METROGRO™ Processing
METROGRO™ fertilizer and soil amendment products are one of the byproducts of wastewater treatment at the Metro Wastewater Reclamation District treatment facility. The Metro District receives about 160 million gallons of the wastewater that is generated in the Metro Denver area each day. Roughly 97 percent of that amount is discharged from households. The remaining 3 percent is discharged from industrial sources and is tightly controlled under the Metro District's Industrial Waste Pretreatment Program, a part of the federal Clean Water Act. All influents to the Metro District's treatment system are closely monitored for nutrients and pollutants through the Pretreatment Program.
The wastewater treatment system controls the flow of wastewater to maximize microbial action on the solids and organic matter. These solids are settled out so that the reclaimed water, cleaned to federal and state regulatory standards, can be returned to the South Platte River. The solids that are removed during the treatment process, about 80 dry tons per day, meet federal and state regulatory standards for beneficial use. Only solids that meet these standards can be identified as biosolids, such as the Metro District's METROGRO™ cake and compost products.
METROGRO™ Cake is anaerobically digested solid material that comes from the wastewater treatment process; the cleaner we make the water, the more solids result. Before the wastewater even arrives at the Metro District for treatment, however, it has been protected by a pretreatment process that keeps harmful or toxic chemicals out of the water. Anaerobic digestion further breaks the wastewater treatment solids down and destroys pathogens. The digested solids are then processed through centrifuges to remove water, leaving a mixture that is fairly homogeneous and has the consistency of thick cake batter. It meets the criteria established in Colorado's Biosolids Regulations for application to farm fields as a soil amendment and fertilizer. Although METROGRO™ Cake is used primarily in agriculture on farmland, it can also be beneficially reused on rangeland, in forests, and in land reclamation projects.
 METROGRO™ Compost is a product produced by mixing METROGRO™ Cake (anaerobically digested solid material that comes from the wastewater treatment process) and wood fiber or yardwaste. This mixture is placed in piles and brought to the appropriate temperatures for the time necessary to destroy more pathogens and, therefore, meet more restrictive processing criteria. After the criteria is reached, the mixture is left to cure and dry before it is screened to remove larger pieces of wood fiber, leaving a material that is very similar to potting soil. Following screening, the compost is ready for unrestricted distribution to consumers in bagged or bulk form. METROGRO™ Compost meets the criteria established in Colorado's Biosolids Regulations for unrestricted distribution to the public for lawns and gardens. METROGRO™ Compost is also used on school playing fields, golf courses, by landscapers, and by municipalities for parks and landscaped roadways.
METROGRO™ products are beneficial to both the soils and the plants they grow whether on home lawns and gardens, parks, field crops or for reclamation of areas such as mine tailings or overgrazed rangeland. Alternative methods for handling biosolids such as incineration or burying in a landfill are a waste of valuable resources. The beneficial use of biosolids means cleaner air and the conservation of limited landfill space.
|
Back to Top