Separation of heavy metals from water may be done by sulphide precipitation. In order to make the metal sulphides more valuable for reuse, they should be as pure as possible. To separate the metals from each other during the precipitation process different parameters as pH, sulphide concentration and redox potential may be controlled. Adjustment of the redox potential to specific values results in separation of copper from cadmium even at the same pH. In the copper precipitation step 98.7 +/- 0.5% was precipitated and the remaining part was transferred to the cadmium precipitation step where 0.7 +/- 0.5% of the copper precipitated. The main part of cadmium (95.6 +/- 1.3%) was precipitated in the second step. These results show that it is possible to separate copper from cadmium by the use of redox potential control.

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This study presents a viable filter media for infiltration basins used by managed aquifer recharge (MAR) plants. Filter media properties for sand filters, such as rapid and slow sand filters, are well established. This article investigates suitable filter media based on operational experience and filter media recommendations for sand filters, which is applied to the Vomb water treatment plant (WTP), a MAR plant in south Sweden. The results from this case study showed that a filter media with an effective grain size (d10) of 0.22–0.38 mm was likely viable based on the grain sizes of the natural glacifluvial deposits. The recommendation also included an optimal d10 range of 0.22–0.30 mm to increase the retention of particles in the filter media rather than particles clogging and reducing the permeability of the aquifer. As a result of using filter media with lower d10-values than the glacifluvial deposits, unsaturated conditions under the infiltration basins will also likely improve. Furthermore, the recommendations presented in this study include limits for certain natural occurring contaminants (such as arsenic and mercury), other grain size grading characteristics and mineral composition.

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