Biofilm method, like activated sludge method, is a method that uses microorganisms to remove organic matter from wastewater. The material that provides a fixed surface for biofilm adhesion and growth is called filler, which is an important factor affecting the development and performance of biofilm method. Biofilm is a fluffy flocculent structure with numerous micropores and a large surface area, possessing strong adsorption capacity. Biofilm microorganisms use organic matter adsorbed and deposited on the membrane as nutrients, converting a portion of the material into cellular material for growth and reproduction, becoming new active substances in the biofilm. 

    Another portion of the material is converted into excrement, releasing energy during the conversion process to meet the needs of microbial growth. The proliferating biofilm falls off and enters the wastewater, which is intercepted in the secondary sedimentation tank and becomes sludge. If the organic load is relatively high and the biofilm cannot oxidize and decompose the adsorbed organic matter in time, unstable sludge can be formed, which needs to be reprocessed. Due to the attached state of microorganisms in the biofilm process, the sludge age is long, resulting in both microorganisms with short generation time and high specific growth rate and microorganisms with long generation time and low specific growth rate in the biofilm process. This leads to more microbial species involved in metabolism in the biofilm process than in the activated sludge process. Alright, that's all for today's presentation!