Copper CMP/CMP Wastewater Treatment - A Classical Method With A Recycling Twist

Challenge
Siemens Water Technologies was approached by a semiconductor tool manufacturer based in Silicon Valley to assist in the design of an automated CMP and copper CMP waste treatment system. After careful economic evaluations, it became clear that the largest cost of ownership of the treatment system was the removal of the hazardous waste sludge from a classical two stage precipitation/clarification system. Any method of precipitation produces copper sludge which would be required to be handled as a hazardous waste in the state of California.

Solution
Siemens Water Technologies looked at another approach which would remove the copper prior to particle flocculation and precipitation. An ion exchange process developed and patented by Siemens Water Technologies marketed as Copper Select™ was considered. This process removes copper from copper CMP wastewater without the need to remove CMP solids present in the water. The copper-free wastewater still bearing the CMP solids could be then sent to a classical precipitation system from flocculation and coagulation of the solids remaining.

Results
Siemens Water Technologies designed a system which had a multi-purpose collection/pH adjustment tank in the lead position. Following this, copper removal was accomplished using the Copper Select technology. Finally, solids were removed in a standard dual chamber continuous precipitation system. Gravity settled solids were feed to a filter press for further dewatering.

After some initial start-up adjustments, the 20-gallon per minute system worked effectively by removing copper in the ion exchange process followed by solids removal in the standard dual-stage precipitation unit. The solids generated from the precipitation system were dewatered utilizing gravity settling followed by further dewatering in the filter press. Analysis of the solids showed copper levels below the 1 ppm level, allowing for non-hazardous landfill disposal. The copper bound to the ion exchange resin was recycled after the resin had achieved capacity and sent to Siemens Water Technologies Recovery Services for regeneration.

Since all metals from spent regenerant are recycled, Siemens Water Technologies was able to provide recycling documentation to the customer for use in state and federal hazardous waste generation documentation. In many states, this recycling effort is rewarded by the state government in the form of tax reduction.