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Pollution Prevention and Control Technologies for Plating Operations


Section 3 - Chemical Recovery

3.1 INTRODUCTION

Various technologies are used by plating shops to separate plating chemicals from rinse waters and air emissions or to concentrate them, thereby making them available for reuse/recycle. Respondents to the Users Survey (see description in Section 1.1.5) employ seven different types of technologies; these are:

  • Atmospheric Evaporation
  • Vacuum Evaporation
  • Ion Exchange
  • Electrowinning
  • Electrodialysis
  • Reverse Osmosis
  • Meshpad Mist Eliminator

Although many of the recovery technology applications identified by the respondents have been successful, there are also many unsuccessful applications. The success/failure rate reported by respondents to the Users Survey varied by technology and application. Exhibit 3-1 presents a summary of the technologies and applications identified during the Users Survey and it shows the average success rating given by the respondents. Technology success was measured by respondents on a scale of 1 to 5, with 1 being the least successful and 5 being the most successful.

 

Exhibit 3-1 Distribution and Ratings of Chemical Recovery Technologies

When evaluating success and failure ratings of the Users Survey, one must consider the reasons why the respondents purchased the recovery technologies. A summary of these data is presented in Exhibit 3-2. In the survey form, the respondents were given a choice of five specific reasons why they may have purchased the technology, plus an opportunity to list "other" reasons. The question was worded and formatted in a way that multiple responses were possible. The results are somewhat surprising in that reducing chemical purchases (i.e., recovering the plating chemicals), which is the primary function of recovery technologies, was not the most frequently given response. Rather, meeting or helping to meet effluent regulations was cited much more frequently. Reducing plating chemical purchases, reducing the quantity of waste shipped off-site and reducing wastewater treatment costs were cited approximately the same number of times as reasons for purchasing the recovery technologies.

The remainder of this section presents the results of the Users Survey, Vendors Survey and literature search with regard to the chemical recovery technologies employed by the survey respondents. The Users Survey requested platers to provide detailed technical, performance and operating cost data for chemical recovery technologies. The vendors were requested to provide technology descriptions, operating data and capital cost data. As a result of obtaining data from these two sources, plus the information from the extensive literature review, this section contains a substantial quantity of information for the following chemical recovery technologies: electrodialysis, electrowinning, atmospheric evaporators, vacuum evaporators, ion exchange, reverse osmosis and mesh pad mist eliminators. A separate subsection of the report is devoted to each of these technologies. Within each subsection, the following are provided: technology overview; development and commercialization; applications and restrictions (with diagrams showing different potential configurations); technology/equipment description; capital costs; operating costs; performance experience; and residuals generation. The capital cost curves contained in Section 3 are based on data collected from the technology vendors and the operating cost curves are based mainly on data from platers. Both the capital and operating cost information are expressed in 1993 dollars. A labor cost of $25 per hour (includes overhead) and an electricity cost of $0.10/kWh have been used, where applicable, in calculating operating costs.


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