How are microorganisms utilized in trickling filters during secondary treatment?

Microorganisms play a crucial role in trickling filters, which are a type of secondary treatment in wastewater management. In this process, microorganisms grow on a fixed bed of media, which provides a surface for biofilm development. The wastewater is distributed over this media, allowing it to trickle down through the microorganisms. As the water flows over the media, the microorganisms metabolize organic pollutants and nutrients, effectively treating the wastewater.

The growth of microorganisms on a bed of media is essential for maintaining a stable and efficient biofilm. This biofilm acts as a natural filter, aiding in the breakdown of organic matter and the removal of contaminants. The design of trickling filters, featuring surfaces that promote maximum microbial growth, is specifically intended to enhance the microbial treatment process. Therefore, the method of utilizing microorganisms in this manner is fundamental to the effectiveness of trickling filters in municipal wastewater treatment.

The other options do not accurately reflect how microorganisms function within this system. For instance, they are not added externally; rather, they develop naturally on the media. Additionally, microorganisms do not settle out of the water during this process, as their primary function is to attach to the media and thrive there. Chemical energization is also unnecessary, as microorganisms typically derive their energy from