The Study On Biodegradation Of Phthalic Acid Esters In Biological Aerated Filters

Phthalic acid esters(PAEs)are important kinds of organic compounds. They are used as plasticizers to improve the flexibility and strength of plastic. With the widely use of phthalic acid esters, they have become important pollutants. Phthalic acid esters are found in water, air, soil, organism and even clay. It is proved that phthalic acid esters could cause cancer, abnormal fetus and matution. At the same time, phthalic acid esters are a class of environmental hormone that influence the procreation and upgrowth of animals.This experimentation uses biological aerated filte(rBAF)to biodegradate phthalic acid esters, and utilizes the adsorption and biodegradation effects of biofilm on the fillings to remove phthalic acid esters. This experimentation selects dimethyl phthalate and di-n-butyl phthalate which are all familiar phthalic acid esters. Two biological aerated filters treat dimethyl phthalate and di-n-butyl phthalate separately, and utilize dimethyl phthalate and di-n-butyl phthalate as sole carbon source and energy source. Waste water flows into and out of biological aerated filters continuously. The concentrations of phthalic acid esters in influent water are about 5mg/L. The pH of influent water is about 7. The dissolved oxygen concentration in the biological aerated filters is larger than 2.0mg/L by aerating. Two biological aerated filters work at 25℃and 10℃, and work at the empty bed contact time(EBCT)of 4h, 2h, 1h and 0.5h at each temperature. As a result, dimethyl phthalate is well removed in the biological aerated filter. In all case, the removal efficiency of dimethyl phthalate is 100%. Di-n-butyl phthalate is removed worse than dimethyl phthalate in the biological aerated filter. The removal efficiency of di-n-butyl phthalate is between 70.27% and 96.81%. Low temperature and short empty bed contact time are bad for biodegradation of phthalic acid esters. The pH of effluent is lower than the corresponding pH of influent. That is because the biodegradation of phthalic acid esters will produce acid compounds, such as phthalic acid monoesters and phthalic acid. So phthalic acid esters are better biodegrated, the pH of effluent is lower. With the reducing of empty bed contact time, the volumetric degradation rates of dimethyl phthalate and di-n-butyl phthalate all increase. So biological aerated filters could biodegradate phthalic acid esters with high adaptability to shock load. It is also found that the degradation of phthalic acid esters is almost at the bottom of the biological aerated filters. Phthalic acid is identified as metabolite of dimethyl phthalate and di-n-butyl phthalate degradation.