Non-Invasive Immobilisation and Removal of Phosphate from Lakes Using Submerged Laminates with Calcite—Preliminary Results.

A novel method for inactivation and removal of orthophosphate (SRP) from eutrophic waters was proposed, based on application of laminates containing calcite mineral (Cc), which serves as a SRP binding agent. Laminates are placed in the water column to allow for SRP sorption onto Cc and then extracted, to remove Cc together with sorbed SRP from the ecosystem. Two Cc materials obtained by planetary ball milling of a ground limestone were used. We investigated (1) physical properties of laminates, (2) their SRP binding efficiency and (3) impact on water chemistry, under variable in-lake situations, simulating turnover, epilimnetic and hypolimnetic conditions, which correspond to equilibrium, oversaturation and undersaturation with respect to Cc, respectively. Laminates coated with Cc removed 9–33% less SRP as compared to loose Cc materials due to deactivation of Cc surface in the laminates. SRP binding by laminates was highly variable (removal of 14–67%) and dependent upon physical and sorption properties of Cc material used as well as environmental conditions, with the highest efficiency in the epilimnetic variant. Under hypolimnetic and turnover conditions, laminates typically slightly, but significantly, enhanced pH, alkalinity, Ca2+ concentration and saturation with respect to Cc, whereas in epilimnetic conditions an opposite effect was seen. Although field validations are needed, we propose laminates as a non-invasive, complementary method to traditional chemical SRP inactivation in lakes, to avoid accumulation of SRP binding agents in the environment and secure sustain SRP elimination from the water bodies. [ABSTRACT FROM AUTHOR]