The Local Agenda 21 Planning Guide - Democrats Against UN ...

The Local Agenda 21 Planning Guide
provided stations for the collection of household hazardous wastes.
For their part, local households switched to products that have been determined to be environmentally superior, reduced usage of
household products containing polluting substances, and disposed of household hazardous wastes at collection points instead of
directly into the sewer system.
Reducing Mercury Discharges
Vatten’s efforts to reduce mercury discharges provide an example of this combined regulatory and cooperative approach. In
Stockholm, the sludge produced at the Henriksdal waste-water treatment plant, the largest of Vatten’s three sewage treatment
facilities, had a particularly high mercury concentration. The concentration was so high that, if left unabated, it would exceed limits
set by new national standards coming into force in 1995. In 1987,Vatten initiated investigations into the sources of mercury in
wastewater, and the reasons why mercury loads in Henriksdal were higher than in other treatment plants.
The investigation process involved identifying all of the possible sources of mercury in Stockholm. An inventory was taken of smalland
medium-sized companies that used mercury in some way in their production or trade, such as companies manufacturing
fluorescent tubes, laboratory devices and instruments, and dental materials. Heavy industries were ruled out as potential sources of
mercury discharges because these industries were not connected to Stockholm’s sewerage and drainage network.
The inventory identified 18 companies, which were then contacted and visited. The investigation concluded that the processes used
by these companies were dealt with in such a way that either no contamination of the wastewater could occur or that accidental
mercury discharges were highly unlikely. Thus, small industries connected to the sewage system were eliminated as possible sources
of mercury.
Analyses conducted during the investigation showed that about 20 percent of the total mercury load in the Henriksdal plant came
from storm drains. These loadings were largely traced to the smoke fumes emitted by crematoria. Tests conducted in the two
crematoria located in the Stockholm area had shown that crematoria smoke emissions contained some 50 kilograms of mercury each
year. These emissions were presumed to find their way to treatment plants via storm water drains.
Samplings of household wastewater indicated that about 15 percent of the total mercury levels entered the sewerage system through
the use of mercury thermometers in the home and from small amounts of mercury in food and in amalgam fillings in teeth.
Samplings of discharges from hospitals, which use instruments and chemicals containing mercury, demonstrated that these
institutions emit some 6 percent of the mercury loading in the Henriksdal plant system. Reduction in mercury discharges from
hospitals was expected due to efforts to minimize the use of instruments and chemicals containing mercury in these institutions.
Based upon these findings, which accounted for only a portion of the mercury levels found in the wastewaters entering the
Henriksdal plant,Vatten hypothesized that remaining discharges came from the more than 1,100 dentists in the Henriksdal area. The
number of dentists in the Henriksdal area was three times the number of dentists connected to Vatten’s other treatment plants. An
investigation showed that sewage from the dental clinics had a mercury concentration 150 to 1,300 times higher than levels found in
sewage from households. A 1988 investigation found that the amalgam separators used in dental offices as a measure to reduce
mercury discharges functioned poorly due to bad construction and poor maintenance. This accounted for the presence of amalgam in
the water traps of sinks installed in these clinics.
To address this situation, Vatten, in cooperation with the local environmental protection authority, developed standards for dental
clinics connected to the municipal sewer system that exceeded Swedish national standards. These local standards, jointly
implemented by the cities of Stockholm, Malmo, and Gothenburg, require that by January 1, 1994, all dentists must use amalgam
separators that have passed the German or Danish national standards for amalgam separators. In addition, the local standards require
that water that comes into contact with amalgam should be treated by an amalgam separator before discharge into the sewer system.
This means that clinics must connect their washing machines, sinks, and dental chair drains to the amalgam separators.
Requirements for the maintenance of these separators are also part of these new local standards.
Using the new standards as a minimum practice requirement, Vatten has initiated cooperative efforts with the Swedish Dental
Federation to address the dual problem of low separator efficiency and the continual leakage of mercury from the amalgam
accumulated in the pipes. An information campaign has been conducted to increase awareness of the problem as well as to promote
the proper handling of amalgam by dental personnel.
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