PHOSLOCK
What is Phoslock?
Phoslock® was developed in Australia by the Commonwealth Scientific and Industrial Research Organisation (CSIRO) in the late 1990s as a tool to manage phosphorus in lakes and other water bodies. It is a lanthanum-modified bentonite clay designed to bind free reactive phosphorus in the water column and at the sediment–water interface.
The Active Component
The active component in Phoslock® is lanthanum, which has a strong and selective affinity for phosphate. When phosphate comes into contact with lanthanum, a stable, insoluble and biologically inert mineral (rhabdophane), a bond is formed resulting in its permanent removal from both water column and sediment. This process removes reactive phosphorus from circulation within the aquatic system.
Phoslock® is composed of approximately 95 % bentonite clay and 5 % lanthanum.
Phoslock & Your Waters Chemistry
Phoslock® technology does not measurably alter the pH or electrical conductivity of the receiving water when applied at recommended doses, as demonstrated through peer-reviewed science and field experience since its commercialisation in 2002. Maintaining stable pH is important because it underpins chemical equilibria, regulatory compliance and treatment performance.
Similarly, conductivity is a key indicator of dissolved ionic content and is routinely monitored in drinking water reservoirs, recreational waters and sensitive aquatic environments.
Phoslock® integrates into existing water chemistry without the need for buffering or secondary water chemistry adjustments.
How Does Phoslock Work?
Phoslock works by utilising the ability of lanthanum to react with phosphate. Removal of phosphate by lanthanum is highly efficient and has a molar ratio of 1:1 which means that one ion of lanthanum will bind with one ion of phosphate. This binding forms the mineral Rhabdophane (an insoluble and biologically inert compound) which strips phosphate from the water.
What Happens When Phoslock is Applied?
Once on the sediment, Phoslock, and the lanthanum phosphate within it, remain as in inert mineral component of the sediment. The nature of the bond between lanthanum and phosphate is such that it will not be broken under any naturally occurring pH range (pH 4-11). Even more importantly, the bond will not be broken under anoxic (low redox potential) conditions, which are prevalent in most lake sediments and many overlying waters. Most other phosphorus binders, especially those containing iron, will release phosphate under anoxic conditions.
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