Struvite Recovery from Anaerobically Digested Dairy Manure

EPA Grant Number: SU835331
Title: Struvite Recovery from Anaerobically Digested Dairy Manure
Investigators: Tao, Wendong
Institution: SUNY College of Environmental Science and Forestry
EPA Project Officer: Nolt-Helms, Cynthia
Phase: II
Project Period: August 15, 2012 through August 14, 2014
Project Amount: $89,943
RFA: P3 Awards: A National Student Design Competition for Sustainability Focusing on People, Prosperity and the Planet - Phase 2 (2012) Recipients Lists
Research Category: Pollution Prevention/Sustainable Development , P3 Challenge Area - Agriculture , P3 Challenge Area - Materials & Chemicals , P3 Awards , Sustainability


Air-lift crystallization has been developed to recover struvite from filtrate of anaerobically digested dairy manure in combination with sludge digester liquor. The major objectives of this project are 1) to optimize struvite crystallization using velocity gradient as a control parameter of air-lift crystallizers; 2) to refine the combination ratio of manure filtrate to sludge digester liquor for elimination of the hindrance of high ionic strength to struvite precipitation while maintaining supersaturation of struvite ions; and 3) to set up and operate a pilot-scale system at Twin Birch Dairy LLC, including solid-liquid separation and struvite recovery from manure filtrate.


In the first year of Phase II, two 7-L air-lift crystallizers will be operated to refine velocity gradient and combination ratio of manure filtrate to sludge digester liquor. Once velocity gradient and combination ratio are optimized, a pilot-scale system will be established at Twin Birch Dairy LLC to demonstrate struvite recovery as a sustainable treatment of anaerobically digested dairy manure. Two graduate students will lead a team of students to demonstrate the developed technology in local dairy farms and wastewater treatment plants. Undergraduate and graduate students trained in environmental resources engineering, agricultural engineering, chemical engineering, and environmental science will be engaged collaboratively in the laboratory tests, construction and operation of the pilot-scale system, and analysis of struvite marketability.

Expected Results:

An air-lift crystallizer avoids clogging and scaling issues associated with water pumps and mechanical mixers, providing farmers with ease of operation and requiring less maintenance for struvite recovery. The strategy to regulate velocity gradient with air flow rate and air pressure will be determined for efficient crystallization of struvite precipitates. Combination of manure filtrate and sludge digester liquor can be a low-cost method to reduce ionic strength of manure filtrate for struvite recovery. Along with anaerobic digesters and solid-liquid separation, struvite recovery will present an environmental-friendly, cost-effective solution to dairy manure management. The revenues of struvite recovery from digested dairy manure can offset the costs of nutrient removal. Digested dairy manure will become a sustainable feedstock for phosphorus fertilizer production.

Supplemental Keywords:

Agricultural wastewater treatment; Bio-based feedstocks; Biofiltration technology; Phosphorus recovery; Sustainable design; Waste to value

Relevant Websites:

Phase 1 abstract

Progress and Final Reports:

  • 2013
  • Final

  • P3 Phase I:

    Sustainably Overcoming Hindrance to Struvite Recovery from Anaerobically Digested Dairy Manure  | Final Report