A Comparative Study on Two Innovative Solutions for Non-Invasive Phosphorus Removal from Aquatic Ecosystems

Phosphorus (P) excess in the aquatic environment is a source of eutrophication leading to the deterioration of water quality and biodiversity loss. Methods of in situ controlling P in lakes and reservoirs mostly require the addition of chemical substances to a water body without the possibility of controlling their future interactions with the environment. This study compared the performance of two solutions, laminates and modules, developed for non-invasive P removal from aquatic ecosystems with the use of calcite mineral as a P-reactive material. Both techniques enable reductions in the orthophosphate (OP) availability in lake water, and its removal from the ecosystem, without the permanent deposition of the P binding agent in the environment. In a laboratory mesocosm experiment, both, laminates and modules, lowered the OP concentration in lake water for at least 6 weeks compared to no treatment; the efficiency of modules was, however, much higher. They effectively eliminated the OP initially available in the system and further captured the OP newly supplied by the decomposition processes, showing continuous OP uptake, while laminates appeared to exhaust their capacity after about 1 week. This was mostly because of technical design—the calcite dose per m2 of the surface area was 168 times higher in modules compared to laminates. Treatment using both techniques caused a slight pH decrease compared to no treatment with a minor change of up to 0.2 point. Modules have the most potential for the implementation in practice as they are able to decrease the OP concentration for relatively long time periods of weeks to months without the need to be exchanged. They offer a refillable and reusable system for P control, removal, and recovery. Field tests should be performed to verify the performance of modules and laminates under in-lake conditions and complex interactions with the aquatic organisms to check for possible limitations and/or synergies between the non-invasive P removal techniques and native processes.