calcium peroxide in engineering.

Description of drawings

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

Detailed ways

The present invention will be further described below in conjunction with specific practical cases, but the protection scope of the present invention will not be limited.

Implementation case 1: Effect of single simple dosing of calcium peroxide on hydrogen sulfide production

(1) In a plexiglass container with a working volume of 4L, the sludge produced by the municipal sewage treatment plant was placed at 4°C for 1 day to naturally settle, and the fermented raw material was obtained after removing the supernatant.

(2) Add 500mL of the sludge obtained in (1) into the reactor, and add 0.1g/g VSS calcium peroxide, stir evenly, fill the reactor with nitrogen, continue for 5min to remove oxygen, and seal the reaction The shaker was placed in a shaker for anaerobic fermentation, wherein the shaker fermentation temperature was 35±1°C, the shaking speed was 125rpm/min, the fermentation time (that is, the residence time of the sludge in the reactor) was 13 days, and the hydrogen sulfide output It is 152.3978*10 ^-4 mg/g VSS.

Implementation case 2: Effect of single simple dosing of calcium peroxide on hydrogen sulfide production

(1) In a plexiglass container with a working volume of 4L, the sludge produced by the municipal sewage treatment plant was placed at 4°C for 1 day to naturally settle, and the fermented raw material was obtained after removing the supernatant.

(2) Add 500mL of the sludge obtained in (1) into the reactor, and add 0.15g/g VSS calcium peroxide, stir evenly, fill the reactor with nitrogen, continue for 5min to remove oxygen, and seal the reaction The shaker was placed in a shaker for anaerobic fermentation, wherein the shaker fermentation temperature was 35±1°C, the shaking speed was 125rpm/min, the fermentation time (that is, the residence time of the sludge in the reactor) was 13 days, and the hydrogen sulfide output It is 90.5266*10 ^-4 mg/g VSS.

Implementation Case 3: Effect of Intermittent and Pulse Dosing of Calcium Peroxide on Hydrogen Sulfide Production

(1) In a plexiglass container with a working volume of 4L, the sludge produced by the municipal sewage treatment plant was placed at 4°C for 1 day to naturally settle, and the fermented raw material was obtained after removing the supernatant.

(2) Add 500mL of the sludge obtained in (1) into the reactor, and add calcium peroxide of 0.1g/gVSS in an intermittent and pulsed manner (the total amount of addition is the same as that of the implementation case (1). The intermittent time is 8 days, and the pulse interval is 15 minutes), stir evenly, fill the reactor with nitrogen, continue for 5min to remove oxygen, seal the reactor and put it into a shaker for anaerobic fermentation, wherein the shaker fermentation temperature is 35 ±1°C, the shaking speed was 125rpm/min, the fermentation time (that is, the residence time of the sludge in the reactor) was 13 days, and the production of hydrogen sulfide was 121.5547*10 ^-4 mg/g VSS.

Implementation Case 4: Effect of Intermittent and Pulse Dosing of Calcium Peroxide on Hydrogen Sulfide Production

(1) In a plexiglass container with a working volume of 4 L, put the sludge produced by the urban sewage treatment plant at 4° C. for 1 day, and remove the supernatant to obtain the fermented raw material.

(2) The sludge obtained in 500mL (1) is added to the reactor, and the calcium peroxide of 0.15g/g VSS is added intermittently and pulsed ((the total amount of addition is the same as that of the implementation case (2), Dosing intermittent time is 8 days, pulse interval is 15 minutes), stir evenly, fill nitrogen into the reactor, continue 5min to remove oxygen, seal the reactor and put it into the shaker for anaerobic fermentation, wherein, the shaker fermentation temperature The temperature is 35±1°C, the shaking speed is 125rpm/min, the fermentation time (that is, the residence time of the sludge in the reactor) is 13 days, and the hydrogen sulfide production is 71.0537*10 ^-4 mg/g VSS.

Comparative case 1

(1) In a plexiglass container with a working volume of 4 L, put the sludge produced by the urban sewage treatment plant at 4° C. for 1 day, and remove the supernatant to obtain the fermented raw material.

(2) Add 500mL of the sludge obtained in (1) into the reactor without adding calcium peroxide, stir evenly, fill the reactor with nitrogen, and continue for 5min to remove oxygen, seal the reactor and put it in a shaker Anaerobic fermentation, wherein the shaking table fermentation temperature is 35±1°C, the shaking speed is 125rpm/min, the fermentation time (that is, the residence time of the sludge in the reactor) is 13 days, and the hydrogen sulfide production is 309.0909*10 ^-4 mg/g VSS.

The hydrogen output of implementation case and comparative example is as shown in table 1:

The fermentation comparative table of table 1 embodiment and comparative example

It can be seen from the table that the hydrogen sulfide production of implementation cases 1 to 4 has been greatly reduced compared with the production of hydrogen sulfide in comparative case 1, especially under optimal conditions, the mode of intermittent and pulse feeding is adopted. The hydrogen sulfide production of the implementation cases 2 and 4 is the largest reduction compared with the hydrogen sulfide production of the comparative case 1.

The above description of the embodiments is for those of ordinary skill in the art to understand and use the present invention. Although the present invention has been disclosed above with preferred embodiments, it is not intended to limit the present invention. Without departing from the spirit and technical solutions of the present invention, those skilled in the art can make many possible modifications to the technical solutions of the present invention, or modify them into equivalent embodiments with equivalent changes. Therefore, any simple improvements and modifications that do not depart from the scope of the present invention should fall within the protection scope of the present invention.

Claims (5)

1. A method for reducing hydrogen sulfide generation in a sludge treatment process is characterized by mainly comprising the following steps:

the method reduces the problem of hydrogen sulfide generation by anaerobic fermentation by adding calcium peroxide with the concentration of 0.05-0.25g/g VSS into the sludge; the calcium peroxide is added into the sludge in an intermittent and pulse adding mode, the adding interval is 10-30 minutes, the sludge is treated discontinuously by the calcium peroxide for 5-10 days, and then the residual sludge is treated in a short time by the calcium peroxide again.

2. The method of claim 1 for reducing hydrogen sulfide production during sludge treatment, wherein: the concentration of calcium peroxide is in the range of 0.05-0.25g/g VSS, preferably 0.1-0.15g/g VSS.

3. The method of claim 1 for reducing hydrogen sulfide production during sludge treatment, wherein: the calcium peroxide is added in an intermittent and pulse manner.

4. The method of claim 1 for reducing hydrogen sulfide production during sludge treatment, wherein: when the calcium peroxide is added in a step-by-step pulse mode, 3 steps of equal addition are preferably adopted, and the optimal addition interval is 10-20 minutes.

5. The method of claim 1 for reducing hydrogen sulfide production during sludge treatment, wherein: when the calcium peroxide is added in an intermittent mode, the interval time of the intermediate addition is preferably 6-8 days.

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