Fixed Film Processes
The fixed film process is a type of biological treatment process that includes plastic, wood, rock, natural synthetic material and fixed synthetic material. This film shall enhance the growth of biological organisms in its surface and inside the porous structure.
Types of fixed film processes:
Following are types of fixed film processes.
Trickling filter consists of bed of porous media for the passage of waste water to flow through. The oxygen supply to trickling filter is by forced ventilation or by natural ventilation. The waste water is distributed evenly on the media surface with the help of flow distributors. The waste water percolates down due to gravitational force where the colloidal organic matter and soluble matter are metabolized by the biofilm that are formed on the surface of media. The excess of media can be removed off and the treated water is passed on to clarifier. The solids settle out and the effluent can be separated. The treated water can be recycled back in to filter medium.
Rotating Biological Contractor:
The rotating biological contractor is a type of fixed film process where the wastewater flows through rotating discs. It was first developed in the year 1960. It uses plastic medium that are configured with rotating discs which are mounted on horizontal shaft. The rotation of shaft can be either by mechanical force or compressed force of air. About 40 percent of media gets immersed inside wastewater. Anaerobic or anoxic rotating biological contractor gets completely immersed inside wastewater. The simple displacement and gravitational force helps in transport of wastewater. Biomass may slough over the rotating discs. The effluent is passed on to secondary clarifier to remove the suspended solids. Oxygen supply is by biomass transfer over the surface.