Baseline data for the Copper Plating and Mechanical Polishing Process. The baseline effluent loading used in this document is an average calculated from 1996 copper concentration data using the analytical detection limit of .02 mg/l for those analyses where copper was reported as non-detectable. Influent loading was determined by the same technique using data from 1994-1996. Using the influent and effluent loadings, an average removal efficiency in the treatment system for copper of 55% was determined. This value is conservative, as copper concentrations in the influent and the effluent are often at or near the analytical detection limit. The expected baseline copper loadings to the wastewater treatment system were calculated by multiplying these average values times the expected flow through the wastewater treatment plant over the years 1997-2001. Measurement and calculation work was performed to determine the mass of copper carried into the rinsewater and removed by the mechanical polishing process. To determine dragout, the process engineers weighed a wafer prior to its introduction to the process and then weighed it again prior to introducing it to the rinsing step. Several measurements were taken to verify that the value measured was reproducible. The quantity of copper removed by the mechanical polishing step was calculated by taking the average thickness of the layer of copper applied to the wafer, the thickness of the final copper depositions after polishing and the wafer surface area to calculate the quantity of copper removed. These per wafer values were then multiplied times the wafer processing plan to calculate the additional mass of copper introduced into the wastewater treatment system. Combining these values with the baseline generated the information provided in Tables 1 and 2 (pp. 16,17). The baseline copper loadings were then combined with the calculated electroplating rinsewater and mechanical polishing loadings to determine the impact of the copper processes on the IWTP sludge and wastewater effluent stream. Projected sludge generation was calculated from projected discharge flows and historical data on sludge production per volume of wastewater treated (Table 2, p.17). The IWTP discharge is regulated under the Clean Water Act, NPDES permit number 3-1295. The permitted discharge limit for copper was set by the State of Vermont Water Quality Division based on in-stream water quality standards for the receiving water. The monthly average copper discharge limit is 6.86 pounds per day and the daily maximum li...
