A novel method for the extraction and recovery of critical nutrients such as phosphate and ammonium from wastewater has been developed by scientists. These nutrients, harnessed through a specially created membrane containing inorganic particles, shift our perception of wastewater from a problem to a valuable asset. The study holds the potential to enrich a circular economy, offering a new source of nutrients for agricultural fertilizers, and addressing looming shortages that could disrupt global food security.
Sara Abu-Obaid, a Ph.D. candidate in Chemical Engineering at the University of Toronto, asserts that we need to change our perspective regarding wastewater management. She believes that wastewater should be seen as a resource capable of yielding water, nutrients, energy, and other valuable commodities to propel us toward a circular economy.
Under the guidance of Professor Ramin Farnood, Abu-Obaid spearheaded the study, recently published in the Chemical Engineering Journal. The research introduces an environmentally friendly approach to extract phosphate and ammonium from wastewater, providing an avenue for their future reuse.
Abu-Obaid’s innovative method involves high-tech membranes embedded with inorganic particles that absorb phosphate and ammonium from wastewater. This economical approach not only recovers these valuable substances but also provides a novel source of raw materials for agricultural fertilizer manufacturers.
Wastewater from various sources, such as bathing, toileting, and laundry, flows into sewers leading to treatment plants. Here, it is treated to a level where it can safely be reintroduced into the environment without causing harm. The treatment process aims to remove solids, organic matter, pathogens, and nutrients, including phosphate and ammonium – key ingredients in fertilizers – that come from household products and human waste.
While phosphorous is crucial for healthy plant growth, an excess can cause eutrophication, leading to detrimental algal blooms that decrease oxygen levels in the water and create ‘dead zones’ where aquatic life is unable to survive. Similarly, long-term exposure to ammonium can be toxic to aquatic organisms.
Current wastewater treatment processes involve the removal of phosphate and ammonium but treat them as waste. Abu-Obaid’s solution offers a new approach: extract these nutrients from the water entirely to utilize them in fertilizer production.
Scientists have raised concerns that the present rate of phosphorus consumption in agriculture could result in critical shortages, threatening global food supplies. Abu-Obaid’s novel approach could help address this issue by turning wastewater into a valuable source of these nutrients.
Contrary to many water filtration membranes that rely on precise pore designs, Abu-Obaid’s technique is unique. Her membrane incorporates minuscule particles of akaganeite and zeolite 13X, which have high affinities for phosphate and ammonium adsorption.
She explains that the process does not require the application of large pressures or size exclusion. Instead, the particles within the membrane perform the extraction, and the membrane serves to hold these particles in place. Although these particles could function independently, incorporating them into a membrane provides a two-stage operation: initially, the particles adsorb the ammonium and phosphate, and then a sodium hydroxide solution washes the membranes, recovering the nutrients and regenerating the particles.
In the study, the membranes effectively captured phosphate and ammonium ions under dynamic water flow conditions, removing 84% of ammonium and 100% of phosphate from synthetic wastewater, even in the presence of other competing ions.
Despite promising results, Abu-Obaid acknowledges that further investigation is needed to explore the design considerations for implementing such systems on a larger scale.
She acknowledges the challenge in justifying the use of this technology to recover nutrients that aren’t yet so scarce as to threaten current supply chains. However, she believes that preemptively establishing potential sustainable sources for
