The City of Appleton, Wastewater Treatment Plant (AWWTP) produces approximately 20,000 wet tons of biosolids per year. That equates to filling Lambeau Field to the height of 15 feet. The AWWTP Biosolids Management Program is committed to effectively manage and utilize 100% of the biosolids produced through beneficial use alternatives such as agricultural land application while maintaining maximum standards of human and environmental health.
The AWWTP Biosolids Management Program adheres to the guidelines and regulations set forth in the United States Environmental Protection Agency's Code of Federal Register (CFR) 40 part 503 and the State of Wisconsin Department of Natural Resources (WDNR) Code 204. Biosolids application by the City of Appleton on farm fields has been a long standing practice that is consistent with the "green" philosophy that is being emphasized now more than ever. The AWWTP continues to evaluate technologies that include biosolids composting and heat transformation that are capable of diversifying beneficial use options beyond traditional land application.
Biosolids are the stabilized and nutrient-rich organic material produced at the end of the domestic sewage treatment process at the AWWTP. The AWWTP utilizes two biological processes, aerobic aeration and anaerobic digestion to break down waste matter and remove nutrients from incoming wastewater streams. The anaerobic process reduces pathogens and minimizes odors, forming a safe and natural agricultural product.
Appleton biosolids are rich in plant essential nutrients such as nitrogen (N), phosphorus (P), and potassium (K) and also contain other essential nutrients like calcium, copper, boron, manganese, molybdenum, sulfur, zinc, and iron. The largest components of AWWTP biosolids is calcium from lime (i.e., calcium oxide) application in the water treatment process. All of the water treatment residuals from the Appleton Water Treatment facility are conveyed to the AWWTP for processing. This form of lime is introduced or combined into the total sanitary wastewater stream where it resembles a form comparable to a 60-69 lime.
Replenishing topsoil with biosolids can promote long-term soil productivity. In addition to organic matter, the lime in AWWTP biosolids makes it a valuable soil conditioner or amendment, particularly for use agriculture. Application rates are based upon soil test results, crop recommendations, and soil buffering capacity considerations. Managed lime applications not only raise soil pH but can also improve soil structure, enhance availability of some nutrients, and promote beneficial bacterial activity.
Increasing soil organic matter has positive effects similar to that of lime, moreover by improving the consistency of sandy soil while providing nutrients used by plants. Improving soil structure and/or tilth promotes dense, healthy root growth, enhancing plants ability for nutrient uptake and water absorption This can lead, in turn, to higher crop productivity than is possible with the use of chemical fertilizers alone.