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Pollution Prevention and Control Technologies for Plating Operations
Section 2 - General Waste Reduction Practices
2.4 DRAG-OUT REDUCTION
2.4.2 Drag-Out Reduction Techniques
The Users Survey indicates that many devices and procedures are used successfully to reduce drag-out. These techniques usually are employed to alter viscosity, chemical concentration, surface tension, velocity of withdrawal, and temperature. Also used are drag-out tanks and similar equipment for capturing lost plating solution and for returning it to the bath.
Most drag-out reduction methods are inexpensive to implement and are repaid promptly through savings in plating and processing chemicals. An additional savings many times the cost of the changes is realized through decreased operating costs of a pollution control system. The reduced drag-out will decrease the need for treatment chemicals and, subsequently, the volume of sludge produced.
For some process solutions, return of drag-out may be impractical. In the case of processing baths which become steadily contaminated by use, the return of drag-out would simply increase the frequency of dumping (ref. 305). For example, PS 116 reported that drag-out recovery with electropolishing was ìcounterproductive.î
The following subsections provide further detail and discuss the results of the Users Survey with respect to drag-out loss prevention. A summary of the Users Survey data relating to drag-out loss prevention is presented in Exhibit 2-10. As with the good operating practices, there is a high usage rate of these pollution prevention methods among respondents and all of the methods have received a success rating above the mid-point of the rating scale.
2.4.2.1 Minimizing Drag-Out Formation
2.4.2.2 Direct Drag-Out Return
2.4.2.3 Drag-Out Recovery and Return