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Priority Pollutant Removal Efficiencies (%) Through Trickling Filter Treatment* <br />Priority Pollutant <br />Range <br />Second <br />Decile <br />Median <br />Eighth <br />Decile <br />Number of POTWs <br />with Removal Data <br />METALS/NONMETAL INORGANICS** <br />Cadmium <br />33-96 <br />33 <br />68 <br />93 <br />6 of 11 <br />Chromium <br />5-92 <br />34 <br />55 <br />71 <br />9 of 11 <br />Copper <br />12-97 <br />32 <br />61 <br />89 <br />9 of 11 <br />Cyanide <br />7-88 <br />33 <br />59 <br />79 <br />8 of 11 <br />Lead <br />4-84 <br />25 <br />55 <br />70 <br />6 of 11 <br />Mercury <br />14-80 <br />33 <br />50 <br />62 <br />9 of 11 <br />Nickel <br />7-72 <br />11 <br />29 <br />57 <br />9 of 11 <br />Silver <br />11-93 <br />38 <br />66 <br />86 <br />8 of 11 <br />Zinc <br />14-90 <br />34 <br />67 <br />81 <br />9 of 11 <br />ORGANICS** <br />Benzene <br />5-98 <br />50 <br />75 <br />93 <br />7 of 11 <br />Chloroform <br />21-94 <br />50 <br />73 <br />84 <br />9 of 11 <br />1,2-trans-Dichloroeth lene <br />14-99 <br />50 <br />50 <br />96 <br />7 of 11 <br />Eth (benzene <br />45-97 <br />50 <br />80 <br />91 <br />10 of 11 <br />Methylene chloride <br />5-98 <br />28 <br />70 <br />85 <br />10 of 11 <br />Naphthalene <br />33-93 <br />40 <br />71 <br />87 <br />6 of 11 <br />Phenol <br />50-99 <br />75 <br />84 <br />96 <br />8 of 11 <br />Bis 2-eth (hex Iphthalate <br />4-98 <br />21 <br />58 <br />81 <br />10 of 11 <br />Butyl benzyl phthalate <br />25-90 <br />37 <br />60 <br />77 <br />9 of 11 <br />Di -n -but I phthalate <br />29-97 <br />41 <br />60 <br />82 <br />10 of 11 <br />Diethyl phthalate <br />17-75 <br />40 <br />57 <br />67 <br />8 of 11 <br />Tetrachloroethylene <br />26-99 <br />53 <br />80 <br />93 <br />10 of 11 <br />Toluene <br />17-99 <br />80 <br />93 <br />97 <br />10 of 11 <br />1,1,1 -Trichloroethane <br />23-99 <br />75 <br />89 <br />97 <br />10 of 11 <br />Trichloroethylene <br />50-99 <br />67 <br />94 <br />98 <br />10 of 11 <br />* Pollutant removals between POTW influent and secondary effluent (including secondary clarification). <br />Based on a computer analysis of POTW removal efficiency data (derived from actual POTW influent and <br />effluent sampling data) provided in U.S EPA's Fate ofPriority Pollutants in Publicly Owned Treatment <br />Works, Volume II, (EPA 440/182/303), September 1982. <br />** For the purpose of deriving removal efficiencies, effluent levels reported as below detection were set <br />equal to the reported detection limits. All secondary trickling filter plants sampled as part of the study <br />were considered. <br />Source: U.S. EPA's Guidance Manual on the Development and Implementation of Local Discharger <br />Limitations Under the Pretreatment Program, December 1987, p. 3-57. <br />R-3 <br />