Formation Of Ozonation By-products Research Articles

Full scale experimental study of an ozonation reactor: Effects of seasonal water characteristics and operating conditions on total organic carbon removal, aldehydes and ketones formation as well as disinfection efficiency

In the present study, for the first time, a full-scale experimental study of an ozonation contactor performance in a Municipal Surface Water Treatment Plant (MSWTP) in Hamedan, Iran was carried out over the course of one year. Effects of seasonal water characteristics and operating parameters were investigated on the removal of organic contents, microorganism destruction and formation of ozonation by-products, especially aldehydes and ketones. It was observed that the highest Total Organic Carbon (TOC) removal occurs during the ozonation step. The results indicated that temperature, pH value, ozone/TOC dosage, and contact time are the most important parameters that affect TOC removal and formation of ozonation by-products. It was observed that turbidity has a slight effect on pH value and TOC removal in the ozonation contactor. The ozonation by-products study showed that ozonation causes an increase of approximately 562% in the total aldehydes and ketones concentration in water that can lead to human health risks. Formaldehyde, acetaldehyde and acetone are the major by-products formed during ozonation (about 60%). Although the concentration of disinfection by-products in MSWTP does not exceed the accepted values in relevant standards, but the reactions of aldehydes with chlorine in post-chlorination step may produce halogenated by-products. These results indicated that actual concentration-contact time (CT) values and ozone dosages in the contactor are much lower than required value for the inactivation of pathogenic microorganisms. Finally, based on this study, some suggestions were made to improve the performance efficiency of the ozonation contactor and control disinfection by-products formation.

Effects of ozonation pretreatment on natural organic matter and wastewater derived organic matter – Possible implications on the formation of ozonation by-products

The aim of this study was to investigate possible implications of natural and wastewater derived organic matter in river water that is subsequently used following treatment for drinking purposes. River water was subjected to lab-scale ozonation experiments under different ozone doses (0.1, 0.4, 0.8, 1.0 and 2.0 mgO3/mgC) and contact times (1, 3, 5, 8 and 10 min). Mixtures of river water with humic acids or wastewaters (sewage wastewater and secondary effluents) at different proportions were also ozonated. Dissolved organic carbon and biodegradable dissolved organic carbon concentrations as well as spectroscopic characteristics (UV absorbance and fluorescence intensities) of different types of dissolved organic matter and possible changes due to the ozonation treatment are presented. River water, humic substances and wastewater exhibited distinct spectroscopic characteristics that could serve for pollution source tracing. Wastewater impacted surface water results in higher formation of carbonyl compounds. However, the formation yield (μg/mgC) of wastewaters was lower than that of surface water possibly due to different composition of wastewater derived organic matter and the presence of scavengers, which may limit the oxidative efficiency of ozone.

Effective Ozonation of Secondary Effluents with Initial Ozone Demand

It is clarified that the ozone consumption during the initial stage of ozonation before dissolved ozone appears is the same value as that during the initial 20 seconds in batch mode experiment. This initial ozone consumption was defined as initial ozone demand (IOD) in this study. IOD of secondary effluent was shown to be 0.3–0.5 mgO3/mgC0. More than 90% of 17β-estradiol (E2) was reduced, and formation of ozonation by-products was controlled within this ozone demand. This state can be also characterized by reduction of the values of UV254, fluorescence intensity at 345 nm (Excitation)/435 nm (Emission) and that at 240 nm/435 nm to 0.06 /cm, 35 and 15, respectively.

Effective Ozonation of Secondary Effluents with Initial Ozone Demand

It is clarified that the ozone consumption during the initial stage of ozonation before dissolved ozone appears is the same value as that during the initial 20 seconds in batch mode experiment. This initial ozone consumption was defined as initial ozone demand (IOD) in this study. IOD of secondary effluent was shown to be 0.3–0.5 mgO3/mgC0. More than 90% of 17β-estradiol (E2) was reduced, and formation of ozonation by-products was controlled within this ozone demand. This state can be also characterized by reduction of the values of UV254, fluorescence intensity at 345 nm (Excitation)/435 nm (Emission) and that at 240 nm/435 nm to 0.06 /cm, 35 and 15, respectively.