CN116199403A - Method for improving carbon source release amount by breaking wall of excess sludge - Google Patents

Abstract

The invention discloses a method for improving the release amount of a carbon source by breaking the wall of excess sludge, which is to couple sodium acetate treatment in the process of alkaline hydrolysis of the excess sludge to promote the wall breaking of the excess sludge and release the carbon source. According to the invention, the water content, the reaction time, the alkali addition amount and the sodium acetate concentration of the sludge are controlled, and the COD, nitrogen, phosphorus, protein, polysaccharide and LDH (lactic dehydrogenase) content and the sludge sedimentation performance in the residual sludge pyrolysis liquid after sodium acetate coupling alkaline hydrolysis treatment are detected to verify the sludge wall breaking effect. The invention effectively realizes the wall breaking of the sludge with lower cost, and releases the biochemical carbon source efficiently and rapidly, thereby improving the recycling efficiency of the sludge.

Description

Method for improving carbon source release amount by breaking wall of excess sludge

Technical Field

The invention belongs to the technical field of environmental protection and energy conservation, and particularly relates to a method for improving the release amount of a carbon source by breaking the wall of excess sludge.

Background

With the rapid promotion of the urban process and the high-speed development of the economic living standard in China, the urban sewage discharge and treatment capacity are increased year by year. Under the background of new times of continuous improvement of urban sewage treatment capability, the sludge is used as an end product of sewage treatment, and the yield of the sludge is also continuously increased. However, under the trend of continuously increasing sludge yield, the improvement of the sludge treatment capacity of China is far lower than the increase of the sludge production amount, and the sludge treatment capacity of China gradually becomes a main environmental problem in the field of urban pollution control of China.

In the face of the high standard requirements of the times on sludge treatment, the traditional sludge treatment means such as sanitary landfill and the like cannot adapt to the times development, and the sludge stabilization means such as sludge digestion, composting and the like also have the problems of long treatment period, low organic matter conversion rate and the like. The problem is mainly that a large amount of organic matters in the sludge are limited by a cell wall barrier and an extracellular polymer barrier and are difficult to release, so that research on the release of the organic matters in the sludge wall breaking promotion gradually becomes a focus of attention in the field of sludge treatment. The sludge cracking effect can promote the hydrolysis of macromolecular substances in EPS, break the cell walls of sludge thalli, release easily degradable substances in the sludge thalli, and degrade macromolecular substances which are difficult to be utilized in extracellular degradation into easily utilized micromolecular substances even through physical and chemical effects, thereby increasing the availability of sludge. At present, the method for promoting the wall breaking of the excess sludge at home and abroad mainly comprises thermal hydrolysis, ultrasonic wave, advanced oxidation treatment, enzymolysis and the like. Although the method can lead to sludge pyrolysis, the method has the problems of high equipment requirement, high energy consumption and the like. Therefore, in order to solve the problem of sludge wall breaking, a brand new treatment mode needs to be explored.

The alkaline hydrolysis can promote the chemical degradation of the sludge floc structure and the lipid substances in cells, has the advantages of convenient treatment, low cost and the like, and is one of the most main sludge cracking methods in the world at present. However, due to the protection of the floccule structure and the extracellular polymer in the sludge, the single alkali hydrolysis treatment has a little shortage of damage to the residual sludge, and the overall wall breaking effect is poor.

Disclosure of Invention

Aiming at the defects in the prior art, the invention provides a method for improving the release amount of a carbon source by breaking the wall of residual sludge, which effectively realizes the wall breaking of the sludge by coupling sodium acetate with alkaline hydrolysis of the residual sludge with lower cost and releases biochemical carbon sources efficiently and rapidly.

The invention discloses a method for improving the release amount of a carbon source by breaking the wall of excess sludge, which is to couple sodium acetate treatment in the process of alkaline hydrolysis of the excess sludge to promote the wall breaking of the excess sludge and release the carbon source.

The excess sludge is produced by a sewage treatment plant in a chemical industry park, and the water content of the excess sludge is controlled to be 95% before sodium acetate coupling alkaline hydrolysis treatment.

The alkaline hydrolysis process is based on the pH value of the residual sludge regulated to 12 by NaOH, the adding amount is 0.1-0.2g NaOH/g VS, and the reaction time is controlled to be 1h.

The adding amount of sodium acetate in the sodium acetate coupling alkaline hydrolysis section is based on that the concentration of sodium acetate in the mud-water mixture reaches 10-30%, preferably 20-30%, and the reaction time is controlled to be 3h.

The method specifically comprises the following steps:

s1: standard water generated after the treatment of the secondary sedimentation tank in the sewage treatment plant enters the next water treatment structure program, and the generated surplus sludge is collected;

s2: the residual sludge collected in the step S1 is subjected to water content adjustment to a specific degree in a concentration or dilution mode, and then is sent to an alkaline hydrolysis working section;

s3: after the residual sludge enters an alkaline hydrolysis reaction stage, controlling the alkali addition amount and the reaction time to generate a sludge-water mixture;

s4: and (3) adding sodium acetate into the mud-water mixture in the step (S3), and controlling the adding amount and the reaction time of the sodium acetate.

According to the invention, the high-concentration sodium acetate required to be added by a sewage plant is combined with the treatment of the excess sludge, the pH is controlled to inhibit the consumption of sodium acetate and promote the death of the sludge, and the wall breaking effect of the sludge is further improved. According to the method, on one hand, valuable components such as organic matters in the excess sludge are released, and on the other hand, bound water in the sludge is released, so that the sludge sedimentation performance is improved, and sludge reduction and resource utilization are realized.

The invention has the technical effects and advantages that:

1. according to the method for improving the release of the carbon source through the wall breaking of the excess sludge, provided by the invention, the wall breaking of the sludge is effectively realized at lower cost in a high-concentration sodium acetate coupled alkaline hydrolysis mode, and organic matters in the sludge particles are released, so that the limitation of sludge recycling is broken to a great extent.

2. The sludge treatment method provided by the invention can effectively inactivate pathogenic microorganisms and parasitic ova in the sludge under the action of high-concentration sodium acetate and alkali, and is more stable and harmless compared with the traditional sludge treatment method. In addition, the mode of breaking the wall of the excess sludge and improving the release of the carbon source also realizes the reduction and the recycling of the sludge to a great extent.

Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention may be realized and attained by the structure particularly pointed out in the written description and drawings.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following description will briefly introduce the drawings that are required to be used in the embodiments or the prior art descriptions, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.

FIG. 1 is a schematic diagram of the volume and pH of a lysate;

FIG. 2 is a schematic diagram of ammonia nitrogen content in the lysate;

FIG. 3 is a schematic representation of total phosphorus content in the lysate;

FIG. 4 is a schematic representation of protein and polysaccharide content in the lysate;

FIG. 5 is a schematic diagram showing the relative release of excess sludge LDH (control based on untreated sludge);

FIG. 6 is a schematic diagram showing the carbon source release of excess sludge;

FIG. 7 is a schematic diagram of dewatered sludge moisture content versus VS/TS;

FIG. 8 is a schematic diagram of the SV and SVI conditions of the excess sludge.

Detailed Description

For the purpose of making the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is apparent that the described embodiments are some embodiments of the present invention, but not all embodiments of the present invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.

Implementation case:

sodium acetate with different concentrations is adopted to couple alkaline hydrolysis of residual sludge to obtain sludge mixed liquor, centrifugal separation is carried out to obtain pyrolysis liquor and dehydrated sludge, and denitrification experiments are carried out by taking the pyrolysis liquor and the dehydrated sludge as carbon sources respectively so as to analyze the actual availability of the pyrolysis liquor and the dehydrated sludge; the specific experimental method is as follows:

(1) Detecting the water content and the VS duty ratio of the residual sludge to be treated, and adjusting the water content to 95 percent;

(2) And (3) placing 100mL of residual sludge with the water content of 95% in a beaker, adding 0.12g of NaOH/g of VS into each group of residual sludge, regulating the pH to 12, standing for 1h, adding sodium acetate with different dosages, stirring uniformly, standing for 3h, taking part of sludge, and centrifuging for 6min at 8000r/min to obtain a lysate and dehydrated sludge. The dosage of each group of medicaments is shown in the following table;

(3) Taking the obtained lysate of each group to detect the release conditions of volume, pH, COD, ammonia nitrogen, total phosphorus, protein, polysaccharide and Lactate Dehydrogenase (LDH), and detecting the water content and VS/TS conditions of each group of dehydrated sludge;

(4) And (3) taking part of residual sludge which is subjected to sodium acetate coupling alkaline hydrolysis treatment in the step (2) and is not subjected to centrifugal treatment, and testing SV and SVI.

The results of the implementation are shown in fig. 1, 2, 3, 4, 5, 6, 7, and 8. Free water in the sludge can be removed by mechanical stress, but bound water is trapped in Extracellular Polymers (EPS) and is not easily released inside the cells. Therefore, when it is desired to release intracellular bound water, it is necessary to destroy EPS and sludge cell membranes. After the sludge is centrifuged under the simple alkaline condition, the volume of the pyrolysis liquid is 38.7mL, and after 5%, 10%, 20% and 30% of sodium acetate are added on the basis of the alkaline condition, the volumes of the pyrolysis liquid are respectively increased by 26.9%, 34.1%, 47.5% and 53.5%, so that the damage of sodium acetate to the sludge floc structure is proved from the side, and the release of bound water in the sludge can be promoted. The pH of the residual sludge is reduced from 12 to 11.5 after alkaline hydrolysis treatment, and the pH of the residual sludge is gradually stabilized at about 10.5 after the sodium acetate is continuously added into the residual sludge. Sodium acetate is a strong alkali weak acid salt, the pH value of a sludge group with high sodium acetate concentration is higher due to hydrolysis, and the pH value of a sludge group which can actually contain sodium acetate is lower, because acid substances such as lysosomes and the like are contained in cells, and the addition of sodium acetate promotes the cell lysis of the sludge, releases more intracellular substances and further promotes the pH reduction of the sludge. With the increase of the concentration of sodium acetate, the sodium acetate and the hydrolysate thereof form a buffer system, so that the pH of the whole sludge is stabilized at about 10.5.

After sodium acetate coupling alkaline hydrolysis treatment, nitrogen-containing substances and phosphorus-containing substances such as intracellular and extracellular proteins, nucleic acids and the like in the excess sludge are released into a liquid phase. The ammonia nitrogen content in the residual sludge lysate is 20.51+ -2.55 mg/L and the total phosphorus content is 20.42+ -1.54 mg/L under the simple alkaline condition, which is caused by the destruction of the sludge floc structure by alkali, thereby releasing nitrogen and phosphorus. The sludge cells contain high concentrations of nitrogen and phosphorus substances, phosphorus being an essential component of cell membranes and cell walls. On the basis that sludge cells with the sludge floc structure are damaged by alkali and are exposed to the environment, the osmotic pressure difference caused by high-concentration sodium acetate promotes the sludge cells to be cracked, so that the release amount of nitrogen and phosphorus is increased along with the increase of the concentration of sodium acetate. The ammonia nitrogen release amount of the 30% concentration sodium acetate coupled alkaline hydrolysis treatment residual sludge is increased by 165.85% compared with that of the pure alkaline condition, and reaches 54.52 +/-1.52 mg/L, and the total phosphorus release amount is increased by 11.02% and reaches 43.4+/-2.55 mg/L.

EPS is a complex biopolymer system composed of proteins, polysaccharides, humic acid and nucleic acid, and is influenced by the quality of the incoming water and the process selection of sewage treatment plants. The EPS network structure around the microbial cells plays a role in protecting under adverse environment. The proteoglycan content in the sludge lysate is similar to the ammonia nitrogen and total phosphorus, and increases with the increase of the sodium acetate concentration. Under the simple alkaline condition, the contents of protein and polysaccharide in the sludge lysate are 2176.04 +/-91.15 mg/L and 514.34 +/-9.05 mg/L respectively. On the contrary, under the condition of 5%, 10%, 20% and 30% sodium acetate coupling alkaline hydrolysis treatment, the total amount of proteoglycan in the sludge lysate is increased by 21.88%, 37.35%, 59.11% and 88.38% respectively. The dissolution of proteoglycan is obviously improved along with the increase of the concentration of sodium acetate, which indicates that the release of part of proteoglycan under the condition of sodium acetate coupling alkaline hydrolysis is from the rupture of sludge cells.

LDH is expressed in all cell plasma, and rupture of the cell membrane and increase in cell permeability results in release of LDH. Thus, extracellular LDH concentration can be used as an indicator of cell lysis. And (3) comparing the extracellular LDH content in the untreated residual sludge as a basis to obtain the relative release amount of the sludge LDH under the condition of sodium acetate coupling alkaline hydrolysis with different concentrations. Under the simple alkaline condition, the relative release amount of the sludge LDH reaches 471 percent. On the basis, after sodium acetate is added, the relative release amount of the sludge LDH is also increased, and when the added amount of the sodium acetate reaches 30%, the relative release amount of the LDH is increased to 827%. The results show that both alkali and sodium acetate promote rupture of sludge cell membranes.

The COD release amount of the residual sludge under the simple alkaline condition is 0.11g/g VS, and after 5%, 10%, 20% and 30% sodium acetate are added, the COD release amount of each group of residual sludge is respectively improved to 0.15, 0.24, 0.36 and 0.39g/g VS. According to the Divalent Cation Bridging (DCB) model, negatively charged EPS forms a sludge matrix by binding divalent cations together, while multivalent cations in sludge flocs can be replaced by monovalent cations such as Na ⁺ Substitution, so when the sludge contains Na ⁺ At this time, a portion of the organics will be released from the polymer matrix.In addition, as the osmotic pressure in the sludge is increased after adding sodium acetate, the microbial cells can be separated from the plasma wall and autolyzed, so that more carbon sources are released.

The water content of the dehydrated sludge after centrifugal dehydration of the residual sludge under the simple alkaline condition is 92.3%, the water content of the dehydrated sludge is greatly reduced along with the increase of the concentration of sodium acetate added, and the water content of the centrifugal sludge after 5%, 10%, 20% and 30% of sodium acetate are respectively 85.3%, 80.1%, 72.0% and 64.6%. After sodium acetate coupling alkaline hydrolysis treatment, part of bound water in the sludge is converted into free water due to EPS decomposition. In addition, the dehydrated sludge contains sodium acetate residues, which are also responsible for the significant decrease in water content. In the process of measuring the VS content of sludge, the temperature is increased to 605 ℃, the boiling point of sodium acetate is 400 ℃, so that the residual sodium acetate is recorded into a VS part, theoretically, the more sodium acetate remains, the higher the VS/TS is, and in each set of actual measured values, the VS/TS is reduced along with the increase of the concentration of the added sodium acetate, because the sodium acetate promotes the cell lysis of sludge, the VS in centrifugal sludge is reduced, and the reduction of organic matters covers the residual sodium acetate effect.

The sludge sedimentation ratio (SV) refers to the volume of the sediment sludge formed after the mixed liquor is kept stand for 30min in a measuring cylinder, and the volume fraction of the sediment sludge is the volume fraction of the original mixed liquor. The Sludge Volume Index (SVI) refers to the volume of settled sludge per gram of dry sludge, in mL/g. SV and SVI can react the sludge coagulation and precipitation performance, and also indirectly react the sludge dehydration degree. The SV and SVI of the residual sludge after the sodium acetate coupling alkaline hydrolysis treatment are reduced in comparison with the simple alkaline treatment, and the higher the concentration of sodium acetate is, the more obvious the reduction is. Compared with simple alkaline hydrolysis treatment, the SV and SVI of the sludge after the 30% sodium acetate coupling alkaline hydrolysis treatment are reduced by 3.56%. There are a lot of documents showing that the alkaline agent can promote the breaking of sludge floc structure and high concentration Na ⁺ The addition of (2) may cause the lysis of sludge cells due to an excessive osmotic pressure difference. Exposure of microbial cells to high concentrations of Na by EPS destruction induced by alkaline agents ⁺ In the environment, this may further promote Na ⁺ Inducing the lysis of sludge cells. Meanwhile, the microbial cell lysis also increases the EPS content and weakens the EPSThe binding stability accelerates the EPS disintegration. The double damage mechanism of alkali and sodium acetate to the sludge breaks the floc structure and releases bound water in the sludge particles, so that the bound water is converted into free water to be dissolved in a liquid phase, and the treated sludge can separate more free water and has better sedimentation performance and dehydration degree.

Although the invention has been described in detail with reference to the embodiments, it will be understood by those skilled in the art that: the technical scheme recorded in the previous embodiment can be modified or part of technical features in the technical scheme can be replaced equivalently; such modifications and substitutions do not depart from the spirit and scope of the technical solutions according to the embodiments of the present invention.

Claims (5)

1. A method for improving carbon source release amount by breaking wall of excess sludge is characterized by comprising the following steps:

sodium acetate treatment is coupled in the process of alkaline hydrolysis of the excess sludge, so that the wall breaking of the excess sludge is promoted to release a carbon source;

the alkaline hydrolysis process is to adjust the pH value of the residual sludge by adopting NaOH, and the adding amount is 0.1-0.2g NaOH/g VS;

the adding amount of sodium acetate in the sodium acetate coupling alkaline hydrolysis section is 10-30% based on the concentration of sodium acetate in the mud-water mixture.

2. The method according to claim 1, characterized by the steps of:

s1: standard water generated after the treatment of the secondary sedimentation tank in the sewage treatment plant enters the next water treatment structure program, and the generated surplus sludge is collected;

s2: the residual sludge collected in the step S1 is subjected to water content adjustment to a specific degree in a concentration or dilution mode, and then is sent to an alkaline hydrolysis working section;

s3: after the residual sludge enters an alkaline hydrolysis reaction stage, controlling the alkali addition amount and the reaction time to generate a sludge-water mixture;

s4: and (3) adding sodium acetate into the mud-water mixture in the step (S3), and controlling the adding amount and the reaction time of the sodium acetate.

3. The method according to claim 2, characterized in that:

in S2, the water content of the excess sludge is controlled to be 95%.

4. The method according to claim 2, characterized in that:

and S3, adjusting the pH value of the residual sludge to 12 by adopting NaOH, and controlling the reaction time to be 1h.

5. The method according to claim 2, characterized in that:

in S4, the adding amount of sodium acetate is 20-30% based on the concentration of sodium acetate in the mud-water mixture, and the reaction time is controlled to be 3h.

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