Some aspects of restoration of degradated sewage receivers

Abstract

Bottom sediments are naturally connected with water body of the river and it is essential inpollutant balance, Natural phosphorus cycle in water environment is sedimentation cycle,Once introduced to water ecosystem can be removed by different chemical, biological andphysical processes and loses its environmental mobility as a sediment component,In studied case the contaminants load was radically reduced by construction of wastewatertreatment plant in city of Lodz, But the water quality improvement was not commensurate tothis reduction, Such situation could be the result of increased phosphorus release fromsediments deposed in the course of decades in river bed, On the distance the phosphateconcentration increases up to 25 km downstream the WWfP outlet and it can not beexplained by other pollution sources. The phosphorus content in the sediment is as high as 27 1 mg kg- dw, The equilibrium phosphate concentration (EPCo) experiment showed that itcould be released to water body, The preliminary results showed that EPCo value exceed in 3 some points limit polish water quality norm and amount to 1.2 mg PO4 dm- in oxic condition,