Study on Dynamic Sedimentation of Sludge
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Based on static sedimentation of sludge, the experimental instrument was improved to simulate dynamic sedimentation of sludge. Results showed that the sludge has good concentration effects when uplifted velocity in sedimentation tube is no more than 5m/h, which has some significance on the design of secondary sedimentation tank and wastewater treatment plants.Keywords:
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The effect of magnetic treatment for municipal sludge of the big MLSS on sedimentation was researched.Based on planning the magnetic experiment of seven different experimental conditions,the effect of magnetic treatment with three different degrees of density was investigated by using hypothesis-test theory to check the data of Sedimentation in the magnetic field.According to the collected hypothesis-test data,it can be assured that the effect of sedimentation for municipal sludge can be improved and the result shows that the parallel magnetic is better than the vertical magnetic,in the parallel magnetic the density is bigger and the effect is better.
Sedimentation
Statistic
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The influence of acid treatment and magnetic treatment on sedimentation performance of activated sludge in wastewater treatment plant was studied. Through the analysis of the curves of the sludge sedimentation under different pH, the observation of the microcosmic photos and the investigation of the performance of centrifugal dewatering, the sedimentation performance of the sludge when the pH was 4 was found to be the best, and the best centrifugal dewatering was obtained under 2000 r/min in 10 min; the differences between the sludge sedimentation curves of the two groups of MLSS sludge under different magnetic field intensity and different magnetic field direction, and the microcosmic photos of the granular sludge before and after the magnetization were compared, which finally got the conclusion that magnetic field could certainly improve the sedimentation performance of the sludge.
Sedimentation
Dewatering
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While sludge settles down in a batch column, sludge concentration becomes high. Sludge concentration change is one of the most critical causes of the sludge settling velocity variation. Therefore, sludge concentration change causes sludge index to change. SVI is more sensitive than other sludge indexes to the change of sludge concentration. And if sludge-water interface has reached final height within 30minutes, SVI is not suitable for prediction of sludge settling characteristic, Therefore, SVIs of each sludge are, in some cases, different although each sludge has the same settling velocity. But SVI has been widely used to interpret sludge settling characteristic by a simple testing method. This work has two purposes. The first purpose is to predict sludge settling velocity by using sludge-water interface settling velocity. And the second purpose is to develop new sludge settling characteristic index to exactly interpret sludge settling characteristic by overcoming the limit of SVI.
Settling
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Sedimentation
Settling
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Activated sludge is one of the best investigated and understood suspensions. But up to now we still lack the factors influencing the sedimentation velocities concerning the main sludge characteristics/properties to describe the settleability of different sludges. Different in terms of SVI, organic loading, sludge retention time, composition, content of polymers, iron or aluminium, density, porosity and particle size distribution. But for the design of clarifiers most of these parameters are disregarded, of none importance or neglectable. With the help of PSD and particle shape analysis we can improve our knowledge of the settleability of activated sludge flocs. The measurements, done with the CIS show the influence of the differential sedimentation in comparison to the effluent of the secondary clarifiers under different conditions. Calculating the sedimentation velocities, the behaviour of activated and precipitated sludge could be explained and conclusions can be drawn to optimize the solid flux in secondary clarifiers.
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While sludge is settling in batch column, sludge concentration becomes high. Because the characteristic of sludge settling changes in function of time due to the sludge concentration change, the sludge settling velocity changes too. Also, because the sludge settling characteristic is influenced by a physical characteristic of sludge and a column height etc, it is difficult to exactly measure the sludge settling characteristic. Although the sludge volume indexes, SVI, SSVI and , are used to predict sludge settling characteristic, these indexes are not reliable values. Because the previously established models for sludge settling velocity predict the sludge settling velocity only, it is difficult to predict sluge-water interface height by using those models. The purpose of this experiment is to establish the empirical model which predicts the sludge interface height change with respect to the sludge physical characteristic and the settling condition.
Settling
Decantation
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Sedimentation
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Sedimentation
Suspension
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For the further study of the solids flux theory, several researchers have proposed models to predict sludge settling velocity for each different concentration by using sludge indexes, SVI, SSVI and . It is difficult to apply the above models to predict sludge-water interface height in a batch column because sludge settling velocity changes while sludge settle down. While sludge settle down in a batch column, sludge concentration becomes high. The sludge concentration change is one of the most critical causes of the change of sludge settling velocity. Also, sludge concentration change causes of sludge index to change. SVI is more sensitive than SSVI or to the change of sludge concentration. Each sludge has physical characteristics of its own which makes the settling velocity for each sludge different. The purpose of this study is to establish the correction factors that are able to compensate the errors derived from each different sludge settling characteristic by using sludge indexes, therefore the correction factors are applicable to the model for the change of sludge-water interface height.
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We compared the catalytic effects of two polymers (soluble starch and apple pectin) on the flocculation of kaolinite suspension. Moreover, the relationship between the zeta potential value and the time when kaolin particle sedimentation occurred was verified, and the mechanism of flocculation was analyzed. Additionally, a constitutive model was proposed to simulate the non-ideal sedimentation of clay particles in an aqueous system under constant gravity. This model not only considers the inhomogeneity of the solute but also simulates the change in clay concentration with time during the deposition process. This model proposes a decay constant (α) and sedimentation coefficient (s). The model can also be used to calculate the instantaneous sedimentation rate of the clay suspensions at any time and any depth for the settling cylinder. These sedimentary characteristics were simulated by adopting the established deposition model. The results show that the model is capable of predicting the time required for the complete sedimentation of particles in the aqueous system, suggesting the feasibility of engineering wastewater treatment, site dredging, etc.
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Settling
Suspension
Deposition
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