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ATTACHMENT C PAGE 4 OF 7 <br /> INITIAL PRECIPITATION OF THE DISSOLVED METALS OF <br /> CONCERN IN THE WASTEWATER, NOTABLY COPPER, LEAD, <br /> AND NICKEL, OCCURS IN THIS TANK. RETENTION TIME <br /> IS NORMALLY 15-20 MINUTES, DEPENDING ON THE FLOW <br /> RATE INTO THE TANK. <br /> B) THE SLURRY IN THE WRT, CONTAINING SOME <br /> PRECIPITATED METALS, IS THEN PUMPED TO THE SECOND <br /> TREATMENT TANK, TERMED THE METAL MIXING TANK <br /> (MMT) . A LIQUID CATIONIC POLYMER IS ADDED TO THIS <br /> TANK. DURING THE RESIDENCE TIME IN THE FMT, ABOUT <br /> 45-50 MINUTES AT 20 GPM, THIS POLYMER ACTS AS A <br /> COAGULANT AND LEADS TO "PIN FLOC" FORMATION, OR <br /> SMALL, BB-SIZED AGGLOMERATES IN THIS TANK. <br /> C) THE SLURRY FROM THE MMT THEN FLOWS OUT THE SIDE OF <br /> THE TANK TO THE FIRST FLOCCULATION TANK AT THE TOP <br /> WHERE ADDITIONAL MIXING OF THE SLURRY OCCURS . <br /> FLOCCULANT IS ADDED TO THE TOP OF THIS TANK . <br /> RESIDENCE TIME IS ABOUT 30-35 MINUTES, DEPENDING <br /> ON THE FLOW. <br /> D) THE SLURRY IS THEN PUMPED FROM THE FIRST <br /> FLOCCULATION TANK TO THE SECOND FLOCCULATION TANK <br /> WHERE SLOW MIXING AND FINAL FLOCKING OF THE <br /> PRECIPITATE TAKES PLACE. ADDITIONAL FLOCCULANT IS <br /> ADDED IF NECESSARY. <br /> E ) FROM THE SECOND FLOCCULATION TANK, THE SLURRY THEN <br /> FLOWS TO THE FIRST CLARIFIER WHERE THE PRELIMINARY <br /> SETTLING OF THE METAL-BEARING SLUDGES OCCURS. <br /> RESIDENCE ' TIME IN THIS CLARIFIER IS VERY LONG <br /> (OVER 2 HOURS AT THE NORMAL FLOW) . <br /> F) THE SUPERNATE FROM THE FIRST CLARIFIER THEN FLOWS <br /> BY GRAVITY TO THE TWO CASCADE TANKS. THESE TANKS <br /> ARE CONNECTED IN SERIES SUCH THAT THE RESIDENCE <br /> TIME IN EACH IS 10 MINUTES AT 15 GPM. <br /> G) THE TREATED WASTEWATER THEN FLOWS FROM THE TOP OF <br /> THE SECOND CASCADE TANK TO THE SECOND CLARIFIER, <br /> WHERE FINAL SETTLING TAKES PLACE. RETENTION TIME <br /> IS GREATER THAN 1 HOUR. <br />