1. 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 / 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