disinfection of municipal wastewater by the systems of suspended and immobilized nano-tio2 in the cement

the photocatalytic activity of nano-tio2 has been used in inactivation of microorganisms, mainly in the form of suspension in a liquid or partially in an immobilized system. using advanced oxidation processasa new approach has been used in the purification of water and wastewater. in this research, the systems of suspended (0.1 g/l) and immobilized nano-tio2 in the cement bed (0.1-2%) under a 160-watt ultraviolet irradiation were used to study the antibacterial properties in water. the estimated nano-tio2 photocatalytic antimicrobial property was exhibited by the colony counting method of the viable bacteria. the test results of the nano-tio2 suspension system indicated that nanoparticles don’t have bactericidal effect on microorganisms in the dark conditon, but in contrast, they exhibit high antimicrobial activity (>99%) under uv irradiation. furthermore, the photocatalytic activity of the immobilized nano-tio2 system in cement bed showed that their antimicrobial properties play a role in bacterial killing (>80%) after uv irradiation and the most favorable concentration of nano-tio2 is found to be 1%, though the bacterial re-growth was observed in the dark condition after uv irradiation. therefore, the beam source should be constantly turned on till the microorganisms exists in wastewater are killed by photocatalytic properties of nano-tio2 and clean water is prepared.