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Remove Phosphorus. Restore Water Quality.

Phoslock® is fast emerging as the best new technology for removing phosphorus from ponds, lakes and reservoirs.

  • Patented Phosphorus Locking Technology
  • Rapid & Permanent Removal of Phosphorus
  • Total Maximum Daily Load (TMDL) Compliance Solution
  • Water Quality Restoration


NSF/ANSI Standard 60 Certified Phoslock phosphorus locking technology is NSF/ANSI Standard 60 certified for use in drinking water. This certification ensures that Phoslock applications, at the maximum use rate specified on the product label, does not contribute contaminants that could cause adverse human health effects. NSF/ANSI Standard 60 is the nationally recognized health effects standard for products which are used to treat drinking water. In addition, this certification requires annual product testing, facility inspections, quality assurance, good manufacturing practices, and product stock inspections. The United States Environmental Protection Agency and all states rely on and accept ANSI accreditations by authorized independent third party accreditation agencies, such as Water Quality Association (WQA).

Phoslock Case Studies

The Problem and Impacts
Phosphorus enrichment of waterbodies negatively impacts water quality. The accumulation and internal recycling of phosphorus in waterbodies has significant and lasting impacts on the aquatic ecosystem, drinking water supplies and recreational uses. In addition, excessive phosphorus levels can result in regulatory implications due to exceeding of total maximum daily load (TMDL) thresholds and state and/or federal water quality standards.

For more information on the impact and problems associated with excessive phosphorus levels in water, visit the following links:

Watershed Management Isn’t Enough 
Proactive waterhshed assessment and management actions are an important best management practices in efforts to reduce the level of phosphorus entering waterbodies. Even when external sources of phosphorus have been curtailed by watershed management practices, the internal recycling of phosphorus in waterbodies can continue to degrade water quality and have lasting impacts on the aquatic ecosystem.

The Solution
Phoslock is a patented phosphorus locking technology to restore water quality in ponds, lakes and reservoirs. Phoslock was developed by the Australian national science agency, Commonwealth Scientific and Industrial Research Organization (CSIRO), to remove phosphorus from water bodies and restore water quality. For over ten years, Phoslock has been successfully used in water resource restoration programs around the world to remove free reactive phosphorus and restore water quality. Although Phoslock is a new technology to the United States (2010), it is rapidly emerging as the most effective phosphorus inactivation and water quality restoration solution for ponds, lakes and reservoirs.

Water Quality Restoration
Phoslock (lanthanum-modified clay) provides an unmatched technology to reset the eutrophication clock (aging process) of waterbodies by removing free reactive phosphorus  and restoring water quality. Phoslock provides water resource managers a new solution to Reset the Clock by specifically targeting and quantifiably removing phosphorus from a waterbody.


How Phoslock Works

Rapid and Permanent Phosphorus Removal
Phoslock has a high affinity to rapidly bind and permanently remove free reactive phosphorus (FRP) from the water column shortly after application. As Phoslock settles to the bottom of a waterbody, lanthanum continues to filter phosphorus by binding FRP released from the sediment on its available sites. The phosphorus bond with Phoslock (lanthanum) is permanent.

Effective in Diverse Water Conditions
Phoslock is an environmentally compatible and effective solution in a wide range of water chemistries in ponds, lakes and reservoirs. Phoslock programs require no buffer to protect water quality and aquatic life during and after application. The removal of phosphorus from the water by Phoslock is attributed to lanthanum that binds to phosphate molecules and forms a highly stable mineral LaPO4.nH2O (Rhabdophane). This mineral integrates within the existing waterbody sediments.

The Result
Significant and measureable reduction in internal phosphorus levels and restored water quality. Phoslock is rapidly emerging as the new standard to remove phosphorus and restore water quality in ponds, lakes and reservoirs.  

Phoslock Program Design and Monitoring
Program design, implementation strategies and project cost are based on site-specific conditions 

  • Water quality management objectives
  • Water quality parameters
  • Nutrient budget assessment (internal and external loading)

Application of Phoslock

To maximize performance, Phoslock is mixed with water in a spray tank and applied as slurry via surface or subsurface injection. See SePRO for guidance regarding application and equipment.

Phoslock Application   Phoslock Application

Phoslock Application (High Volume Surface Spray)




Two Basic Phoslock Management Strategies

Recovery Solution: Begin the water quality recovery process through strategic applications of Phoslock to remove targeted levels of FRP from the water column. This solution may also be rotated with SePRO algaecide applications as needed.

Reset Solution: Reset the ecological clock/trophic status and restore water quality by implementing a Phoslock program to remove a targeted quantity of FRP from the water and sediments. Project planning begins with assessment of water and sediment parameters (laboratory and field analysis) and nutrient budget modeling to allow for development of a custom Phoslock prescription. Application strategies may include a one-time application or a sequential application strategy over time based on site-specific conditions and management objectives.

Given the favorable features of the Phoslock, such as its very low toxicity, its ability to permanently bind FRP over a wide range of water chemistries, and the fact that it does not form flocs, Phoslock is fast emerging as the most effective phosphorus locking technology for in-situ phosphorus management.

Phoslock Treatment side by side
Two adjacent lakes in the the Netherlands (Het Groen Eiland and De Gouden Ham), photo taken six months following a PhoslockŪ application to Het Groen Eiland lake.

Phoslock, coupled with SeSCRIPT analytical services, provides a comprehensive assessment, prescription and implementation system for removing phosphorus and restoring water quality. Learn more about SeSCRIPT Analysis.

Product and Toxicity Summary
Phoslock is a modified bentonite clay product containing lanthanum, a naturally occurring earth element. Several independent organizations have conducted extensive laboratory and field studies on the toxicity of Phoslock using a range of aquatic organisms and the United States Environmental Protection Agency toxicity testing criteria. The results of acute and chronic toxicity tests of Phoslock and lanthanum using a number of sensitive organisms including: several species of water flea (Daphnia); several species of Rainbow fish; freshwater shrimp; benthic organisms such as amphipods, mayflies and midge larvae; demonstrated no toxicity of Phoslock to aquatic organisms at the dose rates used to remove FRP from surface waters.

The possibility of direct exposure of Phoslock and/or lanthanum to the human body is very limited during or after an application of Phoslock. We suggest that there is no risk to human health by a Phoslock application to a water body (including drinking water reservoirs) at dose rates used to remove FRP from surface waters. The safety margin is substantial and sufficient to ensure that the only exposure of lanthanum (in Phoslock) would always be much less than the therapeutic dose used in the medical industry. Handlers and applicators should always follow label and MSDS directions.

Phoslock Technical Information

For more information about Phoslock and assistance in developing a water quality restoration program, contact your SePRO Aquatic Specialist or call 1-800-419-7779, or by e-mail,


Phoslock Label (PDF)

Phoslock Material Safety Data Sheet (PDF)


Phoslock is not an algaecide. If an algae bloom is present, treat with a SePRO algaecide prior to a Phoslock application. Phoslock is a registered trademark of Phoslock Water Solutions Ltd.


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