title: Redox control bioreactor: a unique biological water processor.
abstract: The redox control bioreactor (RCB) is a new hollow fiber membrane bioreactor (HFMBR) design in which oxygen and hydrogen gases are provided simultaneously through separate arrays of juxtaposed hollow fiber (HF) membranes. This study applied the RCB for completely autotrophic conversion of ammonia to N(2) through nitrification with O(2) and denitrification using hydrogen as an electron donor (i.e., autohydrogentrophic denitrification). The hypothesis of this research was that efficient biofilm utilization of O(2) and H(2) at respective HFs would limit transport of these gases to bulk fluid, thereby enabling completely autotrophic ammonia conversion to N(2) through the co-occurrence of ammonia oxidation (O(2)-HF biofilms) and autohydrogenotrophic denitrification (H(2)-HF biofilms). A prototype RCB was fabricated and operated for 215 days on a synthetic, organic-free feedstream containing 217 mg L(-1) NH(4)(+)-N. When O(2) and H(2) were simultaneously supplied, the RCB achieved a steady NH(4)(+)-N removal flux of 5.8 g m(-2) day(-1) normalized to O(2)-HF surface area with a concomitant removal flux of 4.4 g m(-2) day(-1) (NO(3)(-))+NO(2)(-))-N based on H(2)-HF surface area. The significance of H(2) supply was confirmed by an increase in effluent NO(3)(-)-N when H(2) supply was discontinued and a decline in NO(3)(-)-N when H(2) supply was restarted. Increases in H(2) pressure caused decreased ammonia utilization, suggesting that excess H(2) interfered with nitrification. Microprobe profiling across radial transects revealed significant gradients in dissolved O(2) on spatial scales of 1 mm or less. Physiological and molecular analysis of biofilms confirmed that structurally and functionally distinct biofilms developed on adjacent, juxtaposed fibers.
authors: Applied Environmental Technology, Thonotosassa, Florida, USA. dpsmith_aet@verizon.net
authors: Daniel P
authors: DP
authors: Smith
authors: Tony
authors: T
authors: Rector
authors: Kristina
authors: K
authors: Reid-Black
authors: Mary
authors: M
authors: Hummerick
authors: Richard
authors: R
authors: Strayer
authors: Michele
authors: M
authors: Birmele
authors: Michael S
authors: MS
authors: Roberts
authors: Jay L
authors: JL
authors: Garland
mesh_terms: D000641:Ammonia / Q000378:metabolism*; D001420:Bacteria, Aerobic / Q000378:metabolism*; D019149:Bioreactors / Q000382:microbiology*; D004867:Equipment Design; D019544:Equipment Failure Analysis; D010084:Oxidation-Reduction; D010100:Oxygen / Q000378:metabolism*; D014874:Water Pollutants, Chemical / Q000378:metabolism*; D018508:Water Purification / Q000295:instrumentation* / Q000379:methods
chemical_list: D014874:Water Pollutants, Chemical; D000641:Ammonia; D010100:Oxygen