Biotreatment of sulfate-rich wastewater in an anaerobic/micro-aerobic bioreactor system.
The focus of this study was on sulfate-rich wastewater treatment in a novel anaerobic/micro-aerobic bioreactor system. The system was composed of an upward-flow anaerobic sludge blanket (UASB) reactor and a floated bed micro-aerobic reactor, which was packed with elastic porous carriers and was controlled in a situation of dissolved oxygen below 0.5 mg l(-1). The floated bed micro-aerobic reactor was developed for accumulating a higher amount of biomass in carriers with a short hydraulic retention time (HRT) for biological oxidation of hydrogen sulfide to elemental sulfur. During long-term steady state operation, experimental results showed that an average of 70 +/- 6% of sulfate was transformed to hydrogen sulfide in UASB reactor. Moreover, the overwhelming majority of sulfide was oxidized to elemental sulfur and sulfate in micro-aerobic reactor; and the recirculation of effluent to UASB reactor reduced effectively the degree of inhibition caused by sulfate-rich wastewater. In UASB reactor, chemical oxygen demand (COD) removal efficiency increased with COD loading, in contrast, the performance of sulfate removal decreased with the increase in sulfate loading in a range of 1.0-1.75 kg SO4(2-) m(-3) d(-1). In micro-aerobic reactor, sulfide was removed almost completely under the operation of HRT 2.8 h. Furthermore, experimental results of continuous operations revealed that oxidation-reduction potential (ORP) was an adequate parameter for controlling biological oxidation of sulfide. When ORP was regulated in a lower range of -250 to -300 mV, the amount of regenerated sulfate was reduced significantly in micro-aerobic reactor.
Chuang
S H
SH
Department of Environmental Engineering and Management, Chaoyang University of Technology, Taichung County, 413, Taiwan.
Pai
T Y
TY
Horng
R Y
RY
D001420:Bacteria, Aerobic / Q000254:growth & development / Q000378:metabolism*; D001421:Bacteria, Anaerobic / Q000254:growth & development / Q000378:metabolism*; D018533:Biomass; D019149:Bioreactors; D004867:Equipment Design; D010084:Oxidation-Reduction; D010100:Oxygen / Q000032:analysis; D013431:Sulfates / Q000378:metabolism*; D014865:Waste Disposal, Fluid / Q000295:instrumentation* / Q000379:methods*; D014867:Water / Q000737:chemistry; D014871:Water Microbiology
D013431:Sulfates; D014867:Water; D010100:Oxygen