Advanced Oxidation Technologies for Water Disinfection: Combined Treatment

FLORES, MARINA J.; CASSANO, ALBERTO E.; LABAS, MARISOL D.

Jacksonville, Florida,

Conferencia; 18th International Conference on Advanced Oxidation Technologies for Treatment of Water, Air and Soil (AOTs-18).; 2012

Redox Technologies

Despite of a great number of currently available AOTs (e.g., O3 ; H2O2, ultraviolet (UV) as well as their  combinations), there is still a continuous search for new and more effective strategies to generate hydroxyl radicals. In literature, the principal applications of these processes refer to the oxidation of organic compounds, dissolved inorganic compounds and other pollutants. Fewer references were found, however, regarding their use for wastewater disinfection, in special the combined treatment between peracetic acid (PAA) and UV. Peracetic acid (PAA) is a strongly oxidizing biocide that has been extensively used for sterilization in food industries and hospitals. PAA-based products consist of equilibrium mixtures of peracetic acid, hydrogen peroxide, acetic acid and water in different proportions. In them, hydrogen peroxide plays different roles, being implied in the restoration of the equilibrium between the different species after consumption of PAA but also acting as an oxidizing biocide itself. Furthermore, intracellular PAA may also oxidize essential enzymes; thus vital biochemical pathways, active transport across membranes, and intracellular solute levels are impaired. It is possible to go back to the peroxide acids theory to show how the action of UV produces a homolytic rupture in the O–O bond of the PAA molecule, with the subsequent formation of the hydroxyl radical The objective of this work is to study the disinfection efficacy of the combined synergic treatment between ultraviolet irradiation (UV) and peracetic acid (PAA). In all experimental runs it was employed a well-stirred, cylindrical batch reactor having a total reaction volume of 2000 cm3. Stirring was achieved with an external orbital shaking device. A cooling jacket connected to a thermostatic bath surrounded the reactor to keep the reacting system at a constant temperature of 20º C. The top of the reactor had provisions for sampling, pH and temperature measurements. This reactor was irradiated with a Philips TUV lamp with an input power of 15 W. The microorganism used was Escherichia coli ATCC 8739. Different concentrations of PAA commercial solution (15% v/v) were employed in the presence UV radiation (Doses = 1, 2, 3, 4, 5, 6 and 8 mg PAA/L) and 10 seconds of contact time. From the results, it can be concluded that the combination of UV radiation and PAA is a good alternative for water disinfection because an inactivation larger than 99, 99% can be achieved employing short contact times and inactivation reaches irreversible damage.