Fast phosphorus removal

The Japanese firm Asahi Kasei Chemicals claims to have developed the world’s fastest phosphorus adsorbent, together with an efficient water treatment system that uses it for the recovery of phosphorus from treated water.

Occurring in effluent water, phosphorus has been identified as a cause of eutrophication, in which an excess of nutrients in enclosed bodies of water such as lakes and harbours fosters the growth of an algal bloom, disrupting the local ecosystem and rendering the water unsuitable for many purposes.

But each of the conventional methods of large-scale dephosphorisation has its drawbacks. Using biological treatment, it is difficult to maintain consistently low phosphorus concentrations, and coagulation-sedimentation produces a large amount of sludge which requires costly treatment and disposal.

While it is possible to reduce phosphorus concentration to the order of 0.01ppm using adsorbents, the slow speed of adsorption to date has made large-scale application impractical.

Phosphorus is also an important resource, particularly for the production of fertiliser. With studies forecasting the depletion of phosphate mineral deposits in as little as a few decades, recovery from effluent water is potentially a valuable complementary source of the material. Conventional methods of dephosphorisation, however, generally recover phosphorus in the form of a mixture with many impurities.