No abstract

Mercury in the flue gas from waste incineration is predominantly in the vapour phase at temperatures down to 140 °C. Only a small portion of the mercury is metallic Hg°, most of it is oxidized, which has a high vapour pressure at these gas temperatures. Oxidized mercury is absorbed by fly ash and will be captured on fabric filters. By injecting fly ash and lime before a fabric filter a high degree of collection can be achieved, both for hydrochloric acid and for mercury. Up to 90% of the mercury can become attached to the dust. By optimizing the operation and with efficient dust removal it is therefore possible to limit mercury emissions to less than 0.3 g ton-1 of incinerated waste.

No abstract

The mutagenicity of emission samples from three oil-fired and four coal-fired boilers have been compared by using the Salmonella/microsome assay. Very little or no mutagenic activity was observed in samples from five of these boilers. The sample from one oil-fired boiler showed mutagenic activity of about 500 revertants/MJ, and the sample from a coal-fired fluidized bed combustor had an activity of 58,000 revertants/MJ measured with strain TA 98 in the absence of metabolic activation. All samples contained substances that were cytotoxic to the test bacteria, thus making it difficult to obtain linear dose-response curves. Mutagenic activity at low levels may remain undetected due to this toxicity of the samples. Samples with mutagenic activity below the detection limit in the Salmonella test have also been tested for forward mutations at the HGPRT locus in V79 hamster cells. Weak mutagenic effects were detected in two of the samples, whereas the sample from one oil-fired boiler remained negative. In this test, as well as in the Salmonella test, a strong cytotoxic effect could be observed with all samples.

No abstract