Activated sludge process is the biotic conversion of organic matter of wastewater to CO2 and biomass. The biological conversion of organic compounds in activated sludge relies on the efficient transfer of dissolved oxygen. Oxygen mass transfer from the gas phase to the liquid phase and microbial oxygen consumption are critical for effectively removing chemical oxygen demand, microbial growth, cell maintenance, sludge decomposition, and other metabolic processes. Therefore, sufficient aeration is imperative for the activated sludge process. However, aeration is an energy-intensive process with poor mass transfer efficiencies achieving only 30% oxygen transfer efficiency in a typical 4.5m deep activated sludge reactor. Within this energy requirement, 50–90% of the total energy consumption for wastewater treatment is destined for the aeration of the activated sludge processes. Moreover, foulant accumulation in the fine pore diffusers reduces the oxygen transfer efficiency over time and requires increased air flux to maintain the same oxygen supply. Biofouling and scaling on and within the air diffusers further increase the cost of aeration due to the high airflow resistance. Therefore, there exists a need for improved systems and methods for treatment of wastewater.
Nanobubbles (NBs) are ultrafine gas domains in liquid with nano-scale diameters that are, on average, smaller than 1000nm diameter (e.g., about 200nm in diameter or less). NBs have remarkably large interfacial surface areas and have unique physicochemical properties due to their small dimensions. The small size and higher surface tension of NBs increase the interfacial gas–liquid surface area, which in turn promotes mass transfer. In some examples, NBs can be suspended in a composition (e.g., water) for long periods of time (e.g., several months) and produce reactive oxygen species without added catalysts. However, NB applications in water treatment applications have not been explored.
Researchers at Arizona State University, University of Maine, and NASA have developed methods and systems for generating nanobubbles in a composition. In addition, the researchers developed methods and systems for removal of target substances (e.g., pollutants) from a composition using nanobubbles and/or adding payload substances to a composition using nanobubbles.
Related Publications:
Potential Applications:
- Wastewater treatment
- Aquaculture
- Drinking water purification
- Environmental remediation
Benefits and Advantages:
- Enhanced mass transfer efficiency due to large interfacial area of nanobubbles
- Effective removal of nanoplastics and other pollutants from water
- Improved dissolved oxygen levels in treated water, beneficial for aquatic life and water quality
- Stability in water allows for prolonged treatment capabilities without immediate dissipation
- Energy-efficient generation and application processes