Related Experiment Video
Updated: Apr 8, 2026
08:13
A Novel Bioreactor for High Density Cultivation of Diverse Microbial Communities
Published on: December 25, 2015
17.0K
Modeling aerobic granules in continuously flowing wastewater-treatment processes
Joshua P Boltz1, Bruce E Rittmann2
1Woodard & Curran, Portland, Maine, USA.
Summary
Large biological aggregates (LBAs) in wastewater treatment accumulate significant phosphorus. While suspended biomass drives most transformations, LBAs are crucial for enhanced biological phosphorus removal and improved settling characteristics.
Area of Science:
- Environmental Engineering
- Biotechnology
- Wastewater Treatment
Background:
- Wastewater treatment processes utilize biological and physical selection to form large biological aggregates (LBAs) and retain suspended biomass.
- LBAs and suspended biomass have distinct solids residence times (SRTs) and mass-transport resistances, influencing treatment efficiency.
- Understanding the behavior of LBAs and suspended biomass is crucial for optimizing nutrient removal and overall treatment performance.
Purpose of the Study:
- To develop and validate a mathematical model simulating a full-scale wastewater treatment train with LBAs and enhanced biological phosphorus removal (EBPR).
- To investigate the roles of suspended biomass and LBAs in nutrient transformations and polyphosphate accumulation.
- To analyze the structural and compositional characteristics of LBAs, particularly extracellular polymeric substances (EPS).
Main Methods:
- Combined mathematical sub-models for metabolic processes, 1-D biofilm, and migrating spherical carriers.
- Simulated a full-scale demonstration train with anaerobic, anoxic, and oxic zones and side-stream EBPR (S2EBPR).
- Utilized hydrocyclones for physical selection of LBAs.
Main Results:
- Simulation results closely matched experimental observations for COD, nitrogen, and phosphorus removal, and mixed liquor characteristics.
- Suspended biomass accounted for most transformations, but LBAs significantly contributed to polyphosphate accumulation (~2000 mg P/L).
- Simulated LBAs showed higher densities of phosphorus-storing bacteria and accumulated more polyphosphate and EPS, especially protein-EPS, near their core.
Conclusions:
- The developed model accurately represents A2O systems with S2EBPR and aerobic granule behavior.
- LBAs play a vital role in phosphorus accumulation and can improve solids-settling characteristics in wastewater treatment.
- Protein-EPS accumulation within LBAs is influenced by slower hydrolysis kinetics, impacting granule structure and function.
Related Concept Videos
01:29Bioreactor Design and Operational System
119
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...
119
01:18Bioreactor Controls-II
57
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...
57
01:14Scale-Up Processes
82
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...
82