CN111537553A - Method for rapidly determining free water ratio of floc sludge and granular sludge - Google Patents
Method for rapidly determining free water ratio of floc sludge and granular sludge Download PDFInfo
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- CN111537553A CN111537553A CN202010193015.XA CN202010193015A CN111537553A CN 111537553 A CN111537553 A CN 111537553A CN 202010193015 A CN202010193015 A CN 202010193015A CN 111537553 A CN111537553 A CN 111537553A
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Abstract
The invention discloses a method for rapidly determining the free water ratio of floc sludge and granular sludge, which can better analyze the sedimentation performance of the floc sludge and the granular sludge and the sludge-water separation characteristic of residual sludge by determining the free water ratio and belongs to the field of sewage treatment and sludge treatment. The method comprises the following steps: (1) pretreating a sludge sample; (2) testing free water; (3) testing with pure water; (4) and (4) calculating. The method is simple and convenient to operate, and a Differential Scanning Calorimeter (DSC) is utilized to test the ratio of the melting enthalpy change of free water to the evaporation enthalpy change of pure water of a sludge sample to be tested in the temperature rising process, namely the free water ratio of the sludge.
Description
Technical Field
The invention relates to a method for rapidly determining the free water ratio of floc sludge to granular sludge, belonging to the field of sewage treatment and sludge treatment.
Background
At present, the composition analysis of water in sludge has two division bases, one is divided into free water and bound water; the other method further subdivides the combined water in the sludge into capillary water, surface water and intracellular-hydration water. In both division methods, the concept of sludge free water is quite clear, free water surrounded by large and small sludge flocs or particles, which are not directly bound to sludge solids, is relatively easy to separate. At present, the research is more uniform in defining the free water (unbound water) in the sludge, namely the water which can be directly removed completely or partially by a mechanical method. The active sludge method is the current mainstream biological sewage treatment process, the aerobic granular sludge technology is a novel biological sewage treatment technology, the active main body in the process is floc sludge or granular sludge, the free water content of the floc sludge or granular sludge accounts for more than 95% of the total water content, and the floc sludge or granular sludge is a main factor influencing the microorganism aggregation form and the sludge-water separation effect. At present, a great deal of research is still staying in the aspect of analysis of sludge sedimentation performance indexes, and the determination method of sludge-bound water is few and has great limitation. The drying method has long experimental time, and the phenomena of contraction, cracking and the like of the sludge in the drying process cause surface area change to influence water evaporation; the suction filtration method and the filter pressing method cannot remove the water by mechanical force because of small amount of free water, thereby influencing the measurement result; the water activity method is relatively complex in determination and difficult to be practically applied; dilatometry is not suitable for sludge with water content higher than 97%. Therefore, it is necessary to develop a method for rapidly measuring the free water content of sludge, aiming at the problem that the conventional method for measuring the free water content of sludge is not good. In addition, the content of free water in the sludge entering the sludge dewatering link generally accounts for 65-85% of the total water content, and free water is mainly removed through dewatering and can be achieved through plate-and-frame filter pressing, centrifugation and other mechanical modes. The water content of the sludge in the return sludge of the sewage treatment plant is usually more than 99 percent, and the existing dehydration process mainly adopts mechanical dehydration, so that the accurate determination of the free water content is very important for sludge-water separation and subsequent treatment processes.
Disclosure of Invention
The invention provides a method for rapidly determining the ratio of floc sludge to granular sludge free water, which comprises the steps of determining the heat required by the free water melting in the heating process of a sludge sample to be determined by a Differential Scanning Calorimeter (DSC), obtaining the peak area in a thermogram, namely the enthalpy change of the free water in the sludge sample, and calculating the ratio of the enthalpy change to the standard evaporation enthalpy of pure water to obtain the ratio of the sludge free water.
A method for rapidly determining the free water ratio of floc sludge and granular sludge comprises the following steps of (1) pretreating a sludge sample; (2) testing for free water; (3) carrying out comparison test on pure water; (4) and (3) calculating: the method comprises the steps of taking a certain volume of sludge-water mixed liquor, removing supernatant after a certain time of precipitation, weighing a certain volume of precipitated sludge in a crucible, and testing the ratio of the melting enthalpy change of free water to the evaporation enthalpy change of pure water in the temperature rising process of a sludge sample to be tested by DSC, namely the sludge free water ratio.
The technical scheme adopted by the invention is as follows:
a method for rapidly determining the free water ratio of floc sludge and granular sludge comprises the following steps:
step 1: taking a sludge-water mixture of floc sludge or granular sludge from the reactor, standing for precipitation, removing supernatant after sludge and water are fully separated, and taking the precipitated sludge as a sample to be detected;
step 2: quantitatively weighing a completely and uniformly mixed sample to be tested, placing the sample to be tested in a crucible and on a test board of a differential scanning calorimeter, refrigerating the differential scanning calorimeter to-20 ℃, then gradually heating to 10 ℃, and completing a differential scanning calorimetry test to obtain a peak area in a thermogram, namely an enthalpy change H of free water melting in the sludge sample, wherein the unit is J/g;
and step 3: quantitatively weighing pure water as a comparison sample, and testing according to the same differential scanning calorimetry as that in the step 2 to obtain the enthalpy change H of pure water evaporation0The unit is J/g;
and 4, step 4: calculating to obtain the proportion of free water in the sludge sample
Based on the scheme, the following preferred schemes can be adopted for parameters and materials in each step:
preferably, the standing and precipitating time of the mud-water mixture in the step 1 is 30 min.
Preferably, the weighed mass of the sample to be detected in the step 2 is 15-30 mg. Too much sample will reduce the sensitivity of the instrument, and too low sample will cause measurement error, therefore, further, the weighing mass of the sample to be measured in step 2 is preferably about 20 mg.
Preferably, the temperature increase rate in step 2 is 2 ℃/min.
Preferably, the weighed mass of the pure water in the step 3 is 15-30 mg.
Compared with the prior art, the invention has the following beneficial effects:
the invention provides a method for rapidly determining the free water ratio of floc sludge and granular sludge, which utilizes a differential scanning calorimeter DSC to test the ratio of the melting enthalpy change of free water to the evaporation enthalpy change of pure water of a sludge sample to be tested in the temperature rising process, namely the free water ratio of the sludge. The method provided by the invention is simple and convenient to operate, and is beneficial to researching the sedimentation performance and sludge-water separation effect of floc sludge or granular sludge.
Drawings
FIG. 1 is a flow chart of a method for rapidly determining the ratio of free water of floc sludge to free water of granular sludge.
FIG. 2 is a thermogram spectrum of one of the sludge samples tested in step 2 of the example.
Detailed Description
The invention will be further elucidated and described with reference to the drawings and specific embodiments.
Examples
As shown in fig. 1, the purpose of this example is to determine the free water fraction in granular sludge, specifically according to the following steps:
step 1, sample pretreatment
Three sludge-water mixed samples (parallel samples) with the volume of 100mL are taken from the aerobic granular sludge reactor, standing and precipitating are respectively carried out for 30min, sludge and water are separated, the sludge sample from which the supernatant is removed is used as a sample to be detected of a subsequent DSC, and therefore the density of the sample is ensured to be constant.
And accurately weighing three completely and uniformly mixed sludge samples to be detected, which are obtained after precipitation in the step 1, wherein the mass of each sample is 21.5600mg, 24.9600mg and 21.1600 mg. Respectively testing each sludge sample to be tested:
the sample is first placed in a crucible and then placed on the DSC's test stand along with the crucible. And (3) refrigerating the DSC to-20 ℃, heating to 10 ℃ at the speed of 2 ℃/min, carrying out differential scanning calorimetry test in the process, and obtaining a thermogram after the test is finished, wherein the thermogram of one sample is shown in figure 2. As the threshold temperature is adopted in the research, the temperature is minus 20 ℃, only free water in the sludge sample is frozen, and bound water is not frozen. Therefore, from the thermodynamic point of view, only free water in the sludge sample has the heat of vaporization in the temperature rise range from-20 ℃ to 10 ℃, and the change of the heat quantity of the bound water is negligible. The melting range of ice is mainly 3-10 ℃, the temperature rise rate is 2 ℃/min, the temperature change of the free water peak value in the experiment is generally 3-6 ℃, and the temperature change is consistent with the melting temperature range of ice. Therefore, the peak area is calculated from the obtained thermogram spectrum, namely the enthalpy change H of the molten free water in the sample, and the enthalpy changes of the three parallel samples are respectively H in the embodiment1＝-319.33(J/g)、H2＝-317.34(J/g)、H3＝-316.79(J/g)。
Step 3, comparison test of pure water
Taking pure water with the mass of 24.6700mg as a comparison sample to replace the sludge sample in the step 2, placing the pure water in a crucible, and carrying out differential scanning calorimetry test in the step 2, wherein the operation conditions are consistent with the operation in the step 2, and the peak area in the obtained thermogram is the enthalpy change H of pure water evaporation0. In this example, the enthalpy change H of pure water evaporation0＝-336.59(J/g)。
And 4, step 4: calculation of free water fraction in sludge samples
According to the data obtained in the steps 2 and 3, countingCalculating the free water ratio W (%) in the sludge sample, wherein the calculation formula is as follows:
the free water ratios of the three parallel samples of this example were:
the free water ratio of three parallel samples is averaged to obtain the free water ratio of an aerobic granular sludge sample in the reactor as
Of course, the sludge targeted in this example is granular sludge, but it is equally applicable to floc sludge. Therefore, the method can better analyze the sedimentation performance of floc sludge and granular sludge in the reactor and the mud-water separation characteristic of residual sludge through the determination of the free water ratio in the reactor, is beneficial to researching the sedimentation performance of sludge and the mud-water separation effect under different process conditions, and provides guidance for the design of the reactor or the design of a sewage treatment process.
The above-described embodiments are merely preferred embodiments of the present invention, which should not be construed as limiting the invention. Various changes and modifications may be made by one of ordinary skill in the pertinent art without departing from the spirit and scope of the present invention. Therefore, the technical scheme obtained by adopting the mode of equivalent replacement or equivalent transformation is within the protection scope of the invention.
Claims (6)
1. A method for rapidly determining the free water ratio of floc sludge and granular sludge is characterized by comprising the following steps:
step 1: taking a sludge-water mixture of floc sludge or granular sludge from the reactor, standing for precipitation, removing supernatant after sludge and water are fully separated, and taking the precipitated sludge as a sample to be detected;
step 2: quantitatively weighing a completely and uniformly mixed sample to be tested, placing the sample to be tested in a crucible and on a test board of a differential scanning calorimeter, refrigerating the differential scanning calorimeter to-20 ℃, then gradually heating to 10 ℃, and completing a differential scanning calorimetry test to obtain a peak area in a thermogram, namely an enthalpy change H of free water melting in the sludge sample, wherein the unit is J/g;
and step 3: quantitatively weighing pure water as a comparison sample, and testing according to the same differential scanning calorimetry as that in the step 2 to obtain the enthalpy change H of pure water evaporation0The unit is J/g;
and 4, step 4: calculating to obtain the proportion of free water in the sludge sample
2. The method for rapidly determining the ratio of free water of floc sludge to free water of granular sludge as claimed in claim 1, wherein the standing and settling time of the sludge-water mixture in step 1 is 30 min.
3. The method for rapidly determining the ratio of floc sludge to free water in granular sludge according to claim 1, wherein the sample to be measured in step 2 is weighed to be 15-30 mg.
4. The method for rapidly determining the ratio of floc sludge to free water in granular sludge according to claim 3, wherein the sample to be tested in step 2 is preferably 20mg in weight.
5. The method for rapidly determining the ratio of floc sludge to free water in granular sludge according to claim 1, wherein the temperature rise rate in step 2 is 2 ℃/min.
6. The method for rapidly determining the ratio of the free water of the floc sludge to the free water of the granular sludge as claimed in claim 1, wherein the weighed mass of the pure water in the step 3 is 15-30 mg.
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Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104155338A (en) * | 2014-09-01 | 2014-11-19 | 北京石油化工学院 | Method for measuring bound water content in sludge |
| CN104655675A (en) * | 2015-02-12 | 2015-05-27 | 北京市农林科学院 | Method for rapidly measuring content of unbound water |
| CN108562513A (en) * | 2018-07-13 | 2018-09-21 | 天津科技大学 | Different shape moisture measuring device in a kind of sludge |
| CN109725022A (en) * | 2018-12-27 | 2019-05-07 | 湖南科技大学 | A kind of method for fast measuring of combination water content |
| CN110174437A (en) * | 2019-07-04 | 2019-08-27 | 云南中烟工业有限责任公司 | A method of nicotine content in tobacco juice for electronic smoke is quickly measured according to differential scanning calorimetry heat enthalpy value |
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- 2020-03-18 CN CN202010193015.XA patent/CN111537553A/en active Pending
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104155338A (en) * | 2014-09-01 | 2014-11-19 | 北京石油化工学院 | Method for measuring bound water content in sludge |
| CN104655675A (en) * | 2015-02-12 | 2015-05-27 | 北京市农林科学院 | Method for rapidly measuring content of unbound water |
| CN108562513A (en) * | 2018-07-13 | 2018-09-21 | 天津科技大学 | Different shape moisture measuring device in a kind of sludge |
| CN109725022A (en) * | 2018-12-27 | 2019-05-07 | 湖南科技大学 | A kind of method for fast measuring of combination water content |
| CN110174437A (en) * | 2019-07-04 | 2019-08-27 | 云南中烟工业有限责任公司 | A method of nicotine content in tobacco juice for electronic smoke is quickly measured according to differential scanning calorimetry heat enthalpy value |
Non-Patent Citations (1)
| Title |
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| DONG-QIN HE 等: "A Fenton-like process for the enhanced activated sludge dewatering", 《CHEMICAL ENGINEERING JOURNAL》 * |
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Application publication date: 20200814 |