Safferman Steven I, Mashingaidze Ella M, McMackin Stephanie A
Department of Civil and Environmental Engineering, University of Dayton, Dayton, Ohio 45469-0243, USA.
J Environ Sci Health A Tox Hazard Subst Environ Eng. 2003 Sep;38(9):1689-702. doi: 10.1081/ese-120022860.
A dual-media fluidized bed is a unique reactor design containing two distinct media that results in two segregated treatment zones. By the strategic use of these two zones, this design has the potential to remove both BOD and nutrients (nitrogen and phosphorus) in a single compact reactor. Three operational strategies are conceivable. The first is to maintain a microbiological zone close to the influent to achieve BOD and nitrogen removal. The zone above would contain an exchange media to remove phosphorous. In another scenario, the lower zone would be kept aerobic and the higher zone anoxic. This would enhance denitrification. In the third scenario, the first two are combined by having the exchange media serve as the anoxic zone or including an independent third zone (aerobic, anoxic, and exchange). This scenario could result in the comprehensive treatment of BOD, nitrogen, and phosphorus removal. This proof-of-concept research primarily investigated the first scenario and provided preliminary data for the other two. A low-loaded operating strategy was used to minimize the inherent disadvantages of a fluidized bed reactor, primarily caused by excessive biofilm growth. The reactor was operated for approximately 1 year using sand and activated alumina as the two media. Good separation with minimum mixing at the interface resulted. BOD and phosphorus removal and nitrification were consistently very good during non-transitional periods. Denitrification varied depending on the influent concentration, dissolved oxygen, and oxidation/reduction potential. Preliminary data also indicated that when a low recirculation ratio is used, denitrification could be enhanced. There appears to be a potential difficulty, however, in exchanging phosphorous using activated alumina under low oxidation/reduction potential conditions.
双介质流化床是一种独特的反应器设计，包含两种不同的介质，形成两个分离的处理区。通过巧妙利用这两个区域，这种设计有可能在一个紧凑的反应器中同时去除生化需氧量（BOD）和营养物质（氮和磷）。可以设想三种运行策略。第一种是在靠近进水处维持一个微生物区以实现BOD和氮的去除。上方区域将包含一种交换介质以去除磷。在另一种情况下，下部区域保持好氧，上部区域保持缺氧。这将增强反硝化作用。在第三种情况下，将前两种情况结合起来，使交换介质充当缺氧区或包括一个独立的第三区（好氧、缺氧和交换区）。这种情况可以实现对BOD、氮和磷的综合处理。这项概念验证研究主要研究了第一种情况，并为其他两种情况提供了初步数据。采用低负荷运行策略以尽量减少流化床反应器固有的缺点，这些缺点主要是由生物膜过度生长引起的。该反应器使用沙子和活性氧化铝作为两种介质运行了约1年。在界面处实现了良好的分离且混合最小。在非过渡时期，BOD、磷的去除以及硝化作用一直都非常好。反硝化作用因进水浓度、溶解氧和氧化还原电位而异。初步数据还表明，当使用低回流比时，反硝化作用可以增强。然而，在低氧化还原电位条件下，使用活性氧化铝交换磷似乎存在潜在困难。
