First prize is to use the ...

First prize is to use the natural micro-organisms already in the wastewater.  This is the whole principal around the biological nutrient removal processes.  The choice of which configuration is best for a particular application usually depends on the P to COD ratio, the sludge age, and other factors.  The configurations vary from BardenPho, UCT, Johannesburg, Modified Ludzak-Ettinger, and variations of these.  A precaution when dewatering the sludge is not to return the filtrate or supernatant back to the head of works as this often contains higher levels of P released by the microorganisms as they come under stress in the de-watering process.  Algae sounds very promising, but the algae need to be separated from the treated effluent which could be challenging - may require a DAF process.