No abstract

The formation pattern of haloacetic acids (HAAs) was investigated using phenol as a model precursor of HAAs, and the oxidation by-products formed from phenol ozonation, such as hydroquinone, catechol, glyoxal, glyoxylic acid and oxalic acid, were also chlorinated to measure the HAAs formation potential (HAAFP). Of these, phenol showed the highest reactivity with chlorine, yielding the most HAAFP. Even though HAAFP of the tested by-products was lower than that of phenol, it was confirmed that all by-products can act as the precursor of HAAs. Regarding the ozonation of phenol-containing water, the efficiency of ozone in controlling HAAs can be reduced by the formation of oxidation by-products. When comparing conditions for pH 7 and 3, the ozonation for pH 7 was more effective in removing the overall HAA precursors than the ozonation for pH 3. This result was attributed to complete oxidation by the production of the secondary oxidant, such as the OH radical (OH·) from ozone decay, and ionization of phenol.

A B S T R A C TAttached growth micro-organisms are known to be beneficial to the removal of lowconcentration organic matter because they can have a long retention time due to their very slow growth rate compared with the suspended growth micro-organisms suitable for high-concentration organic substance treatment. In this study, the characteristics of the treatment of organic and nitrogen pollutants in low concentrations were investigated by injecting air into the inside of the tube, using a woven-hollow fiber tube as biological media. According to the changes in the hydraulic retention time, the biochemical oxygen demand (BOD) concentrations of the influent and the treated water were 29.8-37.6 mg/L and 8.6-18.5 mg/L, respectively. The suspended solid (SS) of the influent was 33.9-36.7 mg/L, and that of the treated water was 1.6-3.6 mg/L, showing a high SS removal efficiency of more than 90%. The investigation of the BOD and the NH 4 + -N removal efficiency according to the surface loading rate revealed that the effects caused by the increase in the surface loading rate are greater in NH 4 + -N than in BOD. The attached growth micro-organisms decreased by detachment after 20 d, and increased again, securing a constant amount of growth micro-organisms.