The Study On Biodegradation Of DHP, DEHP In Biological Aerated Filters

Phthalic acid esters(PAEs)are a class of environmental hormones and endocrine disruptors. In modern industrial production, they are used as plasticizers to improve the flexibility and strength of plastic. Because of its long history of technological craft, productive outputs, wide applications and the character separated from the materials easily at high temperature, they have become one of the most prevalent contaminants in the environment progressively. Phthalic acid esters are widely found in water, air, soil, organism and even clay. Lots of studies has proved that PAEs are hard to be biodegraded in nature condition, so they are easily cumulate at the food chain , if they enter into human body, they might cause cancer, abnormal fetus or matution.This experimentation uses biological aerated filter to biodegradate DHP or DEHP respectively, and focus on the removal characteristics and relevant impact factors. In addition, a probable pathway of the degradation of DHP or DEHP and microbe of the biomembrane were also discussed. Waste water flows into and out of biological aerated filters continuously. The result indicated that when the T=25℃, EBCT=8h,the removal efficiency of DHP and DEHP could achieve 95.5% and 90.3%. But in other EBCT, the removing rate was not so good as this. And the result also indicated that when EBCT=8h, DHP or DEHP was more harder to be removed at 7℃comparing when it at 25℃, the removing rate was 78.3% and 64.8%. The removing rate would decline along with the decrease of temperature or EBCT, during which EBCT played the main role.At middle-lower BAF filter, PAEs were biodegradated more efficiently because there were high density of organic compounds and Microbe with high activity, the curve of degradation was sharper. But the situation at middle-upper was contrary.Analyzing qualitatively the degradation products of DHP and DEHP with GC-MS, DBP, DMP, MBP, MEHP and PA are all identified. So a probable pathway of the degradation of PAEs is that, first, the side chain of the alcoholic ending cleavages to a short and straight one, following the cleavage of one of the two ester bonds, and then, forming the monoester and PA subsequently.The SEM-images showed that relatively stable microorganisms form on the ceramic carriers, bacillus and cocci take the dominant place. Observe at the pure bacteria’s colony and individual thalli after streaking, and use AFM to observe the dominant degradation highly-effective bacteria, the results are match well with the SEM ones.