Study On Degradation Of Typical Refractory PPCPs Organic Matter Due To The Electric Field Microbial Community Stimulating Effect

At present,the new type of trace pollutants pharmaceuticals and personal care products（PPCPs）has been widespread in the water environment.These organic matter which has the nature of persistent enrichment and hard biodegradable not only caused the water pollution of the environment,but also has a certain influence on human health.The key of removal toxic and refractory organic compounds PPCPs is seeking a city wastewater treatment technology which is effective and economic.In order to solve the problem of feeble degradation efficiency and complex structure and higher activation energy of refractory PPCPs organics in the conventional sewage treatment technology,this paper independent designed and set up the electro-biological coupling system due to the electric field microbial community stimulating effect.It investigated the relationship between electric field and microbial growth and metabolism,studied on degradation of typical refractory PPCPs organic matter removal in the city sewage by the electro-biological coupling system.Also the diversity of microbial community structure is analyzed by High-Throughput and it further reveal the stimulating effect between electric field and the microbial community.The main conclusions are as follows:The results show that an appropriate direct electrical current in the electro-biological coupling system can improve COD_Cr,TOC and ammonium nitrogen reduction,whereas a more than optimum direct electrical current may be harmful.At the same time,there was no significant relation between community richness and diversity and removal efficiency below optimum current density,while above optimal current density,it was just the opposite.Microbial communities mainly including Hydrogenophaga（18.80%）,Saprospiraceae_uncultured（12.15%）,Delftia（6.84%）,Pseudomonas（5.22%）,Pseudoxanthomonas（4.33%）,and Nitrosospira（3.63%）and physicochemical properties well explained the excellent removal performance at the optimum current density of 14.25A/m².To select the three-dimensional particle in the electro-biological coupling system,this paper studied the degradation efficiency of three kinds of PPCPs organic compounds at the static and dynamic experiments.The results showed that the activated carbon was used as the three-dimensional particle and the static adsorption rate of activated carbon to ibuprofen,bezafibrate,and carbamazepine were 21.26%,17.22%,and 11.89%,respectively,and the dynamic degradation rate was about 54.55%,37.23% and 30.11%,respectively.The effects of different current density and different organic matters concentration on the reactors were studied in the stable operation stage of the electro-biological coupling system.The study discovered that the average removal rates of COD_Cr,TOC and ammonia nitrogen in the electro-biological coupling system were 91.12%,91.64% and 98.17%,respectively when the current density was 14A/m²,which was significantly higher than that of the conventional biological aerated filter.With the increase of organic matters concentration,the biodegradability of the wastewater decreased gradually which caused by the biodegradable of the selected PPCPs organic matters,resulting in the removal rate reduction of pollutants in two filters.However,facing the impact of changes in organic loading,the biological aerated filter has better impact resistance and buffering capacity than the conventional biological aerated filter.At the same time,the study of reactors space biodegradability in stable operation showed that the biochemical character of biological aerated filter showed that the biodegradability of the electro-biological aerated filter can be increased from 0.51 to above 0.8,while the biodegradability of the conventional biological aerated filter is not improved,and even lower,which caused by the react of electrocatalytic oxidation which can degrade the refractory organic matter into a biodegradable small molecule organic matter in the electric-biological coupling aerated filter,thus improving the biodegradability of the electric-biological aerated filter.According to the degradation path of PPCPs compounds which were speculated by intermediate products,it found that the degradation of PPCPs compounds were complex.Firstly,they were oxidation by the biological and hydroxyl radical into intermediate molecular weight smaller,and then under a series of redox（including electrocatalytic oxidation reduction and microbial oxidation reduction）,they cracked into small molecular organic compounds or easy to degrade aniline compounds,and finally further oxidized and mineralized into CO₂ and H₂O.