WEF Discussion Forums
Operation and Maintenance
I am trying to learn more about programs used by other utilities to help control mercury from a pretreatment standpoint. For example, does your entity have the following programs in place?
1) Amalgam separator program with local dentists? Inspection process?
2) Programs for photo finishers to remove Hg prior to the collection system? Inspection process?
3) Program that investigates and identifies all potential and real sources of Hg from all non-domestic sources including schools? Inspection process?
4) Other programs or lessons learned?
I was an industrial waste engineer for City of Toronto. We did a joint study on dental practices with Environment Canada. There are 2000 dentists in the City. We amended the City by-law to demand that all dentists install and maintain amalgam traps. The month after the deadline was imposed there was 40-80% reduction in influent mercury at 4 Toronto STPs. The remainder is probably legacy mercury from dental and other uses sitting in sewers - with specific gravity of 11-12 it doesn't like to move in sewer systems. Piles of amalgam can be seen in dental plumbing systems if no amalgam trap is in place.
Plumbing and maintenance of the traps are key issues; You just can't buy a trap and install it willy-nilly or fail to maintain it.
In my opinion 90%+ of all mercury entering an STP may be from dentists.