TABLE OF CONTENTS The process design of rapid infiltration systems is generally governed by the infiltration rate and permeability of the soil. Selection of the hydraulic loading rate can also affect the removal of nitrogen and phosphorus.
The preapplication treatment for RI systems ranges from primary treatment to secondary treatment (see Chap. 8). Hydraulic loading rates range from 20 to 400 ft/year (6 to 120 m/year). As shown in Table 12.1, several RI systems have been operating for more than 40 years with application of primary effluent. The system at Whittier Narrows recharges the potable groundwater and is in an urban area; thus the preapplication treatment is tertiary (filtered secondary).
| Location | Type of wastewater | Year started | Flow, mgd | Hydraulic loading, ft/year | Effluent disposition |
|---|---|---|---|---|---|
| Calumet, Mich. | Raw | 1887 | 1.6 | 116 | Surface |
| Fontana, Calif. | Primary | 1953 | 2.9 | 57 | Groundwater |
| Ft. Devens, Mass. | Primary | 1941 | 1.0 | 100 | Surface |
| Hollister, Calif. | Primary | 1946 | 1.0 | 50 | Surface |
| Lake George, N.Y. | Secondary | 1939 | 1.1 | 140 | Surface |
| Milton, Wis. | Secondary | 1937 | 0.3 | 360 | Groundwater |
| Phoenix, Ariz. | Secondary | 1974 | 13.0 | 200 | Reuse |
| Seabrook Farms, N.J. | Screened cannery | 1950 | 3.4 | 53 | Groundwater |
| Vineland, N.J. | Primary | 1927 | 4.1 | 70 | Surface |
| Whittier Narrows, Calif. | Tertiary | 1963 | 12.5 | 160 | Groundwater |
Most of the 320 RI systems in the United States discharge the treated water indirectly into nearby surface water, as shown in Fig. 2.2.
The typical procedure for design of RI basins is as follows:
Determine the design infiltration...
