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~ ~,; ~ ~ ; <br />C• II. Process Description <br />From past and on going test programs,the most economical method to <br />treat the mine discharge includes cha~~ical addition, coagulation, oxidation and <br />separation of heavy metal precipitates. lime :is added to the discharge to raise <br />the pii high enough for the forriation of zinc hydroxide which is then coagulated <br />by pollrmers and separated front the ef:lueut in a filter bed or standard type <br />t}~ickener. <br />Approximately 9S percent of the soluble zinc is removed at a pH of <br />S - S.S faith a lime dosage of 2S - 30 mg. per liter. Separan NP-10 leas used as <br />the polymer to coagulate the zinc hydroxide and a dosage of 0.3 mg. per liter <br />was found to be sufficient. <br />III. Water Quality <br />From many sets of analysis average discharge concentrations of the <br />mine water is as follotas: <br />- Existing Discharge Concentrations - <br /> (in mg/L) <br />C• Parameter Concentration NPDES himitations <br />Suspended Solids 13.2 25 <br />Iron 0.4 2.0 <br />Lead 0.12 0.2 <br />Zinc{ 7.Sf O.Sf <br />Cadmium 0.02 0.02 <br />Copperx less '1'l~an O.lY 0.05 <br />Mercury less than 0.001 0.001 <br />Oil $ Grease less than 0.1 0.1 <br />IV. Effect of 1Nater Treatment <br />Tixe Bulldog Mine discharge contributes only minor amounts of pollutants <br />to the iVillow Creek Basin. By treating the mine discharge, only a small improve- <br />ment in the drainage will be realized but under the NPDES Permit reRuircments, <br />treatment is mandatory. hir. ]Nights cover.no letter i.s attached to this report <br />for your reference. <br />~. <br />i <br />1 <br />- 151 - - -... .. <br />