Abstract: A slow sand filtering system is disclosed, in which an uncovered filter tank has therein a layer of sand, and an effective filter-enhancing amount of zeolite. The zeolite is topped by a growth of schmutzdecke, with the schmutzdecke comprising a layer of living organism selected from the group consisting of algae, plankton, diatoms, protozoa, rotifers and bacteria.

Abstract: A process of producing molten iron in a blast furnace in which the alkali loading to the blast furnace is at least about four pounds of alkali oxides per ton of hot metal produced, in which the alkali metal content in the furnace slag fluctuates widely due to repetitive accumulation and purging of alkali metals in the furnace over extended operating periods with corresponding fluctuations in the sulfur content and temperature of the molten metal, and in which the MgO content in the furnace slag is in the range of about 6 to about 18% by weight. Olivine is added to the furnace charge, preferably on a substantially continuous basis at an average rate of about 10 to about 100 pounds of olivine per ton of molten iron produced in the furnace, to effect the removal of the alkali metals from the furnace in the furnace slag and thereby stabilize the furnace operation.