Neutralization of sewage sediments by utilization of steel industry wastes

Abstract

Utilization of sewage sediments as a soil modifier is one of effective ways of man-caused disturbed lands reclaiming. To meet modern ecology requirements to reclaimed territories, the sediments must be safe by sanitary indices, have good organoleptic and grain-size properties, apart from being correspondent to norms by heavy metals and other toxic substances content in them. Wastes of urban sewage treatment plants were studied, as follows: raw sediments; excessive active mud, a mixture of wastes. Wastes of JSC EVRAZ ZSMK operation were used as neutralizing additives, as follows: aspiration dust of limestone burning plant, blooming scale. Studies showed a significant decrease in the content of water-soluble compounds of zinc, lead, copper, fluorine due to their precipitation when reacting with the added additives. The effectiveness of the deposition depends on the type of additive, its content, mixing conditions. By simply mixing of the neutralizing additive with the sample under investigation, a decrease of concentration of water-soluble compounds of zinc, copper, and fluorine was achieved. The selective effect of additives on individual elements established. Lime dust provided an excellent effect on zinc – a decrease by 50%, but had no effect on copper. The addition of scale led to a 25% reduction in the content of water-soluble copper, but did not lead to zinc precipitation. Regarding fluorine, lime was significantly more effective (a decrease by 53%) comparing with scale (a decrease of 27%). The total reduction of water-soluble compounds of the elements under study was 32.2% for lime and 32.6% for scale. Mixing the raw sediment with a neutralizing additive under heating conditions contributed to a significant increasing effect regarding copper: the decrease of its water-soluble ions down to 77% was obtained.