CN112794619A

CN112794619A - Chemical reagent adding quantification method for improving dewatering property of old sludge

Info

Publication number: CN112794619A
Application number: CN202011525844.XA
Authority: CN
Inventors: 谭洵; 陈亿军; 何星星; 惠心敏喃; 王平; 张少华; 李源
Original assignee: Wuhan Zhongke Solid Waste Resources Industrial Technology Research Institute Co ltd; Wuhan Institute of Rock and Soil Mechanics of CAS
Current assignee: Wuhan Zhongke Solid Waste Resources Industrial Technology Research Institute Co ltd; Wuhan Institute of Rock and Soil Mechanics of CAS
Priority date: 2020-12-22
Filing date: 2020-12-22
Publication date: 2021-05-14
Anticipated expiration: 2040-12-22
Also published as: CN112794619B

Abstract

The invention discloses a chemical reagent adding and quantifying method for improving the dewatering property of old sludge, which comprises the following steps: 1) adding water into at least one old sludge for stirring, performing steady-state rheological mechanical shear test on the sludge after resuspension, and performing Herschel-Bulkley equation fitting on rheological curve data to obtain yield stress tau of different sludge_yA value; 2) performing a chemical conditioning and filtration response surface test on at least one old sludge, and searching for the optimal addition mass combination of the slurry chemical reagent through the test and analysis; 3) converting the optimized adding mass of the reagent searched in the step 2) to obtain the slurry tau_yNormalizing the value or optimizing the adding quality of the reagent and the mud tau_yValues were subjected to least squares linear regression. And (3) treating and testing other old sludge according to the step 1), and calculating the reagent addition quality of other old sludge slurry by using the obtained normalized value or linear regression equation. The invention can be suitable for the chemical oxidation conditioning of various complicated old sludge.

Description

Chemical reagent adding quantification method for improving dewatering property of old sludge

Technical Field

The invention relates to the technical field of environmental geotechnical engineering, in particular to a chemical reagent addition quantification method for improving the dewatering property of old sludge.

Background

The sanitary landfill is the main disposal mode of the excess sludge of the sewage treatment plant in China, and the landfill disposal mode in the past accounts for 60 percent. The surplus sludge with the increasing yield is subjected to one-time dehydration treatment and then is subjected to sanitary landfill, however, the land resource is limited, the landfill still occupies a large amount of precious land resource, the ecological, industrial and commercial environments around the landfill site are greatly influenced, and particularly in areas with high ecological environment requirements and relatively short land resources. Therefore, in order to improve the capacity of a landfill site and treat and repair the non-standard old landfill pit, the exploration of secondary deep dehydration volume reduction of the filled old sludge is of great significance, and the secondary deep dehydration is also beneficial to reducing the subsequent incineration disposal or resource utilization cost.

Because the sludge is complex in components, high in organic matter content, colloidal and difficult to deeply dehydrate, the water content of the left-out excess sludge accounts for 70-80% of the total mass, and the water content in the landfill old sludge is not obviously changed. Meanwhile, the old sludge is in a series of complex biochemical evolution processes in the landfill environment. Under the condition of oxygen or oxygen-free, soluble organic matters in the sludge moisture can be utilized by microorganisms to be degraded, the humification degree is increased, and the relative molecular weight is reduced. However, organic substances contained in the interior of the sludge polymer body are difficult to be utilized by microorganisms due to physical separation of inorganic particles, intermolecular adsorption, and gradual humification. For example, polysaccharides form insoluble salts or chelates with polyvalent cationsAttached to the surface of clay mineral or oxide; the montmorillonite mineral can adsorb protein and other nitrogen-containing compounds, so that it is not easily decomposed by microorganism or enzyme; these all enhance the stability of organic matter, which can be gradually stabilized in the natural environment and can exist for decades. Under the new disturbance condition, the original organic matter distribution balance is broken, and part of organic matters wrapped and combined in sludge polymers have an opportunity to be transferred into solution again, so that the total organic matter content of municipal residual sludge buried for years is not reduced to a very low degree, and the dehydration characteristic is still very poor (the specific resistance in the filtration stage is higher than 10)¹¹m/kg). Therefore, the selection of a pretreatment method with proper comprehensive benefits is needed to improve the dewatering property of the old sludge.

Chemical oxidation technology is an effective method for pretreating sludge to improve the dewatering capacity of the sludge, and has high competitive potential compared with other methods when cost control is achieved. In the practice of dewatering engineering, the reagent cost is high, and due to strict control of the on-site use of explosive hazardous reagents, the usage amount of the reagents needs to be calculated as accurately as possible, and simultaneously, the economic optimized addition quality combination is efficiently obtained for old sludge with different properties through a small amount of tests. Therefore, an efficient method for quantifying the amount of reagent added is required. Different common quantization adding references have been proposed in previous patents. Based on the volume molar concentration (mmol/L) of the effective components in the sludge (for example, biological nano-iron-H in Chinese patent CN 201810149289.1)₂O₂Is added to the system in the form of a suspension in which the concentration of iron ions is measured in moles per liter). Or the mass percent (%) of the effective components in the unit volume of the sludge when the sludge is pretreated (for example, the three reagents in CN105800909A are added in the volume percent of the total amount of the sludge). Or the mass (mg/g DS) of the solid matter relative to the sludge is taken as a measuring standard (for example, three types of fenton reagent in Chinese patent CN201110300223.6 are added based on the dry weight of the sludge, and the fenton effective component is added based on each kilogram of absolute dry sludge in Chinese patent CN 201610976644.3). In Chinese patent CIn N201611244154.0, the organic matter content is considered to be a key factor influencing the chemical conditioning of the sludge, and the addition is carried out based on the mass (mg/g VS) of the effective components relative to the organic matter of the sludge.

Old sludge is subjected to biochemical evolution in a landfill environment and is greatly influenced by initial conditions and environmental conditions. The prior patented method has important reference value, but does not comprehensively aim at the physical and chemical characteristics of old sludge, the implementation of the scheme has no clear old sludge dehydration improvement mechanism guidance, and an addition amount prediction model is difficult to obtain so as to efficiently calculate the chemical agent addition combination with optimized economy. Therefore, the prior patent method is difficult to achieve the economic optimization of the combination of the addition amount of the reagents for treating the old sludge with complicated change of the treatment property.

Xun Tan et al found that the chemical oxidation has different mechanisms for improving the dewatering property of different types of sludge, and is reflected in the distribution characteristics of organic matters before and after oxidation treatment. For undisturbed sedimentation tank sludge, the oxidation treatment promotes the decomposition of extracellular polymers or partial cell destruction, the release of floccules or intracellular encapsulated water improves the dehydration effect, and the content of organic matters released into the solution is higher than that mineralized by oxides in the solution. For anaerobic digestion, ultrasound or heat treatment of sludge, organic matter has been partially transferred from the polymer to the solution in the initial treatment, and the mineralization of the organic matter in the solution is more pronounced than the migration in the further oxidation treatment, improving the dewatering. The findings were published in Separation and Purification Technology (2020, (237), 116317). The organic matter distribution characteristics of old sludge under oxidation treatment belong to the latter type.

The property difference between different old sludge is not only the organic content, because the pressure dehydration of the sludge suspension is the typical physical process of solid-liquid separation, but the network characteristics of liquid phase, solid phase and suspension structure all affect the chemical conditioning and separation process. One of the most complex problems involved, since a variety of physicochemical properties have a combined influence. Is there a key combination of properties that represent an impact on chemical conditioning in addition to organic matter content? How can the combination of different properties be considered and how can the combination affect the pretreatment and filtration processes? How to reduce the previous test procedure to reliably achieve an economically optimized reagent addition combination? Is a main problem for further understanding the old sludge treatment by chemical oxidation at present. Therefore, a reagent adding quantification method is needed to treat the old sludge with complex properties, and the addition amount of the reagent is calculated more accurately and efficiently while the dehydration performance is improved, so as to more comprehensively evaluate the use cost of the reagent for treating the old sludge by chemical oxidation.

Disclosure of Invention

The invention provides a chemical reagent adding quantification method for improving the dewatering property of old sludge to make up for the defects in the prior art, which can solve the problem of inaccurate calculation of the suitable usage amount of old sludge chemical reagents and avoid poor dewatering effect or ineffective increase of economic cost caused by insufficient or waste of added reagents. The invention can be applied to special old sludge with different initial characteristics, different landfill time and complex biochemical evolution process, and has good guiding function on the engineering practice of improving the dehydration property of the old sludge (VS/TS: 10-50%).

In order to achieve the purpose, the invention adopts the following technical scheme:

the invention provides a chemical reagent adding and quantifying method for improving the dewatering property of old sludge, which comprises the following steps:

1) adding water into at least one old sludge, stirring, and suspending to obtain slurry in a pumpable flowing state; performing steady-state rheological mechanical shear test on the slurry, and performing Herschel-Bulkley equation fitting on the obtained rheological curve data to obtain the yield stress tau of different slurries_y(Pa)；

2) Performing at least one old sludge chemical conditioning and filtration response surface test: setting the target specific resistance of the chemically conditioned slurry to be an acceptable value according to the requirement of filtering difficulty, adding a chemical reagent into the slurry in the step 1), conditioning, measuring the specific resistance, and searching the optimal adding quality of the chemical reagent when the chemically conditioned slurry meets the acceptable value of the specific resistance by a response surface methodCombined and measured in mud yield stress tau_ySelecting a response surface test central point for reference; the chemical reagents comprise a first reagent A and a second reagent B;

3) dividing the optimized adding mass of the chemical reagent of the slurry obtained in the step 2) by the yield stress tau of the slurry corresponding to the step 1)_yObtaining a normalized value; or optimizing the adding quality of the chemical reagents of more than two kinds of mud obtained in the step 2) and the yield stress tau of the mud corresponding to the step 1)_yPerforming least square normal linear regression on the values to obtain a linear regression equation; other old sludge to be treated is repeatedly operated according to the step 1) to obtain the yield stress tau of the corresponding sludge_yAnd calculating by using the obtained normalization value or linear regression equation to obtain the optimized addition quality of the chemical agents of other old sludge slurry to be treated.

According to the method, in the step 1), the water content of the slurry in the pumpable flowing state obtained by suspension accounts for 85-95% of the total mass of the slurry, and preferably 93.02-93.30%.

According to the method, in the step 1), preferably, the water content accounts for 93.16 +/-0.14% of the total mass, the organic matter content VS/TS of the old sludge resuspension slurry is 10-50%, and the yield stress tau is_yIs 0.01 to 5.00 Pa.

According to the method, in the step 1), before the steady-state rheological mechanical shear test, premixing 150mL of sludge suspension is carried out for 15-20 minutes at a stirring speed of 150 rpm.

In a particular embodiment, the rheological measurement conditions of the steady state rheomechanical shear test according to the method of the invention are: shear rate from 0.1s^-1Linearly increasing to 1000s^-1In the range of up to 1000s^-1Hold for 30s then from 1000s^-1Linear down to 0.1s^-1The rise and fall curves may record 50 sets of shear rate and shear stress data, respectively; the test temperature is constant at 23 ℃; the data result is presented on a linear coordinate rheological curve chart, and Herschel-Bulkley rheological equation fitting is carried out on the data to obtain the yield stress tau of different mud_y(Pa). Preferably, the assay is of the same typeAnd (4) three parts.

In particular embodiments, the rheological measurement conditions of the steady state rheomechanical shear test according to the method of the invention may also be: shear rate from 0.1s^-1Logarithmic increase to 200s^-1From 200s again^-1Linearly increasing to 1000s^-1In the range of up to 1000s^-1Hold for 30s then from 1000s^-1Linear down to 200s^-1From 200s^-1Logarithmic reduction to 0.1s^-1(ii) a The test temperature is constant at 23 ℃; the data result is presented on a linear coordinate rheological curve chart, and Herschel-Bulkley rheological equation fitting is carried out on the data to obtain the yield stress tau of different mud_y(Pa). Preferably, the test is performed in triplicate.

According to the method of the invention, in the step 2), preferably, the first reagent A and the second reagent B are added into the slurry obtained in the step 1) according to the optimized adding quality of the chemical reagent obtained by searching, and are conditioned, and a specific resistance test is carried out to verify whether the searched result meets the standard.

According to the method, in the step 2), the chemical conditioning is oxidation pretreatment, and the optimized addition mass of the chemical reagent comprises the addition mass of the first reagent A and the second reagent B or the mass ratio of the first reagent A and the second reagent B.

In a particular embodiment, the first reagent a is a catalytic species, which may be: at least one of ferrous sulfate pentahydrate, iron powder, zero-valent iron or nano zero-valent iron or a mixture thereof, and the second reagent B is a free radical generator which can be: at least one of hydrogen peroxide, sodium peroxide, calcium peroxide, persulfate, percarbonate, or a mixture thereof.

According to the method, in a specific scheme, when a chemical conditioning and filtration response surface test of old sludge is carried out in the step 2), the optimal addition quality of the chemical reagent of the sludge obtained in the step 2) is divided by the yield stress tau of the sludge corresponding to the step 1)_yAnd obtaining a normalized value.

According to the method of the invention, in a specific scheme, when the step 2) is used for carrying out the chemical conditioning and filtration response surface tests of at least two old sludges, the steps are carried out2) Optimizing the adding quality of the chemical agents of the obtained at least two kinds of mud and the yield stress tau of the mud corresponding to the step 1)_yAnd performing least square normal linear regression on the values to obtain a linear regression equation.

According to the method of the invention, in the step 3), preferably, the water content of various old sludges is kept the same after the old sludges are added with water and suspended to a pumpable flowing state.

According to the method, the step 4) is further included, various old sludge is subjected to chemical conditioning according to the chemical reagent addition quality combination obtained in the step 3), preferably, specific resistance test or plate-and-frame filter pressing dehydration is also performed, and further, the reagent addition quality combination is finely adjusted according to the dehydration result, so that the dehydration property of the old sludge is greatly improved under the condition of economic optimization.

In a specific embodiment, after plate-and-frame filter pressing dehydration, lime or sulfuric acid can be added into the filtrate with the pH value exceeding the range of 6.5-8.5, so that the pH value of the filtrate is in the range of 6.5-8.5. And carrying out conventional solid-liquid separation on the insoluble precipitate in the filtrate. The insoluble precipitate is mixed with sludge cake and enters the subsequent solid waste disposal link.

Through the technical scheme, the old sludge rheological mechanical characteristics which comprehensively influence the consumption of the chemical agent are accurately mastered, the yield stress of the old sludge suspension is taken as the reference, the reference of the usage amount of the chemical agent is improved, the method can effectively adapt to the special old sludge in the biochemical evolution process, the reagent addition quantification method developed can improve the reagent usage amount prediction capability, and the investment cost of the reagent is accurately calculated.

The invention has the following beneficial effects:

(1) the method can adapt to special old sludge with different initial characteristics, different landfill time and complex biochemical evolution process, is suitable for chemical oxidation conditioning of old sludge with different physical and chemical characteristics, overcomes the discomfort of reagent addition amount metering based on sludge volume, solid matter content or organic matter content in the prior art, selects a quantification method based on the yield stress of old sludge suspension which comprehensively influences chemical conditioning, expands the application range of the chemical oxidation conditioning technology, breaks through the limitation of good conditioning effect only suitable for part of fresh sludge, and avoids the improper reagent addition amount design possibly caused by conditioning of old sludge with different characteristics.

(2) The reagent addition quantity with optimized economical efficiency is obtained gradually through a small amount of tests (at least one group of response surface tests), and then the reagent addition quantity is used for calculating the reagent addition quantities of other old sludge with different properties, so that early test procedures are reduced, time and workload are saved, reagent addition quantity combinations can be searched efficiently, stably and gradually, and the test efficiency is greatly improved. The chemical reagent input cost can be evaluated through a small number of gradual tests in the early stage of engineering, and support is provided for comprehensively formulating a chemical conditioning and dehydration process scheme.

Drawings

FIG. 1 is a schematic flow chart of a chemical agent addition quantification method for improving the dewatering property of old sludge according to an embodiment of the invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

The method of the invention enables the amount of reagent used for treating the old sludge to be matched with the yield stress of the old sludge slurry. The measuring standard based on the yield stress is effective for treating the complicated old sludge, the economically optimized reagent addition amount with the dehydration performance up to the standard is obtained through a group of response surface tests, and further preferably, at least two groups of response surface tests can be carried out to obtain data, the linear relation between the economically optimized reagent combination and the measuring standard can be efficiently, stably and gradually obtained, meanwhile, the measuring standard is used for quantifying the addition amount of the other complicated old sludge with different properties, complicated response surface tests are not required to be carried out on the complicated old sludge with different properties, and the time and the test cost are saved. The chemical conditioning controlled by the method can obviously reduce soluble organic substances in the solution, simultaneously avoid polymer damage caused by over-strong oxidation, and achieve the purpose of improving the dewatering property of old sludge, and simultaneously, the reagent addition combination is economically optimized. The obtained economically optimized reagent combination can pertinently improve the adaptability of chemically treating the old sludge.

As shown in fig. 1, an embodiment of the present invention provides a chemical agent addition quantification method for improving the dewatering property of old sludge, including the following steps:

step S1: adding water into at least one old sludge, stirring, and suspending to obtain slurry in a pumpable flowing state; performing steady-state rheological mechanical shear test on the slurry, and performing Herschel-Bulkley equation fitting on the obtained rheological curve data to obtain the yield stress tau of different slurries_y(Pa), performing rheological mechanical parameter test in triplicate and averaging;

step S2: performing at least one old sludge chemical conditioning and filtration response surface test: setting the target specific resistance of the chemically conditioned slurry to be an acceptable value according to the requirement of filtering difficulty, adding a chemical reagent into the slurry in the step S1 for conditioning, measuring the specific resistance, searching the optimal addition mass combination of the chemical reagent when the chemically conditioned slurry meets the acceptable value of the specific resistance by a response surface method, and taking the yield stress tau of the slurry as the optimal addition mass combination_ySelecting a response surface test central point for reference; the chemical reagents comprise a first reagent A and a second reagent B; adding the first reagent A and the second reagent B into the slurry obtained in the step S1 again according to the optimized adding quality of the chemical reagent obtained by searching for conditioning, and performing specific resistance test to verify whether the searched result reaches the standard;

step S3: dividing the optimized adding mass of the chemical reagent of the slurry obtained in the step S2 by the yield stress tau of the slurry corresponding to the step S1_yObtaining a normalized value; or optimizing the chemical reagent addition quality of the two or more slurries obtained in the step S2 and the yield stress tau of the slurry corresponding to the step S1_yPerforming least square normal linear regression on the values to obtain a linear regression equation; other old sludge to be treated is repeatedly operated according to the step S1 to obtain the yield stress tau of the corresponding mud_yThe value of the one or more of,and calculating by using the obtained normalization value or linear regression equation to obtain the optimized addition quality of the chemical agents of other old sludge slurry to be treated.

Step S4: and (4) carrying out chemical conditioning on various old sludge according to the chemical reagent optimized addition mass combination obtained in the step S3, and also carrying out specific resistance test or plate-and-frame filter pressing dehydration to adjust the pH value of the filtrate.

The chemical conditioning is oxidation pretreatment, and the optimal addition mass of the chemical reagent comprises the addition mass of the first reagent A and the second reagent B or the mass ratio of the first reagent A to the second reagent B.

In the method provided by the embodiment of the invention, the structural network characteristics of the sludge suspension comprehensively reflect the influence rule of the reagent addition. The suspension rheology reflects the flow characteristics of the suspension. Most old sludge suspensions exhibit shear-thinning behavior, while the shear viscosity of the sample tends to be constant with increasing shear rate, with pseudoplastic fluid characteristics. The apparent viscosity of the sample is significantly related to the organic content. The yield stress represents the degree of difficulty of flow of the sludge suspension in combination, depending on the internal organic-inorganic polymer structure of the sludge, and due to the resistance of the polymer to deformation, only shear stresses greater than the yield stress are available to drive flow, which is generally considered to be related to the strength of the three-dimensional flocculent network in which the interconnections exist. The greater the difficulty of the suspension flow, the greater the resistance of the network to deformation, the more complete the network structure and the greater the degree of connection between the polymers. Therefore, more oxidizing agent is needed to mineralize soluble organics in solution beyond the polymer.

The strong oxidation reagent combination has good effect on improving the sludge dewatering property of the sedimentation tank. However, the reagent cost is high at present, the use of hydrogen peroxide is strictly controlled, and the reagent addition quantification method can be used for calculating the use amount of the reagent as accurately as possible through a small amount of tests. The existing method takes the volume molar concentration (mmol/L) of effective components in the sludge, the mass (mg/L) in unit sludge volume, the mass (mg/g DS) of solid matters relative to the sludge, the mass (mg/g VS) of organic matters relative to the sludge and the like as measuring standards, and is not a key factor influencing chemical conditioning and dehydration. The properties of old sludge are complex, and an accurate reagent economy optimization addition combination is difficult to calculate by only taking a single factor as a reference. And the rheological mechanical characteristics of the suspension comprehensively reflect the structural network characteristics of the old sludge suspension. A series of biochemical evolutions can occur to the old sludge in the landfill process, organic matter substances are gradually humified, and the difference of the properties of the old sludge is large due to the difference of landfill time and landfill conditions under the condition that the organic matter contents of the two types of old sludge are the same or close to each other. Although the relation between the sludge rheological property and the organic matter content is complex, the structural network characteristic of the suspension is comprehensively reflected, and the dosage of a quantitative reagent is more reliable by considering the rheological mechanical property.

The reagent addition quantification method and the test control technology of the invention solve the problem of insufficient applicability of old sludge chemical conditioning and overcome the technical shortages of complicated test in the early stage.

The present invention will now be described in further detail by taking as an example a chemical oxidation conditioning agent, a method of quantifying the agent addition of old sludge suspension yield stress based on key factors affecting chemical conditioning, but the present invention is not limited to the following examples. The starting materials used in the following examples are all commercially available, unless otherwise specified.

Example 1

The embodiment is a quantification method taking rheological mechanical parameters of old sludge as a reagent addition standard, and under the condition of improving the specific resistance of the old sludge to the same degree, the quantification method is compared with a quantification method taking organic matter content and dry basis content as the reagent addition standard alone, and comprises the following steps:

s1: five kinds of old municipal sludge No.1, No.5, No.2, No.8 and No.3 are selected as objects, and the water content of the collected original samples is respectively as follows: 75.71 + -0.58%, 84.53 + -0.35%, 89.46 + -0.27%, 76.24 + -0.67%, 83.25 + -0.35%. Adding water into the original sludge, stirring, and re-suspending to obtain pumpable flowing mud with water content of 93.16 +/-0.14% of the total mass of the mud. Performing old sludge suspension shear rheology test to obtain suspension yield stress tau_yValues, rheological mechanical parameter tests were performed in triplicate and averaged; see table 1.

S2: the tests of chemical conditioning and filtration response surface of No.1 and No.5 old sludge were carried out. The specific resistance of the slurry after the setting chemical conditioning is reduced to 10¹¹m/kg (belonging to easy filtration). Searching a component A (ferrous sulfate pentahydrate) and a component B (30% hydrogen peroxide) by a response surface method to chemically condition 150.00g of slurry to ensure that the specific resistance of the slurry reaches an added mass combination when the specific resistance reaches a target value, setting economic weights of the reagent A and the reagent B (belonging to specific parameter analysis on response surface test results), wherein the unit mass component B is 2.5 times of the unit mass component A, and obtaining a unique economically optimized reagent added mass combination when the specific resistance of the slurry reaches the target value, namely No.1 (B)_opt：0.68g，A_opt: 1.62g) and No.5 (B)_opt：2.03g，A_opt: 3.07 g). The mud conditioned by the combination is (1 +/-0.33) multiplied by 10¹¹m/kg, and the optimized quality combination of the reagent is verified to reach the standard.

S3: the value of the economically optimized addition quality in step S2 is related to the associated mud yield stress τ_yThe values (dimension Pa) are subjected to least squares regression linear fitting to obtain linear regression equations for calculating the reagent-optimized addition mass of other old sludge to be treated, B (y-0.3619 x +0.3339) and A (y-0.3887 x + 1.2483). Calculating the yield stress tau of other old sludge slurry to be treated by using the obtained linear regression equation_yThe value corresponds to the economically optimized addition quality. See table 2.

S4: and (4) according to the addition mass combination of the chemical reagents with optimized economy calculated in the step S3, carrying out oxidation treatment on the old sludge to be treated, then carrying out specific resistance test, and testing the pH value of the filtrate, wherein the results are shown in Table 2.

Meanwhile, in order to calculate the conditioning effect of the reagent by comparing different measurement standards, a linear regression equation is established by using the addition amount of two old sludge reagents obtained by S2 and the organic matter content VS/TS and the dry basis weight TS of the sludge: regression equation parameters for reagent addition based on VS/TS (% dimension): b (y-0.0687 x-1.0707), a (y-0.0738 x-0.2604); regression equation parameters for reagent addition based on TS (% dimension): b (y ═ 7.5x-48.520), a (y ═ 8.056 x-51.224). The method is applied to calculating the addition amounts of other three sludge reagents to be measured and comparing the specific resistance of the chemically conditioned slurry, and is shown in Table 2.

It can be seen that the use of a base yield stress τ_yAfter chemically conditioning the slurry with the addition of the reagent at the value, the specific resistance value had dropped to 10¹¹m/kg, belongs to easy filtration and achieves the conditioning target. And the addition amounts of the TS and VS/TS based on the sludge are higher than those of the former reagent, so that the waste of unnecessary reagents is caused, and the reagent use cost is increased. It is noted that the organic matter content of the No.8 and No.3 samples is relatively close, if the reagent is added on the basis of VS/TS, the reagent amount needed to be added for the two types of old sludge is close, and the samples are based on the yield stress tau_yThe reagent is added on the basis of the value, and under the condition of improving the specific resistance to the same degree, the amount of the reagent B required for conditioning No.8 old sludge is 78.3 percent of the amount of the reagent B required for conditioning No. 3. The reason is that sample No.8 has a lower yield stress than sample No.3, and the degree of linkage between the suspension polymers is lower, and the flow is easier. Therefore, even under the condition that the organic matter content is close, the sample No.8 can reduce the specific resistance to the same degree only by the conditioning of a smaller amount of reagent than the sample No. 3. Therefore, based on the yield stress τ_yThe reagent addition quantification method based on the value can adapt to old sludge with more complex and variable physicochemical properties, the obtained reagent addition combination is optimized economically under the condition of simplifying test procedures, the reagent addition quantification method achieves the technical effect which cannot be achieved by other methods, and the adaptability is superior to that of other methods.

TABLE 1

TABLE 2

Example 2:

the embodiment is a quantification method based on old sludge suspension yield stress as a reagent addition standard, and when old sludge with different physical and chemical properties is treated, the influence of a test program of a previous response surface on reagent amount prediction is considered, and the method comprises the following steps:

s1: five kinds of old municipal sludge No.1, No.5, No.2, No.8 and No.3 are selected as objects, the original sludge is added with water and stirred, and the sludge is re-suspended into pumpable flowing state sludge with the water content of 93.16 +/-0.14 percent of the total mass of the sludge. Performing old sludge suspension shear rheology test to obtain suspension yield stress tau_yValues, rheological mechanical parameters were measured in triplicate and averaged. See table 1.

S2: and carrying out tests on the chemical conditioning and filtration response surfaces of No.1, No.5, No.2, No.8 and No.3 old sludge. The specific resistance of the slurry after the setting chemical conditioning is reduced to 10¹¹m/kg (belonging to easy filtration). Searching a component A (ferrous sulfate pentahydrate) and a component B (30% hydrogen peroxide) through a response surface method, chemically conditioning 150.00g of slurry to ensure that the specific resistance of the slurry reaches a target value, adding a mass combination, setting an economic weight, wherein the unit mass component B is 2.5 times of the unit mass component A, and obtaining a unique economically optimized reagent added mass combination B when the specific resistance of the slurry reaches the target value_optAnd A_optThe results are shown in Table 3. Repeated tests prove that the specific resistance of the conditioning slurry can reach the standard according to the optimized addition quality combination of the reagent.

S3: converting the economically optimized value of the additive mass resulting from No.1 in step S2 to the corresponding mud yield stress τ_yIs normalizedChanging the value: b: 0.71, A: 1.69. the value is used for calculating the reagent addition amount of other old sludge slurry to be treated, and the reagent addition amount is compared with the reagent addition amount which is directly obtained by response surface tests of other old sludge and is optimized in economy. See table 3.

S4: according to the addition mass combination of the chemical reagent with the optimized economical efficiency obtained by the response surface test of the step S2 and the Fenton reagent addition mass combination obtained by the normalization calculation of the step S3, the old sludge to be treated is oxidized and then is subjected to the specific resistance test, and the result shows that the specific resistance of all samples is improved to 10¹¹m/kg or less.

Table 3 shows the amounts of other old sludge agents added B and A calculated using one old sludge No.1 response surface test result, and the calculated result and the response surface test result B are shown_optAnd A_optThe difference in (a). Table 4 shows the amounts of other old sludge agents calculated by the linear regression equation used in example 1, and also shows the results of calculation and the results of response surface test B_optAnd A_optThe difference in (a). It can be seen that the actual addition amount calculated by using the regression equation and the actual response surface result B_optAnd A_optThe difference in (a) is reduced. Therefore, the addition amount can be calculated by using a response surface test result of old sludge during rapid evaluation, and more than two groups of response surface tests can be performed when the technical scheme is perfected. This embodiment is based on the yield stress τ_yThe reagent addition quantification method based on the value can adapt to the evaluation of technical schemes in different stages, and can achieve corresponding technical effects under the conditions of simplifying test procedures and ensuring accuracy.

TABLE 3

TABLE 4

Example 3:

the embodiment adopts a quantification method with old sludge slurry rheological mechanical parameters as a reagent addition standard to treat old sludge with close physical and chemical properties and obtain the effect verification that the reagent addition is used for treating the old sludge, and the method comprises the following steps:

s1: selecting objects of old municipal sludge A1 and A2, and collecting original sludge with water content of 83.21 +/-0.38% and 84.57 +/-0.29%. Adding water into the original sludge, stirring, and re-suspending to obtain pumpable flowing mud with water content of 93.16 +/-0.14% of the total mass of the mud. Performing shear rheological test on old sludge suspension, averaging the three tests to obtain the yield stress tau of the suspension_y1.52. + -. 0.13Pa and 1.47. + -. 0.15 Pa.

S2: a1 old sludge chemical conditioning filtration and response surface test is carried out. The specific resistance of the slurry after the setting chemical conditioning is reduced to 10¹¹m/kg (belonging to easy filtration). Searching a component A (ferrous sulfate pentahydrate) and a component B (30% hydrogen peroxide) through a response surface method, chemically conditioning 150.00g of slurry to ensure that the specific resistance of the slurry reaches a mass combination when the specific resistance reaches a target value, and setting an economic weight, wherein the unit mass component B is 2.5 times of the unit mass component A to obtain a unique economically optimized reagent addition mass combination when the specific resistance of the slurry reaches the target value, (B)_opt：0.71g，A_opt: 1.34 g). The slurry conditioned by the combination is (9.89 +/-1.33) multiplied by 10¹⁰m/kg, and the combination verification reaches the standard.

S3: converting the economically optimized value of the added mass of A1 in step S2 to the corresponding slurry τ_yNormalized value of (a): b: 0.47, A: 0.88. using derived normalized τ_yAnd calculating the addition mass of the A2 old sludge suspension reagent as B: 0.69g, A: 1.29 g.

S4: according to the addition quality combination of Fenton' S reagent with optimized economical efficiency calculated in step S3, the old sludge to be treated is oxidized,the specific resistance after conditioning is (9.97 +/-1.21) multiplied by 10¹⁰m/kg, reaching the conditioning target.

The above examples show that chemical conditioning can be well adapted to old sludge with complex physicochemical properties under the quantification method based on old slurry yield stress of the invention, and under the condition of simplified test procedures, the obtained reagent addition combination is economically optimized, thereby breaking through the limitation that the chemical conditioning method is only suitable for part of fresh sludge and has good conditioning effect, and avoiding improper reagent addition amount design possibly caused by conditioning old sludge with different properties. Meanwhile, the method can adapt to the evaluation of technical schemes in different stages, in reagent engineering, test procedures are selected according to working stages, time and workload are saved, reagent addition amount combinations can be searched efficiently, stably and gradually, and test efficiency is greatly improved. The chemical reagent input cost can be evaluated through a small number of gradual tests in the early stage of engineering, and support is provided for comprehensively formulating a chemical conditioning and dehydration process scheme.

The response surface method in the invention can be directly referred to the related prior art, such as the related contents on the monograph of Liyun swallow and Hu Ying editions of Experimental design and data processing. The technical details of the present invention, such as adding water to re-suspend the old sludge, can be referred to the relevant contents of Tan et al in Separation and Purification Technology (2020, (237), 116317). The measurement of the organic matter content of the old sludge can be measured by referring to the standard method for measuring the organic matter content of the solid waste in HJ 761-2015 of the national environmental protection standard in China. The steady-state rheological mechanical test of the old sludge slurry can be carried out by referring to the general rule of the measuring method of the JY/T0590-2020 rotational rheometer in the education industry standard of the people's republic of China.

It is obvious that the above-mentioned embodiments of the present invention are only examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention, and that various other modifications and variations can be made by those skilled in the art based on the above description.

Claims

1. A chemical reagent adding quantification method for improving the dewatering property of old sludge is characterized in that: the method comprises the following steps:

1) adding water into at least one old sludge, stirring, and suspending to obtain slurry in a pumpable flowing state; performing steady-state rheological mechanical shear test on the slurry, and performing Herschel-Bulkley equation fitting on the obtained rheological curve data to obtain the yield stress tau of different slurries_yA value;

2) performing at least one old sludge chemical conditioning and filtration response surface test: setting the target specific resistance of the chemically conditioned slurry to be an acceptable value according to the requirement of filtering difficulty, adding a chemical reagent into the slurry in the step 1) for conditioning, measuring the specific resistance, searching the optimal addition mass combination of the chemical reagent when the chemically conditioned slurry meets the acceptable value of the specific resistance by a response surface method, and taking the yield stress tau of the slurry as the optimal addition mass combination_ySelecting a response surface test central point for reference; the chemical reagents comprise a first reagent A and a second reagent B;

2. The chemical reagent addition quantification method according to claim 1, characterized in that: in step 1), the slurry obtained by suspension has a water content sufficient to make the slurry in a pumpable flowing state.

3. Root of herbaceous plantThe chemical agent addition quantification method according to claim 1 or 2, characterized in that: the content VS/TS of the old sludge re-suspended slurry with the water content accounting for 93.16 +/-0.14 percent of the total mass is 10 to 50 percent, and the yield stress tau_yIs 0.01 to 5.00 Pa.

4. The chemical reagent addition quantification method according to claim 1 or 2, characterized in that: in the step 1), before a steady-state rheological mechanical shear test, premixing 150mL of sludge suspension for 15-20 minutes at a stirring speed of 150 rpm.

5. The chemical reagent addition quantification method according to any one of claims 1 to 4, characterized in that: in the step 2), the chemical conditioning is oxidation pretreatment, and the optimized addition mass of the chemical reagent comprises the addition mass of the first reagent A and the second reagent B or the mass ratio of the first reagent A to the second reagent B.

6. The chemical reagent addition quantification method according to claim 5, characterized in that: the first reagent A is a catalytic substance which is selected from at least one of ferrous sulfate pentahydrate, iron powder, zero-valent iron or nano zero-valent iron or a mixture thereof, and the second reagent B is a free radical generator which is selected from at least one of hydrogen peroxide, sodium peroxide, calcium peroxide, persulfate and percarbonate or a mixture thereof.

7. The chemical reagent addition quantification method according to any one of claims 1 to 6, characterized in that: in the step 2), when a chemical conditioning and filtration response surface test of old sludge is carried out, dividing the optimized adding mass of the chemical reagent of the slurry obtained in the step 2) by the tau of the slurry corresponding to the step 1)_yAnd obtaining a normalized value.

8. The chemical reagent addition quantification method according to any one of claims 1 to 7, characterized in that: in the step 2), when chemical conditioning and filtration response surface tests of at least two old sludges are carried out, the sludge obtained in the step 2) is subjected toOptimizing the adding quality of chemical reagents of at least two kinds of mud and tau of mud corresponding to the step 1)_yAnd performing least square normal linear regression on the values to obtain a linear regression equation.

9. The chemical agent addition quantification method according to any one of claims 7, characterized in that: in the step 3), various old sludge is added with water and suspended to a pumpable flowing state, and then the water content of the old sludge is the same.

10. The chemical reagent addition quantification method according to any one of claims 1 to 9, characterized in that: further comprising step 4): chemically conditioning various old sludge according to the addition amount combination of the chemical reagents obtained in the step 3), and performing specific resistance test or plate-and-frame filter pressing dehydration; adding lime or sulfuric acid into the filtrate with the pH value exceeding the range of 6.5-8.5 after filter pressing and dehydration by using a plate frame to ensure that the pH value of the filtrate is in the range of 6.5-8.5; and carrying out conventional solid-liquid separation on the insoluble precipitate in the filtrate, mixing the insoluble precipitate into the sludge cake, and then carrying out subsequent solid waste disposal.