The Red Wing City Council recently declined to purchase a 340-acre farm on Mount Carmel Road to use for land application of municipal biosolids. This decision was made with significant input from members of the community and Planning and Sustainability Commissioners. Many citizens had not realized the challenges facing communities like Red Wing regarding the disposal of biosolids. The challenges remain, and Council directed staff to pursue short-term and long-term solutions for this ongoing problem. The following will give residents background information as to the challenges.
The Red Wing Wastewater Treatment Plant (WWTP) treats over 620 million gallons of wastewater annually. Wastewater treatment is a combination of physical, chemical and biological processes, each optimized to remove or degrade specific types of materials. A byproduct of each process is the generation of solids that must be managed. Treated solids, suitable for land application, are commonly termed “biosolids.” The Red Wing WWTP annually generates approximately 2.5 million gallons of biosolids. This has increased significantly over the past two years, largely due to the Federal Clean Water Act, which mandated phosphorus removal.
Red Wing biosolids are applied to agricultural land as a fertilizer each spring and fall. The current available biosolids storage capacity limits the combined spring and fall land application to approximately 1.3 million gallons, making it necessary to utilize other off-site facilities for the remaining 1.2 million gallons. These include the West Central Wisconsin Biosolids Facility in Ellsworth and the Cannon Falls and Zumbrota WWTPs. The utilization of off-site facilities is more costly. Normal spring and fall land application can be accomplished for approximately $0.05 per gallon, while off-site storage locations cost approximately $0.125 per gallon. In 2009, the 1.2 million gallons of biosolids transferred to off-site facilities resulted in an additional operating cost of $90,000.
Biosolids management in Minnesota is regulated by the Minnesota Pollution Control Agency (MPCA) under delegated authority from the United States Environmental Protection Agency. Land application represents the most common form of biosolids management in the state. Biosolids from more than 90 percent of the 57 major facilities in the state are land applied. Other options available are incineration and landfilling.
MPCA requirements dictate the type of land (soil type, slope, high seasonal water table, depth to bedrock), biosolids suitability (nutrients, metal contaminates) and the degree of treatment necessary prior to application. Goodhue County places additional restrictions on application sites. Each site is individually permitted and annual reports, including metal and nutrient analyses, are required to demonstrate compliance with the permit requirements. Land application is essentially a nutrient management program with requirements for monitoring and applying. The application program requires the background and crop uptake of the land be monitored. Additionally, applications must maintain certain setbacks and buffers from features on and near the site. Application rates are based on the actual nitrogen content in the biosolids, the available nitrogen in the soil and the nitrogen requirements for the crop that will be grown during the next growing cycle. The material is applied with an applicator that injects the liquid biosolids below the ground directly into the root zone. This is the same process used for injection of liquid manure. Subsurface injection minimizes runoff and odors, and reduces the potential to attract birds, rodents and other animals. There are two general categories of biosolids, namely Class A and Class B. Class A biosolids are pathogen free. Class B biosolids have significantly reduced pathogen levels and are applied in conjunction with site restrictions to minimize the potential for human or animal contact. Both classes of biosolids meet the state and federal regulations for land application when applied to properly managed sites.
The City Council directed staff to work with surrounding farmers to secure sites to spread Class B biosolids as the short-term solution, while continuing to research long-term Class A biosolids solutions through grants and/or state and federal bonding.