Sewage sludge is a product of wastewater treatment. Wastewater and stormwater enter the sewage system and flow into wastewater treatment facilities, where the solid wastes are separated from the liquid wastes through settling. At this point, they are processed and “digested,” or decomposed by bacteria. These separated processed solids – sewage sludge – contain numerous known and unknown hazardous materials. This includes everything that is flushed into the sewer system, including: household, medical, chemical, and industrial waste; chemicals and metals that leach from the sewer pipes themselves; and novel materials that are created in the wastewater treatment plant as a result of the combination of chemicals and organic compounds present.
Once treated, sewage sludge is then dried and added to a landfill, applied to agricultural cropland as fertilizer, or bagged with other materials and marketed as “biosolid compost” for use in agriculture and landscaping. That’s right – this chemical soup, often full of toxic compounds, nanomaterials, hormones, and dangerous pathogens, are applied to the very food we eat. While certain sanitation processes do decrease some health risks, chemicals such as PCBs, flame retardants, heavy metals, and endocrine disrupters – many of which are carcinogens – are not filtered out. Instead, they accumulate in the soil and are taken up by crops, putting human health at risk.