Related Experiment Video
Updated: Jun 15, 2026
06:00
Determination of the Settling Rate of Clay/Cyanobacterial Floccules
Published on: June 11, 2018
Dynamics in flocculation and settling properties studied at a full-scale activated sludge plant
Britt-Marie Wilén1, Doug Lumley, Ann Mattsson
1Water Environment Technology, Chalmers University of Technology, Göteborg, Sweden. britt-marie.wilen@chalmers.se
Summary
Activated sludge settling and flocculation dynamics were studied at a full-scale plant. Performance varied seasonally, with better summer flocculation and lower turbidity, but higher winter shear sensitivity.
Area of Science:
- Environmental Science
- Chemical Engineering
- Water Treatment Technology
Background:
- Activated sludge processes are crucial for wastewater treatment.
- Secondary settlers are key for solid-liquid separation.
- Plant operation at maximum capacity presents unique challenges for settler performance.
Purpose of the Study:
- To investigate the dynamics of settling and flocculation properties in secondary settlers.
- To assess physical parameters influencing secondary settler capacity and performance.
- To understand seasonal variations in activated sludge properties.
Main Methods:
- Analysis of extensive process data from a full-scale activated sludge treatment plant.
- Evaluation of physical parameters affecting secondary settler performance.
- Assessment of seasonal changes in sludge settling, compaction, and flocculation.
Main Results:
- Significant variations in settling and compaction properties were observed, linked to short sludge age.
- Flocculation properties improved during summer, correlating with lower effluent turbidity and suspended solids.
- Higher shear sensitivity (floc stability) was noted in winter due to lower water temperatures.
- Sludge floc morphology differed seasonally: rounder colonies in summer, more open, net-like structures in winter.
Conclusions:
- Seasonal variations significantly impact activated sludge settling and flocculation performance.
- Sludge age and water temperature are critical factors influencing settler efficiency.
- Optimizing operational strategies based on seasonal dynamics is essential for effective wastewater treatment.
Related Concept Videos
01:06Coagulation
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...
01:18Bioreactor Controls-II
In aerobic fermentations, oxygen is vital for microbial growth and metabolite production. Since air comprises only about 20% oxygen and the gas is poorly soluble in water—just 9 ppm at 20°C—supplying sufficient oxygen becomes a critical challenge, especially in high-demand processes like yeast growth or citric acid production. Even a fully saturated broth may offer only a few seconds of oxygen availability.To address this, sterile or scrubbed air is introduced into the fermentor via a sparger...
01:29Bioreactor Design and Operational System
Bioreactors are engineered vessels designed to cultivate microorganisms under controlled conditions for industrial bioprocessing. They maintain sterility and allow precise regulation of pH, temperature, oxygen, and nutrient levels to optimize microbial growth and metabolite production. Bioreactors range from small laboratory units of 1 liter to industrial systems holding up to 500,000 liters, though only about 75% of their volume is actively used for fermentation. The remaining headspace...
01:30Biological 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...
01:14Scale-Up Processes
The scale-up of microbial fermentation processes is essential in industrial biotechnology, allowing the transition from laboratory-scale experiments to commercial-scale production while aiming to maintain product yield and quality. This process requires meticulous adjustment of equipment design, process parameters, and contamination control strategies to accommodate increasing culture volumes.At the laboratory scale, cultures are typically maintained in 1 to 10-liter glass or autoclavable...
01:23Factors Affecting Dissolution: Particle Size and Effective Surface Area
Dissolution kinetics, an essential aspect of oral drug delivery, is significantly influenced by the drug's particle size. According to the Noyes-Whitney dissolution model, the dissolution rate correlates directly with the drug's surface area. The larger the surface area, the higher the drug's solubility in water, leading to a faster drug dissolution rate. Reducing particle size increases the effective surface area, enhancing the dissolution process. Micronization and nanosizing are employed to...