The role of wetlands in the removal of heavy metals from the leachate (on the example of the Lipinka River catchment, southern Poland)

The possibility of using Portland cement to improve the sedimentation properties of activated sludge

“…Due to the Fe and Al content, dosage of cement milk may be related to the application of chemical coagulants to activated sludge. Improved sedimentation properties of activated sludge (and consequently reduced bulking) may be achieved using salts of aluminium and iron [7,11]. Kida et al [7] showed that large amounts of the latter reduce the SVI of activated sludge.…”

“…Improved sedimentation properties of activated sludge (and consequently reduced bulking) may be achieved using salts of aluminium and iron [7,11]. Kida et al [7] showed that large amounts of the latter reduce the SVI of activated sludge. In other studies, Iron(II) sulphate (FeSO 4 •H 2 0) dosed at 30 mg Fe/L was shown to result in a reduction of SVI from >300 to 50 mL/g [10].…”

“…Activated sludge settleability is defined in terms of the sludge volume index (SVI) and zone settling velocity (ZSV). The bulking of sludge is usually characterised by a sedimentation rate of less than 0.3 m/h, and a sludge volume index (SVI) above 150 mL/g [1,[5][6][7]. The SVI is the most important indicator applied in measuring sludge settleability.…”

“…To prevent and counteract bulking and foaming of sludge, it is necessary, in the first instance, to apply certain technological operations (a high degree of recirculation, addition of digested sludge, and a change in the organic loading rate and oxygen concentration) [5,7]. Improved activated sludge sedimentation may be achieved using chemical oxidants (ozone, sodium hypochlorite, hydrogen peroxide) [8,9], aluminum and iron salts [10][11][12] or organic synthetic polymers [13].…”

“…Improved activated sludge sedimentation may be achieved using chemical oxidants (ozone, sodium hypochlorite, hydrogen peroxide) [8,9], aluminum and iron salts [10][11][12] or organic synthetic polymers [13]. It is also possible for powdered mineral materials to be used [7,14,15].…”