Functional material for concentrating and recovering organic carbon in sewage and producing acid by side-stream anaerobic fermentation and preparation method and application thereof

Abstract

The present application relates to sewage treatment and resource technology field, particularly to a kind of for sewage organic carbon concentration recovery and side stream anaerobic fermentation acid production functional material and its preparation method and application.It includes: wood fiber class biomass is mixed with zinc chloride grinding, firing, and biochar is obtained;Biochar is mixed with tannic acid solution, stirring, and after removing liquid, tannic acid loaded biochar is obtained;Then mixed with iron ion, manganese ion, and after stirring, remove liquid and dry to obtain dry material;The dry material is pyrolyzed, and the functional material is obtained.The present application utilizes the high adsorption of biochar to colloidal and low molecular weight dissolved organic matter in sewage and the capture advantage of flocculant to particulate organic matter to achieve high capture effect on sewage organic matter.Biochar has magnetism, and combined with flocculant to form magnetic floc to achieve the purpose of magnetic separation, to quickly settle.The captured sludge is used for hydrolysis acidification to produce VFAs.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of sewage treatment and resource utilization, in particular to a functional material for concentrating and recovering organic carbon in sewage and producing acid through side-stream anaerobic fermentation, and a preparation method and application thereof. BACKGROUND

[0002] There is a rich resource of organic carbon in municipal sewage, and the concept of sewage resource utilization is also promoting the recycling and utilization of organic carbon in municipal sewage. However, the traditional sewage treatment plant has high energy consumption, high emission, and low recovery, which is contrary to the current low-carbonization and resource recovery. Anaerobic digestion technology is an effective means of organic carbon resource utilization, which can decompose organic matter into volatile fatty acids (VFAs), methane and other high-value-added substances, and is often used to treat high-concentration organic carbon sewage / sludge, such as excess sludge. Some scholars also produce acid or methane by anaerobic digestion of primary sludge. However, this technology is mainly suitable for high-concentration wastewater / sludge, and the chemical oxygen demand (COD) of conventional sewage is only 200-500 mg / L, which is difficult to hydrolyze and acidify efficiently. Therefore, some scholars propose a technology combining "carbon capture and concentration + anaerobic digestion" to improve the utilization rate of organic carbon in municipal sewage. The difficulties of this technology are: 1) developing an economical and efficient capture method; 2) improving the effect of hydrolysis and acidification. Therefore, research on these two aspects is an important basis for improving the resource utilization of sewage organic carbon.

[0003] Therefore, it is a major direction of water treatment to capture and separate these organic carbon resources for redirection to achieve reuse. Currently, the main technologies for capturing and concentrating organic carbon in sewage include physical and chemical capture technology (flocculation, adsorption, etc.), activated sludge adsorption capture technology, and membrane separation technology. Capturing and concentrating organic carbon through these technologies and then using it for anaerobic digestion to produce acid or methane are effective ways of resource utilization. In the primary treatment unit, flocculants are added to accelerate the sedimentation rate and remove organic matter. This technology for strengthening the effect of the primary treatment unit with flocculants is called chemically enhanced primary treatment (CEPT). The flocculants used in CEPT are mainly inorganic flocculants such as iron salts, aluminum salts, and high polymer salts, as well as some organic flocculants such as chitosan and polyacrylamide (PAM). These flocculants combine with particles and dissolved substances in sewage to capture organic matter in the sewage through compression of the double electric layer, electric neutralization, sweeping net capture, and adsorption-bridging. Metal salts generate colloids through hydrolysis and are removed by natural sedimentation.

[0004] Bio-adsorption technology is to remove the particulate and dissolved organic matter in wastewater by the rapid adsorption of activated sludge. Among them, the high-rate activated sludge process (HRAS) is becoming an important part of the high-efficiency and energy-saving wastewater treatment process. For example, the a-stage of AB (bio-adsorption and oxidation) system, contact stabilization (CS) and traditional system (step feed, plug flow, complete mixing reactor system) as a form of HRAS, is transforming the energy-intensive process of municipal wastewater treatment plant (WWTP) into a low-energy and sustainable technology.

[0005] Membrane separation technology is a process of separating organic matter and impurities in water by using the characteristics of semi-permeable membrane, including microfiltration, ultrafiltration, nanofiltration and reverse osmosis. It has the advantages of high separation efficiency and simple operation. Especially, MBR technology has been deeply researched since 1970s, and now it has mature and large-scale application. Although membrane separation has high organic carbon recovery effect, membrane cleaning and membrane pollution are always the main difficulties, which makes the cost of membrane separation technology high.

[0006] CEPT treatment method has the advantages of convenient, simple operation, high capture rate of particulate organic matter, etc. for capturing organic carbon of municipal wastewater, but its capture ability for colloidal and low molecular weight dissolved state is limited. Although its flocculation accelerates the settlement of organic matter, it still relies on gravity natural settlement to achieve concentration. In addition, the acid production rate of anaerobic fermentation of organic concentrated sludge obtained by capture is slow, carbon loss is serious and conversion rate is low. SUMMARY

[0007] In order to solve the above problems, the present application provides a functional material for wastewater organic carbon concentration recovery and side-stream anaerobic fermentation acid production, and a preparation method and application thereof. The present application adopts magnetic biochar adsorption coupling flocculation technology, utilizes the high adsorption of biochar to colloidal and low molecular weight dissolved organic matter in wastewater and the capture advantage of flocculant to particulate organic matter, to achieve high capture effect of wastewater organic matter. At the same time, biochar has magnetism, which can combine with flocculant to form magnetic floc to achieve the purpose of magnetic separation, so as to settle quickly. The captured sludge is used for hydrolysis acidification to produce VFAs, and the magnetic biochar can improve the efficiency of microbial electron transfer to improve the effect of hydrolysis acidification.

[0008] In order to achieve the above purpose, the present application provides the following technical scheme:

[0009] The present application provides a preparation method of a functional material for wastewater organic carbon concentration recovery and side-stream anaerobic fermentation acid production, comprising the following steps:

[0010] 1) mixing and grinding lignocellulosic biomass with zinc chloride to obtain a grinding material;

[0011] 2) firing the grinding material obtained in step 1) to obtain biochar;

[0012] 3) mixing and stirring the biochar obtained in step 2) with a tannic acid solution, and obtaining tannic acid-loaded biochar after removing the liquid;

[0013] 4) mixing and stirring the tannic acid-loaded biochar obtained in step 3) with iron ions and manganese ions, and obtaining a dried material after removing the liquid and drying;

[0014] 5) pyrolyzing the dried material obtained in step 4) to obtain a functional material.

[0015] Preferably, the mass ratio of the lignocellulosic biomass to zinc chloride in step 1) is 1:2.

[0016] Preferably, the firing conditions in step 2) include a temperature of 700℃, a time of 2h, and a heating rate of 10℃ / min.

[0017] Preferably, the mass ratio of the biochar to the volume of the tannic acid solution in step 3) is 5g:500mL;

[0018] The concentration of the tannic acid solution is 5g / L;

[0019] The stirring is magnetic stirring, and the time is 18h.

[0020] Preferably, the mass ratio of carbon in the tannic acid-loaded biochar to iron ions and manganese ions in step 4) is 5:1:1;

[0021] The stirring is magnetic stirring, and the time is 2h.

[0022] Preferably, the pyrolysis conditions in step 5) include a temperature of 700℃ and a time of 2h.

[0023] The application also provides a functional material prepared by the preparation method of the above technical solution.

[0024] The application also provides a combination for concentrating and recovering organic carbon in sewage and producing acid through side-stream anaerobic fermentation, which comprises the functional material, a flocculant, and a coagulant aid of the above technical solution.

[0025] Preferably, the flocculant comprises polyaluminum chloride, and the coagulant aid comprises polyacrylamide.

[0026] The application also provides the application of the combination of the above technical solution in concentrating and recovering organic carbon in sewage and producing acid through side-stream anaerobic fermentation, which comprises the following steps:

[0027] A, the sewage is mixed with a flocculant, a functional material, and reacts for 15 minutes, and then a coagulant is added to carry out flocculation reaction for 20 minutes, and then solid-liquid separation is carried out to obtain concentrated sludge;

[0028] The addition amount of the flocculant is 20-30 mg / L, the addition amount of the functional material is 50-150 mg / L, and the addition amount of the coagulant is 2 mg / L.

[0029] B, the concentrated sludge obtained in step A is mixed with anaerobic inoculated sludge and 2-bromoethanesulfonic acid sodium to carry out anaerobic fermentation.

[0030] The beneficial effects of the present application are:

[0031] The functional material is added to realize higher capture rate of organic carbon in sewage, especially to increase the conversion of dissolved and colloidal organic components to organic concentrated sludge; and to realize the increase of the content of volatile fatty acids converted by anaerobic digestion of organic concentrated sludge. BRIEF DESCRIPTION OF DRAWINGS

[0032] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed in the embodiments will be briefly introduced as follows.

[0033] Figure 1 The capture effect of different forms of COD in municipal sewage by natural sedimentation, PFC, Fe&Mn-BCs, Fe&Mn-BCs+PFC;

[0034] Figure 2 The hydrolysis acidification COD concentration of PFC flocculation sludge and Fe&Mn-BCs+PFC sludge;

[0035] Figure 3 The hydrolysis acidification VFAs concentration of PFC flocculation sludge and Fe&Mn-BCs+PFC sludge. DETAILED DESCRIPTION

[0036] The present application provides a preparation method of a functional material for organic carbon concentration recovery and side-stream anaerobic fermentation acid production of sewage, comprising the following steps:

[0037] 1) wood fiber biomass is mixed with zinc chloride and ground to obtain a ground material;

[0038] 2) the ground material obtained in step 1) is fired to obtain biochar;

[0039] 3) the biochar obtained in step 2) is mixed with a tannic acid solution and stirred, and after removing the liquid, a tannic acid loaded biochar is obtained;

[0040] 4) mixing the tannic acid loaded biochar obtained in step 3) with iron ions and manganese ions, stirring, removing liquid, and drying to obtain a dried material;

[0041] 5) pyrolyzing the dried material obtained in step 4) to obtain a functional material.

[0042] In the present application, the lignocellulosic biomass preferably includes rice husks. In the present application, the mass ratio of the lignocellulosic biomass to zinc chloride is preferably 1:2. In the present application, the zinc chloride optimizes the pore structure of the biochar, increasing the micropores and mesopores of the biochar. In the present application, the grinding conditions preferably include grinding in a quartz mortar, passing through a 200-mesh sieve, and taking the undersize as the ground material.

[0043] In the present application, the conditions for the calcination preferably include a temperature of 700℃, a time of 2h, and a heating rate of 10℃ / min. In the present application, the calcination is preferably performed in an argon atmosphere. In the present application, the inorganic substances on the biochar are preferably removed by washing with a hydrochloric acid solution having a concentration of 2mol / L after the calcination.

[0044] In the present application, the mass ratio of the biochar to the tannic acid solution is preferably 5g:500mL. In the present application, the concentration of the tannic acid solution is preferably 5g / L. In the present application, the stirring is preferably magnetic stirring, and the time is preferably 18h. In the present application, the tannic acid coats and disperses the metal ions, solving the problem of metal aggregation in the biochar.

[0045] In the present application, the mass ratio of the carbon in the tannic acid loaded biochar to the iron ions and manganese ions is preferably 5:1:1. In the present application, the stirring is preferably magnetic stirring, and the time is preferably 2h. In the present application, the reagent for providing iron ions is preferably ferric chloride hexahydrate, and the reagent for providing manganese ions is preferably manganese sulfate.

[0046] In the present application, the conditions for the pyrolysis preferably include a temperature of 700℃ and a time of 2h.

[0047] The present application also provides a functional material prepared by the preparation method described in the above technical solution.

[0048] The application also provides a combination for organic carbon concentration recovery and side-stream anaerobic fermentation acid production of sewage, which comprises the functional material, the flocculant and the coagulant aid according to the technical scheme.

[0049] The application also provides application of the combination according to the technical scheme in organic carbon concentration recovery and side-stream anaerobic fermentation acid production of sewage, which comprises the following steps:

[0050] A. mixing the sewage functional material for 30 min, then mixing with the flocculant and the coagulant aid for flocculation reaction for 17 min, and then performing solid-liquid separation to obtain concentrated sludge;

[0051] The addition amount of the flocculant is 20 / L, the addition amount of the functional material is 100 mg / L, and the addition amount of the coagulant aid is 2 mg / L.

[0052] B. mixing the concentrated sludge obtained in step A with anaerobic inoculation sludge and 2-bromoethanesulfonic acid sodium to perform anaerobic fermentation.

[0053] In order to further illustrate the application, the application will be described in detail below in combination with examples, but they should not be understood as limiting the protection scope of the application.

[0054] Example 1

[0055] (1) Preparation of the functional material

[0056] Preparation method of the functional material:

[0057] In order to increase micropores and mesopores of the biochar, wood fiber biomass (rice husk) and zinc chloride are mixed in a mass ratio of 1:2, then ground in a quartz mortar, and then mixed uniformly; the mixture is heated to 700 DEG C at a rate of 10 DEG C / min in a tube furnace under an argon atmosphere and then burned for 2 h; then the biochar is washed with 2 mol / L hydrochloric acid to remove inorganic substances; the biochar is denoted as Zn-BCs. 5 g of Zn-BCs is added into 5 g / L of 500 ml tannic acid solution, and the pH value is adjusted to 7.0; the mixture is mixed under magnetic stirring for 18 h; then the solution is filtered to obtain biochar loaded with tannic acid; then the C:Fe 3+ :Mn 2+The ratio of Fe:Mn is 5:1:1 (mass ratio), iron ions are provided by a ferric chloride reagent with six waters, manganese ions are provided by a manganese sulfate reagent, and the mixture is magnetically stirred in a 500 ml beaker for 2 h. The phenolic hydroxyl groups of the tannin acid coated on the surface of the biochar are used to complex with the metal, adhere and disperse the metal, and then the pH value is adjusted to 7.0. The solution is then filtered off and washed with ultrapure water until it is colorless. Finally, it is dried and pyrolyzed in a tube furnace at 700°C for 2 h to obtain Fe&Mn biochar, denoted as Fe&Mn-BCs.

[0058] (2) Capture and concentration of organic carbon in wastewater

[0059] Rewritten as: mix the raw wastewater with Fe&Mn-BCs (dosing amount is 100 mg / L), fast stirring at 200 rpm for 30 min, then add polymeric ferric chloride PFC with a dosage of 20 mg / L, fast stirring at 200 rpm for 2 min, then add coagulant PAM (2 mg / L), slow stirring for 15 min. The mixture is then sent to the sedimentation tank for solid-liquid separation.

[0060] (3) Anaerobic fermentation for acid production

[0061] The concentrated sludge at the bottom of the sedimentation tank is discharged into the anaerobic fermentation for acid production reaction device by a sludge pump. The VSS of the concentrated sludge is adjusted to 15 g / L, and 300 ml of the adjusted sludge is loaded into a 500 ml reactor, 10 ml of anaerobic inoculated sludge is added, 15 mmol of 2-bromoethanesulfonic acid sodium (BES) is added, the fermentation time is 9 d, the temperature is 37°C, and the rotation speed is 150 rpm. The fermentation broth is transported to the main process of wastewater treatment as a carbon source product for recycling, and the residue at the bottom is sent to the magnetic material recovery device. Fe&Mn-BCs are stripped from the anaerobic sludge by hydraulic shearing, and separated under the action of a magnetic field. The obtained Fe&Mn-BCs are returned to the raw wastewater end for mixing and reuse.

[0062] The results are as follows:

[0063] From Figure 1 it can be seen that the addition of Fe&Mn-BCs greatly improves the capture effect of dissolved and colloidal organic matter. Figure 1Natural sedimentation, flocculation, biochar adsorption in the control group, and the combination of Fe&Mn-BCs+PFC form a control group, the purpose is to prove the capture ability of the prepared material. Among them, the operation of each part is: natural sedimentation: after mixing the municipal wastewater, place it in a 500ml beaker for 1h, then measure each index; flocculation (PFC): add municipal wastewater in a 500ml beaker, add flocculant PFC (20mg / L), fast stirring at 200rpm for 2min, then add PAM (2mg / L), slow stirring for 15min, finally, stand for 1h, then measure each index; biochar adsorption (i.e. Fe&Mn-BCs): add 100mg / L of Fe&Mn-BCs in a 500ml beaker filled with wastewater, fast stirring at 200rpm for 30min, then measure each index. Flocculant & biochar (i.e. Fe&Mn-BCs+PFC): add biochar first, then add flocculant.

[0064] From the above examples, it can be seen that the addition of Fe&Mn-BC can effectively improve the concentration of SCOD in the wastewater and improve the hydrolysis rate of the sludge. Figure 2

[0065] From the above examples, it can be seen that the addition of Fe&Mn-BC can effectively improve the concentration of SCOD in the wastewater and improve the hydrolysis rate of the sludge. Figure 3 From the above examples, it can be seen that the addition of Fe&Mn-BC can effectively improve the concentration of SCOD in the wastewater and improve the hydrolysis rate of the sludge.

[0066] From the above examples, it can be seen that the addition of Fe&Mn-BC can effectively improve the concentration of SCOD in the wastewater and improve the hydrolysis rate of the sludge.

[0067] Although the above examples make a detailed description of the present application, it is only a part of the embodiments of the present application, not all the embodiments, and people can also obtain other embodiments according to the present embodiment without creativity, which all belong to the protection scope of the present application.​

Claims

1. The use of a functional material in the concentration and recovery of organic carbon in sewage and in the production of acids by side-stream anaerobic fermentation, characterized in that, The preparation method of the functional material comprises the following steps: 1) mixing and grinding lignocellulosic biomass and zinc chloride to obtain a grinding material; the mass ratio of the lignocellulosic biomass to the zinc chloride is 1:2; 2) firing the grinding material obtained in step 1) to obtain biochar; 3) mixing and stirring the biochar obtained in step 2) with a tannic acid solution, and then removing the liquid to obtain tannic acid-loaded biochar; the mass ratio of the biochar to the volume of the tannic acid solution is 5g:500mL; The concentration of the tannic acid solution is 5g / L; the stirring is magnetic stirring, and the time is 18h; 4) mixing and stirring the tannic acid-loaded biochar obtained in step 3) with iron ions and manganese ions, and then removing the liquid and drying to obtain a dried material; the mass ratio of carbon in the tannic acid-loaded biochar to the iron ions and the manganese ions is 5:1:1; the stirring is magnetic stirring, and the time is 2h; 5) pyrolyzing the dried material obtained in step 4) to obtain a functional material; The application comprises the following steps: A, mixing sewage with a flocculant and a functional material and reacting for 15min, then mixing with a coagulant and carrying out flocculation reaction for 20min, solid-liquid separation, to obtain concentrated sludge; The dosage of the flocculant is 20-30mg / L, the dosage of the functional material is 50-150mg / L, and the dosage of the coagulant is 2mg / L; B, mixing the concentrated sludge obtained in step A with anaerobic inoculated sludge and 2-bromoethanesulfonic acid sodium and carrying out anaerobic fermentation.

2. The use of a functional material according to claim 1 in the concentration and recovery of organic carbon in wastewater and in the production of acids by side-stream anaerobic fermentation, characterized in that, The firing conditions of step 2) comprise: a temperature of 700℃, a time of 2h, and a temperature rising speed of 10℃ / min.

3. The use of a functional material according to claim 1 in the concentration and recovery of organic carbon in wastewater and in the production of acids by side-stream anaerobic fermentation, characterized in that, The pyrolysis conditions of step 5) comprise: a temperature of 700℃ and a time of 2h.

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