Wastewater treatment processes fall mainly into the activated sludge method and the biofilm method. The activated sludge method requires a large footprint, produces a large amount of excess sludge and has low resistance to shock loads, while filamentous bacteria readily cause sludge bulking. The biofilm method instead installs biological media in the tank; the media act as carriers for micro-organisms and a large microbial population grows on them. It offers strong resistance to load shocks, a small footprint and a small amount of excess sludge.
2. Classification of Biological Filler Media
Biological media are divided into hanging media and floating media. Hanging media are made by stringing individual media elements into a strand of the size required by the project, then fixing both ends of each strand to a support frame. Types include combined fibre media, three-dimensional elastic media, elastic combined media, biological ring three-dimensional elastic media, soft media and semi-soft media. Floating media are placed directly into the aerobic tank, where they remain in suspension. Types include spherical floating media, combined floating ball media and cylindrical floating media.
3. Hanging Media Series
1. Combined Fibre Media
Combined fibre media combine the advantages of soft and semi-soft media: they provide a skeleton that cuts bubbles and holds the structure, together with vinylon filaments of large specific surface area. In wastewater the fibre bundles are evenly distributed and biofilm attachment is easy, making them suitable for a wide range of sewage and wastewater treatment duties.
Product structure and function
Structure: the media consist of three parts - combined fibre discs, plastic sleeves and a centre rope. The discs are threaded onto the centre rope and spaced by the sleeves to the required size to form a single strand.
Each disc uses an 80 mm diameter snowflake-shaped plastic ring as its skeleton, with twelve strands of aldehyde-treated vinylon fibre fixed around the outer ring to form a single disc unit.
The plastic sleeves are injection moulded from polyethylene pellets and set the spacing between the upper and lower discs.
The centre rope connects the discs and sleeves, and is used to fix the media to the support frame during installation.
Materials: the snowflake-shaped discs and the sleeves are injection moulded from polyethylene; the filaments are aldehyde-treated vinylon; the centre rope is made from polyethylene yarn.
2. Three-Dimensional Elastic Media
The elastic filaments are made of polyolefin (polyamide) and offer corrosion resistance, temperature resistance and ageing resistance.
