Nalco, Inc. Polymers N8701 (NALMET®) and N8186 (ULTRION®)


This system has been treating dental-unit wastewater for 4 years and is able to remove mercury levels to the single digit parts per billion (ppb, microgram per liter) range. Dental-unit wastewater is pumped into a treatment tank. The pH is adjusted and the polymers are added and mixed. The two polymers are an aqueous 20-40% solution of aluminum hydroxychloride and polyquaternary amine at pH 4.0 (Nalco polymer N8186, ULTRION® Nalco Chemical Company, Naperville, IL) and an aqueous solution of polymeric precipitant and salt at pH 11.5-13.0, which has metal chelating molecules bound to a polymer backbone (Nalco polymer N8702, NALMET® Nalco Chemical Company). The company recommends a pH range of 6.0-9.0 as optimal for the use of these polymers. The sludge produced is dewatered with an industry standard plate and frame filter press. The dewatered sludge can be recycled at licensed mercury retorting facilities or disposed of at licensed hazardous waste landfills. The point of contact is Dr. Pek Lee Choo, 630-305-2394. The addition of polishing systems after polymer treatment can remove mercury levels down to non-detectable levels at the part per trillion range (ppt, nanogram per liter).

For more information, visit the Nalco, Inc. web site.


Netzsch® filter press (foreground) with the treatment tank in background. The polymer-treated wastewater is pumped through the filter press to dewater the sludge. The filtrate is discharged to the sewer or additional mercury can be removed with polishing technologies from SolmeteX, Inc. The mercury containing dewatered sludge is collected and sent for recycling at a licensed retorting facility. The system runs in a batch mode. For a 110-chair clinic, the system is operated 4 times per month.