Operation and performance of membrane-aerated sequencing batch biofilm reactors for the treatment of wastewater containing volatile organic compounds.

摘要

The Sequencing Batch Biofilm Reactor (SBBR) is a wastewater treatment system which combines the operating advantages of the Sequencing Batch Reactor (SBR), biofilm operation, and membrane aeration. This combined system provides a system for the treatment of low-strength wastewaters containing volatile organic components while minimizing volatile emissions.; The operation and performance of the SBBR was investigated using conventional SBR operating procedures (i.e., fill, react, and draw periods). Using hydraulic residence times (HRT) as low as 1.5 days, the SBBR provided treatment of both a high-strength synthetic wastewater (i.e., containing 100-200 mg/L of toluene) and a contaminated groundwater (i.e., containing benzene, toluene, ethylbenzene, and xylenes (BTEX) at a total concentration of 0.6-3.5 mg/L) down to levels typically below 20 {dollar}mu{dollar}g/L. Volatile emissions from the SBBR were below 0.73% of the total mass of volatile compounds introduced to the reactor using these operating strategies.; The degradation of a trichloroethylene (TCE) contaminated wastewater by supplying growth substrate (i.e., toluene) via the membrane aeration system was also examined. Operating the SBBR with a 3 day HRT and alternating the supply of toluene and TCE, 74% of the TCE was degraded. Volatile losses of TCE during this study were approximately 19%.; Detailed experimental studies on the aeration system indicated that the mass transfer coefficient for oxygen was independent of the gas composition, pressure, and flow rate in the aeration system. The aeration system operating strategy (i.e., flow, purge, and dead-end) also had no significant effect on the mass transfer coefficient; however, dead-end operating strategies could not be used in respiring systems since the observed oxygen transfer rate decreased due to a reduction in the partial pressure of oxygen in the aeration system.; A mathematical model developed for the membrane aeration system accurately predicted oxygen transfer to the SBBR under a variety of operating strategies and confirmed the experimental finding that dead-end operation could not be used effectively. This model can be used to optimize oxygen transfer and to design large-scale membrane aeration systems.