The Washington DC water treatment plant appears to use sedimentation tanks for both treating water before consumption and for treating sewage that is then discharged.
My question: What happens to the sedimentation after it is collects? None of the articles that I have read discuss this.
It seems to me that the sediment in the water source won't necessarily be toxic, but I suspect that the sediment in the sewage contains a brew of toxic metals and organics. So does that need to be treated as toxic waste? Is the source sediment used for fertilizer, or is it just sent to a landfill? Is there an issue with dust?