Using of sewage sludge in silicate technologies.

Using of sewage sludge in silicate technologies.

Abstract

Sewage sludge from the cleaning of municipal wastewater has been commonly used after anaerobic fermentation partly in agriculture as fertiliser but most of this waste has been problematic because often concentration limits of toxic compounds are exceeded. Their storage in a dump is not perspective and is probably expensive. The best way of liquidation is manufacturing at high temperature process, where the toxic organic compounds produce harmless gaseous products. In contrast, inorganic compounds from simpler oxides or elements, this can play a negative role for human health and the environment. The best technological solution is the incorporation of a separation unit in the process. Mercury is the most dangerous and frequent in various forms. The phase stability of this liquid metal is not advantageous for high temperature process of burning but it is possible to separate it in a drying step. Experimental works were focused on the determination of drying and the simultaneous escaping of mercury in temperature range from 80 to 290°C in open crucibles with various thickness of dried material and defined free surfaces. Some experiments were oriented to the evaluation of influence of solid admixtures on the basis of limestone. It can be concluded, that the essential decreasing of mercury content in the sewage sludge is influenced by the formation of intensive gaseous flow from the solid phase. After the drying period at temperature about 200°C when the burning process starts sharply, temperature in solid phase achieves 350 – 450°C. The use of powder limestone as a solid phase for the improvement of the sewage sludge properties was demonstrated as the other characteristics of evaporation of water and mercury. The sewage sludge or dried products may be used in a massive production of cements where temperature in a cement rotary kiln about 1500°C guarantees a perfect transformation of organic compounds. The achieved results in presented work prove that a seriously environmental pure process of liquidation of mercury in the processed sewage sludge requires the incorporation of a drying unit into the technological process.

SPONAR, J., HAVLICA, J.

01.01.1999

Brno

80-214-1371-9

1st Meeting on Chemistry & Life, Book of Abstracts

84