Algal pathway for recovering nutrients from urban wastewater as struvite

摘要

An algal-based process capable of treating urban wastewaters in a single step to the mandated discharge standards for organic carbon (BOD), ammoniacal nitrogen (NH3-N), and phosphates (PO4-P) has been demonstrated previously. In this study, hydrothermal liquefaction (HTL) of the algal biomass cultivated in urban wastewaters is demonstrated as a viable approach to recover the valuable nitrogen- and phosphorous-content of urban wastewater. In the first part of this study, the characterization of the HTL byproducts produced using algal biomass is presented. Next, experimental conditions under which the nutrients can be extracted from the byproducts are explored. Then, using the extracted nutrients, struvite precipitation experiments are described. Finally, a mass balance model is described to investigate the recovery potential of the system and to further compare it to the laboratory results of the study.;Results from a pilot scale study conducted at a local wastewater treatment plant are presented to demonstrate that this algal-based approach has the potential to recover nearly 20% of the NH3-N and more than 90% of the PO4-P in the wastewater, as struvite. Chemical and microscopic analysis revealed more than 12 wt. % P-content in the wastewater-derived struvite. Scanning electron microscopy images depicted uniformly distributed sizes of irregular crystals of wastewater-derived struvite. Low calcium content of the wastewater-derived struvite generated in this study shows minimum amorphous calcium phosphate impurities.