Evaluation of alternative electron donors for denitrifying moving bed biofilm reactors (MBBRs).

The effectiveness of four different electron donors, specifically methanol, ethanol, glycerol, and sulfide (added as Na(2)S), were evaluated in post-denitrifying bench-scale moving bed biofilm reactors (MBBRs). With the requirement for more wastewater treatment plants to reach effluent total nitrogen levels approaching 3 mg/L, alternative electron donors could promote more rapid MBBR startup/acclimation times and increased cold weather denitrification rates compared to methanol, which has been most commonly used for post-denitrification processes due to low cost and effectiveness. While the application of alternative substrates in suspended growth processes has been studied extensively, fixed film post denitrification processes have been designed to use primarily low yield substrates like methanol. Bench-scale MBBRs were operated continuously at 12 degrees Celsius, and performance was monitored by weekly sampling and insitu batch profile testing. Ethanol and glycerol, though visually exhibited much higher biofilm carrier biomass content, performed better than methanol in terms of removal rate (0.9 and 1.0 versus 0.6 g N/m(2)/day, respectively.) Maximum denitrification rate measurements from profile testing suggested that ethanol and glycerol (2.2 and 1.9 g N/m(2)/day, respectively) exhibited rates that were four times that of methanol (0.49 g N/m(2)/day.) Sulfide also performed much better than either of the other three electron donors with maximum rates at 3.6 g N/m(2)/day and with yield (COD/NO(3)-N) that was similar to or slightly less than that of methanol.

Recombinant human complement C5a receptor antagonist reduces infarct size after surgical revascularization.

OBJECTIVES: This study tested the hypothesis that a recombinant human C5a antagonist, CGS 32359, attenuates neutrophil activation and reduces infarct size in a porcine model of surgical revascularization. METHODS: CGS 32359 (0.16-16 micromol/L) dose-dependently inhibited superoxide production by human C5a-activated porcine neutrophils (18 +/- 3.7 vs 1.6 +/- 0.5 nmol/5 min/5 x 10(6) neutrophils; P <.05) and reduced neutrophil adherence to coronary endothelium from 194 +/- 9 to 43 +/- 6 neutrophils/mm(2) (P <.05). The left anterior descending coronary artery was occluded for 50 minutes, after which saline solution (n = 8), mannitol-buffer vehicle (n = 9, 102 mg/kg bolus, 102 mg. kg(-1). h(-1)), or CGS 32359 (CGS, n = 7, 60 mg/kg bolus, 60 mg. kg(-1). h(-1)) was infused. After ischemia, 1-hour arrest was achieved by means of multidose hypothermic (4 degrees C) blood cardioplegia, followed by 2.5 hours of off-bypass reperfusion. The ligature on the left anterior descending artery was released before the second infusion of cardioplegic solution. RESULTS: Area at risk was similar in all groups (saline solution, 27% +/- 2%; mannitol-buffer vehicle, 26% +/- 2%; CGS, 26% +/- 2% left ventricular mass). Infarct size (area necrosis/area at risk) was significantly reduced by CGS (18% +/- 6%, P <.05) versus saline solution (52% +/- 3%) and mannitol-buffer vehicle (60% +/- 4%). Postischemic systolic shortening (sonomicrometry) in the area at risk was significantly improved with CGS (0.8% +/- 0.9%) compared with saline solution (-3.7% +/- 1.1%) and mannitol-buffer vehicle (-6.4% +/- 1.0%). Myeloperoxidase activity from accumulated neutrophils was less in the ischemic zone of CGS (0.014 +/- 0.002 U/100 mg tissue; P <.05) than mannitol-buffer vehicle (0.133 +/- 0.012 U/100 mg tissue). CONCLUSIONS: We conclude that the recombinant human C5a receptor antagonist CGS 32359 inhibits surgical ischemia-reperfusion injury after coronary occlusion.