ABSTRACT
W HERE used in wastewater treatment systems, the trickling filter follows primary treatment (primary settling), and must include a secondary settling tank or clarifier (as shown in Figure 9.1) to remove solids generated by the biological activity. Trickling filters are widely used for the treatment of domestic and industrial wastes or combinations of the two. The process is a fixed film or attached growth biological treatment method designed to remove BODs and suspended solids (through biological oxidation and settling) but can also be designed to remove nitrogen. Although the ternfilter is the accepted designation for this unit, no physical filtration occurs; contaminants are removed by biological action. The medium placed in a tank under the wastewater distributor can be crushed rock (see Figures 9.2 and 9.3), plastic-sheet packing formed into modules, or random plastic packing of various shapes.
