Metal Finishing Guide Book

2012 Organic Finishing Guidebook Issue

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Page 255 of 331

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 cir- cular tanks (see Fig. 1). The larger circular clarifiers are quite common in con- tinuous 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 treat- ment 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 in- 254

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