The Application of Ion-Exchange and Modified Rinsing Procedures to Minimize Treatment Costs

INTRODUCTION The capital cost of treating wastewater generated from a metal finishing operation is primarily a function of the rinse water volume to be treated. Many wastewater treatment systems installed during the 1970's were oversized since water conservation measures were not always fully exploited. It is anticipated that systems designed during the 1980's in response to the pretreatment regulations will be less costly due to the increased awareness of this factor. However, the approach of minimizing water usage does not necessarily result in the lowest cost treatment system. It would be more cost-effective to focus on minimizing the quantity of process chemicals lost in the drag-out and to segregate residual drag-out loads into small rinse volumes that can be recovered or treated in a simple and inexpensive batch treatment system. By reducing pollutant loads discharged from the process line, operating costs as well as capital costs can be minimized. Background information on this approach is described below with an example of a system design to illustrate the application of in-line process controls.