Thomas S. Barron, PE
The Palo Alto Regional Water Quality Control Plant (RWQCP) is one of three publicly owned treatment works that discharges treated wastewater to South San Francisco Bay.
In response to its own stringent copper discharge limit, the RWQCP has had to reduce the copper content of wastewaters received at the plant. This effort is focused upon all sources of copper, including stormwater runoff, as well as residential, commercial and industrial activities. Since most of the industrial copper in the Palo Alto area is discharged by metal finishing operations, particularly those associated with computer parts manufacture, the industrial portion of the copper source reduction efforts focuses on printed circuit board manufacturing and other metal finishing operations.
To achieve the needed reductions from the industrial sector while minimizing local economic impacts, the RWQCP (responding to input from the environmental community) opted to develop discharge reduction requirements based on pollution prevention, rather than pollution control. This is one of the first examples of the use of such requirements in place of more traditional pollutant concentration limitations or pollution control equipment requirements. RWQCP staff have been gratified by the positive response of both the business and environmental communities to the chosen regulatory approach.
What The Discharge Reduction Project Accomplished
In recent years the industrial contribution of waste copper to the RWQCP has been in the range of 750 to 850 pounds per year, which is about 16% of the total amount received at the plantís headworks. Approximately 250 pounds per year of this industrial copper have been discharged by 13 metal finishing and circuit board manufacturing facilities.
Source reduction efforts and wastewater treatment improvements at these 13 sites have reduced waste copper discharges by one-fourth below 1992 levels, reaching a level of 188 pounds for 1996. Additional reductions are expected in 1997.How The Project Was Organized
The RWQCP formed a Metals Advisory Group, comprised of local businesses, individual citizens, and environmental organizations, that helped formulate this regulatory approach. This group met at each stage of the regulatory development process, and provided input in the following areas:
How Pollution Prevention Measures Were Identified
In 1993, the RWQCP began exploring the feasibility of the pollution prevention approach by conducting reviews of six volunteer metal finishing & circuit board facilities. These studies identified direct relationships between water pollutant discharges and: (1) water conservation, and (2) hazardous materials use reduction.
Next, these studies and similar evaluations conducted elsewhere were used to develop a set of pollution prevention measures, called "Reasonable Control Measures," or "RCMs." These measures are a set of "minimum" water pollution prevention standards for metal finishing operations.
Each RCM had to satisfy a number of criteria, including requirements that it be widely applicable, generally feasible for all operations, have a simple payback period of five years or less, and meet safety and product quality criteria.
Sewer Ordinance Provides Shops With Two Choices
In December 1994, the RWQCP adopted a new ordinance incorporating pollution prevention requirements for service area businesses that discharge copper. Metal finishers that work with copper have two options for compliance:
How The Ordinance Was Implemented
Individual Site Reviews Identified Copper Sources - In January 1995, the project team evaluated 84 individual waste copper sources at the 13 metal finishing and circuit board businesses in the RWQCP service area. These evaluation visits gave each site a list of the new control measures that it would have to install if it chose to have a concentration-based local limit. The 84 waste copper sources included:
Relative Sizes of Waste Copper Sources In 1994, the 13 sites discharged to the sewer an estimated 254 pounds of copper in treated wastewaters. As shown by Exhibit 2, about 84% of this copper came from etching baths and their rinses. About 67% of the 254 pounds of discharged copper was contributed by 13 microetch baths, located at 4 circuit board manufacturers. Another 17% of the total waste copper load came from other kinds of etch baths, operated by 10 metal finishing and circuit board shops. Smaller amounts of waste copper came from surface preparation and copper plating baths.
Overall Control Measure Status If all 20 or the possible control measures had been present at each of the 84 waste copper sources, then there could have been as many as 1,680 control measures for all 13 shops combined. Adding 5 potential treatment system measures at each of the 13 sites, the overall total is 1,745 potential measures.
However, a total of only 1,272 of the 1,680 source control measures were found to either be in use or judged to be "not applicable" at the 84 waste copper sources that were active in early 1995. This overall total of 1,272 measures is 76% of the 1,680 score that is possible for 84 sources.
Adding the tally of five control measures that potentially apply to wastewater treatment systems brings the overall percentage of measures up to 79%. These totals also include equivalent measures proposed by the sites as substitutes for one or more of the original list of 20 measures.
The designation of "not applicable" was given where a specific measure was judged to be technically inappropriate, for example:
Individual Control Measure Use In the January 1995 on-site reviews, the project team found that the control measures having to do with bath management and treatment were in use (or not applicable) at nearly all of the waste sources. However, drag-out minimization, countercurrent rinsing, and rinsewater flow control measures were much less common, appearing at only 35% to 64% of the waste copper sources.
Exhibit 3 shows these results for all 13 sites together, with bar graphs that include the additional measures that the sites put in place by July 1996. The blank spaces at the top of each bar graph represent measures that the sites could have installed, but had not yet done so.
Additional Copper Discharge Reduction Studies - During 1995, four sites requested pollution prevention studies to establish a mass limit for them, so that they could then choose between a concentration- and a mass-based local limit. Three other businesses declined a study, as they each had already made their choice to have a concentration limit. The remaining six firms had already had their study done.
One of the newly studied sites had cost-effective projects that could reduce its waste copper discharge. The other three each had technically feasible projects, but none that satisfied the requirement for an economic payback period of 5 years or less. These results were used to propose the annual copper mass discharge for each site. Separate reports have been published to document these studies.
Local Limit Choices - In late 1995, the 13 metal finishers and circuit board manufacturers weighed the results of their preliminary control measure evaluations and facility-specific pollution prevention studies.
Eight facilities chose to install the Reasonable Control Measures and meet a 1month rolling average concentration limit of 0.4 mg/l of copper, while five chose to achieve the annual copper discharge mass limit determined during their facility-specific study. One concentration limit site, in a decision unrelated to the new discharge requirements, announced that its operations would be moved outside the service area by the end of 1995.
Projects Implemented by the Sites - Exhibit 4 summarizes the number of projects that have been undertaken. In October, 1995, each company submitted a plan for implementing the projects needed to comply with its new discharge limits. One site immediately implemented the needed changes, while several others began their work in early 1996. All sites except for one completed their discharge reduction projects by the required date of July 1, 1996. This one firm continues to evaluate a number of alternative projects as substitutes to about 25 control measures out of its total of 420.
Exhibit 5. Annual Copper Discharges
Exhibit 6 summarizes the overall discharge reductions obtained by various kinds of projects. Improved wastewater treatment system operations caused the greatest reductions, accounting for an estimated 28 pounds per year of copper. Process changes and drag-out minimization were also significant. This category includes one site's conversion of an electroless copper line to direct metalization, and two sites that began pre-treating microetch drag-out solutions by electrowinning.
Exhibit 6. Discharge Reduction Results
On-Going Monitoring Program - The Palo Alto RWQCP is continuing its present program of monitoring copper discharges at each of the 11 metal finishing and circuit board sites. Exhibit 9 is an example of the discharge charts being prepared for each site. In addition, the RWQCP has issued procedures for wastewater sampling techniques, discharge flow measurements, and methods for computing 1month rolling average copper concentrations and mass loads. Provisions have also been made for sites that wish to request an increase their mass limit due to production expansions, or to convert from one type of discharge limit to the other. So far, three sites have made these types of changes.
Exhibit 7. Costs per Pound of Copper Discharge Reduction
Exhibit 8. Payback Periods for Projects and Sites
This fact sheet is an account of a project sponsored by the Palo Alto Regional Water Quality Control Plant. You may contact the plant at (415) 329-2598.
Exhibit 9. Example Copper Discharge Chart - Site K