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Attachment C Page 5 of 8 <br /> SIGMA CIRCUITS Inc . , CITATION DIVISION <br /> FIELD SITE <br /> TREATMENT UNIT OPERATION <br /> UNIT 1 (Continued ) <br /> D) The slurry is then pumped from the first flocculation <br /> tank to the second flocculation tank where slow mixing <br /> and final flocking of the precipitate takes place. <br /> Additional flocculent is 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 (over 2 <br /> hours at the normal flow ) . <br /> F) The supernate from the first clarifier then flows by <br /> gravity to the two cascade tanks . These tanks are <br /> connected in series such that the residence time in <br /> each is 10 minutes at 15 gpm. <br /> G) The treated wastewater then flows from the top of the <br /> second cascade tank to the second clarifier , where <br /> final settling takes place. Retention time is greater <br /> than 1 hour . <br /> H) From the second clarifier , the water flows by gravity <br /> to the transfer tank , where it is pumped to the <br /> accumulation tanks. These tanks are plumbed to be used <br /> in alternate fashion ( i .e. , One is filling while the <br /> other is holding water for sampling and analysis prior <br /> to discharge) . <br /> I ) The contents of the accumulation tanks are sampled <br /> while filling and also when full . When one <br /> accumulation tank is full , the flow is switched over to <br /> the other tank and the first one is sampled and <br /> analyzed for metals. The process is reversed when the <br /> other tank is full . <br />