Freeze–thaw combined with activated carbon improves electrochemical dewaterability of sludge: Analysis of sludge floc structure and dewatering mechanism

2021 ◽  
Author(s):  
Kai Hui ◽  
Lei Song ◽  
Zhenzhou Yin ◽  
Hongwei Song ◽  
Zehao Wang ◽  
...  
Keyword(s):  
Activated Carbon ◽  
Extracellular Polymeric Substances ◽  
Combined Treatment ◽  
Electrochemical Treatment ◽  
Sludge Dewatering ◽  
Element Analysis ◽  
Sludge Flocs ◽  
Freeze Thaw ◽  
Floc Structure ◽  
Sludge Cake

Abstract Freeze–thaw (F/T) and electrochemistry are environment-friendly and efficient sludge treatment technologies. In this study, F/T and electrochemistry were combined in the pretreatment of sludge dewatering in the laboratory, and activated carbon (AC) was added to improve the electrochemical dewatering performance of sludge. During the experiment, the effect of F/T on the floc structure was analyzed by a laser particle analyzer and scanning electron microscope. F/T treatment not only improved the dewatering performance of sludge, but also promoted the aggregation of sludge flocs into larger particles. The median diameter (D50) increased from 45.27 µm to 128.94 µm. Then, the intracellular polymer of large-particle sludge was analyzed by three-dimensional excitation–emission matrix (3D-EEM). The tightly bound extracellular polymeric substances (TB-EPS) still contained a large amount of protein substances, which hindered the improvement of sludge dewatering performance. AC was added to the thawed sludge solution before electrochemical treatment (EP). The conductivity of AC enhanced the effect of EP, thereby cracking the sludge flocs. Thus, the light intensity of TB-EPS in the 3D-EEM fluorescence spectroscopy was decreased, and the D50 was also reduced to 105.3 µm. The final specific resistance of filtration and water content were reduced by 96.39% and 32.17%, respectively. Element analysis of the sludge cake after dehydration showed that the addition of AC significantly improved the combustion efficiency of the sludge cake. Moreover, preliminary economic analysis showed that the cost of this research was low, which indicated the potential application value of combined treatment.

Study on the effect of chitosan conditioning on sludge dewatering

2019 ◽  
Vol 79 (3) ◽  
pp. 501-509 ◽  
Author(s):  
Jin Zhang ◽  
Qing Hu ◽  
Jie Lu ◽  
Shuang Lin
Keyword(s):  
Moisture Content ◽  
Extracellular Polymeric Substances ◽  
Waste Water Treatment ◽  
Sewage Treatment ◽  
Organic Polymer ◽  
Sludge Dewatering ◽  
Sludge Treatment ◽  
Residual Sludge ◽  
Sludge Cake ◽  
Polymer Flocculant

Abstract The difficulty of residual sludge dehydration is the major problem in sewage treatment. The reduction of moisture content in sludge can reduce the sludge volume significantly and is conducive to the subsequent disposal of sludge. As an organic polymer flocculant, chitosan (CTS) is widely used in water and waste water treatment. In this study, CTS was used in sludge treatment to improve the sedimentation and dehydration properties of sludge. When treated with CTS, the moisture content of sludge cake decreased from 85.9% to 83.0%, the SV30 decreased to about 1/2, and the sludge volume reduced to 82.9%. Further analysis showed that the zeta potential (ζ-potential) of the sludge changed from negative value to positive value, and the D50 of the sludge was larger than that of the raw sludge. In addition, when the moisture content of the sludge cake was reduced to the lowest, the concentration of extracellular polymeric substances (EPS) and SCOD was the largest and the |ζ| decreased to the lowest. CTS improved the dehydration and sedimentation performance of sludge mainly by factors of electrical neutralization, adsorption bridging and dissolution of EPS.

Characteristics of different fractions of microbial flocs and their role in membrane fouling

2011 ◽  
Vol 63 (2) ◽  
pp. 262-269 ◽  
Author(s):  
H. J. Lin ◽  
W. J. Gao ◽  
K. T. Leung ◽  
B. Q. Liao
Keyword(s):  
Microbial Community ◽  
Membrane Fouling ◽  
Extracellular Polymeric Substances ◽  
Denaturing Gradient Gel Electrophoresis ◽  
Sludge Flocs ◽  
Microbial Flocs ◽  
Thermomechanical Pulping ◽  
Gradient Gel Electrophoresis ◽  
Sludge Cake ◽  
The Difference

Characteristics of different fractions (small flocs vs. large flocs) of sludge flocs from a submerged anaerobic membrane bioreactor treating thermomechanical pulping (TMP) whitewater were determined using various analytic techniques, including extraction and chemical analysis of extracellular polymeric substances (EPS), particle size analyzer, and polymer chain reaction (PCR)-denaturing gradient gel electrophoresis (DGGE). The results showed that the fraction of smaller flocs contained a higher level of bound EPS and had a higher fractal dimension as compared to the fraction of larger flocs. PCR-DGGE analysis indicated that there were significant differences in microbial community between the fraction of smaller flocs and large flocs. The microbial community of the smaller flocs was similar to that of the sludge cake layers, indicating the pioneering role of the microbial community in smaller flocs in membrane fouling. These findings provide a new insight in the difference of membrane fouling potential between smaller flocs and larger flocs fraction.

scholarly journals Improvement of phosphorus release from sludge by combined electrochemical-EDTA treatment

2021 ◽  
Vol 83 (8) ◽  
pp. 1824-1833
Author(s):  
Yunfeng Xu ◽  
Fanglu Hu ◽  
Xin Wang ◽  
Yangwei Qu ◽  
Lu Xu ◽  
...  
Keyword(s):  
Metal Ions ◽  
Extracellular Polymeric Substances ◽  
Ethylenediaminetetraacetic Acid ◽  
Organic Phosphorus ◽  
Electrochemical Treatment ◽  
Phosphorus Release ◽  
Dissolved Phosphorus ◽  
Sludge Flocs ◽  
Edta Treatment ◽  
Reactive Phosphorus

Abstract In this paper, combined with the addition of ethylenediaminetetraacetic acid (EDTA), the electrochemical treatment of waste activated sludge (WAS) was investigated to explore its effect on the release of phosphorus (P) from WAS. The results showed that during the electrochemical treatment, the addition of EDTA could significantly promote the release of P from the WAS to the supernatant, the optimal amount of EDTA was 0.4 g/g total suspended solids (TSS), when the release of total dissolved phosphorus (TDP), organic phosphorus (OP) and molybdate reactive phosphorus (PO43−-P) were 187.30, 173.84 and 13.46 mg/L, respectively. OP was the most likely form of P to be released during this process. Moreover, combined electrochemical-EDTA treatment could promote the release of P and metal ions from extracellular polymeric substances (EPSs) to the supernatant, and increase the solubility and disintegration of sludge. EDTA chelated the metal ions of sludge flocs and phosphate precipitates to cause sludge floc decomposition, thereby promoting the release of P from WAS.

Conditioning effect of lysozyme combined with freeze-thaw on the municipal sludge dewatering performance

BioResources ◽  
2019 ◽  
Vol 14 (3) ◽  
pp. 7375-7386
Author(s):  
Feng Lin ◽  
Jigeng Li ◽  
Xiaolin Zhu ◽  
Peiran Yu ◽  
Mengru Liu
Keyword(s):  
Water Content ◽  
Bound Water ◽  
Municipal Sludge ◽  
Sludge Dewatering ◽  
Capillary Suction ◽  
Freeze Thaw ◽  
Floc Structure ◽  
Conditioning Effect ◽  
Dewatered Sludge ◽  
Bound Water Content

The effects of lysozyme (LZM) and freeze-thaw conditioning, alone or in combination, on sludge dewatering performance were comparatively investigated. After the optimization of the dewatering conditions using response surface methodology (RSM), the co-conditioning exhibited obvious superiority to the separate conditioning in improving the dewaterability of municipal sludge, with the capillary suction time (CST) and the water content (W) of the dewatered sludge reduced to 12 ± 0.5 s and 52.0% ± 0.4% from 61.8 s and 73.0%, respectively. The co-conditioning appeared not only to destroy the structure of extracellular polymeric substance (EPS) and microbial cell wall by virtue of enzymatic conditioning, but it formed larger particles and compact sludge floc structure with the help of freeze-thaw conditioning. Additionally, the bound water content of sludge decreased by 47.5% after co-conditioning, consistent with the enhancement in sludge dewaterability. All the results showed that LZM in combination with freeze-thaw conditioning had a great potential in sludge reduction, providing more opportunity of resource utilization for the dewatered sludge.

Enhancing paper sludge dewatering by waste polyester fiber and FeCl3 for preparation of Fe-rich biochar

BioResources ◽  
2021 ◽  
Vol 16 (2) ◽  
pp. 2326-2345
Author(s):  
Xin Zhang ◽  
Guolin Tong ◽  
Yiheng Zhou ◽  
Guoyi Li ◽  
Hui Zhang
Keyword(s):  
Extracellular Polymeric Substances ◽  
Catalytic Effect ◽  
Paper Sludge ◽  
Sludge Dewatering ◽  
Filtration Resistance ◽  
Sludge Recycling ◽  
Sludge Cake ◽  
Polyester Textile ◽  
Floc Strength ◽  
Sludge Dewaterability

The paper sludge conditioning effects of waste polyester textile fibers as skeleton builders combined with ferric chloride (FeCl3) were evaluated and the sludge dewatering mechanism was explored. The catalytic effect of Fe-rich sludge biochar (Fe-SB) on enhancing sludge dewaterability was evaluated. Results showed the combined fiber-FeCl3 conditioning significantly promoted the sludge dewaterability compared with conditioner alone, leading to a 77.5% decrease in specific filtration resistance and a 68.9% increase in net yield. The decrease of extracellular polymeric substances (EPS) contents showed that the EPS were difficult to extract and sludge floc strength was enhanced as a result of chemical reactions such as complexation processes and charge neutralization. Hence, the enhancement of sludge dewaterability was primarily due to the sludge cake with a porous and incompressible structure formed by fiber and FeCl3, and the rigidity structure of fiber. Moreover, the Fe-SB prepared by fiber-FeCl3 conditioning sludge could effectively activate persulfate to enhance the sludge dewaterability, with water content of dewatered sludge decreasing by 14.6%. The Fe-SB had dual functions of the heterogeneous catalyst of persulfate and skeleton builder. This study presents a sludge recycling method that combined physicochemical conditioning and sludge biochar materials prepared by pyrolysis.

scholarly journals Evaluation of hydrophobically associating cationic starch-based flocculants in sludge dewatering

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Pan Hu ◽  
Shaohang Shen ◽  
Hu Yang
Keyword(s):  
Extracellular Polymeric Substances ◽  
Synergistic Effects ◽  
Structure Activity Relationship ◽  
Activity Relationship ◽  
Structural Factors ◽  
Cationic Starch ◽  
Sludge Dewatering ◽  
Sludge Flocs ◽  
Structure Activity ◽  
Sludge Dewaterability

AbstractTwo series of binary graft cationic starch-based flocculants (CS-DMCs and CS-DMLs) with different hydrophilicity and charge density (CD) were prepared by graft copolymerization of acrylamide with 2-(Methacryloyloxy)-N,N,N-trimethylethanaminium chloride and methacrylic acid 2-(benzyldimethylaminio) ethyl chloride, respectively, on the starch (St) backbone. The sludge dewatering performance of CS-DMCs and CS-DMLs were evaluated and compared based on the changes in filter cake moisture content (FCMC), specific resistance of filtration (SRF), fractions and components of extracellular polymeric substances, and various physiochemical characteristics of sludge flocs and cakes. Increase in CD of the St-based flocculants caused improved sludge dewaterability. Under the similar CD, CS-DML with relatively high hydrophobicity exhibited lower FCMC and SRF, larger and denser sludge flocs, and better permeability of sludge cakes than CS-DMCs due to the synergistic effects of charge neutralization, bridging flocculation and hydrophobic association. Furthermore, a second-order polynomial model on the basis of phenomenological theory was successfully applied to quantitatively evaluate the influences of the two important structural factors of these St-based flocculants, i.e., hydrophobicity and CD, on the sludge dewaterability. The structure–activity relationship of the St-based flocculants in sludge dewatering was obtained according to the theoretic simulation. The dewatering mechanisms was discussed in depth on the basis of the experimental and simulated results; besides, the FCMC and optimal dose can be predicted by the established structure–activity relationship. This current work offered a novel and valuable way to exploit and design of low-cost and high-performance graft natural polymeric flocculants applied in efficient conditioning of sludge.

Comparison of lime and alum as oily sludge conditioners

1997 ◽  
Vol 36 (12) ◽  
pp. 117-124 ◽  
Author(s):  
Tay Joo Hwa ◽  
S. Jeyaseelan
Keyword(s):  
Specific Resistance ◽  
Sewage Treatment ◽  
Sewage Treatment Plant ◽  
Treatment Plant ◽  
Oily Sludge ◽  
Sludge Dewatering ◽  
Capillary Suction ◽  
Sludge Cake ◽  
Solids Content ◽  
Optimum Chemical

Chemical conditioning improves sludge dewatering. Choice of chemical conditioners is very much dependent on the characteristics of the sludges and the type of dewatering devices. Lime, alum, ferric chloride and polyelectrolytes are commonly used chemical conditioners. Anaerobic digested sludge samples collected from a sewage treatment plant with different oil contents varying from 1.8% to 8.0% by weight have been examined in the laboratory to find out their specific resistance, capillary suction time and filter yield. Lime and alum were used separately as conditioners. Different dosages of conditioner varying from 2% to 12% by weight were used to determine the optimum chemical dosage for varying oil contents. Lime dosages of about 6% were found to yield favourable characteristics. Addition of alum decreases the specific resistances and capillary suction times of oily sludges rapidly up to 4% dosages. Alum dosages beyond 4% only increase the solids content in the sludge cake and increase the sludge volume to be handled. A correlation between CST and specific resistance to filtration was established. CST can be measured easily and quickly in the laboratories. Using the CST and the correlation a quick prediction on dewaterability can be established.

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