Characteristics of the filler: Traditional biofilm processes use fillers with hydrophobic surfaces, which are difficult to colonize, have long colonization cycles, and are prone to concentrated biofilm detachment. The filler used in the moving bed process differs from traditional fillers and has the following structure: The horizontal filaments of the filler are made of hydrophilic acrylic fiber, connected by a high-strength central rope (200kg/cm2). Horizontal fiber filaments are spaced at regular intervals along the central rope, with upper and lower filaments offset at a certain angle, creating a three-dimensional distribution in space. 

The fiber filaments have a diameter of 3mm, with each filament composed of three finer strands, all processed and wound together through a special technique. The filaments transition from sparse to dense from the inside out, allowing the filler to accumulate large amounts of active sludge both internally and externally, unlike conventional fillers. Moreover, the sludge entering the interior of the filler has strong adhesion and a long retention time. 
The surface of this filler is very rough with high porosity, making it highly conducive to microbial attachment and growth, which shortens the colonization time and system startup period. 
Structural characteristics: Due to the excellent elasticity and toughness of the fiber filaments, under the action of circulating water flow, the filaments continuously oscillate near their equilibrium positions, enhancing mass transfer efficiency. This also ensures that excess biofilm attached to the filler is evenly shed, maintaining a certain level of microorganisms on the surface with high biological activity. Additionally, it delays the aging process of the biofilm, prevents excessive growth of the anaerobic layer, and effectively reduces concentrated detachment or clogging of the biofilm. The unique structure of the filler allows active sludge to attach from the inside out, with strong adhesion and long retention time in the central part, forming a food chain. The interior forms an anaerobic zone, while the exterior is an aerobic zone. Since the fiber filaments are separated and radiate outward, with large pores, there is no clumping phenomenon commonly seen in soft fillers.

The diagram below illustrates the process principle of the moving bed.