Laserfiche WebLink
Attachment C Page 4 of 8 <br /> SIGMA CIRCUITS Inc . , STOCKTON DIVISION <br /> FIELD SITE <br /> TREATMENT UNIT OPERATION <br /> UNIT 1 (Continued ) <br /> Process: <br /> A ) Wastewater from the process is collected in the WRT . In <br /> addition , the WRT also receives metal -bearing filtrate <br /> from the filter press in this system, clarified waste for <br /> rework , and miscellaneous waste (MW) from the MWRT in <br /> small increments. <br /> Sodium hydroxide (caustic soda) is added to raise the pH <br /> to about 9 . A special metal complexant / precipitant is <br /> also added to this tank . Small amounts of sodium sulfide <br /> are also added to aid in metal removal from solution . <br /> Initial precipitation of the dissolved metals of concern <br /> in the wastewater , notably copper and lead in this plant , <br /> occurs in this tank . Retention time is normally 45-60 <br /> minutes , depending on the flow rate into the tank . <br /> B ) The slurry in the WRT, containing some precipitated <br /> metals, is then pumped to the second treatment tank , <br /> termed the Metal Mixing Tank (MMT ) . A liquid cationic <br /> polymer is added to this tank . During the residence time <br /> in the MMT, about 45-50 minutes at 20 gpm, this polymer <br /> acts as a 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 the <br /> tank to the Flocculation and Settling Tank (FST) at the <br /> top where slow mixing and some settling of the slurry <br /> occurs . Flocculent is injected into the slurry as it <br /> enters the top of this tank . Residence time is about 80- <br /> 90 minutes , depending on the flow. <br />