Grantee Research Project Results
2013 Progress Report: Struvite Recovery from Anaerobically Digested Dairy Manure
EPA Grant Number: SU835331Title: Struvite Recovery from Anaerobically Digested Dairy Manure
Investigators: Tao, Wendong , Mayer, Douglas , Mazinani, Ehsan , Ukwuani, Anayo
Current Investigators: Tao, Wendong , Mayer, Douglas , Mazinani, Ehsan , Ukwuani, Anayo , Agyeman, Fred , Abdulai, Hamidu , Austin, Scott , Das, Jonathan Masih , Robinson, Jesse , Stephan, Emily , White, Krystal , Wolcott, Scott , Elniski, Autumn
Institution: The State University of New York
EPA Project Officer: Page, Angela
Phase: II
Project Period: August 15, 2012 through August 14, 2014 (Extended to November 14, 2014)
Project Period Covered by this Report: August 15, 2012 through August 14,2013
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 - Sustainable and Healthy Communities , P3 Challenge Area - Chemical Safety , P3 Awards , Sustainable and Healthy Communities
Objective:
Air-lift crystallization in a batch operation mode 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 Phase II of this project, 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.
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.
Progress Summary:
After several batches of struvite recovery with an air-lift crystallizer made of PVC pipes, it was found that significant amounts of struvite powder were deposited to the surfaces of PVC pipes and drainage tubes, and retained at the bottom of the crystallizer. The crystallizer design was then modified to avoid powder retention inside the crystallizers so that struvite formed could be harvested as powder or pellets. Moreover, the freeboard of the crystallizer needs to be extended to prevent from spill of foam during operation. Based on the modified design, we are building two 7-L air-lift crystallizers, one with Harvel clear rigid schedule 40 PVC pipes and the other with white schedule 40 PVC pipes. The clear PVC pipes have smooth interior surfaces, permitting maximum flow rates and minimizing accumulation of precipitates. The two crystallizers will be operated in parallel for comparison of struvite recovery efficiency.
Filters packed with electric arc furnace slag are cost-effective methods to raise pH for struvite recovery from filtrate of anaerobically digested dairy manure. Laboratory experiments showed that the maximum alkalinity dissolution efficiency is 761 mg CaCO3/kg electric arc furnace slag. Furnace slag could increase dairy wastewater pH up to 11.
Struvite recovery requires manure filtrate having total suspended solids below 1 g/L. We have been investigating the effects of different feeding modes on filtration rate. A larger scale of filtration system is being set up. Laboratory experiments will be performed to select a farm organic waste for enhancement of manure filtration.
Effluent and centrate of anaerobic sludge digesters at two municipal wastewater treatment plants were filtered through sand filters to reduce total suspended solids below 1 g/L. Filtrate of the sludge digester effluent and centrate was then mixed with filtrate of anaerobically digested dairy manure and used for struvite recovery. However, low orthophosphate concentrations were found in the sludge digester liquor. Rather, it was found that ammonia recovery could improve struvite recovery and produce another value-added product. Ammonia recovery decreases ionic strength which is one of the major interferences to struvite recovery from anaerobically digested dairy manure. Both ammonia and struvite recovery requires high pH. The optimum pH for both ammonia and struvite recovery is being investigated.
It was found that struvite precipitates grew very slowly in the air-lift crystallizer as in the other crystallizers reported in the literature. Struvite pellets and other particulate materials have been reported to enhance struvite crystallization to some extent. We are looking for cost-effective alternatives to make struvite pellets with struvite powder. Struvite powder could be harvested through a short crystallization process.
Future Activities:
The 2-stage filtration system has been operated to accumulate manure filtrate for struvite recovery tests. Filtration rate is increased by changing feeding mode. Ammonia recovery is more practical than combination of manure filtrate with sludge digester effluent for overcoming hindrance to struvite recovery from anaerobically digested dairy manure. Furnace slag filters have been successfully tested to increase pH of manure filtrate for nutrient recovery. Because a new PhD student was recruited for this project one semester later than originally planned, crystallization tests have been delayed. Overall, the project objectives are being accomplished despite such a delay.
Journal Articles on this Report : 1 Displayed | Download in RIS Format
Other project views: | All 8 publications | 3 publications in selected types | All 3 journal articles |
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Wen J, Tao W, Wang Z, Pei Y. Enhancing simultaneous nitritation and anammox in recirculating biofilters:effects of unsaturated zone depth and alkalinity dissolution of packing materials. Journal of Hazardous Materials 2013;244:671-680. |
SU835331 (2013) |
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Supplemental Keywords:
agricultural wastewater treatment, bio-based feedstocks, biofiltration technology, phosphorus recovery, sustainable design, waste to valueRelevant Websites:
Progress and Final Reports:
Original AbstractP3 Phase I:
Sustainably Overcoming Hindrance to Struvite Recovery from Anaerobically Digested Dairy Manure | Final ReportThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.