Gao Naiyun

Increased formation of halomethanes during chlorination of chloramphenicol in drinking water by UV irradiation, persulfate oxidation, and combined UV/persulfate pre-treatments.

Ultraviolet/persulfate (UV/PS) has been widely used to generate sulfate radicals for degradation of water organic pollutants in previous studies. However, its impacts on disinfection byproduct formation during post-chlorination of degraded compounds is unclear. The objective of this study was to evaluate the impacts of UV irradiation, PS oxidation, and the combined UV/PS advanced oxidation process (AOP) pre-treatments on halomethane formation during the following chlorination of chloramphenicol (CAP), a model antibiotic commonly found in wastewater-impacted water. Results showed that CAP could be transformed to more trichloromethane (TCM) than monochloromethane (MCM) and dichloromethane (DCM) in the presence of excess chlorine. UV photolysis, PS oxidation and UV/PS AOP all directly decomposed CAP to produce halomethanes (HMs) before post-chlorination. Moreover, UV and UV/PS pre-treatments both enhanced the formation of all the HMs in the subsequent chlorination. PS pre-oxidation decreased the TCM formation during post-chlorination, but increased the yields of MCM, DCM and total HMs. UV pre-irradiation significantly increased the bromide utilization of HMs, whereas UV/PS pre-oxidation decreased the bromine incorporation and utilization of HMs from the chlorination of CAP in a low-bromide water. UV irradiation, PS oxidation, and UV/PS AOP can inactivate pathogens and degrade organic pollutants, but this benefit should be weighed against a potential risk of the increased halomethane formation from degraded organic pollutants with and without post-chlorination.

Microcystin-RR degradation by ozonation

AbstractBench-scale tests were conducted to investigate the ozonation of Microcystin (MC)-RR obtained from cyanobacterial blooms in this study. The effects of ozone dose, initial MC-RR concentration, solution pH, and coexisting anions on the MC-RR ozonation kinetics were evaluated. Results showed that the MC-RR ozonation well followed the pseudo-first-order degradation kinetics under different experimental conditions. At pH 7 and 461.5 μg/L MC-RR, the degradation rate constant dramatically increased from 0.0125 to 0.0623 min−1 with the increase of the ozone dose from 0.31 to 1.35 mg/L, but was not significantly affected by the initial MC-RR concentration. Typically, an acidic condition favored the MC-RR degradation. As the pH increased from 3.1 to 10.1, the rate constant decreased from 0.1906 to 0.0102 min−1 at an O3 dose of 0.82 mg/L. Different inorganic anions exhibited different behaviors in the MC-RR degradation. slightly enhanced the decomposition, while , Cl−, and slowed the degradation to different...

Research on Algae Removal by Electro-flotation/Photo-catalytic Oxidization Combined Process

The lake-type raw water was treated in Photo-catalytic Oxidization reactor. Under the condition of the inflow discharge control in 15L/h, the padding packing compares 2/5, UV lamp 30W, added no chemicals, pH 7.35, use the electro-flotation to treat it by two groups of plates to treat the water continuously. Then investigate the removal effect of pollutants after electro-flotation/Photo-catalytic Oxidization Combined Process. The results indicate that after the process the average removal rates of CODMn, TN and UV254 can reach 45.21%, 20.12% and 55.11% respectively and the average removal rate of Chl-a can reach 82.0% and its removal rate is steadily under 75%~89% when the Chl-a of raw water is 4.52mg/m3 during continuous operation for 9 hours.

Pretreatment of Micro-polluted Raw Water by Using TiO2/PP Photocatalytic Oxidation and Biofilms Combination Process

A novel type of TiO2/PP composite filler was produced by loading TiO2 on polypropylene (PP). Then the composite filler was used to pretreat micro-polluted lake water after natural biofilm culturing. The experiment results showed that, under the continuous operating conditions of inflow rate 120 L/h, filling ratio of filler 0.4, UV lamp power 72 W, pH of lake water 7.35, the average removal of CODMn, NH3-N, and TP were 22.77%, 29.53%, and 28.53%, separately. The technology has a certain prospect for the pretreatment of micro-polluted water with effecitive removal.

Competition adsorption of NO 3 − and ClO 4 − on activated carbon

In-situ experiments were conducted to study the adsorption isotherms of ClO<inf>4</inf>− and NO<inf>3</inf>− onto 6 kinds of activated carbon(25°C). The results shows adsorption capacity of GAC is bigger than PAC, and may have some relationship with the iodine value of carbon. Competition adsorption exists between NO<inf>3</inf>− and ClO<inf>4</inf>−. At NO<inf>3</inf>−: ClO<inf>4</inf>−=5∶1(mass ratio) in double component adsorption experiment, adsorption capacity of ClO<inf>4</inf>− decreased by 37.5~56.5% compared with single component system. Then adsorption capacity decreased little after increasing more NO<inf>3</inf>− ratio.

Notice of Retraction The role of free bromine during bromate formation in UV photolysis

Considerable amount of bromate were observed during UV irradiation in free chlorine solutions containing bromide, whereas much less were formed in UV catalyzed chloramine solutions containing bromide. Assuming that free bromine is the key intermediate of bromate, a simple model is developed to predict bromine species profiles either in UV catalyzed free bromine solutions or in UV catalyzed Cl2-bromide system. Pseduo-first order rate constants were derived from results of experiment. Validation from experimental data shows the model can favorably simulate the formations of bromate as well as free chlorine or free bromine decay in spite of the simplicity of the model. Hence it is likely that this model is applicable to predict bromate ion formation and bromine decay in water purification process where UV and pre-chlorination are employed.