CN117819701A - Preparation of a novel conductive biological filler and method for treating organic wastewater thereof - Google Patents

Abstract

The present invention relates to a preparation method of a novel conductive biological filler and a method for treating organic wastewater, belonging to the technical field of wastewater treatment. The present invention comprises S1: dissolving sodium alginate and chitosan in ultrapure water heated in a constant temperature water bath to prepare a mixed solution; S2: adding polyvinyl alcohol powder and ferric chloride to the mixed solution to prepare a mixed gel; S3: subjecting the mixed gel to repeated freezing and thawing processes, and then freeze-drying to obtain a conductive biological filler, and using the prepared conductive biological filler to treat high-concentration organic wastewater, thereby increasing the degradation rate of the biological filler and improving the removal effect of pollutants.

Description

Preparation of a novel conductive biological filler and method for treating organic wastewater thereof

Technical Field

The invention belongs to the technical field of wastewater treatment and relates to a preparation method of a novel conductive biological filler and a method for treating organic wastewater thereof.

Background technique

The global annual wastewater production is about 359 billion cubic meters, mainly including domestic sewage, agricultural wastewater and industrial wastewater. Among these wastewaters, organic wastewater accounts for a relatively high proportion, such as new landfill leachate, food processing and fermentation wastewater and other high-concentration organic wastewater, which poses a serious threat to the soil environment and surface water/groundwater. High-concentration organic wastewater, that is, wastewater with a COD concentration greater than 2000mg/L, has the characteristics of high suspended matter content, high chroma, obvious odor, high organic matter concentration, and complex water quality components, which makes it difficult to treat.

According to the depth of treatment, sewage treatment can be divided into primary treatment and secondary treatment. Primary treatment aims to remove suspended solids, usually using physical methods; secondary treatment further removes colloids and soluble pollutants in sewage, usually using biological methods.

The biofilm method is a type of biological method and is usually used in the secondary sewage treatment process. However, when using the biofilm method to treat high-concentration organic wastewater, the growth and metabolism of microorganisms is slow, and the biofilm will age after a period of time. Problems such as this limit the effectiveness of using the biofilm method to treat high-concentration organic wastewater.

Therefore, it is necessary to provide a new type of conductive biofiller preparation and a method for treating organic wastewater, improve the treatment efficiency of the biofiller for high-concentration organic wastewater, shorten the treatment time, and thus improve the treatment effect of the biofiller for high-concentration organic wastewater.

Summary of the invention

In order to overcome the problems existing in the background technology, the present invention proposes a method for preparing a new type of conductive biological filler and treating organic wastewater therewith. By preparing a conductive biological filler, an electric field is used to stimulate microorganisms, thereby increasing their biological activity and promoting the degradation of pollutants by microorganisms, thereby improving the treatment effect of the biological filler on high-concentration organic wastewater.

In order to achieve the above object, the present invention is implemented by the following technical solutions:

In one aspect, the present invention provides a method for preparing a novel conductive biofiller, the method comprising the following steps:

S1: Sodium alginate and chitosan are dissolved in ultrapure water heated in a constant temperature water bath respectively, and then the constant temperature water bath is continuously heated and magnetically stirred until the raw materials are completely mixed and dissolved to obtain a mixed solution.

S2: adding polyvinyl alcohol powder and ferric chloride to the mixed solution obtained in step S1, while continuously stirring mechanically to obtain a mixed gel.

S3: putting the mixed gel obtained in step S2 into a mold and freezing it, then thawing it at room temperature, repeating the freezing and thawing process, and then freeze-drying it to obtain a conductive biofiller.

Preferably, the mass ratio of sodium alginate, chitosan, polyvinyl alcohol powder and ferric chloride is sodium alginate: chitosan: polyvinyl alcohol: ferric chloride = 3: 1: 18: 1 to 3: 1: 30: 1. Adding ferric chloride (FeCl3) and chitosan (CS) to the biological filler can effectively improve the biocompatibility of the filler and reduce the resistance of the filler, so that the biological filler has better conductivity, thereby enhancing the stimulation effect of the electric field on microorganisms.

Preferably, in step S1, the ultrapure water temperature is 90° C. and the magnetic stirring time is 30 min.

Preferably, in step S2, the mechanical stirring time is 15 minutes.

Preferably, in step S3, the mixed gel is frozen at -10°C for 3 hours and then thawed, and the process is repeated twice.

Another aspect of the present invention provides a method for treating high-concentration organic wastewater using the prepared conductive biofiller, the method comprising the following steps:

Q1: Connect the two carbon plates in the reactor to the positive and negative electrodes of the DC power supply through wires, adjust the position of the aeration head of the aeration device, and place the aeration head at the bottom of the reactor.

Q2: Add biofilm-forming biofiller and high-concentration organic wastewater to be treated into the reactor.

Q3: Start the DC power supply, adjust the voltage and current, then turn on the aeration device and adjust the aeration flow rate, and the conductive biological filler begins to treat the high-concentration organic wastewater.

Preferably, in step Q3, the aeration flow rate is 0.8 L/min, the voltage is 3 V, and the current is 10 mA.

Beneficial effects of the present invention:

1. The present invention prepares a biofiller with conductive properties and uses an electric field to stimulate the microorganisms in the biofiller to achieve efficient removal of pollutants such as COD and NH ₄ ⁺ -N in high-concentration organic wastewater. After 24 hours of treatment, the COD removal rate can reach more than 90%, and the NH ₄ ⁺ -N removal rate can reach more than 60%.

2. The present invention adds ferric chloride to enable the conductive biological filler to precipitate Fe ³⁺ and participate in the extracellular electron transfer of microorganisms. At the same time, the positively charged ferric hydroxide colloid can better adsorb negatively charged microorganisms to accelerate the enrichment of microorganisms on the biological filler, effectively shorten the time for forming biofilm, and further improve the treatment efficiency of high-concentration organic wastewater.

3. The present invention makes the originally brittle sodium alginate gel more resilient by adding chitosan, and the addition of degradable substances further improves the biocompatibility of the conductive biological filler.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a flow chart of the method for preparing the conductive biofiller of the present invention.

FIG2 (a) is a graph showing the COD concentration and pH change of the elution solution of 100 g of conductive biofiller at different ratios; FIG2 (b) is a graph showing the resistance and specific surface area change of 100 g of conductive biofiller at different ratios.

FIG3 is scanning electron micrographs of conductive biofillers at different ratios, wherein (a) to (f) correspond to scanning electron micrographs of polyvinyl alcohol (PVA): sodium alginate (SA) = 10:1, 8:1, 6:1, 4:1, 2:1, and 1:1, respectively.

FIG4 is a graph showing the porosity and swelling rate of 100 g of the conductive biological filler prepared by the present invention at different ratios, wherein (a) is a graph showing the porosity, and (b) is a graph showing the swelling rate.

5 is a graph showing changes in COD and NH ₄ ⁺ -N removal rates during wastewater treatment in Example 1 of the present invention and Comparative Example 2, wherein (a) is a graph showing changes in COD removal rates, and (b) is a graph showing changes in NH ₄ ⁺ -N removal rates.

Detailed ways

The present invention is further described in detail below in conjunction with specific embodiments.

In the embodiments of the present invention and the comparative examples, the pH is measured by a Lei magnetic pH meter, the COD concentration is measured by a Hach rapid digestion method, the NH ₄ ⁺ -N concentration is measured by a Hach DR3900 spectrophotometer by Nessler spectrophotometry, the resistance is measured by a Shanghai Chenhua electrochemical workstation, the specific surface area is measured by a fully automatic specific surface area nitrogen adsorption method, the porosity is calculated by weighing the mass of the conductive biological filler before and after rehydration and the mass before and after preparation using an analytical balance, and the swelling rate is calculated by measuring the radius of the conductive biological filler using a vernier caliper.

Example 1

Weigh 6 portions of raw materials according to the mass ratio of sodium alginate (SA): chitosan (CS): polyvinyl alcohol (PVA): ferric chloride = 3:1:18:1, 3:1:24:1, and 3:1:30:1, and mark them for later use, where the PVA:SA ratio is 6:1, 8:1, and 10:1, respectively.

First, add 300 mL of ultrapure water into three beakers and heat them to 90°C in a water bath. Then, add 3 portions of weighed sodium alginate and chitosan into the three beakers respectively and mark them. After adding, stir magnetically for 30 minutes until the raw materials are completely dissolved.

Then, 3 portions of weighed polyvinyl alcohol powder and ferric chloride were added into 3 beakers respectively, and stirred for 15 minutes by mechanical stirring. The mixed solution showed a gel state.

The gel-like substance was placed in a mold, placed in a refrigerator, frozen at -10°C for 3 hours, then taken out, thawed at room temperature, then placed in a refrigerator again, frozen at -10°C for 3 hours, taken out, thawed at room temperature, and then freeze-dried to obtain 3 portions of conductive biofillers.

Comparative Example 1

This comparative example adopts the same method as Example 1 to prepare the conductive biofiller, except that, in this comparative example, when weighing the raw materials, three parts of raw materials are weighed according to sodium alginate (SA): chitosan (CS): polyvinyl alcohol (PVA): ferric chloride = 3:1:3:1, 3:1:6:1, 3:1:12:1, among which PVA:SA is 1:1, 2:1, 4:1, respectively, to prepare 3 parts of conductive biofiller.

Six portions of conductive biological fillers prepared in Example 1 and Comparative Example 1 were respectively immersed in water for rehydration. The COD concentration and pH value of the dissolution liquid during the rehydration process were measured. The resistance, swelling rate, porosity and specific surface area of the filler blocks were measured. A scanning electron microscope experiment was performed. The results are shown in FIG2 .

It can be seen from Figure 2(b) that the resistance of the filler under different ratios decreases as the ratio of PVA:SA decreases, while the specific surface area increases accordingly. When PVA:SA=6:1, the resistance of the filler is small and the specific surface area is moderate. The filler under this ratio has better conductivity and larger specific surface area than the filler with high PVA content; although the filler with low PVA content has good conductivity and large specific surface area, according to Figure 2(a), when the PVA content is low, the COD dissolution concentration is large, indicating that the low PVA content has a greater impact on the overall stability of the filler, which is easy to cause the contents of the filler to flow away.

It can be seen from Figure 3 that as the PVA:SA ratio increases, the amount of pores on the filler surface gradually increases. In Figure (f), the magnification is different from that of other ratios because the filler is very easy to break after freeze-drying. In Figure (c), there are more pores on the surface of the filler, and the overall pores are more uniform, which also reflects the spatial network structure formed by the self-crosslinking of PVA; in Figure (e), the pores on the surface of the filler are larger and less uniform, and it can be seen that the overall filler cross-section is biased to one side during the brittle fracture process, which indicates that the filler structure is not stable enough at low PVA content.

It can be seen from Figure 4 that the porosity of the filler under different ratios decreases with the increase of the PVA:SA ratio, while the swelling rate increases. Too high porosity will lead to a smaller physical volume in the filler and lower overall mechanical strength, which indicates that the filler under a high PVA:SA ratio has stronger spatial stability. A high swelling rate indicates that the filler has good water absorption performance, which indicates that the filler under a high PVA:SA ratio has good water absorption performance and more internal water-containing pores. In addition, it can be clearly observed during the swelling experiment that the filler with a PVA:SA ratio of 6:1 has different degrees of disintegration in water, while the fillers with PVA:SA ratios of 2:1 and 1:1 are mostly broken and cannot maintain a complete shape.

In summary, the PVA content has a great influence on the performance of conductive biofillers. When the PVA content is high, the filler has good conductivity, high specific surface area, uniform and stable porous morphology, good water absorption, and optimal comprehensive performance under the condition of meeting basic stability.

The filler sample with the raw material ratio of 3:1:18:1 prepared above was selected for organic wastewater treatment.

Connect the two carbon plates in the reactor to the positive and negative electrodes of the DC power supply through wires, adjust the position of the aeration head of the aeration device, and place the aeration head at the bottom of the reactor.

Add biofilm-forming biofillers and organic wastewater with a COD concentration of 5000±320 mg/L and an NH ₄ ⁺ -N concentration of 500±88 mg/L into the reactor.

Start the DC power supply, adjust the voltage to 3V and the current to 10mA, turn on the aeration device, adjust the aeration flow rate to 0.8L/min, and the biological filler begins to treat the organic wastewater.

After 24 hours of treatment, the organic wastewater was taken out and the COD concentration and NH ₄ ⁺ -N concentration therein were measured. The results are shown in FIG5 .

Comparative Example 2

In this comparative example, the conductive biofiller is prepared in the same manner as in Example 1, and the organic wastewater is treated in the same manner, except that the conductive biofiller is not electrified in this comparative example.

The measurement results of COD concentration and NH ₄ ⁺ -N concentration in the organic wastewater after treatment in this comparative example are shown in FIG5 .

As can be seen from Figure 5, the removal rate of COD in Example 1 can reach 92%, and the removal rate of _NH4 ⁺ -N can reach 64%, while the removal rate of COD in Comparative Example 1 is only 82%, and the removal rate of _NH4 ⁺ -N is only 41%. The effect of applying the electric field is better than that of simply using the new conductive filler. It is confirmed that the electric field stimulates microorganisms and improves their activity, so that more efficient treatment can be carried out with better treatment effect.

Comparative Example 3

This comparative example uses the same method as Example 1 to prepare and treat organic wastewater, except that in this comparative example, the biological filler does not contain ferric chloride.

The treatment effect of the biological filler on high-concentration organic wastewater in this comparative example is lower than that in Example 1. When the biological filler lacks ferric chloride, the ion content inside the filler decreases, and its conductivity is greatly weakened, and the overall treatment performance is reduced under the action of the applied electric field.

Comparative Example 4

This comparative example uses the same method as Example 1 to prepare and treat organic wastewater, except that in this comparative example, the biological filler does not contain chitosan.

The treatment effect of the biological filler on high-concentration organic wastewater in this comparative example is lower than that in Example 1. When the biological filler lacks chitosan, the prepared filler is brittle and easy to break and fall off, which is not conducive to the operation of the filler in the reactor. In addition, the filler is very easy to disintegrate after absorbing water in the reactor, thereby affecting the treatment effect of the biological filler on high-concentration organic wastewater.

Comparative Example 5

This comparative example uses the same method as Example 1 to prepare and treat organic wastewater, except that in this comparative example, the biological filler does not contain chitosan and ferric chloride.

The treatment effect of the biological filler on high-concentration organic wastewater in this comparative example is lower than that in Example 1. Since the biological filler lacks chitosan and ferric chloride, the problems of Comparative Examples 2 and 3 occur at the same time. The filler prepared in this comparative example is brittle as a whole and has weak electrical conductivity. At the same time, the filler is fragile after freeze-drying, and its structural strength is extremely poor, which makes it unable to treat high-concentration organic wastewater normally.

Finally, it should be noted that the above preferred embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that various changes can be made in form and details without departing from the scope defined by the claims of the present invention.

Claims (7)

1. A preparation method of a novel conductive biological filler is characterized by comprising the following steps: the preparation method of the novel conductive biological filler comprises the following steps:

s1: respectively dissolving sodium alginate and chitosan in ultrapure water heated by a constant-temperature water bath, and then continuously heating by the constant-temperature water bath and magnetically stirring until the raw materials are completely mixed and dissolved to obtain a mixed solution;

s2: adding polyvinyl alcohol powder and ferric trichloride into the mixed solution obtained in the step S1, and continuously and mechanically stirring to obtain mixed gel;

s3: and (2) putting the mixed gel obtained in the step (S2) into a mould, freezing, thawing at room temperature, repeating the freezing and thawing process, and then performing freeze drying to obtain the conductive biological filler.

2. The method for preparing the novel conductive biological filler according to claim 1, wherein the method comprises the following steps: in the preparation process, the mass ratio of the sodium alginate, the chitosan, the polyvinyl alcohol powder and the ferric trichloride is as follows: chitosan: polyvinyl alcohol: ferric trichloride=3:1:18:1 to 3:1:30:1.

3. The method for preparing the novel conductive biological filler according to claim 1, wherein the method comprises the following steps: in the step S1, the temperature of the ultrapure water is 90 ℃, and the magnetic stirring time is 30min.

4. The method for preparing a novel conductive biological filler according to claim 1, which is characterized in that: in the step S2, the mechanical stirring time is 15min.

5. The method for preparing the novel conductive biological filler according to claim 1, wherein the method comprises the following steps: in the step S3, the mixed gel is frozen for 3 hours at the temperature of minus 10 ℃ and then thawed, and the repetition number is 2.

6. An organic wastewater treatment using the conductive bio-filler prepared by the method for preparing a novel conductive bio-filler according to any one of claims 1 to 5, characterized in that: the method for treating the high-concentration organic wastewater comprises the following steps of:

q1: connecting two carbon plates in the reactor with the anode and the cathode of a direct current power supply through wires, adjusting the position of an aeration head of an aeration device, and placing the aeration head at the bottom of the reactor;

q2: adding biofilm-formed biological filler and high-concentration organic wastewater to be treated into a reactor;

q3: and starting a direct current power supply, regulating voltage and current, then opening an aeration device, regulating aeration flow, and starting the conductive biological filler to treat the high-concentration organic wastewater.

7. The method for treating high-concentration organic wastewater according to claim 6, wherein: in the step Q3, the aeration flow is 0.8L/min, the voltage is 3V, and the current is 10mA.