(656e) Ammonium Byproduct Management Via Zeolites and Struvite Precipitation | AIChE

(656e) Ammonium Byproduct Management Via Zeolites and Struvite Precipitation

Authors 

Hannigan, C. - Presenter, Montana State University
Phillips, A., Montana State University
Henry, E., Lehigh University
Ugur, E., Montana State University
Khosravi, M., Montana State University
Cunningham, A., Montana State University
Microbially Induced Calcite Precipitation (MICP) is a biocementation process where microorganisms, typically urease-producing bacteria, induce calcium carbonate (calcite) precipitation from calcium ions and carbonate ions present in the environment. This process has gained significant attention for its potential in various applications, including soil stabilization, groundwater remediation, and bio-concrete production. Despite its potential benefits, several limitations have been identified, hindering its widespread applications in various fields. One major concern revolves around the production of ammonium byproduct during MICP. Biocementation waste containing ammonium ions (NH4+) can accumulate in the soil environment, posing risks to vegetation, groundwater resources, and aquatic life due to its toxic nature. Researchers have explored ammonium removal from wastewater using zeolite and struvite precipitation. Zeolites, with their high surface area and cation exchange capacity, can adsorb ammonia ions from aqueous solutions effectively. Microbially induced struvite precipitation (MISP) is a new biocementation technique for soil improvement and can reduce the byproduct ammonia by converting them into hydrogen ions and magnesium ammonium phosphate hexahydrate, a stable insoluble compound also known as struvite. The objective of our study was to incorporate zeolite and struvite precipitation to overcome the limitations associated with MICP. First, we assessed the ammonium adsorption capacity of granular and powdered zeolites at different concentrations of ammonium enriched microbial culture, 0.75 g/ml and 0.5 g/ml in batch cultures. It was found that zeolite considerably decreased ammonium concentrations up to almost 80% ammonium removal. Higher concentrations of zeolites performed better with powdered zeolites performing the best out of all samples with around 80% removal efficiency. Struvite’s adsorption was then assessed using a microbial culture with MgCl2 * 6H2O and K2HPO4. It was found that struvite contributed to 90% ammonium removal. Ammonium removal was then assessed using a triplicate column study. Three types of columns were assessed: a control column (where only MICP was promoted), a column consisting of only struvite precipitation (MISP), and a combination of struvite and microbial cementation (MICP+MISP). Magnesium and phosphate were added to microbial and cementation medias for struvite precipitation columns. It was found that struvite precipitation effectively reduced ammonium concentrations present in column effluent. Results indicate that incorporation of zeolites or struvite to MICP process can significantly decrease the concentration of ammonium byproducts in biocementation waste, thereby mitigating its environmental effects.