Effects of Controlling and Not Controlling Solids Retention Time in Glycerol-Driven Denitratation Authors: Kristen McCarty, Gabrielle Young, Luke Plante Background & Objectives: Help Holston Army Ammunition Plant (HAAP) meet nitrogen discharge requirements Evaluate bioremediation through denitratation to convert ammonium nitrate to ammonium nitrite to allow for anaerobic ammonium oxidation (anammox) to convert ammonium nitrite into di-nitrogen gas Operate a sequencing batch reactor (SBR) Nitrogen balance, biomass concentration, DNA and RNA sampling Results & Evaluation: Majority of the time not wasting Influent feed sometimes low in target nitrate Influent feed sometimes high in target nitrite Reactor performance: ~20% nitrate conversion to nitrite Table 2. Reactor Data 3:1 COD:NO3--N ratio 3 day Solids Retention Time (SRT) Accumulate nitrite & less electron donors Conclusions: Recycle can lead to ~100% conversion in a WWTP Reactor takes time to adjust to new SRT Research Design & Program Description: Influent: 30 mg N/L ammonium, 100 mg N/L nitrate, and excess micronutrients Hydraulic retention time (HRT) = 1 day The pH was maintained at 7.50 +/- 0.05 using sodium bicarbonate and hydrochloric acid Glycerol used as external carbon source Figure 3. Influent N species concentrations Table 1. Reactor Phases per Cycle (4 cycles/day) Figure 2. Denitratation Biomass shown at left; traditional denitrifiers shown at right Time Phase Description 80 min Settle No mixing, bacteria settle, Vol: 6L 10 m Decant No mixing, pump out effluent, Vol: 6 to 4.5L 270 min Feed & React Mixing, Feed & Glycerol added, Vol: 4.5 to 6L Varied Waste Mixing, pump out effluent Future Plans: Optimize COD:N Ratio Change SRT Ratios Combine with Annamox Simulate WWTP more realistically: equalization, recycle Figure 1. Reactor Configuration Figure 4. Effluent N species concentrations