A composite carrier, its preparation method and its application in treating coking wastewater

Abstract

The present invention belongs to the field of wastewater treatment technology, specifically relating to a composite carrier, its preparation method, and its application in treating coking wastewater. The specific technical solution includes: a composite carrier comprising sodium alginate colloid, magnesium silicate, activated carbon, zero-valent iron, and polybutylene succinate. The composite carrier provided by the present invention can facilitate rapid granulation of anaerobic sludge, increase particle size, shorten reaction system startup time, improve COD degradation rate, and enhance the system's resistance to shock loads.

Description

Technical Field

[0001] The invention belongs to the technical field of sewage treatment, and particularly relates to a composite carrier, 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 composition, 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] Currently, the main methods for treating coking wastewater include physical, chemical, and biological methods. Existing physical and chemical treatment technologies suffer from 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, highly toxic organic pollutants in the wastewater pose a threat to the survival and reproduction of microorganisms. Large fluctuations in water quality can impact the system and even lead to system failure.

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

[0005] However, in actual applications, UASB reactors have problems such as low resistance to shock loads and long start-up time. The key to the UASB reactor's resistance 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 microorganisms' resistance to shock due to its sedimentation performance, thereby greatly improving the capacity and effect of the anaerobic bioreactor. 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 reactor's start-up time by 6-10 months. Therefore, achieving rapid granulation of anaerobic granules is a key link in the treatment of UASB in coking wastewater.

[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 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, the mass ratio of sodium alginate colloid: magnesium silicate: activated carbon: zero-valent iron: polybutylene succinate is (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) Sodium alginate gel is added dropwise to the CaCl2 solution and solidified to obtain the desired composite carrier.

[0014] Preferably, the sodium alginate gel is suspended and added dropwise to a 2% CaCl2 solution, with the volume ratio of the sodium alginate gel to the CaCl2 solution being 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 the 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: It provides a new composite carrier that can be used as a crystal nucleus for rapid granulation of anaerobic sludge. The carrier includes various materials, such as magnesium silicate and sodium alginate. Magnesium silicate can adsorb organic matter, metal ions (small amounts of metal cations can promote anaerobic sludge granulation), and gases. Replacing magnesium silicate with a combination of diatomaceous earth and magnesium ions does not achieve the same or similar effects. This is because magnesium silicate has a strong adsorption capacity for metal elements; however, the adsorption capacity of diatomaceous earth is affected by pH and temperature, making it weaker than that of magnesium silicate, and it lacks the ability to adsorb magnesium ions. Furthermore, magnesium silicate is insoluble in water, allowing it to remain stable in the reaction system and not easily lost with the effluent. However, diatomaceous earth is hygroscopic, and magnesium ions are readily soluble in water. Both are easily lost, requiring constant replenishment with the incoming water, and cannot remain stable in the system. Furthermore, anaerobic granulation requires increasing the hydrophobicity of the sludge, and the hygroscopicity of diatomaceous earth is also detrimental 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; and zero-valent iron can enhance pollutant removal and methane production, while replacing it with divalent or trivalent iron would not achieve the same effect. The PBS in the carrier can enhance the bioaffinity of ZVI (reduced zero-valent iron).

[0022] The composite carrier of the present invention can help anaerobic sludge to granulate quickly, increase 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 UASB reactor operation;

[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 Schematic diagram of the granulation effect of the KF reactor after 130 days of operation;

[0026] Figure 4 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 of the KN reactor after 130 days of operation. DETAILED DESCRIPTION

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

[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 heat in an 80-100°C water bath until fully dissolved to obtain sodium alginate colloid. Mix activated carbon, magnesium silicate adsorbent, sodium alginate colloid, PBS, and ZVI (zero-valent iron) in appropriate proportions to obtain a sodium alginate gel. The amount of PBS used is half the amount of zero-valent iron, and the amount of sodium alginate colloid used is 5-50 times the amount of zero-valent iron. Add the sodium alginate gel dropwise to a 2% CaCl2 (w / w) solution (the volume ratio of sodium alginate gel to CaCl2 solution is 1:5-50). Cure at 4°C for 4-8 hours. Rinse three times with ultrapure water and dry with absorbent paper to obtain the desired composite carrier. Store in a refrigerator at 4°C.

[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 quickly granulate using the composite carrier as crystal nuclei, thereby improving the sewage treatment capacity and shock resistance of microorganisms.

[0034] The following will be combined with the accompanying drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, rather than all 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 data obtained in each repetition are valid data.

[0035] Example 1: Preparation of composite carrier

[0036] Various composite supports were prepared as follows: 2g of sodium alginate was added to 100mL of pure water and incubated at 80°C in a water bath until fully dissolved to obtain a sodium alginate colloid. The components of each composite support were then mixed with the sodium alginate colloid in the desired mass ratio to obtain a sodium alginate gel. The sodium alginate gel was then added dropwise to a 2% CaCl₂ solution at a volume ratio of 1:10. The gel was cured at 4°C for 8h, rinsed three times with ultrapure water, blotted dry with absorbent paper, and stored in a refrigerator at 4°C until ready for use. The specific compositions of the components of each composite support are shown in Table 1. The data in Table 1 are weight-based.

[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 using a 60 mm diameter, 600 mm height, and 3.5 L effective volume. Water was fed from a bottom inlet bucket, while a peristaltic pump simultaneously pumped water upwards to achieve internal circulation, maintaining an upward flow rate of 0.5 m / h. The reactor was started at a medium temperature, and the internal temperature of the UASB reactor was maintained at 35 ± 1°C using a temperature controller and heating wire.

[0042] Each composite carrier was paired with an identical UASB reactor; the control reactor was designated the CK reactor, the reactor containing KS carrier 1 was designated the KS1 reactor, and so on. Each UASB reactor was loaded with 1.7 L of the same batch of acclimatized anaerobic sludge from a Chengdu wastewater treatment plant (30-minute sludge settling ratio of 40%). The influent pH was controlled at 6.9-7.1, and the COD:N:P ratio was 300:5:1. The CK reactor was treated identically to the other groups, except that the composite carrier was omitted.

[0043] Synthetic coking wastewater, consisting of phenol, resorcinol, p-cresol, quinoline, and pyridine (mass ratio 3:2:1:1:1), was added to 100 L of pure water (total addition amount: 2.24 g / L) and mixed thoroughly. 1 mL / L of trace element concentrate was then added. 2.84 g / L of sucrose was also 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] To improve the biodegradability of the wastewater, 30% domestic sewage and 70% synthetic coking wastewater were added during the startup phase. The reactor was fed with a 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 startup phase and a steady-state operation phase. The HRT (hydraulic retention time) was 27.5 hours. From day 0 to 80, the reflux rate was 2000%; from day 80 to 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 startup is considered successful when the COD removal rate of the reactor is higher than 74%. The shock load test is carried out on the 164th to 170th day of operation of the reactor. The influent concentration increases from 4754mg / L to 7284mg / L, and the load increases from 4.14kg COD / (m 3 d) gradually increased to 54% of the original, i.e. 6.38 kg COD / (m 3 On day 171, the influent load was restored to 4.19±0.2kg COD(m 3 d) to evaluate the UASB's ability to withstand shock loads. COD was measured using the national standard potassium dichromate method, with recovery to a COD removal rate of 74% or higher defined as post-shock recovery. The successful startup time for each reactor group and the enhanced biological treatment performance during stable operation 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 efficiency 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 of AGS (anaerobic granular sludge) generally ranges from 0.14 to 5.0 mm. In the present invention, AGS is defined as sludge particles with a diameter greater than 1 mm. The granulation effect of each composite carrier prepared in Table 1 after 130 days of operation 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 vector 62.22％ 17.78％ 0.89％ KS vector 1 65.16％ 26.67％ 1.15％ KS carrier 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 merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the 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 fall within the scope of protection determined by the claims of the present invention.

Claims

1. A method for treating sewage using a composite carrier, characterized in that: The composite carrier components include sodium alginate colloid, magnesium silicate, activated carbon, zero-valent iron and polybutylene succinate, and the mass ratio of sodium alginate colloid: magnesium silicate: activated carbon: zero-valent iron: polybutylene succinate is 10:0.9:2:2:

1. The composite carrier is used for anaerobic granulation.

2. The method according to claim 1, wherein: The sewage is coking wastewater.

3. A method for anaerobic granulation using the composite carrier according to claim 1.

4. The method according to claim 3, wherein: Anaerobic granulation is carried out using the composite carrier as the crystal nucleus.

5. The method according to claim 3, wherein: The activated sludge is anaerobic granulated using composite carriers as crystal nuclei.

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