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74 <br /> 11-3 SINGLE-PASS (INTERMITTENT) PACKED-BED FILTERS 719 <br /> TABLE 11-4 <br /> Summary of ISF performance with respect to the removal of BOD and nitrogen <br /> _. - <br /> - BOD, Total nitrogen <br /> Influent Effluent % <br /> Study and location mg/L mg/L removal Influent Effluent removal <br /> Grantham-et al. (1949), Florida' 148 .14 90 37 32 14 <br /> Furman et al. (1955), Florida 57 4-8 92 30 16 47 <br /> f Sauer(1976), Wisconsin 123 9 93 ndf nd, nd <br /> Ronayne et al. (1984),Oregon 217 3.2 98 58 30 48 <br /> Effert et al. (1988),Ohio 127 4 97 42 38 10 <br /> Stinson Beach, California(1987-1990) 203 11 94 57 41 28 <br /> Noy(1991), Davis, California 82 0.5 99 14 7.2 47 <br /> Town of Paradise, California(1992) 148 6 96 38 19 50 <br /> 'Relatively high hydraulic loadings(1.7 to 4 ga1/ft2-d)and shallow beds(18 to 30 in). <br /> �nd=no data. <br /> High hydraulic loading rates(2 to 10 gal/fF-d). <br /> Design Considerations <br /> Factors of importance in the design of ISF systems include type and size of filter <br /> medium, depth of filter bed,hydraulic loading rate, organic loading rate, and dosing <br /> frequency and duration. These design considerations are examined'in the following <br /> material. Typical design criteria for ISF systems are summarized in Table 11-6.Cor- <br /> responding design criteria for multipass filters are given in the following section. A <br /> range of values is given in Table 11-6 because the specific design values used will <br /> depend on treatment objectives. For example, if the effluent is to be disposed of <br /> p in <br /> ieachfields which are in a clayey soil, then only BOD and TSS removal are of im- <br /> portance to prevent the formation of biological mats, and a larger-size filter medium <br /> and higher hydraulic and organic loading rates can be used. If, on the other hand, <br /> the removal of viruses is important, then lower hydraulic and organic loading rates <br /> must be used (see Fig. 11-7). E <br /> Types and sizes of filter media: Sand, as noted previously, is the most <br /> commonly used filter medium. Most,sands are mined from river deposits. The gra- i <br /> dation of sand as well as other granular filter media is determined by using a series of. <br /> l <br /> TABLE 11-5 ' <br /> I � <br /> Fecal coliform removal in ISF systems ra <br /> Fecal coliform, <br /> Type of system No./100 mL o� <br /> Study and location and pretreatment Influent Effluent removal <br /> Sauer(1976),Wisconson Home/septic tank 590,000 650 99.9 <br /> Ronayne et al. (1984),Oregon Home/septic tank 260,000 407 99.8 <br /> Effert et al. (1985),Ohio Home/septic tank 219,000 1600 99.3 <br /> Effert et al. (1985), Ohio Home/aerobic unit 5890 123 97.9 <br /> 9 <br />