Mercury and cadmium report proposes landfill restrictions

A long-delayed Environment Agency report on mercury and cadmium recommends that wastes bearing the metals should be barred from co-disposal landfills.1 It also suggests tougher controls on metals in industrial minerals and fuels - and draws attention to the Government's failure to control mercury releases from dental premises.

The report, commissioned from WS Atkins by the Agency's predecessor, HM Inspectorate of Pollution, was completed in 1994. The delay appears to be due partly to Department of Health sensitivities over mercury releases from dental premises.

Aquatic discharges of cadmium and mercury have declined significantly, driven by North Sea Conference agreements to achieve a 70% reduction in inputs by 1995 on a 1985 baseline. The UK claims to have met the target for both metals, although its performance on atmospheric emissions is more questionable (ENDS Report 244, pp 19-22 ).

The report highlights the uncertain fate of the metals in landfills. Landfill "only represents a delay in reaching the hydrosphere and the sea," it argues - though it concedes that the time lag may be of the order of centuries.

The report recommends that "consideration should be given" to banning mercury and cadmium wastes from co-disposal landfills. "Restriction of these materials to inert special waste landfills (sic) will incur increasing landfill cost penalties and therefore is an additional factor in encouraging waste minimisation," it says. Presumably the authors are recommending pre-treatment of such wastes to reduce leachability followed by disposal in monofill sites.

In a separate project record,2 the authors say: "We feel that, on the precautionary principle, waste containing soluble and potentially soluble mercury and cadmium should be excluded from co-disposal landfills unless conclusive evidence can be shown that no environmental releases will occur."

They identify waste from the chlor-alkali industry, spent batteries and combustion residues as potential sources. And household waste already contains up to 5ppm of mercury and up to 12ppm of cadmium.

An emerging concern for landfills is that rising sales of nickel-cadmium rechargeable batteries are likely to result in higher concentrations in waste.

Battery recycling in the UK remains "embryonic", the report notes. The recycling rate was about 5% last year (ENDS Report 271, p 41 ). The report suggests that NiCd batteries were a potential source of 516 tonnes of cadmium in 1995. Mercury button cells are a significant mercury source but, according to the industry, are being phased out this year.

The report also examines the potential for controlling large releases from users of bulk minerals, coal and oil. It suggests that integrated pollution control authorisations could stipulate use of the least contaminated materials not incurring excessive cost. It further suggests that users should be required to obtain analysis certificates showing metal concentrations.

The report has nothing new to add on the significant amounts of mercury discharged to sewer by dental surgeries. DoE studies found that 81% of mercury in sewage - amounting to 5-7 tonnes per year - could be due to amalgam discharges from dental premises (ENDS Reports 247, p 10 , and 256, p 13 ).

Up to 95% of amalgam can be removed by separators fitted to dentists' chairs. The UK has accepted a Paris Commission recommendation that such equipment be fitted by January 1997. But the Agency says that the Government is only now preparing a code of practice promoting voluntary installation of separators. However, if the code is not completed quickly or does not deliver "a substantial and rapid decrease" in discharges, the Agency says it will push for regulations.

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