A comparative analysis is performed of the electrochemical methods and formation conditions of nanodisperse titanium dioxide (TiO2), considering its photocatalytic activity in the purification of water systems from the hard-degradable organic pollutants. A mechanism of nano-porous structure formation on the solid support of metal Ti is discussed, as well as the possibility to obtain the nanodisperse  TiO2 using the regulated periodic current with the reverse impulse. The role of the barrier layer in nano-pores formation is mentioned. A photocatalytic reactor design was improved.     The advantages of using the photo-catalytic heterogenic processes are outlined for the destructive treatment of persistent toxicants belonging to the class of benzothiazoles (BT). Large-scale industrial output and various uses of these substances results in their penetration into the waste waters and natural environment.  The photo-catalytic BT destruction processes were studied under the UV-irradiation,  рН = 3.0-7.5 and in the presence of TiO2 as photoinductor. It was found that the decomposition time of BT molecule makes up to 12 hours, and two main intermediates are formed -  ОВТ and diOBT (Fig.1):     Fig.1.General scheme of BT degradation under the photo-catalytic treattment   To accelerate the BT destruction process, microorganisms of Rhodococcus Rhodochrous strain were introduced during the combined photo- and microbiological treatment, due to their high resistance to the UV-irradiation, high activity within the pH range  from 3.0 to 7.5 and regeneration capacity due to the oxygen blowing. It was found that during the combined photo- and microbiological treatment the BT decomposition time can be reduced up to 0.5-0.6 hours. The conditions of the complete demineralization of benzothiazole were determined.      The other toxic compound which decomposition was studied is 2-aminobenzothiazol (ABT). Under the treatment with photo-inductor ТОКFe/Н2О2 the photocatalytic decomposition of ABT was reached in 20 hours, whereas during the combined treatment with FeNTA/R. Rhodochrous the complete decomposition of ABT is reached within 15 hours both with and without UV-irradiation. It was shown that the main intermediate formed during this treatment is 2-amino-6hydroxybenzothiazole (6ОН-АВТ) which is less toxic than ABT (Fig.2):