low-rate filter, which is also referred to as standard-rate filter, was the backbone of
secondary biological treatment for over 50 years. The low-rate biological filter is
about 1.5–2.5 m (5–8 ft) deep. Its rock media vary from 3.8 to 6.4 cm (1.5 to 2.5 in)
nominal diameter and can be dosed with either fixed nozzle distributors or rotary
Fig. 3.17 Trickling filter
variations. (Source: US
EPA)
Fig. 3.18 Typical roughing filter installation. (Source: US EPA)
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secondary biological treatment for over 50 years. The low-rate biological filter is
about 1.5–2.5 m (5–8 ft) deep. Its rock media vary from 3.8 to 6.4 cm (1.5 to 2.5 in)
nominal diameter and can be dosed with either fixed nozzle distributors or rotary
Fig. 3.17 Trickling filter
variations. (Source: US
EPA)
Fig. 3.18 Typical roughing filter installation. (Source: US EPA)
3 Biological Processes
121