Wollastonite: A win-win for sustainable phosphorus management

In the summers of 2014 and 2015, massive algal blooms in Lake Erie made headlines across North America, particularly in 2014 when toxins produced by microcysts in the blue-green algae shut down Toledo’s water works, leaving hundreds of thousands of people without access to safe drinking water. The problem affects lake and rivers across the continent, threatening human health, wildlife populations, recreational opportunities, and commercial fisheries. With the warmer summers associated with climate change, the problem is only expected to get worse.

Phosphorus run-off from point sources like factories and sewage treatment plants and non-point sources like lawns and farm fields is the primary culprit behind these harmful outbreaks. Numerous efforts are underway to reduce the amount of phosphorus finding its way into our waterways. A growing body of research indicates that wollastonite is effective at capturing phosphorus from water in a number of applications.

Several studies demonstrate that wollastonite can be very effective at removing phosphorus from municipal wastewater treatments systems, particularly in constructed wetlands. Ongoing research in Ontario also suggests that wollastonite will adsorb significant amounts of phosphorus from greenhouse nutrient solutions. These point sources tend to have relatively high concentrations of phosphorus.

Recent research demonstrates that wollastonite powder is the most effective option for adsorbing phosphorus from water that has a relatively low concentration of phosphate but is still prone to algal blooms. While other substances were less effective at adsorbing phosphate as the phosphorus concentration in the solution decreased, wollastonite powder remained effective. It removed more phosphorus, a higher percentage of total phosphorus, and worked faster at all concentrations tested. This is likely due to the particle size of the powdered wollastonite, the porosity of the material, and the chemistry of the substance.

While some substances remove phosphorus by precipitation, which renders it practically immobile, phosphates adsorbed onto wollastonite molecules are less tightly bound and can re-enter the phosphorus cycle when environmental conditions are appropriate. This means that the wollastonite used to remove phosphorus from water sources where it isn’t needed or wanted can be re-used as a fertilizer source of calcium, magnesium, silicon, and phosphorus. Recycling phosphorus in this way not only protects waterways: it helps preserve dwindling phosphate deposits used for agricultural fertilizers –  a win-win for sustainability!