Innovative Enhancement of the Design and Precision of the Capillary Suction Time Testing Device

Scholz, Miklas

doi:10.2175/106143009x407276

Cited by 10 publications

(9 citation statements)

References 25 publications

(48 reference statements)

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“…After 30 min of sedimentation, followed by decantation, 25.0 cm 3 of separated sludge was collected in order to determine capillary suction time CST [21][22][23], which is a measurement of the dewaterability of sludge. In CST measurements, a new prototype developed in the University of Warmia and Mazury in Olsztyn, Poland (DWTEST-Dewatering tester, schematically illustrated in Figure 1), was used.…”

Section: Methodsmentioning

confidence: 99%

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Study of Sludge Particles Formed during Coagulation of Synthetic and Municipal Wastewater for Increasing the Sludge Dewatering Efficiency

Smoczyński

Kalinowski

Creţescu

et al. 2019

Water

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Municipal wastewater sludge was produced by chemical coagulation of synthetic wastewater (sww) based on Synthene Scarlet P3GL disperse dye and real municipal wastewater (nww), coagulated by commercial coagulants PAX (prepolymerised aluminum coagulant) and PIX (a ferric coagulant based on Fe2(SO4)3). An attempt was made to correlate the sludge’s dewatering capacity (in terms of capillary suction time—CST) with operation parameters for wastewater treatment, size distribution and specific surface area of the sludge particles. It was found that the presence of phosphate ions in the system facilitates the removal efficiency of the above-mentioned dye (L) due to the interaction between the dye molecules and H2PO4− ions. Unlike sww, negatively charged organic substances (sorg) in nww are directly adsorbed on the surface of colloidal particles {Fe(OH)3} and {Al(OH)3} (prtc). It was also discovered that an increase in the dose of a coagulant led to an increase of CST for sww sludge and to a decrease of CST for nww sludge. It has been suggested that flocs composed of spherical {Al(OH)3} units possessed more internal space for water than aggregates consisting of rod-shaped {Fe(OH)3} units and, consequently, it is more difficult to remove water from Al-sww sludge than from Fe-sww. The results obtained showed that smaller particles dominate in sww sludge, while larger particles are prevalent in nww sludge. To explain this distinct difference in the size distribution of particles in sludge obtained with the use of Al3+ and Fe3+, simple models of aggregation and agglomeration-flocculation processes (aaf) of treated wastewater have been proposed. Except for PIX in nww, the analyzed particles of the investigated types of sludge were characterized by similar specific surface area (Sps), regardless of the kind of sludge or the applied coagulant. Slightly larger, negatively-charged sorg bridges, anchored directly on the surface of positive prtc are more effective in closing the structure of nww sludge than small L bridges of the dye molecules anchored on the surface of prtc via H2PO4−. All the discovered aspects could lead to improved performance of wastewater treatment plants (WWTP) by increasing the efficiency of sludge dewatering.

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Section: Methodsmentioning

confidence: 99%

“…Under laboratory conditions, so-called capillary suction time (CST) is a measure of the sludge's dewatering capacity [21]. Reproducibility and precision of CST measurements [22,23] are important, both for theoretical considerations [24] and in practice, e.g., for determination of an appropriate dose of an inorganic flocculant [25].…”

Section: Introductionmentioning

confidence: 99%

Study of Sludge Particles Formed during Coagulation of Synthetic and Municipal Wastewater for Increasing the Sludge Dewatering Efficiency

Smoczyński

Kalinowski

Creţescu

et al. 2019

Water

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“…Different methods to estimate how easy it is to dewater sludge are available: CST, specific resistance to filtration [12], conditioned filtrate, filtrate total solids and streaming current [13]. The most commonly used method is currently the CST test, which has been proven to be cost-effective, rapid and simple-toexecute [10,11,14,15]. The standard test provides only one value per experiment.…”

Section: Dewatering Testsmentioning

confidence: 99%

Highlights of the novel dewaterability estimation test (DET) device

Scholz

Almuktar

Clausner

et al. 2019

Environmental Technology

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Many industries, which are producing sludge in large quantities, depend on sludge dewatering technology to reduce the corresponding water content. A key design parameter for dewatering equipment is the capillary suction time (CST) test, which has, however, several scientific flaws, despite that the test is practical and easy-to-perform. The standard CST test has a few considerable drawbacks: its lack of reliability and difficulties in obtaining results for heavy sludge types. Furthermore, it is not designed for long experiments (e.g. >30 min), and has only two measurement points (its two electrodes). In comparison, the novel dewaterability estimation test (DET) test is almost as simple as the CST, but considerably more reliable, faster, flexible and informative in terms of the wealth of visual measurement data collected with modern image analysis software. The standard deviations associated with repeated measurements for the same sludge is lower for the DET than for the CST test. In contrast to the CST device, capillary suction in the DET test is linear and not radial, allowing for a straightforward interpretation of findings. The new DET device may replace the CST test in the sludge-producing industries in the future.

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“…The key measure of efficiency with respect to the sludge dewatering process is traditionally the CST test value [20,21]. The capillary suction pressure generated by a filter paper is used to suck liquid from the sludge sample.…”

Section: Dewaterability Testsmentioning

confidence: 99%

“…This might be explained by the more likely presence of naturally developing microorganisms within synthetic domestic wastewater compared to the synthetic raw water. The presence of any microorganism is associated with a relatively large area and a higher viscosity [21], ultimately impacting on the floc size distribution and CST value.…”

Section: Floc Size Distribution In Synthetic Domestic Wastewatermentioning

confidence: 99%

Impact of Sludge Floc Size and Water Composition on Dewaterability

et al. 2014

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In order to observe the impact of different water compositions on sludge dewaterability, assessments of floc sizes using a particle size analyzer and of sludge dewaterability based on the capillary suction time (CST) test were carried out. Synthetic raw water had small floc sizes, and synthetic domestic wastewater had both larger median floc sizes and a better correlation between sludge dewaterability and median floc sizes. The floc size distribution results showed that synthetic raw water is associated with a narrow particle size distribution. In comparison, synthetic domestic wastewater produced a wider distribution. However, the CST values were similar for both waters. Compared to synthetic wastewater, natural wastewater had the largest distribution with generally larger particle sizes.

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Innovative Enhancement of the Design and Precision of the Capillary Suction Time Testing Device

Cited by 10 publications

References 25 publications

Study of Sludge Particles Formed during Coagulation of Synthetic and Municipal Wastewater for Increasing the Sludge Dewatering Efficiency

Study of Sludge Particles Formed during Coagulation of Synthetic and Municipal Wastewater for Increasing the Sludge Dewatering Efficiency

Highlights of the novel dewaterability estimation test (DET) device

Impact of Sludge Floc Size and Water Composition on Dewaterability

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