APPLICATION OF MODIFIED STEELMAKING SLAG IN POULTRY-PROCESSING INDUSTRIAL WASTEWATERS PURIFICATION SYSTEM
Currently the problem of meat-processing and poultry-processing industrial wastewaters purification is rather urgent. Over 70 % of pollutants in meat-processing plants’ wastewaters are fat-protein complexes, prone to aerobic oxidation and to formation of substances, which have offensive odor. The concentration of suspended matter in such industrial wastewaters can amount to 7300 mg/dm3. The possibility of using a reagent, obtained as a result of slaking electric-furnace steelmaking slag acidic modification, has been considered. As a modifying reagent the concentrated sulfuric acid was used. The modified product was dried to constant mass at temperature no more than 55 °С and then ground to powdery condition. The acidic treatment of OEMW hydraulically-cooled electric-furnace steelmaking slag results in leaching of basic oxides with the formation of crystals of calcium sulfate dehydrate, ferrous sulfate and colloidal silicic acid. Coagulation of finely-dispersed silicic acid takes place on the surface of calcium sulfate dihydrate particles at the moment of its crystallization, which promotes the formation of finely-dispersed structure of CaSO4·2H2O with high amorphization degree. This allows using the obtained reagent as a ferrosilicon flocculant-coagulant in multicomponent wastewaters purification system. The ferrosilicon flocculant-coagulant was used for purifying wastewaters from the slaughter room of poultry-processing plant of ZAO «Prioskolye» with COD 7350 mg/dm3 and initial turbidity 349 NTU. The end of coagulation process and the sediment formation are observed after 13 minutes of settling. It is demonstrated that the obtained reagent at consumption rate - 1.0 g/dm3 provides wastewater purification efficiency - 87 %.