Junmei Li

Adsorption of sunset yellow FCF from aqueous solution by chitosan-modified diatomite

Sunset yellow (SY) FCF is a hazardous azo dye pollutant found in food processing effluent. This study investigates the use of diatomaceous earth with chitosan (DE@C) as a modified adsorbent for the removal of SY from wastewater. Fourier transform infrared spectroscopy results indicate the importance of functional groups during the adsorption of SY. The obtained N2 adsorption-desorption isotherm values accord well with IUPAC type II. Our calculations determined a surface area of 69.68 m2 g(-1) for DE@C and an average pore diameter of 4.85 nm. Using response surface methodology, optimized conditions of process variables for dye adsorption were achieved. For the adsorption of SY onto DE@C, this study establishes mathematical models for the optimization of pH, contact time and initial dye concentration. Contact time plays a greater role in the adsorption process than either pH or initial dye concentration. According to the adjusted correlation coefficient (adj-R2>0.97), the models used here are suitable for illustration of the adsorption process. Theoretical experimental conditions included a pH of 2.40, initial dye concentration of 113 mg L(-1) and 30.37 minutes of contact time. Experimental values for the adsorption rate (92.54%) were close to the values predicted by the models (95.29%).

Study on Ventilation and Smoke Control System of Subway Transfer Stations

As a representative form of public transportation, subway system is undertaken to satisfy constantly increasing transport needs and developed commonly in many big cities. Among several catastrophes in subway stations, including fire, flood, earthquake, explosion, toxic gas leakage etc., fire is the most threatening hazard to passengers. Subway fires had caused huge casualties and property losses during the past decades. With the development of metro line network, more and more transfer stations appeared. Compared with the general subway station, smoke control system of transfer station has its particularity and complexity. A typical cross-shaped metro transfer station is used as an example for the study. Effect of two different schemes of ventilation and smoke control in extreme conditions in which multiple fires happen simultaneously on both platforms in the transfer station are studied by using numerical simulation method. In fire scenario No.1, air is supplied in underground one while independent smoke control is taken in underground two and three. In scenario No.2, based on scenario No.1, tunnel fans are used to assist in smoke control by opening screen door. Fire source is designed for t2 rapid fire with peak 2MW. The results show that, smoke spread in second underground floor can be controlled effectively by both schemes, the measure used in scenario 2 effectively raises the wind speed downward the stairs while lower temperature around stairs, so that stairs round fire source can be used as emergency evacuation passages for a longer time, guaranteeing a better smoke control performance in interchange station. Connecting the underground third floor with tunnel ventilation system by opening PSD can increase the downward air flow velocity and decrease the air temperature at staircases near the fire. Period during which the staircase near fire can be used for evacuation is increased. Reliable smoke control performance for transfer station can be got.

Phosphorus removal in a membrane-assisted BNR process with focus on evolutions of PAOs and DPAOs

A bench-scale UCT (University of Cape Town)-type membrane bioreactor (UCT-MBR) fed with low-strength synthetic wastewater was operated to investigate phosphorus removal with reference to poly-phosphate accumulating organisms (PAOs) and denitrifying poly-phosphate accumulating organisms (DPAOs). A series of kinetic assays of PAOs and DPAOs were also conducted to analyze the metabolic activities of PAOs and DPAOs. Results showed that 93% of chemical oxygen demand (COD) and 77% of total nitrogen could be removed at 0.08 kgCOD kg(-1) MLSS d(-1) and 0.015 kgN kg(-1) MLSS d(-1) loading (MLSS: mixed liquor suspended solids). Removal efficiencies of total phosphorus increased during the experimental phase, with an ultimate removal efficiency of 96.1%. Kano and Kaer increased from 1.95 and 6.29 mgPO4(3-)-P g(-1) MLSS h(-1) to 5.47 and 11.13 mgPO4(3-)-P g(-1) MLSS h(-1) for DPAOs and PAOs respectively, with the increased ratio of DPAOs to PAOs from 31 to 49% implying DPAO metabolic activity increased faster than that of PAOs during the DPAO accumulation phase. Pano-uptake increased by 6.6 mg L(-1) and the ratio of PTano-uptake to PTupt increased from 58.97 to 91.62%. The ratio of DPAOs to PAOs tended to stabilize at around 50% over time.