Residues from Water Precipitation via Ferric Hydroxide Threaten Soil Fertility

From the moment it was first indicated that use of aluminum chloride during purification of drinking water might be one of the triggers of Alzheimer’s disease, it took only a few years to almost abandon this practice worldwide. Now, two years after the initial evidence was presented that the cheapest possible replacement for aluminum chloride (ferric hydroxide, better known as ferrous sludge) significantly threatens soil fertility, there is almost no action. A robust case study was conducted among European drinking water treatment plants. First, it is reported that some samples of ferrous sludge can reduce phosphorus availability by more than 70%. This creates a precondition for a significant reduction in fertility over a decade. Because the legislation usually responds to similar findings with great delay, the extent to which managers of drinking water treatment plants are willing to change process settings by themselves has also been assessed. The findings obtained allow us to expect that a long continuation of this hazardous practice can be expected, since managers of drinking water treatment plants show little willingness to switch from the ongoing questionable technology (harmful to nutrient cycles in soil) to environmentally favorable (though slightly more costly) solutions.