Abstract: An advanced water treatment method processes a continuous flow of water in a sequence of stages including pre-filtering to remove solids, conditioning to adjust pH, blending with a recycled dense microalgae culture, and passing the resulting mixture through an enclosed, environmentally-controlled photobioreactor where nutrients, PCB's, trace metals and other pollutants and regulated compounds are taken up by the algae. The flow from the PBR is separated using cross-flow filtration to produce a treated water flow and a dense microalgae flow that is recycled to the blending stage upstream. Thus, whereas the algae is recycled, the water entering the system is treated by flowing sequentially through the stages of the system, without any recycling or repetition of treatment stages.