EURO-ECO 2009 Hanover 3 - 4 Dezember 2009	Environmental, Engineering - Economic and Legal Aspects for Sustainable Living
	European Academy of Natural Sciences, Hanover European Scientific Society, Hanover University of Bremen, Bremen

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In many regions all over world the environmental and potable water system pollution as a result of a mass anthropogenic influence is a real danger for the health of communities. Sulfates and the phosphates are in the list of the most widespread and the largest water bodies pollutants.

Entry of a big quantity of phosphates and sulfates in the water bodies is a consequence of the enterprises’ disposal of the polluted and underrefined sewage.

That’s why the development of the new methods of the sewage treatment and the increase of effectiveness of the existing ones are the problems of current importance.

For the sewage treatment from sulfates and phosphates we offer to use the Stary Oskol electric-steel making plant’s slag which is a micronized powder with a complex composition in which calcium and magnesium oxides in free and combined form predominate (table 1,2). This material relates to the group of autodecompositing metallurgical slags.

Table 1.Averaged composition of slag of Stary Oskol electric-steel making plant, %

CaO	MgO	Al2O3	FeO	MnO	SiO2	Cr2O3	M0
50,0–56,3	10,0–12,0	7,0–9,0	1,0–2,5	0,01–0,11	20,0–30,0	0,08–0,13	1,7–2,2

Table 2. Physical-chemical characteristics of slag

Characteristic	Unit	Values
Magnetic fraction content	%	8,5–11,6
True strength	kg/m3	3320–3330
Packed strenght	kg/m3	1100–1120
Content of (Ca+MgO)	%	3,6–12,4
pH of aqueous extract	–	10,65–10,75
Moisture	%	2,6–3,8
Specific surface	m2/kg	280–310

In free form calcium oxide exists like CaO and in combined form – like different silicates (for example, CaSiO₃. With addition of slag to aquatic environment the solution of CaO happens with formation of Ca(OH)₂ and then the reaction with formation of poorly soluble sulfate and phosphate compounds is possible.

PO43-+ 3Ca2+ → Ca3(PO4)↓;

SO42-+ Ca2+ → CaSO4↓

Tests carried out on real sewage show the effectiveness of treatment: phosphates-98,5%, sulfates- 99,2%. So, during these test we proved the perspectivities of the offered method of the sewage treatment.

For the increase of effectiveness of the sewage treatment from sulfates and phosphates and for the growth of slag’s specific surface we recommend its modification intended for the solution of calcium and magnesium minerals which are contained in its composition. In this case during modification

of slag the hydrochloric acid activation is more advisable. It’s know that the mineral γ-2CaO SiOּ – the belit predominates and its solubility in hydrochloric acid can run up to 60%. Slag minerals: helenite Ca₂Al[AlSiO₇] 2SiOּrankinite 3CaO₂, periclase MgO, calcite CaCo₃ and portlandite are also soluble in water. That’s why hydrochloric acid is recommended to use as activator of slag because it decrease expenditure of this slag as a reagent and a sorbent. Tests show that the method of sewage treatment from these ions is use of sorbent and reagent.