Metal Finishing Guide Book


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Fig. 1. Lamella-type clarifier. (Lamella is a registered trademark of Parkson Corp., Lake Bluff, IL) overall purpose of this type of equipment is to remove solids from water streams by gravitational settling in a relatively small area. In much the same way that the polymeric detackifier/flocculent programs remove paint solids,the basic principle involves capturing lightweight dispersed solids and increasing their density/weight with the organic polymers or inorganic materials. Clarifiers come in various designs, ranging from large rectangular pits to circular tanks (see Fig. 1). The larger circular clarifiers are quite common in continuous treatment type systems with daily flow rates in excess of 250,000 gal/day. For smaller systems, as are typically found in metal fabrication operations, the lamella-type clarifier is quite common (see Fig. 2).The lamella makes use of stacked flow plates to effectively increase the settling surface area to equal that of a much larger tank-type clarifier, resulting in a system that will separate a large amount of solids while requiring a relatively small amount of floor space. The basic mode of operation followed in industrial waste treatment is: 1. The water stream containing spent detergent solutions, rinse solutions, waste process water, and any other waterborne waste materials is cycled into the treatment system, either continuously or in a batch process; 2. Chemical additions are made to the wastewater, including adjustments to pH and reduction of metals such as hexavalent chromium; 3. Treatment chemical additions are made to the adjusted wastewater to aid precipitation (settling) of solids; this treatment may consist of addition of in711

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