A new wastewater treatment equipment, the bi-external recycling biological fluidized bed (BRBFB), which is an effective equipment, was investigated. Anaerobic digestion, aerobic aeration and settlement processes with a fixed sequential procedure were compacted into this reactor. By five different treatment courses, the optimization of the combined operation procedure in the system was determined to be a 12-hour cycle including an inflow process, a 4 h anaerobic digestion process, a 4 h aerobic aeration process, a 2 h settlement process and a 2 h recess process including effluent discharge process. By utilizing BRBFB to treat a synthetic dyeing wastewater, 90% of COD_ Cr is removed for a higher-concentration water (COD_ Cr 1 000-1 200 mg/L), and 82% of COD_ Cr is removed for a lower-concentration water (COD_ Cr 400-600 mg/L). Near 100% color is removal and discharging standards for industry wastewater are achieved.
This paper aims to investigate exact solutions for a second-grade fluid flow with the inverse method. By assuming the relation between the vorticity field and the streamfunction, the exact solutions of the motion of plane second-grade fluids are investigated and obtained. The solutions obtained include simple Couette flows, slit jet flows and uniform flows over a series of distributed obstacles.
This is a study on the mass transport of a solute or contaminant in oscillating flows through a circular tube with a reactive wall layer. The reaction consists of a reversible component due to phase exchange between the flowing fluid and the wall layer, and an irreversible component due to absorption into the wall. The short-time dispersion characteristics are numerically investigated, incorporating the coupling effects between the flow oscillation, sorption kinetics, and retardation due to phase partitioning. The effects of various dimensionless parameters e.g., Da （the Damkoehler number）, α （phase partitioning number）, F （dimensionless absorption number）, and δ （dimensionless Stokes boundary layer number） on dispersion are discussed. In particular, it is found that there exist trinal peaks of the breakthrough curves in some cases.
