Characteristic and correlation analysis of influent and energy consumption of wastewater treatment plants in Taihu Basin

The water quality and energy consumption of wastewater treatment plants(WWTPs)in Taihu Basin were evaluated on the basis of the operation data from 204 municipal WWTPs in the basin by using various statistical methods.The influent ammonia nitrogen(NH3-N)and total nitrogen(TN)of WWTPs in Taihu Basin showed normal distribution,whereas chemical oxygen demand(COD),biochemical oxygen demand(BOD5),suspended solid(SS),and total phosphorus(TP)showed positively skewed distribution.The influent BOD5/COD was 0.4%-0.6%,only 39.2%SS/BOD5 exceeded the standard by 36.3%,the average BOD5/TN was 3.82,and the probability of influent BOD5/TP>20 was 82.8%.The average energy consumption of WWTPs in Taihu Basin in 2017 was 0.458 kWh/m^3.The specific energy consumption of WWTPs with a daily treatment capacity of more than 5×10^4 m^3 in Taihu Basin was stable at 0.33 kWh/m^3.A power function relationship was observed between the reduction in COD and NH3-N and the specific energy consumption of pollutant reduction,and the higher the pollutant reduction is,the lower the specific energy consumption of pollutant reduction presents.In addition,a linear relationship existed between the energy consumption of WWTPs and the specific energy consumption of influent volume and pollutant reduction.Therefore,upgrading and operation with less energy consumption of WWTPs is imperative and the suggestions for Taihu WWTPs based on stringent discharge standard are proposed in detail.

Probing the interplay between chain diffusion and polymer crystal growth under nanoscale confinement： a study by single molecule fluorescence microscopy

Motions of single poly(ε-caprolactone)(PCL) molecules during the formation of the dendrite crystals in ultrathin films are captured by single molecule fluorescence microscopy. The relationship of single molecule diffusion coefficient with the crystal growth rate, together with radius curvature, side-branch spacing of dendrite crystal and morphology are examined. The results support Mullins-Sekerka(MS) instability as the origin of lamellar branching induced by a diffusion field generated by a gradient of polymer segment density ahead of the crystal. Further analysis of the molecular trajectories has recognized different types of motions, depending on the distance to the crystal front: Fickian diffusion in regions far away from the crystal, sub-diffusion in regions adjacent to the crystal, and directed motion between these two regions. Anti-correlation of successive steps is discovered accompanying the sub-diffusion, providing a clear signature of macromolecule crowding at the crystal growth front. This anomalous diffusion process in polymer ultrathin films presents a new insight into the understanding of the retarded dynamics of interfacial mass transport towards the crystal front. It is considered to play a decisive role in controlling the crystal growth and evolution of crystal morphology.