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Related Concept Videos

Coagulation01:06

Coagulation

Colloidal solids are solid particles suspended in solution. They are usually negatively charged, attracting a compact primary layer of positively charged ions, which attract more counterions to form an electrical double layer. Electrostatic repulsion between the charged double layers prevents the particles from colliding, stabilizing the colloids. These solids are often undesirable because they can contain toxins that are difficult to remove. Coagulation is a technique that helps aggregate and...
Colloidal precipitates01:09

Colloidal precipitates

The high insolubility of some precipitates can result in an unfavorable relative supersaturation. This can lead to colloidal particles with a large surface-to-mass ratio, where adsorption is promoted. For instance, in the precipitation of silver chloride, silver ions are adsorbed on the surface of the colloidal particles, forming a primary layer. This layer attracts ions of opposite charge (such as nitrate ions), forming a diffuse secondary layer of adsorbed ions. This electric double layer...
Biological Treatment of Effluent and Waste Water01:30

Biological Treatment of Effluent and Waste Water

Biological wastewater treatment relies on the metabolic activity of microorganisms to remove pollutants from sewage. In modern treatment systems, this process is organized into sequential stages that progressively reduce solid material, dissolved organic matter, and microbial contamination. Each stage plays a distinct role in improving water quality and preparing the effluent for safe discharge or reuse.Primary and Secondary TreatmentPrimary treatment is a physical process that removes large...
Solubility03:00

Solubility

Solution, Solubility, and Solubility Equilibrium
A solution is a homogeneous mixture composed of a solvent, the major component, and a solute, the minor component. The physical state of a solution—solid, liquid, or gas—is typically the same as that of the solvent. Solute concentrations are often described with qualitative terms such as dilute (of relatively low concentration) and concentrated (of relatively high concentration).
In a solution, the solute particles (molecules, atoms, and/or ions)...
The Colloidal State01:29

The Colloidal State

The formation of a colloidal system is exemplified by an aqueous solution containing Cl− ions is introduced to another containing Ag+ ions, resulting in the precipitation of solid AgCl as extremely tiny crystals. Instead of settling out as a filterable precipitate, these crystals remain suspended in the liquid, showcasing a colloidal system.A colloidal system involves colloidal particles within the approximate range of 1 to 1000 nm in at least one dimension, dispersed in a medium called the...
Centrifugation01:05

Centrifugation

Centrifugation is a separation technique based on differences in density or size. It is commonly used to separate solids from aqueous interferents. During centrifugation, the sample is placed in centrifugation tubes and spun at high angular velocity, which allows centrifugal force to act differentially on the different densities or masses of the components. After spinning, the supernatant liquid is decanted. Depending on the specific application, either the pellet or the supernatant is retained...

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Related Experiment Video

Updated: Jun 27, 2026

Extraction of Structural Extracellular Polymeric Substances from Aerobic Granular Sludge
06:10

Extraction of Structural Extracellular Polymeric Substances from Aerobic Granular Sludge

Published on: September 26, 2016

Stratification structure of sludge flocs with implications to dewaterability.

Guang-Hui Yu1, Pin-Jing He, Li-Ming Shao

  • 1State Key Laboratory of Pollution Control and Resources Reuse, Key Laboratory of Yangtze River Water Environment, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, PR China.

Environmental Science & Technology
|November 27, 2008
PubMed
Summary

Sludge dewaterability is significantly impacted by proteins (PN) and the protein-to-polysaccharide ratio (PN/PS) in the supernatant and slime layers. These factors, often overlooked, are key to effective sludge volume reduction.

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Area of Science:

  • Environmental Science
  • Water Treatment Engineering
  • Biochemistry

Background:

  • Sludge dewatering is crucial for reducing sludge volume in wastewater treatment plants (WWTPs).
  • Understanding factors affecting sludge dewaterability is essential for optimizing treatment processes.
  • Existing methods for sludge analysis may not fully capture the complex interactions within sludge flocs.

Purpose of the Study:

  • To investigate the influence of sludge floc composition on dewaterability using a novel stratification approach.
  • To identify specific sludge components and fractions that correlate with improved sludge dewaterability, measured by capillary suction time (CST).
  • To challenge the assumption that supernatant and slime layers have minimal impact on sludge dewaterability.

Main Methods:

  • Sludge samples from 14 diverse WWTPs were stratified into five layers: supernatant, slime, loosely bound EPS (LB-EPS), tightly bound EPS (TB-EPS), and pellet using centrifugation and ultrasound.
  • Protein (PN) and polysaccharide (PS) content were analyzed in each fraction.
  • Capillary suction time (CST) was measured to assess dewaterability.
  • Statistical analysis (correlation) was performed to link PN, PS, and PN/PS ratios with CST.

Main Results:

  • Protein (PN) and polysaccharide (PS) distribution varied across the five sludge layers.
  • Normalized CST showed a significant positive correlation with PN (R2 > 0.72, p < 0.01) and PN/PS (R2 > 0.51, p < 0.01) in the supernatant, slime, and LB-EPS fractions.
  • No significant correlation was found between CST and PN, PN/PS in the pellet or whole sludge, or with PS in any fraction.

Conclusions:

  • Proteins (PN) and the protein-to-polysaccharide ratio (PN/PS) in the supernatant and slime layers are critical determinants of sludge dewaterability.
  • These findings highlight the importance of considering these typically discarded fractions for optimizing sludge dewatering processes.
  • The study provides new insights into sludge floc composition and its direct impact on dewatering efficiency.