Ju-Chang Huang

HEAVY METAL REMOVAL FROM WASTEWATER IN FLUIDIZED BED REACTOR

An innovative process for removing heavy metals including Cu, Ni and Zn from industrial wastewater has been developed. The new technology was based on inducing the nucleated precipitation of heavy metals on the sand surface in a fluidized bed reactor. The results showed that pH had a great effect on heavy metal removal efficiency and the optimum pH was about 9.0 to 9.1. At this pH value, heavy metal removal efficiency could be achieved above 92 and 95% when influent heavy metal concentrations were 10 and 20 mg/l, respectively. When pH was greater than 8.7, above 92.4% of the precipitation was composed of metal hydroxide. Hydraulic retention time (HRT) had almost no effect on heavy metal removal efficiency when HRT was greater than 7.1 min. Scanning electron microscope (SEM) analysis indicated that carbonate injection with a drip-wise manner was more conducive than that with a slug dosing manner for precipitation to be coated on the sand surface.

High-rate wastewater treatment by aerobic upflow sludge blanket reactor: System performance and characteristics

A laboratory study was conducted to investigate the characteristics of an aerobic upflow sludge blanket reactor (AUSB) treating synthetic wastewater at a high organic loading. The response of the system was evaluated at different operating conditions, such as pressurization, extent of flow recirculation, and hydraulic retention time. Aeration shear to the biomass in the reactor was totally eliminated by employing oxygenation under pressurization in an external chamber. As a result, the biomass concentration in the reactor could be maintained at 7-10 g VSS l-1. The AUSB system was able to handle efficiently a volumetric loading of as high as 3.8 kg TOC m-3 d-1, which was possibly due to high reactor biomass level and higher bioactivity as indicated by higher sludge specific oxygen uptake rates. However, the treatment capacity of the AUSB was somewhat limited by the substrate and oxygen transport in the sludge bed due to low mixing intensity. The effluent TOC of the AUSB system was relatively higher due to its operation at a high organic loading. The AUSB system performed well under a short term loading shock, and the bacterial activity in the oxygenation chamber was demonstrated to contribute to its improved substrate removal capacity under the shock loading.