Using molecular dynamics, the lowest energy configurations of n?dodecane, n?octadecane, and n?nonadecane were constructed, and the interactions between oil molecules and wax molecules were studied at different water contents (mass fractions). The molecular dynamics model of crude oil emulsion system based on different mass fraction water content was constructed. The effect of water molecules dissolved in the system on the viscosity of waxy crude oil was studied. The radial distribution functions of wax molecules in different water content systems were compared. The results show that carbon number is the main factor to determine the interaction energy between crude oil molecules. With the increase of water content, the distance between molecules increases, while the interaction energy decreases. After water molecules are dissolved in the system, the distance between wax molecules and electrostatic interaction become larger, the distribution of wax molecules becomes disordered, and the flow characteristics of crude oil are improved.

The effect of dissolved oxygen (DO) concentration on aerobic granular sludge (AGS) treatment on simulated municipal sewage was studied in SBR reactor. By changing the amount of aeration, the DO concentration in SBR reactor was controlled respectively in the range of 3 mg/L≤ρ（DO）＜4 mg/L, 2 mg/L≤ρ（DO）＜3 mg/L and 1 mg/L≤ρ（DO）＜2 mg/L. The concentrations of COD, NH {}_{\mathrm{4}}^{+} -N, NO {}_{\mathrm{3}}^{—} -N, NO {}_{\mathrm{2}}^{—} -N, TN and P in the effluent were detected. The results show that the removal rates of COD, NH {}_{\mathrm{4}}^{+} -N and P are affected little by the DO concentration, but the removal rate of TN is affected significantly. When 3 mg/L≤ρ（DO）＜4 mg/L, 2 mg/L≤ρ（DO）＜3 mg/L和1 mg/L≤ρ（DO）＜2 mg/L, the removal rate of TN is 62.14%, 71.81% and 82.11% respectively; when 1 mg/L≤ρ（DO）＜2 mg/L, the removal rate of TN reached the best for the AGS system and the system was stable. The average removal rates of COD, NH {}_{\mathrm{4}}^{+} -N and P were 90.43%, 96.97% and 76.00%, respectively.