NOVELTY - An apparatus for treating algae in liquid-based algae-containing medium, comprises pressure wave generator (26) having treatment region containing the liquid-based algae-containing medium; and drive pulse generator (10) coupled to the pressure wave generator for supplying drive pulse to generate shaped pulsed pressure wave in the treatment region.    USE - As an apparatus for treating algae in a liquid-based algae-containing medium; producing biofuel from a liquid-based algae-containing medium; and for dewatering algae contained in a liquid-based algae-containing medium (claimed).    ADVANTAGE - The apparatus reduces the water content of an algae-containing medium. The production of biofuel from algae is performed efficiently, without pre-drying the algae. The electrohydraulic pressure wave generator advantageously generates a fast pressure wave rise time and provides focused energy over a broader area, thus delivers greater amount of positive pressure wave energy than the electromagnetic pressure wave generator or the piezoelectric pressure wave generator. The pressure waves focused through the use of focusing reflectors.    DETAILED DESCRIPTION - An apparatus for treating algae in liquid-based algae-containing medium, comprises pressure wave generator (26) having treatment region containing the liquid-based algae-containing medium; and drive pulse generator (10) coupled to the pressure wave generator for supplying drive pulse to generate shaped pulsed pressure wave in the treatment region; where the shaped pulsed pressure wave comprises first phase near instantaneous increase in pressure to exert compressive force on the algae in the liquid-based algae-containing medium, followed by a second phase of negative pressure to exert tensile strain on the algae in the liquid-based algae-containing medium, to obtain treated medium comprising algae having disrupted cellular structures. An INDEPENDENT CLAIM is included for method for producing biofuel (40) from a liquid-based algae-containing medium and for dewatering algae contained in a liquid-based algae-containing medium, involving directing the liquid-based algae-containing medium into a treatment region; applying shaped pulsed pressure wave to the liquid-based algae-containing medium in the treatment region, where the shaped pulsed pressure wave comprises a first phase near instantaneous increase in pressure to exert a compressive force on the algae in the liquid-based algae-containing medium, followed by a second phase of negative pressure to exert a tensile strain on the algae in the liquid-based algae-containing medium, to obtain a treated medium comprising algae having disrupted cellular structures and biofuel from the disrupted algae; and separating the biofuel from the treated medium.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic block diagram of apparatus of producing biofuel from algae by application of shaped pulsed pressure waves.    Drive pulse generator (10)    Shock wave generator (20)    Feed back sensor (24)    Pressure wave generator (26)    Separator (30)    Biofuel (40)