What happens to the sludge that gets removed during treatment?Sludge is not simply thrown away. It contains valuable organic matter and nutrients. Large treatment systems almost always include sludge digestion, which uses anaerobic bacteria (bacteria that live without oxygen) in heated tanks to break down the organic solids. Digestion reduces sludge volume by about 50 percent, kills most pathogens, and produces biogas—a mixture of methane and carbon dioxide that many plants capture and burn to generate heat or electricity. After digestion, the remaining material, now called biosolids, undergoes dewatering (mechanical pressing or centrifuging to remove water). Depending on local regulations and contaminant levels, biosolids may be land-applied as a soil amendment for farming or landscaping, sent to a landfill, or incinerated. Some advanced systems even dry biosolids into fuel pellets.https://www.molewater.com/products/wastewater-treatment-system