Date of Award:


Document Type:


Degree Name:

Master of Science (MS)


Biological Engineering

Committee Chair(s)

Ronald Sims


Ronald Sims


Charles Miller


Joan McLean


Phillip Heck


Rotating Algae Biofilm Reactor (RABR) technology has been researched in studies over the past decade directed at nutrient management for water resource recovery facilities (WRRFs). This study investigated the growth of slow-release fertilizer crystals, referred to as struvite, in the algae biofilms of Rotating Algae Biofilm Reactors (RABRs) at the Central Valley Water Reclamation Facility, the largest water resource recovery facility in the State of Utah. RABRs used anaerobic digester (AD) filtrate as their nutrient source. AD effluent is high in nutrients like nitrogen and phosphorus. The levels of both phosphorus and nitrogen (in the form of ammonia) are regulated by the State of Utah, and WRRFs must limit the amounts deposited into receiving waters including rivers, streams, and lakes. Struvite, being partially composed of both ammonia nitrogen and phosphorus, can help remove both elements from the water when it is formed by natural chemical precipitation. Because struvite is also an effective slow-release fertilizer, struvite formation helps treat wastewater, recycle phosphorus and ammonia nitrogen, and provide economic value from wastewater.

RABRs were built as laboratory scale, bench scale, and pilot scale. AD effluent filtrate was analyzed to determine ion concentration data and this data was then used to calculate and predict struvite solubility over a range of pH values and used in computer modeling to predict likely precipitates. Chemical instrumentation including Scanning Electron Microscope (SEM) and Electromagnetic X-Ray Dispersion Spectroscopy (EDS) technologies were used to identify crystals in RABR biofilms and to determine their composition.

Results of this research showed that struvite could precipitate at the pH values of the AD effluent filtrate. Further, high light intensity representative of sunlight increased the pH inside of the biofilms which enhanced struvite formation. Chemical instrumentation analysis by SEM/EDS showed that struvite had formed in the pilot RABR biofilm. It was also observed that the pilot scale RABR produced struvite within the biofilm when the biofilm was exposed to the atmosphere for a sufficient time to allow evaporation of water (at least 2 minutes). This research has demonstrated that struvite precipitation using RABRs can provide an innovative technology for nutrient management by WRRFs.



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