Composite carrier, preparation method thereof and application of composite carrier in coking wastewater treatment

Abstract

The invention belongs to the technical field of sewage treatment, and particularly relates to a composite carrier, a preparation method thereof and application of the composite carrier in coking wastewater treatment. According to the specific technical scheme, the composite carrier comprises the following components: sodium alginate colloid, magnesium silicate, activated carbon, zero-valent iron and poly (butylene succinate). The composite carrier provided by the invention can assist in rapid granulation of anaerobic sludge, increase the particle size of particles, shorten the starting time of a reaction system, improve the COD degradation rate and enhance the impact load resistance of the system.

Description

Technical Field

[0001] The invention belongs to the technical field of sewage treatment, and in particular relates to a composite carrier and a preparation method thereof and application thereof in treating coking wastewater. Background Art

[0002] Coking wastewater is a type of difficult-to-treat industrial wastewater with complex components, high organic load and strong toxicity. Its main components include phenols, nitrogen heterocyclic compounds (pyridine, indole, quinoline, etc.), aromatic hydrocarbons and other difficult-to-degrade organic matter.

[0003] At present, the main methods for treating coking wastewater include physical, chemical and biological methods. Existing physical and chemical treatment technologies have problems such as high energy consumption, pollution transfer and secondary pollution. Biodegradation technology is widely used due to its economical and environmentally friendly characteristics. However, when using biological methods to treat coking wastewater, the highly toxic organic pollutants in the wastewater will threaten the survival and reproduction of microorganisms; when the water quality fluctuates greatly, the system will be impacted and may even cause system collapse.

[0004] Currently, upflow anaerobic sludge blanket (UASB) is a commonly used process for biological wastewater treatment. UASB can convert pollutants into clean energy (CH4), achieve energy recovery, and reduce energy costs.

[0005] However, UASB reactors have problems such as low resistance to shock loads and long start-up time in practical applications. The key to the resistance of UASB reactors to shock loads lies in the formation of anaerobic granular sludge (AGS). Mature anaerobic granular sludge has a dense structure. In addition to effectively retaining microorganisms and improving the diversity of microbial communities, it can also improve the shock resistance of microorganisms due to its sedimentation performance, thereby greatly improving the capacity and effect of anaerobic bioreactors. However, anaerobic bacteria grow slowly, and toxic compounds in coking wastewater (such as phenols) are bioinhibitory, which will further inhibit the formation of granular sludge in UASB and extend the start-up time of the reactor by 6-10 months. Therefore, achieving rapid granulation of anaerobic granules is a key link in the treatment of coking wastewater using UASB.

[0006] Therefore, if a composite carrier can be provided to help accelerate and strengthen the anaerobic granulation of coking wastewater and improve the effect of methane production, it will be of great practical significance. Summary of the invention

[0007] The purpose of the present invention is to provide a composite carrier and a preparation method thereof and application thereof in treating coking wastewater.

[0008] To achieve the above-mentioned purpose of the invention, the technical solution adopted by the present invention is: a composite carrier, wherein the composite carrier components include sodium alginate colloid, magnesium silicate, activated carbon, zero-valent iron and polybutylene succinate.

[0009] Preferably, by mass ratio, sodium alginate colloid: magnesium silicate: activated carbon: zero-valent iron: polybutylene succinate = (10-100): (0.3-1.2): 2:2:1.

[0010] Preferably, the method comprises the following steps:

[0011] (1) adding sodium alginate into pure water and fully dissolving it to obtain sodium alginate colloid;

[0012] (2) mixing activated carbon, magnesium silicate, sodium alginate colloid, zero-valent iron and polybutylene succinate in proportion to obtain sodium alginate gel;

[0013] (3) Add sodium alginate gel dropwise into the CaCl2 solution and solidify to obtain the desired composite carrier.

[0014] Preferably, the sodium alginate gel is suspended and dropped into a 2% CaCl2 solution, and the volume ratio of the sodium alginate gel to the CaCl2 solution is 1:5-50.

[0015] Correspondingly, a method for treating sewage using the composite carrier or the composite carrier prepared by the method.

[0016] Preferably, the sewage is coking wastewater.

[0017] Correspondingly, a method for anaerobic granulation is performed using the composite carrier or the composite carrier prepared by the method.

[0018] Preferably, anaerobic granulation is carried out using the composite carrier as a crystal nucleus.

[0019] Preferably, the activated sludge is anaerobically granulated using the composite carrier as the crystal nucleus.

[0020] The present invention has the following beneficial effects: the present invention provides a new composite carrier, and anaerobic sludge can be rapidly granulated with the composite carrier as a crystal nucleus. The carrier includes a variety of materials such as magnesium silicate and sodium alginate. Among them, magnesium silicate can adsorb organic matter, metal ions (a small amount of metal cations can promote anaerobic sludge granulation) and gas. If magnesium silicate is replaced with a composition of diatomaceous earth and magnesium ions, the same or similar effect cannot be achieved. This is because magnesium silicate has a strong adsorption capacity for metal elements; while the adsorption of diatomaceous earth is restricted by pH and temperature, the adsorption capacity is weaker than that of magnesium silicate, and magnesium ions do not have adsorption capacity. In addition, magnesium silicate is insoluble in water and can exist stably in the reaction system and is not easily lost with the effluent; while diatomaceous earth has water absorption, and magnesium ions are easily soluble in water. Both are easily lost and need to be replenished with the influent, and cannot exist stably in the system. In addition, anaerobic granulation requires improving the hydrophobicity of sludge, and the water absorption of diatomaceous earth is also not conducive to anaerobic granulation.

[0021] The sodium alginate in the carrier can co-metabolize with the coking wastewater to degrade pollutants; the activated carbon can adsorb COD in the coking wastewater; zero-valent iron can enhance the removal of pollutants and the ability to produce methane, while it is difficult to achieve the same effect by replacing it with divalent or trivalent iron. The PBS in the carrier can improve the bioaffinity of ZVI (reduced zero-valent iron).

[0022] The composite carrier of the present invention can help anaerobic sludge to granulate quickly, increase the particle size, shorten the start-up time of the reaction system, increase the COD degradation rate, and enhance the system's ability to resist shock loads. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a schematic diagram of the working of the UASB reactor;

[0024] Figure 2 This is a schematic diagram of the granulation effect of the blank control group (CK) reactor running for 130 days;

[0025] Figure 3 This is a schematic diagram of the granulation effect of the KF reactor running for 130 days;

[0026] Figure 4 This is a schematic diagram of the granulation effect of the KS4 reactor after 130 days of operation;

[0027] Figure 5 This is a schematic diagram of the granulation effect of the KP reactor after 130 days of operation;

[0028] Figure 6 Schematic diagram of the granulation effect after the KN reactor was operated for 130 days. DETAILED DESCRIPTION

[0029] The invention provides a new composite carrier which can simultaneously enhance the effect of anaerobic granulation of coking wastewater and the ability of producing methane.

[0030] The composite carrier includes sodium alginate colloid, magnesium silicate, activated carbon, zero-valent iron (pure iron) and polybutylene succinate (PBS). The preferred scheme is: by mass ratio, sodium alginate colloid: magnesium silicate: activated carbon: zero-valent iron: PBS = (10-100): (0.3-1.2): 2:2:1.

[0031] The present invention also provides a preparation process of the composite carrier, which specifically comprises the following steps:

[0032] Add 2g of sodium alginate to 100mL of pure water, and place in a water bath at 80-100℃ until fully dissolved to obtain sodium alginate colloid. Mix activated carbon, magnesium silicate adsorbent, sodium alginate colloid, PBS and ZVI (zero-valent iron) in proportion to obtain sodium alginate gel. Among them, the amount of PBS is half of that of zero-valent iron; the amount of sodium alginate colloid is 5-50 times that of zero-valent iron. Suspend and drop the sodium alginate gel into a 2% CaCl2 (w / w) solution (the volume ratio of sodium alginate gel to CaCl2 solution is 1:5-50), solidify at 4℃ for 4-8h, rinse with ultrapure water 3 times, and dry with absorbent paper to obtain the desired composite carrier. Store in a refrigerator at 4℃.

[0033] The composite carrier can be directly applied to wastewater for sewage treatment, and is particularly suitable for coking wastewater treatment. The composite carrier can also be applied to wastewater to help anaerobic sludge to quickly granulate with the composite carrier as a crystal nucleus, thereby improving the sewage treatment capacity and impact resistance of microorganisms.

[0034] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Unless otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art. The data obtained are all average values ​​obtained after at least 3 repetitions, and all the data obtained in each repetition are valid data.

[0035] Example 1: Preparation of composite carrier

[0036] Prepare various composite carriers as follows: add 2g of sodium alginate to 100mL of pure water, and place in a water bath at 80℃ until fully dissolved to obtain sodium alginate colloid. Mix the components of each composite carrier and the sodium alginate colloid in the required mass ratio to obtain sodium alginate gel. Add the sodium alginate gel dropwise to a 2% CaCl2 solution in the volume ratio of sodium alginate gel to CaCl2 solution of 1:10, solidify at 4℃ for 8h, rinse with ultrapure water 3 times, dry with absorbent paper, and store in a refrigerator at 4℃ for later use. The specific composition of the components of each composite carrier is shown in Table 1, and the data in Table 1 are mass relationships.

[0037] Table 1 Comparison table of components of composite carriers

[0038]

[0039]

[0040] Example 2: Demonstration of the effects of various composite carriers

[0041] 1. Press Figure 1The UASB reactor was assembled in a 3.5 L manner. The diameter of the UASB reactor was 60 mm, the height was 600 mm, and the effective volume was 3.5 L. The reactor was fed with water from the bottom water inlet bucket, and at the same time, the peristaltic pump sucked water back to the upper part of the reactor to achieve internal circulation, maintaining an upward flow rate of 0.5 m / h. The reactor was started at medium temperature, and the internal temperature of the UASB reactor was controlled at 35 ± 1 ° C using a temperature controller and a heating wire.

[0042] Each composite carrier corresponds to an identical UASB reactor; the control group reactor is marked as the CK reactor, the reactor with KS carrier 1 added is marked as the KS1 reactor, and so on. The same batch of 1.7L of domesticated anaerobic sludge from a sewage treatment plant in Chengdu (30min sludge settling ratio is 40%) was added to each UASB reactor. The influent pH was controlled at 6.9-7.1, COD:N:P=300:5:1. The treatment of the CK reactor was the same as that of the other groups, except that no composite carrier was added.

[0043] Artificial synthetic coking wastewater includes phenol, resorcinol, p-cresol, quinoline, and pyridine (mass ratio 3:2:1:1:1). The above components are added to 100L pure water in proportion and mixed (the total addition amount is 2.24g / L), and then 1mL / L of trace element concentrate is added. 2.84g / L sucrose is added to the synthetic wastewater to help the sludge quickly adapt to the synthetic wastewater. The composition of the trace element concentrate is shown in Table 2.

[0044] Table 2 Trace element concentrate composition

[0045]

[0046] In order to improve the biodegradability of wastewater, 30% domestic sewage and 70% artificial coking wastewater were added during the startup phase. The reactor was fed with continuous flow, and the pH was adjusted to 7.0±0.1 with NaHCO3. The phosphorus source of the influent was controlled by KH2PO4, and the nitrogen source was controlled by NH4Cl.

[0047] The experiment was divided into a start-up period and a stable operation period. The HRT (hydraulic retention time) was 27.5 hours. From day 0 to day 80, the reflux rate was 2000%; from day 80 to day 195, the reflux rate was 285%.

[0048] Start-up period (0-26 days): On the first day, 4 g / L of each composite carrier was added to the reactor. The OLR (organic loading rate) of phenols and nitrogen-containing heterocyclic substances in the influent was increased from 0.6 kg COD / (m 3 ·d)(After adding sucrose, OLR increased to 2.8kg COD / (m 3 ·d)) gradually increased to 4.0kg±0.3kg COD / (m 3 ·d).

[0049] Stable operation period (26-130 days): the influent is all artificial synthetic coking wastewater, no sucrose is added, and the OLR is about 4±0.3kg COD / (m 3 ·d).

[0050] 2. The COD removal rate of the reactor is higher than 74% and the startup is considered successful. The shock load test was carried out on the 164th to 170th day of the reactor operation. The influent concentration increased from 4754 mg / L to 7284 mg / L, and the load increased from 4.14 kg COD / (m 3 ·d) gradually increased to 54% of the original, i.e. 6.38kg COD / (m 3 ·d). On the 171st day, the influent load was restored to 4.19±0.2kg COD(m 3 ·d) to evaluate the ability of UASB to resist shock load. The COD was measured using the national standard potassium dichromate method, and the COD removal rate recovered to more than 74% was defined as post-shock recovery. The successful startup time of each group of reactors and the enhanced effect of biological treatment during the stable operation period are shown in Table 3.

[0051] Table 3 Biological treatment enhancement effect during stable operation period

[0052]

[0053] The results showed that on the 170th day, the KS4 reactor gradually developed tolerance to the shock load, and the COD removal rate remained above 67%, while the COD removal rate of the control group dropped to 39% under the same environmental pressure. On the 171st day, the influent load was restored to 4.19±0.2kg COD / (m 3 ·d) It was observed that the COD removal rate of KS4 recovered to 80% on the 182nd day and no longer fluctuated; the CK reactor recovered to 52% on the 188th day and no longer fluctuated. On the 195th day, the CK group system collapsed.

[0054] 3. During the entire operation process, the distribution of particle size is as follows Figure 2-6 As shown (in order: CK, KF, KS4, KP and KN reactors). According to the research of Schmidt and Ahring, the diameter range of AGS (aerobic granular sludge) is generally 0.14-5.0 mm. In the present invention, AGS is defined as sludge particles with a diameter greater than 1 mm. After 130 days of operation, the granulation effect of each composite carrier prepared in Table 1 is shown in Table 4.

[0055] Table 4 Comparison of granulation effects of composite carriers in each group

[0056] Composite carrier D>0.3mm D>1mm D>2mm CK 60.00％ 16.67％ 0.44％ KF vector 66.67％ 26.67％ 0.89％ KN carrier 64.44％ 20.00％ 0.89％ KP carrier 62.22％ 17.78％ 0.89％ KS vector 1 65.16％ 26.67％ 1.15％ KS Vector 2 64.54％ 25.54％ 0.94％ KS vector 3 63.84％ 19.12％ 0.78％ KS Vector 4 69.45％ 27.45％ 2.62％

[0057] The embodiments described above are only descriptions of the preferred modes of the present invention and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations, modifications, and substitutions made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A composite carrier, characterized in that: The composite carrier component comprises sodium alginate colloid, magnesium silicate, activated carbon, zero-valent iron and polybutylene succinate.

2. The composite carrier according to claim 1, characterized in that: In terms of mass ratio, sodium alginate colloid: magnesium silicate: activated carbon: zero-valent iron: polybutylene succinate = (10-100): (0.3-1.2): 2:2:

1.

3. The method for preparing the composite carrier according to claim 1 or 2, characterized in that: The method comprises the following steps: (1) adding sodium alginate into pure water and fully dissolving it to obtain sodium alginate colloid; (2) mixing activated carbon, magnesium silicate, sodium alginate colloid, zero-valent iron and polybutylene succinate in proportion to obtain sodium alginate gel; (3) Add sodium alginate gel dropwise into the CaCl2 solution and solidify to obtain the desired composite carrier.

4. The preparation method according to claim 3, characterized in that: Sodium alginate gel is suspended and dropped into 2% CaCl2 solution, and the volume ratio of sodium alginate gel to CaCl2 solution is 1:5-50.

5. A method for treating sewage using the composite carrier according to claim 1 or 2 or the composite carrier prepared by the method according to claim 3 or 4.

6. The method according to claim 5, characterized in that: The sewage is coking wastewater.

7. A method for anaerobic granulation using the composite carrier according to claim 1 or 2 or the composite carrier prepared by the method according to claim 3 or 4.

8. The method according to claim 7, characterized in that: Anaerobic granulation is carried out using the composite carrier as the crystal nucleus.

9. The method according to claim 7, characterized in that: The activated sludge is anaerobic granulated with composite carrier as crystal nucleus.

Images