Submitted to: Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 5/19/2015
Publication Date: 9/8/2015
Citation: Szogi, A.A., Vanotti, M.B. 2015. Phosphorus recovery prior to land application of biosolids using the “Quick Wash” process developed by USDA. In: Proceedings of RAMIRAN 2015 16th International Conference Rural-Urban Symbiosis, September 8-10, 2015, Hamburg, Germany.
Technical Abstract: Objectives: To present the case study of a new treatment process, called “quick wash”, that was developed by the USDA-ARS for extraction and recovery of phosphorus from animal manure solids but research has shown the approach is equally effective to recover phosphorus from biosolids prior to application to soil. This presentation will discuss the adaptation of this process to the recycling of municipal biosolids and the potential environmental benefits for urban and rural communities. The quick wash process: As an alternative to improve the nitrogen (N) and phosphorus (P) balance in animal wastes, the quick wash process was developed for rapid wet extraction of P from raw solid manure and recovery of manure P in solid concentrated form. This process consists of selectively extracting P from solid animal waste using mineral or organic acid solutions, and recovery of P from the extract by adding lime and an organic polymer forming a calcium-containing P precipitate. The quick wash process has three products: 1) a washed solid residue with a N:P ratio optimal for use in crop production; 2) a concentrated solid P material that can be transported long distance and used as an effective P fertilizer; and 3) a liquid effluent that could be applied to near-by cropland as liquid fertilizer or recycled into the treatment system. Environmental benefits: Excess soil P beyond the assimilative capacity of soils is currently a major factor to discontinue application of biosolids to land nearby municipal wastewater treatment plants. For this reason, municipalities incur in hefty fees for transportation and landfilling biosolids that otherwise could be used as soil amendment to maintain soil quality. However, recovering P from biosolids using the quick wash process can provide environmental benefits for both rural and urban communities. The quick wash process selectively recovers more than 80 % of the P from solid waste, while leaving most of the N in the washed solid residue. Consequently, the washed solid residue has a more balanced nutrient composition for crop production and is safe for land application. Because the quick wash process is conducted at ambient temperature, it avoids loss of oxidizable organic carbon (C) and N from washed solid residues. Thus, the land application of washed solid residues contribute with C and N to maintaining soil quality while reducing the environmental risks of excess soil P. The concentrated phosphorus materials contain more than 90% of its phosphorus in plant available form that provides a recycled phosphorus source for use as crop fertilizer. Conclusion: Nutrient pollution, caused by too much P in the environment, is one of America’s most wide-spread, costly and challenging environmental problems, impacting many sectors of the U.S. economy that depend on clean water. These environmental problems can be mitigated with the quick wash process, because P is selectively extracted from animal wastes and municipal bio-solids prior to land application. The inclusion of this process in a waste management system offers farmers and municipalities a new and welcomed opportunity to minimize P losses into the environment and sustain soil quality while recovering and recycling phosphorus as a valuable product.