A bench case study was performed on a processed waste sample from a printed circuit board manufacturer near Charlotte NC. The client supplied approximately ten (10) gallons of lead bearing waste to LES’ facility on December 18, 1995. The waste sample had a slight blue color with a foamy film on the surface. The pH of the raw sample was 5.5. A portion of the feed sample was collected and submitted for lead and zinc analysis; the results are presented in Table 1.
The balance of the lead waste was processed through the ENVIRO-CLEAN PROCESS pilot carbon unit. The system consisted of a feed pump, pH controller and two (2) carbon columns. Each column contained about 200 grams of proprietary treated granular activated carbon. Effluent samples were collected and analyzed for total lead and zinc. This validation study was conducted to verify the system’s capability to remove lead to acceptable discharge levels. The effluent lead and zinc results are presented in Table 1.0, with the time periods marked in parenthesis, designating when the sample was collected during the test run.
TABLE 1.0 ENVIRO-CLEAN EFFLUENT ANALYSIS
|Sample||Lead (mg/l)||Zinc (mg/l)|
|Sample #1 (5 hrs)||<2||30|
|Sample #2 (17 hrs)||<2||18|
|Sample #3 (19 hrs)||<2||24|
|Sample #4 (21 hrs)||<2||14|
|Sample #5 (23 hrs)||<2||29|
|Sample #6 (30 hrs)||<2||19|
Enviro-Clean Process Results
The ENVIRO-CLEAN PROCESS was able to produce a low level lead and zinc effluent and meet the client s target heavy metal discharge limit of 10 mg/l and 50 mg/l . The pilot unit’s effluent concentration averaged 99.8% for lead and 81.7% for Zinc. The ENVIRO-CLEAN PROCESS produced an effluent which met or exceeded the client’s targeted heavy metal discharge limits.
The effluent from the ENVIRO-CLEAN PROCESS can be recycled at the plant eliminating a significant quantity of water being discharged; one option is to recycle the effluent (or some percentage of it ) back to the production operation. It was estimated that the client could save $4,200 each year from water savings. The estimated water savings are based on water pretreatment and discharge cost reductions totaling $1.00 per 1000 gallons.