A method of photodynamic disruption of target cells within a target cell site wherein the target cells are associated with one or more of a sterilization procedure, a biofilm eradication procedure, a sterilization procedure of a medical prosthesis, a treatment of an infection at a tissue site, eradication of cancer cells and a fluid or food decontamination process. Surface acting agents such as benzalkonium chloride or polymyxin B sulfate or both may be utilized. A controllable light source capable of delivering light at a plurality of duty cycles is utilized to cause photoactivation of the photosensitive material resulting in degradation of target cells within the site.