Starch production wastewater treatment method based on sludge recycling

Abstract

The invention discloses a starch production wastewater treatment method based on sludge recycling. According to the method, sludge obtained through anaerobic treatment and aerobic treatment in sequence is put into the process of performing anaerobic treatment and then aerobic treatment again, and due to the fact that the sludge contains rich nutrient components needed by anaerobic and aerobic microorganisms and is provided with the microorganisms needed by anaerobic and aerobic microorganisms, it is guaranteed that the sludge adapts to the anaerobic and aerobic environment; the sewage treatment effect is greatly improved. Meanwhile, nitrogen and phosphorus substances added for wastewater treatment can be reduced, and resource utilization is achieved.

Description

Technical Field

[0001] The present application relates to the technical field of starch production, and in particular to a method for treating starch production wastewater based on sludge recycling. Background Art

[0002] Starch is a green and renewable resource. The demand for sustainable development of mankind makes starch more and more popular. Oxidized starch is a starch derivative obtained by chemical modification of native starch. It is widely used in papermaking, food, medicine and other industries.

[0003] In the process of producing oxidized starch, inevitable industrial wastewater is often produced. The main components of the wastewater are starch, protein and sugar. Generally, it is non-toxic, but the COD is very high, usually 10000-25000 mg / L, and the SS is 3000-4000 mg / L. The sewage treatment is difficult and the operation cost is high. If these starch wastewaters are discharged directly without treatment, the organic matter contained in the water will quickly consume the dissolved oxygen in the water after entering the water body, causing the water body to lack of oxygen and affecting the survival of fish and other aquatic animals. At the same time, it will promote the decomposition of organic matter on the bottom of the water under anaerobic conditions, produce odor, deteriorate the water body, pollute the environment, and damage human health. Therefore, it must be treated.

[0004] In the related art, the treatment of starch production wastewater is relatively limited. Summary of the invention

[0005]

Issues to be solved

[0006] The starch wastewater treatment process disclosed in one of the existing technologies is as follows: (1) the wastewater is diverted, a portion of the wastewater is treated by flotation, the clear liquid is reused, and the suspended matter and the remaining wastewater are injected into the sedimentation tank and aerobically treated first; (2) the clear liquid after aerobic treatment in the sedimentation tank enters the concentration tank for hydrolysis; (3) the clear liquid after hydrolysis enters the water collection well and the pH value is adjusted to 7.0-8.0; (4) the treated liquid enters the EGSB anaerobic tank for anaerobic reaction after flotation; (5) the biogas slurry is aerobically treated and then discharged in compliance with the standards.

[0007] The starch wastewater treatment process disclosed in the second prior art is as follows: S101: discharging the starch wastewater into the regulating tank through a pipeline, adjusting the pH value of the starch wastewater to form the first starch wastewater; S102: pumping the first starch wastewater into the heating reflux well, and heating the first starch wastewater to form the second starch wastewater; S103: the second starch wastewater flows into the anaerobic tank by gravity, and the second starch wastewater is anaerobically fermented to produce biogas and primary sewage, and the biogas is stored in a temporary storage tank for further processing; S104: discharging the primary sewage into the primary aerobic tank, and aerobically degrading the activated sludge in the primary sewage; S105: discharging the primary sewage after aerobic degradation into the secondary sedimentation tank, and the supernatant forms the secondary sewage; S106: discharging the secondary sewage into the secondary aerobic tank, and aerobically degrading the activated sludge in the secondary sewage; S107: discharging the secondary sewage after aerobic degradation into the final sedimentation tank, and the upper clear liquid forms the final sewage for discharge in compliance with the standards.

[0008] The above-mentioned prior art starch wastewater treatment process is highly dependent on the optimization of the temperature, pH value, microbial strain additives and other conditions of the anaerobic and aerobic processes, and the treatment effect is very limited.

[0009] The present application aims to solve at least one of the technical problems existing in the prior art. To this end, one purpose of the present application is to propose a starch production wastewater treatment method based on sludge recycling to better improve the wastewater treatment effect.

[0010]

Methods for solving the problem

[0011] The inventors of the present invention have conducted repeated and in-depth research to solve the above problems and realized that the sludge obtained by anaerobic treatment and aerobic treatment in sequence can be re-introduced into the process of first anaerobic treatment and then aerobic treatment. Since the sludge contains rich nutrients required by microorganisms in anaerobic and aerobic conditions and the sludge itself has the microorganisms required by anaerobic and aerobic conditions, it can ensure that it is compatible with anaerobic and aerobic environments, greatly improving the sewage treatment effect. Thus, the invention was completed.

[0012] The present application provides a method for treating starch production wastewater based on sludge recycling, comprising the following steps:

[0013] A. Implement flocculation treatment on starch production wastewater;

[0014] B. Anaerobic treatment of starch production wastewater after flocculation treatment;

[0015] C. Aerobic treatment of starch production wastewater that has been anaerobic treated;

[0016] D. performing solid-liquid separation treatment on the starch production wastewater that has been aerobically treated, and obtaining sludge from the solid phase components obtained by the solid-liquid separation;

[0017] E. Feeding the sludge into the anaerobic treatment site to sequentially carry out step C treatment and step D treatment, and the liquid phase component obtained from the solid-liquid separation is the target treated wastewater.

[0018] In any embodiment, after step D and before step E, the method further comprises step F: feeding the sludge to a place substantially the same as the place for the anaerobic treatment.

[0019] In any embodiment, after step D and before step F, the method further comprises step G: performing a modification treatment on the sludge; wherein the modification treatment comprises the following steps:

[0020] G1: fully gelling a material comprising at least a binder, a hydrogel monomer and sludge in a liquid phase comprising at least water, and subjecting the material to microfiltration to obtain a hydrogel;

[0021] G2: Dry the hydrogel at 45 to 60 degrees Celsius.

[0022] In any embodiment, the modification treatment further comprises the step G3, washing the sludge before the step G1.

[0023] In any embodiment, the hydrogel monomer is added in an amount of 4.7 to 16% based on the weight of the sludge.

[0024] In any embodiment, during step G1, ultrasonic dispersion is assisted.

[0025] In any embodiment, during the washing process, the sludge is blocked by a microfiltration membrane.

[0026] In any embodiment, the adhesive is selected from at least one of polyvinyl alcohol, carboxymethyl cellulose, sodium polyacrylate, gelatin, sodium caseinate, gum arabic, guar gum, xanthan gum, agar, and carrageenan.

[0027] In any embodiment, the hydrogel monomer is at least one of collagen, chitosan, hydroxypropyl methylcellulose, hyaluronic acid, hydroxypropyl methylcellulose, polyacrylamide, sodium alginate, and methacryloyl gelatin.

[0028] In any embodiment, the binder is used in an amount of 0.5 to 4% based on the weight of the sludge.

[0029] [Effects of the invention]

[0030] The starch production wastewater treatment method based on sludge recycling provided in this application re-inserts the sludge obtained by anaerobic treatment and aerobic treatment into the process of first anaerobic treatment and then aerobic treatment. Since the sludge contains rich nutrients required by microorganisms in anaerobic and aerobic conditions and the sludge itself has the microorganisms required for anaerobic and aerobic conditions, it ensures that it is compatible with anaerobic and aerobic environments, greatly improving the sewage treatment effect. At the same time, it can also reduce the amount of nitrogen and phosphorus added to wastewater treatment and realize resource utilization. DETAILED DESCRIPTION

[0031] The following specifically discloses the embodiments of the present application. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there may be cases where detailed descriptions of well-known matters and repeated descriptions of actually identical structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate understanding by those skilled in the art. In addition, the following description is provided for those skilled in the art to fully understand the present application and is not intended to limit the subject matter described in the claims. "Scope" disclosed in the present application is limited in the form of lower limit and upper limit, and a given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of a special range. The scope limited in this way can be including end values ​​or not including end values, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a scope. For example, if the scope of 60-120 and 80-110 is listed for a specific parameter, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range values ​​1 and 2 are listed, and if the maximum range values ​​3, 4 and 5 are listed, the following scope can be all expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In the present application, unless otherwise specified, the numerical range "ab" represents the abbreviation of any real number combination between a and b, wherein a and b are real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" are listed in this document, and "0-5" is just an abbreviation of these numerical combinations. In addition, when a parameter is expressed as an integer ≥ 2, it is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0032] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0033] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0034] If there is no special explanation, all steps of the present application can be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), which means that step (c) may be added to the method in any order. For example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0035] If there is no special explanation, the "include" and "comprising" mentioned in this application represent open-ended or closed-ended expressions. For example, the "include" and "comprising" may represent that other components not listed may also be included or only the listed components may be included or only the listed components may be included.

[0036] If not specifically stated, in this application, the term "or" is inclusive. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, any of the following conditions satisfies the condition "A or B": A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0037]

Starch production wastewater treatment method

[0038] The starch wastewater targeted by the treatment method disclosed herein can be wastewater generated by any form of starch production, such as cassava starch, sweet potato starch, potato starch, etc., but not limited thereto. Of course, the starch wastewater here includes wastewater directly discharged from starch production, in which starch particles are clearly visible, and can also be wastewater obtained through separation processes such as filtration, precipitation, etc.

[0039] As for the specific composition of pollutants in starch production wastewater, it will not have a special impact on the treatment effect of this treatment method. The following are some of the main pollutant compositions of starch production wastewater tested by this method. For example, the main pollutant composition of corn starch wastewater produced by a food factory A is: COD

[0040] 8,500-11,000mg / L, BOD 3,200-4,800mg / L, SS 800-1,000mg / L, protein <80mg / L. For example, the main pollutants of potato wastewater produced by a food factory A are: COD 4,200-7,800mg / L, BOD 2,100-3,300mg / L, SS1,100-1,300mg / L, protein 300-450mg / L. The main pollutants of corn starch wastewater produced by a food factory A are: COD 6,300-8,900mg / L, BOD 2,500-3,900mg / L, SS 700-900mg / L, protein 150-220

[0041] Of course, it is easy for technicians in the field to think that the wastewater obtained by mixing these starch wastewaters in a certain proportion is obviously also applicable to this solution.

[0042] The starch production wastewater treatment method comprises the following steps:

[0043] A. Implement flocculation treatment on starch production wastewater;

[0044] B. Anaerobic treatment of starch production wastewater after flocculation treatment;

[0045] C. Aerobic treatment of starch production wastewater that has been anaerobic treated;

[0046] D. performing solid-liquid separation treatment on the starch production wastewater that has been aerobically treated, and obtaining sludge from the solid phase components obtained by the solid-liquid separation;

[0047] E. Feeding the sludge into the anaerobic treatment site to sequentially carry out step C treatment and step D treatment, and the liquid phase component obtained from the solid-liquid separation is the target treated wastewater.

[0048]

Flocculation treatment

[0049] It is known that the functions of flocculation treatment are reflected in the following aspects: A. Removal of suspended matter: reduce wastewater turbidity and reduce subsequent treatment load. B. Removal of colloidal substances: destroy the stability of colloids through the bridging effect of flocculants. C. Initial degradation of organic matter: some high-molecular organic matter is encapsulated and removed during the flocculation process.

[0050] The specific process of flocculation treatment can be demonstrated as follows: A1, pretreatment stage, A2, flocculant addition;

[0051] A3, mixing and reaction. For the A1 process, the main function is to adjust the pH to optimize the charge neutralization effect of the flocculant (such as PAM). The actual operation can be, for corn starch wastewater: pH 6.5-7.5 (natural weak acid, need a small amount of alkali neutralization); for potato starch wastewater: pH 5.0-6.0 (contains anthocyanins, need NaOH to adjust to above 7.0). Reagent: NaOH or HCl, the dosage is usually 10-50mg / L. Of course, floating oil can also be removed according to actual needs.

[0052] For the A2 process, some conventional flocculants can be listed. For the inorganic flocculant PAC (polyaluminium chloride), the applicable pH is 6.5–7.5 and the dosing concentration is 50–200mg / L. The organic flocculant PAM (polyacrylamide) can be applied to neutral to weak alkaline, with a more suitable concentration of 0.1-10mg / L; the composite flocculant PAC+PAM is more suitable for 6.0-8.0, PAC 100–300mg / L, PAM 0.5–3mg / L, etc. The flocculant can be added by dry dosing or wet dosing. The dry dosing method is to add the flocculant powder directly to the reaction tank through a metering pump. The wet dosing method is to configure the flocculant into a solution form, such as a PAM solution (concentration 1wt%~5wt%) injected through an ejector. As for the flocculant addition mixing speed: 40–80rpm (to avoid shear degradation of the flocculant). The reaction time after the addition of the flocculant may suitably be 10-30 minutes (eg, to fully form alum flocs).

[0053] For the A3 process, mechanical stirring can be used as an auxiliary. A reference method is that the first stage is rapid stirring (>100rpm, 1-2 minutes) to evenly disperse the flocculant. The second stage is slow stirring (20-40rpm8-15 minutes) to promote the growth of alum flowers. Wastewater temperature: When it is >40℃, it needs to be cooled (such as drainage in the potato wastewater drying process) to avoid high temperature accelerating PAM degradation. Use an air flotation device or a grease trap to remove grease (such as wax on the surface of potatoes) in the wastewater.

[0054]

Anaerobic treatment

[0055] As used in this article, the term "anaerobic treatment" is also referred to as oxygen-free treatment. It is well known that the effects of anaerobic treatment are reflected in the following aspects: First, it efficiently degrades organic matter, that is, it converts macromolecular organic matter such as starch and protein into biogas (methane, carbon dioxide) and water, and the COD removal rate can reach 60% to 90%. Second, it reduces the subsequent treatment load. After pretreatment, the COD of wastewater can be reduced to 1,000-2,000 mg / L, creating conditions for aerobic biological treatment.

[0056] The specific process of anaerobic treatment can be demonstrated as follows: A1, pretreatment stage; A2, hydrolysis and acidification stage; A3, treatment stage of anaerobic reactor. For stage A1, H regulation can be implemented, the purpose of which is to maintain an anaerobic environment (pH 6.5-7.5). The specific operation can be to add NaOH or HCl to control the pH at around 7.0 (the natural pH of starch wastewater is mostly 6.0-6.5). The medium temperature condition is controlled at 30-35℃, and the high temperature condition is controlled at 50-55℃.

[0057] For the A2 stage, its function is to hydrolyze large molecular organic matter (such as starch and protein) into small molecular organic matter (such as glucose and amino acids) to improve the metabolic efficiency of anaerobic bacteria. The key process parameters involved are as follows, such as the hydraulic retention time (HRT) of 2-4 hours, the pH controlled at 6.0-6.5, and the temperature controlled at room temperature or medium temperature (+1-2℃ insulation) as in the A1 process above.

[0058] For the A3 stage, some conventional anaerobic reactors can be listed, such as UASB (upflow anaerobic sludge blanket), EGSB (expanded bed anaerobic sludge bubbling reactor), IC (internal circulation anaerobic reactor), etc., but not limited to these. For UASB, HRT can be 6-12 hours, and MLSS can be 10-20g / L; for EGSB, HRT is more appropriately controlled at 4-8 hours, and MLSS is more appropriately controlled at 8-15g / L; for IC, HRT can be 3-6 hours, and MLSS can be 15-25g / L.

[0059] During the treatment operation of the anaerobic reactor, the water can be evenly distributed through the water distributor to avoid short-circuiting.

[0060] Aerobic treatment

[0061] As used in this text, the term "aerobic treatment" is also referred to as aerobic treatment or aerobic treatment. It is well known that the role of aerobic treatment is reflected in the following aspects: Deep degradation of organic matter: First, the COD remaining after anaerobic treatment. Second, simultaneous nitrogen and phosphorus removal: removal of ammonia nitrogen (total nitrogen ≤ 15 mg / L) and total phosphorus (≤ 0.5 mg / L) through nitrification / denitrification process. Third, improve the stability of effluent: degrade perishable organic matter and reduce the risk of biological contamination in subsequent treatments (such as membrane separation).

[0062] The specific process of aerobic treatment can be demonstrated as follows: A1, pretreatment stage, A2, aerobic stage. For stage A1, the pH can be fine-tuned to 7.0-7.5 by NaOH or HCl, and the temperature can be room temperature 20-25℃, and heating is required in winter (for example, potato wastewater <10℃ needs to be heated to 15℃).

[0063] For the A2 aerobic stage, some typical aerobic types are biological contact oxidation (BCO) membrane bioreactor (MBR), etc. For BCO, the relevant parameters that can be demonstrated are HRT 4-6 hours and filler filling rate 30%-50%; for MBR, the key process parameters that can be demonstrated are HRT 3-5 hours and membrane flux 10-20L / m 2 ·h.

[0064] It is known to those skilled in the art that the A2 aerator stage is supplemented with aeration. The aeration device may be a microporous aerator, a disc aerator, or an air pump. In the case of a microporous aerator, the dissolved oxygen (DO) can be controlled at 2-4 mg / L. In the implementation of the disc aerator, the DO can be maintained at 1.5-3 mg / L. In the implementation of the air pump, the air pump power can be controlled at 0.3-0.8 kW / m depending on the wastewater flow and DO requirements. 3 .

[0065] [Solid-liquid separation to obtain sludge]

[0066] It is known to those skilled in the art that the solid-liquid separation can be performed by static separation for large-scale production, or by centrifugal separation for small-scale laboratories. The solid phase obtained by the solid-liquid separation can be directly taken out by a pump.

[0067]

Sludge feeding place for anaerobic treatment

[0068] It should be understood that after the sludge is fed to the anaerobic treatment site, step C treatment and step D treatment are successively carried out, which may be once or multiple times. Here, once or multiple times refers to a cycle combination consisting of step C treatment and step D.

[0069] In a non-limiting but more suitable situation, before feeding the sludge to the anaerobic treatment site for treatment, the sludge is fed to a site substantially the same as the anaerobic treatment site. In this way, it can be ensured that before the sludge is recycled to step C and step D, the conditions such as the microbial species attached to the sludge are substantially similar to those of the subsequent anaerobic treatment, thereby improving the anaerobic treatment effect.

[0070] [Treatment of sludge before feeding to the anaerobic treatment site]

[0071] In a non-limiting but more suitable situation, after step D and before step F, step G is further included: modifying the sludge; wherein the modification treatment includes the following steps:

[0072] G1: fully gelling a material comprising at least a binder, a hydrogel monomer and sludge in a liquid phase comprising at least water, and subjecting the material to microfiltration to obtain a hydrogel;

[0073] G2: The hydrogel is dried at 45 to 60 degrees Celsius. Exemplary drying temperatures include 46-60 degrees Celsius, 48-60 degrees Celsius, 50-60 degrees Celsius, 52-60 degrees Celsius, 55-60 degrees Celsius, 58-60 degrees Celsius, 45-58 degrees Celsius, 48-56 degrees Celsius, 48-55 degrees Celsius, 48-53 degrees Celsius, 48-50 degrees Celsius, etc.

[0074] The purpose of the above-mentioned modification treatment in the invention is embodied as follows: in the hydrogel-based sludge obtained by the modification treatment, the three-dimensional porous structure of the hydrogel is partially dispersed in the sludge and partially exposed outside the sludge. The hydrogel dispersed in the sludge can strengthen the overall structure of the sludge, and then promote the sludge to adhere to the microorganisms (such as methanogens) required for anaerobic treatment. The hydrogel exposed outside the sludge can adsorb the target removal substances outside the sludge (especially starch particles that have not been aerobically treated), and adsorb external microorganisms, by utilizing the porous adsorption of the hydrogel, so as to finally adhere to the surface of the sludge.

[0075] In step G1, it can be understood that although only hydrogel monomers are mentioned, it does not mean that the addition of crosslinking agents etc. to the liquid phase for gelation is absolutely excluded. When the gelation mode of the hydrogel monomers is photogelation, the crosslinking agent can be omitted.

[0076] The gelation site in step G1 can be a mixed solution of water and C1-4 ethanol, or can be all water, such as a mixed solution of water and ethanol in a volume ratio of 3:1.

[0077] In a non-limiting but more suitable implementation, ultrasonic dispersion is used during step G1. The role of ultrasonic dispersion is to make the hydrogel in the hydrogel-based sludge have a better dispersion state in the sludge. It is expected that the hydrogel can appear in the sludge and exposed outside the sludge as much as possible, avoiding the situation where the hydrogel and the sludge are only dispersed on the surface.

[0078] The power and time of ultrasonic dispersion can be obtained through conventional experiments. For example, the power of ultrasound is 800-1500 W. Ultrasonic dispersion can be carried out during the entire gelation process or can be carried out during part of the gelation process.

[0079] A non-limiting but suitable amount of the binder is 0.5 to 4% based on the weight of the sludge, further exemplified by 0.52-4%, 0.55-4%, 0.6-4%, 0.65-4%, 0.7-4%, 0.75-4%, 0.80-4%, 0.85-4%, 0.90-4%, 0.95-4%, 1-4%, 1.1-4%, 1.2-4%, 1.4- 4%, 1.5-4%, 2-4%, 2.3-4%, 2.5-4%, 2.8-4%, 3-4%, 3.5-4%, 3.8-4%, 0.5-3.8%, 0.5-3.6%, 0.5-3.4%, 0.5-3%, 0.5-2.8%, 0.5-2.5%, 0.5-2%, 0.5-1.5%, 0.5-1%, 0.5-0.8%, etc. If the amount of adhesive is too much, the porous structure of the hydrogel may be blocked and its adsorption capacity may be reduced; if the amount of adhesive is too little, the basic connection effect between the sludge and the hydrogel cannot be achieved.

[0080] Non-limiting but more suitable adhesives are selected from at least one of polyvinyl alcohol, carboxymethyl cellulose, sodium polyacrylate, gelatin, sodium caseinate, gum arabic, guar gum, xanthan gum, agar, and carrageenan. Of course, other forms conventionally used in the art may also be used.

[0081] As for the hydrogel monomer, a chemical cross-linked hydrogel or a light-triggered hydrogel can be selected. Non-limiting but more suitable hydrogel monomers are at least one of collagen, chitosan, hydroxypropyl methylcellulose, hyaluronic acid, hydroxypropyl methylcellulose, polyacrylamide, sodium alginate, and methacrylated gelatin.

[0082] The amount of the hydrogel monomer added is 4.7 to 16% based on the weight of the sludge, and further exemplified as 4.8-16%, 5-16%, 5.5-16%, 6-16%, 6.5-16%, 7-16%, 8-16%, 8.6-16%, 9-16%, 10-16%, 10.5-16%, 11-16%, 11.6-16%, 12-16%, 13-16%, 13.5-16%, 14-16%, 14.5 -16%, 15-16%, 4.7-15.4%, 4.7-15%, 4.7-14.3%, 4.7-13.6%, 4.7-13.0%, 4.7-12.2%, 4.7-11.9%, 4.7-11.1%, 4.7-10.7%, 4.7-10%, 4.7-9.5%, 4.7-9%, 4.7-8.2%, 4.7-7.4%, 4.7-6.5%, 4.7-5.5%, etc. If the amount of hydrogel monomer is too much, the hydrogel will be wrapped too much on the sludge surface, reducing the exposed part of the sludge surface, which is not conducive to the attachment of microorganisms to the sludge surface, thereby damaging the anaerobic treatment effect; if the amount of hydrogel monomer is too little, the basic adsorption capacity cannot be achieved.

[0083] The actual role of microfiltration in the invention is to effectively intercept microorganisms (especially those required for anaerobic treatment) separated from sludge and prevent them from being lost to the liquid phase of the gel reaction. The size of the microfiltration membrane has no special effect on this application, so it is not demonstrated in this article.

[0084] The purpose of drying in step G2 is that the specific temperature of 45 to 60 degrees Celsius can prevent excessive death of microorganisms attached to the sludge during the drying process, thereby reducing the effect of subsequent anaerobic treatment. It is easy to imagine that drying in step G2 can be carried out by air drying, freeze drying, or low-temperature vacuum drying.

[0085] In a non-limiting but more suitable implementation, the modification treatment further includes step G3, washing the sludge before step G1.

[0086] Here, washing is to properly remove the microbial species suitable for aerobic treatment attached to the sludge, to prevent these microorganisms from metabolically competing with the subsequent anaerobic treatment microorganisms, thereby reducing the anaerobic treatment effect.

[0087] The washing can be performed by water rinsing at an appropriate flow rate, and the specific flow rate can be adjusted according to the experimental needs. The temperature of the water rinsing is based on the fact that anaerobic bacteria do not die on a large scale, for example, 45 to 60 degrees Celsius.

[0088] In order to prevent the anaerobic bacteria required for anaerobic treatment from being lost during the washing process, the microfiltration membrane is used to block the sludge.

[0089] In a non-limiting but more suitable implementation, an oxidant is added to the scrubbing liquid (such as water), and the oxidant is at least one of a Fenton oxidant and ozone.

[0090] The role of the oxidant in the invention is to decompose the residual small amount of protein and other macromolecular organic matter in the sludge to reduce the damage of these organic matter to the gel reaction. It can be appreciated by those skilled in the art that since the oxidant may damage the anaerobic bacteria attached to the sludge, the concentration and amount of the oxidant can be controlled. The amount of oxidant added is based on 0.05-1% of the weight of the sludge. The concentration of the oxidant is based on the loss of disinfection and sterilization, and can be controlled to be less than half of the lower limit of the conventional disinfection and sterilization concentration.

[0091] In a non-limiting but more suitable implementation, the oxidant is added with a biological enzyme, and the biological enzyme is selected from at least one of protease, lipase, and amylase. The role of the biological enzyme in the invention is to decompose a small amount of residual protein, starch and other macromolecular organic matter in the sludge to reduce the damage of these organic matter to the gel reaction. The non-limiting but more suitable amount of the biological enzyme added is 0.02-0.3% based on the weight of the sludge.

[0092] [Implementation process of embodiments and comparative examples]

[0093] Hereinafter, the embodiments of the present application will be described. The embodiments described below are exemplary and are only used to explain the present application, and should not be construed as limiting the present application. If no specific techniques or conditions are indicated in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. If the manufacturer is not indicated in the reagents or instruments used, they are all conventional products that can be obtained commercially.

[0094] [Starch production wastewater example 1]

[0095] Experimental sampling was conducted from the type a starch production wastewater of Dongguan Dongmei Food Co., Ltd. The sampling was referenced to the HJ 493-2009 standard to obtain wastewater sample A. The pollutant components of the sample were analyzed using GC-MS7890B Agilent gas phase mass spectrometer GC-MS as follows: COD 10200mg / L, BOD 4600mg / L, SS 980mg / L, protein 47mg / L.

[0096] [Starch production wastewater example 2]

[0097] Experimental sampling was conducted from the type B starch production wastewater of Dongguan Dongmei Food Co., Ltd., and the sampling was referenced to the HJ 493-2009 standard to obtain wastewater sample B. The pollutant components of the sample were analyzed using GC-MS7890B Agilent gas phase mass spectrometer GC-MS as follows: COD 7500mg / L, BOD 3000mg / L, SS 1250mg / L, protein 420mg / L.

[0098] [Starch production wastewater example 3]

[0099] Experimental sampling was conducted from the C-type starch production wastewater of Dongguan Dongmei Food Co., Ltd., and the sampling was referenced to the HJ 493-2009 standard to obtain wastewater sample C. The pollutant components of the sample were analyzed using GC-MS7890B Agilent gas phase mass spectrometer GC-MS as follows: COD 8800mg / L, BOD 3600mg / L, SS 850mg / L, protein 210mg / L.

[0100] [Example 1]

[0101] According to the process conditions in Table 1, the treatment method for [starch production wastewater example 1] includes the following steps:

[0102] S1. The starch production wastewater was pumped into the flocculation tank. After adjusting the pH to 6.5-7.5, PAM flocculant was added thereto. The PAM concentration was 2 mg / L. After adding the flocculant, the flocculation reaction was maintained for 20 minutes, and it was allowed to stand for a long time until obvious stratification occurred.

[0103] S2. The supernatant obtained from the flocculation treatment is pumped into the secondary hydrolysis acidification tank for acidification, and then the supernatant is passed into the first-stage water collection well and the pH is adjusted to 7-8. The treated liquid is then floated by the flotation machine and enters the second-stage water collection well and the temperature is controlled at 28-32°C and the pH value is 6.5-7.0. Then it enters the EGSB anaerobic tank for anaerobic reaction. Methanogens and acetogens are fed into the EGSB anaerobic tank. The methanogens and acetogens use active granular bacterial agents purchased by Shanghai Yiwante.

[0104] S3. The treated wastewater is pumped into the membrane bioreactor (MBR) for aerobic treatment. The HRT in the MBR is controlled for 4 hours and the membrane flux is 15L / m 2 ·h.

[0105] S4. The wastewater obtained by aerobic treatment is pumped into a sedimentation tank for sufficient sedimentation, and the sludge at the bottom of the sedimentation tank is pumped into a sludge collection tank.

[0106] S5. Take part of the sludge from the sludge collection tank and modify the sludge. The modification process includes:

[0107] S51, spreading the sludge on the microfiltration membrane and placing the microfiltration membrane in a flushing tank, and flushing the sludge in the tank with clean water at room temperature, and then fully drying the sludge on the microfiltration membrane at 60 degrees Celsius, and then transferring the sludge to a gel tank;

[0108] S52, install an ultrasonic disperser for the gel tank, add an appropriate amount of water to the gel tank, then put the sludge obtained in step S52, the adhesive (PVA), the hydrogel monomer (sodium alginate) and an appropriate amount of the cross-linking agent calcium chloride solution into the gel tank, turn on the ultrasonic disperser and adjust the ultrasonic power to 1200W and the ultrasonic dispersion time to 30 minutes, so that the gel tank undergoes a gel reaction. Then, the mixed solution in the gel tank is subjected to microfiltration to obtain a hydrogel;

[0109] S53: air-drying the hydrogel at 60 degrees Celsius until no obvious moisture is observed and no obvious stickiness is felt when touched.

[0110] S6. Feed the modified sludge into the anaerobic treatment site, with the sludge input amount being 4 g / 1 L of sewage, and repeat the above S2, S3, and S4 in sequence while keeping the conditions of each process unchanged during the repetition process, and the number of repetitions is 1, and the obtained supernatant is the target treated wastewater.

[0111] [Example 2]

[0112] On the basis of Example 1, S5 is changed to "taking part of the sludge from the sludge collection tank, and the sludge No changes Sexual treatment ”.

[0113] [Example 3]

[0114] On the basis of Example 1, S52 is changed to "install an ultrasonic disperser in the gel tank, add an appropriate amount of water to the gel tank, and then put the sludge obtained in step S52, the adhesive (PVA), and the hydrogel monomer (sodium alginate) into the gel tank and No added crosslinking agent calcium chloride The solution was turned on and the ultrasonic disperser was adjusted to 1200W and the ultrasonic dispersion time was 30min. The gel tank did not generate gel reactants. Then, the mixed solution in the gel tank was subjected to microfiltration treatment.

[0115] [Example 4]

[0116] Based on Example 1, the S52 adhesive was changed to Equal amount of hydrogel monomer (sodium alginate) And keep the ratio of sodium alginate to calcium chloride unchanged Increase the amount of calcium chloride .

[0117] [Example 5]

[0118] Based on Example 1, the S52 hydrogel monomer was replaced with an equal amount of adhesive.

[0119] [Example 6]

[0120] On the basis of Example 1, the ultrasonic dispersion in S52 is changed to Waiting time .

[0121] [Example 7]

[0122] On the basis of Example 1, the microfiltration membrane in S51 is omitted.

[0123] [Example 8]

[0124] Based on Example 1, the treatment method is directed to [Starch production wastewater example 2].

[0125] [Example 9]

[0126] Based on Example 1, the treatment method is directed to [Starch production wastewater example 3].

[0127] [Examples 10-12]

[0128] Based on Example 1, the conditions such as the adhesive and the hydrogel monomer were changed according to Table 1.

[0129] [Example 13]

[0130] Based on Example 1, the drying temperature of the hydrogel product was changed to 80 degrees Celsius.

[0131] [Example 14]

[0132] Based on Example 1, the amount of the binder was changed to "7% based on the weight of the sludge".

[0133] [Example 15]

[0134] Based on Example 1, the amount of hydrogel monomer was changed to "30% based on the weight of sludge".

[0135] [Comparative Example 1]

[0136] On the basis of Example 1, the operation of "pumping the sludge at the bottom of the sedimentation tank into the sludge collection tank" in S5 and S4 is omitted, and S6 is changed to "repeat the above S2, S3, and S4 in sequence and keep the conditions of each process unchanged during the repetition process, and the number of repetitions is 1, and the obtained supernatant is the target treated wastewater."

[0137] The process conditions of the above embodiments and comparative examples are shown in Table 1.

[0138] Table 1 Process conditions of various embodiments and comparative examples

[0139]

[0140]

[0141]

[0142]

[0143]

evaluate

[0144] The following evaluations were performed on the wastewater obtained by the treatment methods of the various embodiments and comparative examples prepared according to Table 1:

[0145] [COD removal rate]

[0146] The treated wastewater was analyzed for various pollutants in the same manner as described in "[Starch production wastewater example 1]" above to obtain the COD content after treatment.

[0147] COD removal rate = (COD before treatment - COD after treatment) divided by COD before treatment (expressed as a percentage).

[0148] [BOD removal rate]

[0149] The treated wastewater was analyzed for various pollutants in the same manner as described in "[Starch production wastewater example 1]" above to obtain the BOD content after treatment.

[0150] BOD removal rate = (BOD before treatment - BOD after treatment) divided by BOD before treatment (expressed as a percentage).

[0151] Table 2 Test results of various embodiments and comparative examples

[0152] COD removal rate (%) BOD removal rate (%) Example 1 95.3 92.4 Example 2 78.2 77.4 Example 3 83.4 80.9 Example 4 88.1 85.6 Example 5 81.5 78.7 Example 6 90.6 88.3 Example 7 92.4 89.5 Example 8 96.1 93.0 Example 9 95.8 91.8 Example 10 95.9 92.8 Embodiment 11 96.5 93.1 Example 12 94.9 92.0 Example 13 91.0 88.2 Embodiment 14 89.3 87.4 Embodiment 15 92.2 90.7 Comparative Example 1 67.4 63.8

[0153] It can be seen from Tables 3 and 4 that the COD and BOD of Example 1 are significantly higher than those of Comparative Example 1, which indicates that the addition of sludge to the anaerobic treatment site has a technical contribution to the sewage treatment effect;

[0154] The COD and BOD of Example 1 are higher than those of Example 2, which indicates the technical contribution of sludge modification to the sewage treatment effect;

[0155] The COD and BOD of Example 1 are higher than those of Examples 3 and 5, which indicates the technical contribution of hydrogel formation in sludge modification to the sewage treatment effect;

[0156] The COD and BOD of Example 1 are higher than those of Example 4, which indicates the technical contribution of the binder in sludge modification to the sewage treatment effect;

[0157] The COD and BOD of Example 1 are higher than those of Example 6, which indicates the technical contribution of ultrasonic dispersion in sludge modification to the sewage treatment effect;

[0158] The COD and BOD of Example 1 are higher than those of Example 7, which indicates the technical contribution of microfiltration membrane separation during washing in sludge modification to the sewage treatment effect;

[0159] The COD and BOD of Example 1 are higher than those of Example 13, which indicates that too high a hydrogel temperature during sludge modification will damage the sewage treatment effect;

[0160] The COD and BOD of Example 1 are higher than those of Example 14, which indicates that too high a binder content in sludge modification may impair the sewage treatment effect;

[0161] The COD and BOD of Example 1 are higher than those of Example 15, which indicates that excessive hydrogel in sludge modification may damage the sewage treatment effect.

[0162] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them; although the present application is described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application, and they should all be included in the scope of the claims and specification of the present application. In particular, as long as there is no structural conflict, the various technical features mentioned in the various embodiments can be combined in any way. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions that fall within the scope of the claims.

Claims

1. A method for treating starch production wastewater based on sludge recycling, characterized in that: The following steps are involved: A. Implement flocculation treatment on starch production wastewater; B. Anaerobic treatment of starch production wastewater after flocculation treatment; C. Aerobic treatment of starch production wastewater that has been anaerobic treated; D. performing solid-liquid separation treatment on the starch production wastewater that has been aerobically treated, and obtaining sludge from the solid phase components obtained by the solid-liquid separation; E. Feeding the sludge into the anaerobic treatment site to sequentially carry out step C treatment and step D treatment, and the liquid phase component obtained from the solid-liquid separation is the target treated wastewater.

2. The method for treating starch production wastewater based on sludge recycling according to claim 1, characterized in that: After step D and before step E, the method further comprises step F: feeding the sludge into a place substantially the same as the place for the anaerobic treatment.

3. The method for treating starch production wastewater based on sludge recycling according to claim 2, characterized in that: After step D and before step F, the method further includes step G: modifying the sludge; The modification process The following steps are involved: G1: fully gelling a material comprising at least a binder, a hydrogel monomer and sludge in a liquid phase comprising at least water, and subjecting the material to microfiltration to obtain a hydrogel; G2: Dry the hydrogel at 45 to 60 degrees Celsius.

4. The method for treating starch production wastewater based on sludge recycling according to claim 3, characterized in that: The modification treatment further includes step G3, washing the sludge before step G1.

5. The method for treating starch production wastewater based on sludge recycling according to claim 3, characterized in that: The hydrogel monomer is added in an amount of 4.7 to 16% based on the weight of the sludge.

6. The method for treating starch production wastewater based on sludge recycling according to claim 5, characterized in that: During step G1, ultrasonic dispersion is assisted.

7. The method for treating starch production wastewater based on sludge recycling according to claim 4, characterized in that: During the washing process, the sludge is blocked by a microfiltration membrane.

8. The method for treating starch production wastewater based on sludge recycling according to claim 1, characterized in that: The adhesive is selected from at least one of polyvinyl alcohol, carboxymethyl cellulose, sodium polyacrylate, gelatin, sodium caseinate, gum arabic, guar gum, xanthan gum, agar, and carrageenan.

9. The method for treating starch production wastewater based on sludge recycling according to claim 1, characterized in that: The hydrogel monomer is at least one of collagen, chitosan, hydroxypropyl methylcellulose, hyaluronic acid, hydroxypropyl methylcellulose, polyacrylamide, sodium alginate, and methacryloyl gelatin.

10. The method for treating starch production wastewater based on sludge recycling according to claim 1, characterized in that: The amount of the binder used is 0.5 to 4% based on the weight of the sludge.

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