The void fraction in the MBBR refers to the percentage of voids or gaps between the media (usually plastic media) in the wastewater treatment reactor. These voids are used to provide sufficient surface area for the attachment and growth of biofilm, thus effectively removing organic substances and pollutants from the wastewater. The void fraction in MBBR typically varies depending on the type and shape of the media, generally ranging from 30% to 70%. The choice within this range depends on specific wastewater treatment requirements and the needed surface area for biofilm attachment.
A higher void fraction usually implies a larger surface area, thus accommodating more biofilm and increasing treatment capacity. However, excessively high void fractions may result in too large voids between the media, affecting the uniform distribution and treatment efficiency of the wastewater. Factors such as media type, size, shape, arrangement, design parameters of the MBBR biofilm reactor, and wastewater characteristics all affect the void fraction of MBBR media.
Media with a good void fraction have a significant impact on the MBBR system. The void fraction determines the available surface area for biofilm attachment, with a higher void fraction indicating more surface area available for biofilm attachment, thereby enhancing biodegradation efficiency, especially in the initial stages of the project. In the aeration tank, a good void fraction strengthens oxygen transfer, facilitating the transfer of oxygen from the wastewater to the biofilm, providing sufficient oxygen for microbial respiration and maintaining biofilm activity. An appropriate void fraction helps ensure uniform wastewater flow between the media, ensuring even contact between organic substances in the wastewater and the biofilm, thereby improving wastewater treatment efficiency. Additionally, a good void fraction can enhance system stability and treatment capacity, reducing energy consumption and maintenance costs for your MBBR system.
Aquasust's technical engineers teach you how to calculate the void fraction of MBBR media, understand the operation of MBBR systems, and provide assistance in designing and optimizing wastewater treatment systems.
The void fraction of MBBR (Moving Bed Biofilm Reactor) media is typically calculated by measuring the volume of the media and the volume of the media particles.
You need to know the total volume of the media, which is the volume when the media fills the entire tank.
Measure the volume of the media particles. You can add the media to a known volume of water and measure the change in water volume in the tank to determine the volume of the media particles.
Void volume = total media volume - volume of media particles.
Void fraction = (Void volume / Total volume of media) * 100%.
Different ranges of void fractions applicable in different projects:
Urban wastewater treatment plants:
Applicable range of void fraction: 40% to 60%
Reason: Urban wastewater treatment plants typically have relatively stable water quality characteristics. An intermediate void fraction can provide sufficient surface area for biofilm attachment to meet the needs of wastewater treatment and ensure stable operation.
Industrial wastewater treatment (e.g., food processing plants, pharmaceutical plants):
Applicable range of void fraction: 50% to 70%
Reason: Industrial wastewater usually contains higher concentrations of organic compounds and other pollutants, requiring more surface area for biofilm attachment to treat these wastewater streams. A higher void fraction can provide more surface area to meet the demands of high-load industrial wastewater treatment.
Small or decentralized wastewater treatment systems (e.g., rural areas, remote areas):
Applicable range of void fraction: 30% to 50%
Reason: Small or decentralized wastewater treatment systems typically have smaller scales and lower treatment capacities, resulting in lower wastewater loads. A lower void fraction can reduce system costs while providing adequate treatment efficiency.
Please note that the above ranges of void fractions are for reference only, and adjustments should be made based on specific circumstances. If you want to learn more about MBBR systems, please contact Aquasust's engineers. We are your most reliable partner in wastewater treatment.